eChapters

Dahlia (Dahlia variabilis Desf., family: Asteraceae, origin: Mexico) is regarded as a premium specialty cut flower besides its utilization for garden decoration and growing as a potted flowering plant. The dahlia flower symbolizes elegance, inner strength, creativity and dignity. It is herbaceous rooted perennial valued for their majestic and attractive display of colourful spectacular flowers. The generic name “Dahlia” was coined by Swedish botanist “Andreas Dahl”. Dahlia was introduced in India during 1857 under the auspices of the “Agri-Horticultural Society of India”, Calcutta. Dahlia exhibit wide range of flower from and size ranging from miniatures (less than 2.5 cm across), to giant (more than 40 cm in diameter). Dahlia flowers profusely and its easy cultivation have made these very popular worldwide. The commercial value of this crop has been exploited in certain countries only. The Netherlands is claimed to be the largest producer of tuberous rooted dahlias. Other countries cultivating Dahlia as a specialty cut flower are Japan, France, South Africa, the U. K., Italy, Germany and the United States. The commercial cultivation of dahlia in Indian subcontinent is limited to hills and plains of Eastern India (Misra and Misra, 2017).

Holland takes the lead in dahlia bulb production cultivation neeary 400 ha, followed by France and Chile. There are 41 international associations concerned with the cultivation and spreading awareness about dahlia as a potential specialty cut flower and flowering potted perennial. Societies such as National Dahlia Society in the UK, the American Dahlia Society (ADS), other groups of New Zealand in European countries, France and Germany have been maintaining Dahlia germplasm for developing novel flower colour and breeding dahlias for their uniform and profuse flowering, longer flower duration, stem sturdiness and longer vase life.

Lily is one of the most beautiful and popular ornamental bulbous flowers. They belong to the genus Lilium of the family Liliaceae, which comprises of 110 species classified into seven taxonomic sections: Lilium, Pseudolirium, Martagon, Sinomartagon, Archelirion, Leucolirion and Oxypetalum. All species are distributed over the mountainous area in the Northern Hemisphere (10° to 60°), mainly in Asia, North America and Europe. Especially, China, Nepal, Korea and Japan are the major centres of lilium gene pool around the world. Being second amongst the bulbous flower crops in the commercial market, Lilium has 4^th position among cut flowers in Flora Holland (Flora Holland Annual Report 2017). In the language of flowers lily is known as symbol of purity and innocence. Majority of cultivated lilies are either hybrids or selections. A large number of species and hybrids can be used in ornamental gardens even though the lily requires little more attention than any other bulbs. Many species of lily (L. leichtlinii, L. lancifolium, Lilium candidum and L. auratum) are also edible and having medicinal value.

Importance and uses

Lilies are one of the most important bulbous ornamental plants with varies uses, grown in border, beds, pots, landscape gardens and are excellent cut flowers of magnificent appearance and beautiful flowers. Roman naturalist and writer, Plinius, recorded that salves and oils were prepared from leaves and flowers of the Madonna lily, or L. candidium. Some species are also known for medicinal and food values, which increased its economic importance many folds. The mucilaginous substance coming out from the bulbs while cooking is used as an ointment for tumours, ulcers and inflammations. The plant was really more of a miniature household pharmacy. Different compounds have been reported in this genus, such as carbohydrates, proteins, fats, amino acids, vitamins, alkaloids, phenolics, flavonoids, carotenoids, sterols, steroidal saponins, and steroidal glycoalkaloids. Alkaloids, steroidal saponins, flavonoids and polysaccharides have been isolated from L. lancifolium and L. brownii var. colchesteri bulbs. Flowers of Lilium candidium contain an alkaloid. Extract of Lilium polyphyllum bulb has been used as refrigerant, expectorant, aphrodisiac, diuretic, antipyretic and tonic (Warrier et al., 1997; Dhyani, 2007). In the customary system of medicine, this species reported to restore health immediately and works as antioxidant in the body. Lily oil is an aid in childbirth. The white lily was also renowned as a cosmetic.

Statice, botanically known as Limoniumis very highly demanded ornamental plant. It is also known as ‘Sea Lavender’ owing to its color and place of growth. The genus name Limonium is from Greek name ‘leimon’ which translates to origin ‘a meadow’, most suitable as many species are found growing near marshy lands or salty areas of sea shore. The statice plants have very wide adaptability and can be seen growing under a wide range soil and climatic conditions like sea shores, marshy lands, deserts and plains etc. Statice figures in top 20 cut flowers sold worldwide but information on its trade, volume, export-import and number of stems sold etc. is not available. The reason for this may be attributed to classification systems, data collection categories and frequently changing nature of the assortments in the international flower market. Comprehensive trade statistics are difficult to locate for Statice. However, Statice figured in top 10 imported products in the Netherlands way back during 2013, 2014 and 2015. Though it is presently not among the top 10 flowers category, still it enjoys the immense popularity among the growers owing to its ease in cultivation and other characteristics. It is cultivated as annual as well as perennial crop, as different species have been domesticated for this purpose.

Jasmines constitute a group of traditional flower crops which are commercially grown for their fragrant flowers and essential oil production. There are trailing, climbing, and erect growing species and cultivars in the genus Jasminum. The genus Jasminum comprises of more than 200 species which are known to occur in different tropical and subtropical regions of the world. The countries growing Jasmines on a commercial scale are India, France, Italy, Morocco, Algeria, North Africa, Egypt and Spain. More than 80 Jasminum species are found in India, of which only four species viz., Jasminum sambac (Mogra / Gundumalli), Jasminum auriculatum (Jui / Mullai), Jasminum multiflorum syn Jasminum pubescens (Kunda / Kakda) and Jasminum grandiflorum (Jai / Pitchi) are widely used for commercial cultivation. Jasmines are commercially grown in many parts of the country as a dry land crop. The leading states in jasmine production are South Indian states like Tamil Nadu, Karnataka and Andhra Pradesh. In India, the commercial cultivation of jasmines are popular in Athoor, Coimbatore, Dharampuri, Dindigul, Erode, Krishnagiri, Madurai, Nilakottai, Periakulam, Salem, Thiruchirapalli, Thirunelveli, Thiruvallur, Tirumanagalam, Vellore, Virudhunagar etc. in Tamil Nadu; Bangalore, Bellary, Kolar, Mysore, Shimoga, Tumkur etc. in Karnataka ; Hyderabad, Khammam, Mahbubnagar, Mancherial, Ranga Reddy, Sangareddy, Vikarabad, Warangal Rural, Yadadri etc. in Telangana; Anantapur, Chittoor, Cuddapah, East Godavari, Guntur, Krishna, Kurnool, Nellore, Prakasam, West Godavari etc. in Andhra Pradesh; Ahmednagar, Aurangabad, Pune, Sangli etc. in Maharashtra; Ahmedabad, Anand, Bharuch, Bhavnagar, Kutch, Vadodara etc. in Gujarat; Gazipur, Jaunpur, Kannauj etc. in Uttar Pradesh; Ajmer, Jaipur, Kota, Udaipur etc. in Rajasthan; Panskura Ranaghat etc. in West Bengal; Guwahati, Hoja, Jorhat etc. in Assam ; and parts of Punjab and Delhi. Jasmines contributes markedly to the national economy and it is estimated that annually more than 20 crores worth of jasmine flowers are produced and traded in India and are also exported to countries like Malaysia, Singapore, Sri Lanka, UAE and United States (Safeena et al., 2017).

Marigold (Tagetes spp.) is an important annual flower crop; native to Central and South America especially Mexico and belongs to family Asteraceae (Compositae). It is commonly known as “Gainda” in India and also called as “Friendship Flower” in United States of America. Loose flowers of marigold are in great demand throughout the year. It is commercially grown in tropical and subtropical regions of India owing to its ease in cultivation, hardy nature, wider adaptability and year round availability of single, semi-double and double flowers of vibrant colours. Marigold is grown over an area of about 66.09 thousand hectares with production of 603.18 thousand MT loose flowers in India. Major states involved in loose flower production of marigold are Karnataka, Madhya Pradesh, Gujarat, Andhra Pradesh, West Bengal, Maharashtra, Haryana and Chhattisgarh. In India, Assam is the only state, which produces marigold for both cut as well as loose flower purpose on an area of about 0.61 thousand hectare (Anonymous, 2016a).

Marigold is a cross-pollinated flower crop and it is pollinated by insects (Kaneko et al., 1990). It bears terminal and solitary inflorescence, known as head or capitulum, which possesses long and hollow peduncle with swollen apex and campanulate involucres (Setshogo, 2005). Capitulum consists of peripheral ray florets and central disc florets. Ray florets are pistillate, ligulate, sessile, epigynous and zygomorphic, whereas, disc florets are bisexual, tubular, sessile, epigynous and actinomorphic (Subrahmanyam, 1996 & Setshogo, 2005).

African marigold (Tagetes erecta L.) is a diploid species (2n = 2x = 24), while, French marigold (Tagetes patula L.) is a tetraploid species (2n = 4x = 48) with basic chromosome no. of x = 12 as revealed by breeding work of various researchers (Towner, 1961, Chen and Lin, 1981, Chen and Lin, 1982, Serrato-Cruz et al. 2000, Zhang et al., 2011). Tagetes erecta and Tagetes tenuifolia are diploid species, whereas, Tagetes patula, Tagetes minuta, Tagetes biflora and Tagetes remotiflora species are tetraploid in nature (De, 2017). On the basis of floral morphology; three different types of male sterile systems i.e. apetaloid, petaloid and gynomonoecious types was observed in African marigold (Prakash et al., 2016). Out of these, apetalous male sterility (femina type) is more reliable and preferred over petalous male sterility because later is more prone to break down (Goldsmith, 1968 & Janakiram, 2004). Apetaloid male sterility was controlled by single recessive gene (Prakash et al., 2016). A monogenic recessive male sterile apetalous mutant was detected from T. erecta population by Khoshoo (1979). Cyto-genetic male sterility is also found in marigold (De, 2017). Petaloid and gynomonoecious male sterile systems were controlled by cytoplasmic inheritance (Prakash et al., 2016). In marigold, cytoplasmic genetic male sterile lines were also developed for commercial production of F_l sterile hybrids (Pratibha et al., 2000).

Lotus being a national flower of India, is closely associated with religion and culture. It is a perennial, aquatic crop that is grown and consumed throughout Asia. The edible parts of lotus are Leaves, flowers, seeds and rhizomes, and the flowers are also used in religious ceremonies. Lotus flowers are also, used for extraction of perfumes. It is one of the oldest plants in the world Archaeologists in China found Lotus seeds with estimated ages of 5,000 years in 1972 in Yunnan Provincelagoons.

During the pre-historic period, the South India Dravidians used lotus flowers (pundarika) as their food, much earlier than the people of the Indus Valley civilization (3000-2000 BC). However, there is no evidence of lotus being present during the Indus Valley culture of the Mohenjo Daro and Harappa period in northern India. The Rigveda reference that lotus was made by the Aryans (2000-1500 BC) wherein it is also mention that lotus can be used as food. Subsequently, lotus was mentioned in the Vedas, Upanishads, Puranas, Slokas, plays and other ancient Sanskrit literature. The lotus symbol is not only mentioned in the scriptures of Hinduism but it also occurs in the Buddhist and Jainism literature.

In the Arthasastra (350-300 BC) by Kautilya, the great diplomat during the golden age of Chandra Gupta, it is recorded that one of the varieties of sandal wood possesses the fragrance of lotus. The Mughal kings were also attracted towards the beauty of lotus. While describing Agra, the Mughal king Jehangir (1605-1627 AD) in his memories Tuzuk-i-Jehangiri, mentioned a memorable scene of a tank full of exquisite red lotus flowers, the like of which he had not seen before.

Floriculture is a high value industry. It is increasingly regarded as a feasible diversification option from traditional field crops due to increased per unit returns and increasing habit of ‘Greeting with Flowers’ during all the occasions. With increasing awareness among consumers and pressure from the artificial floral products on the fresh flower industry, and continued competition even amongst the growers, whole salers and retailers, quality is becoming increasi ngly important. The aspects related to visual quality of the product are the main determining indices of consumer’s acceptability of flowers.

The important flower crops in the international market are rose, carnation, lisianthus, chrysanthemum, gerbera, hydrangea, gladiolus, gypsophila, bird of paradise, orchids, anthurium, tulip and lilies etc. Cut flowers have the highest economic value and are the most perishable. Their high respiration rates, rapid deterioration, and susceptibility to damage require the utmost care during postharvest handling for quality maintenance. The post-harvest losses can be both, quantitative as well as qualitative, which ultimately result in loss in terms of its monetary value.

Floriculture industry is facing main problem due to highly perishable nature of its flowers which demand for appropriate post-harvest handling techniques to maintain the quality. With changing scenario in international floriculture trade, perfection in post-harvest technology is mandatory to offer quality plant products to the consumers round the year. The post-harvest life of cut flowers and flowering pot plants can be extended relatively by a range of treatments and technologies. Quality factors that influence the post- harvest keeping quality and flower longevity are environmental factors as well as the influence of the pathogenic organisms. Due to perishable nature of cut flowers, huge post-harvest loss is there which ranges from 30-50 per cent. Qualitative losses which include consumer acceptability of fresh produce are much more difficult to measure than quantitative losses. Quantitative losses can occur during the entire post-harvest and marketing chain due to lack of proper post harvest handling (Bhattacharjee, 2006). These losses could be on a higher side, which might be due to lack of knowledge on ‘post-harvest handling’ of cut flowers and proper infrastructure for post-harvest management and storage. However, all these losses can only be minimized by proper technique of harvesting, post-harvest handling, packaging, storage, marketing and value addition of flowers.

Flowers and various parts of the plant have been used for decoration and to commemorate various religious, festive, matrimonial and social gathering events in day to day life. The main drawback of fresh flowers and foliage is being highly perishable and delicate which cannot retain their beauty for longer durations. Moreover fresh flowers are not available round the year which can be overcome by the dehydration and drying techniques. Since ancient times, in Egyptian pyramids, fragrant dried flowers and herb garlands were encased along with mummified bodies. Japanese people created “Oshibana”, the “preserved flower art” of enduring designs to retain the exquisite beauty of the living plants centuries ago.

Later on, this craft making technique spread from Japanese to Victorian England because of their beautiful long lasting appearance. During middle ages monks dried flowers, foliage, and herbs for use in decorative motifs or for colouring their handprinted books.

Dried flower arrangements have been popular in Europe for centuries, and as early as 1700 AD, colonial Americans used dried flowers to brighten their homes, especially during the dark winter months.

Earlier botanists practiced dried flowers in the form of herbarium for the purpose of identification of various plant species. Though drying of flower was well known even in the past but for the first time the flowers were dried commercially in Germany (Sankari and Anand, 2014).

Floriculture has flourished with a considerable growth and a useful crop diversification option, particularly for small farmers over the past three decades. The commercial production of the cut greens has started in India in recent years and has huge demand in the market. They are suited for year round production with low investment and less care and maintenance. Cut greens or fillers are an important component of the floricultural industry and their commercial value depends on vegetative characters, such as stem length, leaf colour, density and side branching. Cut foliages (leaves and stems), which are attractive in form, colour and freshness, are lasting and in great demand. They have various other uses in making attractive fresh floral designs and floral arrangements, such as bouquets, wreaths, decoration of house interiors, etc. Evergreen plants with green, silver or variegated leaves are usually used and species with berries are now also becoming popular. Fillers are critical components in most arrangements as the flowers themselves,used to increase the volume and size of the bunch and provide colour contrast. These floral produce have various other uses in making attractive fresh floral designs and floral arrangements, such as bouquets, wreaths, decoration of house interiors, etc. Colour, freshness, stem length, freedom from pests, fragrance and vase life are important quality aspects of fillers. In the International market, fillers accounts for about 16 percent of the total trade by volume with an annual turnover of more than Rs 800 crores including selling of ornamental leaves, filler flowers, dry and dyed flowers along with berries and capsules. On the contrary, fillers representvery less quantum with poor quality in the domestic market and are unsuitable for cut flower bouquets. Their share in the market is very low and fetches nominal rates.

Flower arrangement is the art of using plant materials and flowers to create an eyecatching and balanced composition or display. Among all art forms, flower arrangements today take as prominent a place. The art engages ones personal involvement in welcoming guests and bringing cheer to the surroundings. It is rightly said, “Flowers are the music of the ground. From earth’s lips spoken without sound. “Professionally designed floral designs, arrangements or artwork incorporate the elements of floral design: line, form, space, texture, and color, and the principles of floral design: balance, proportion, rhythm, contrast, harmony, and unity.

Composition of Arrangements

There are a few compositions of flower arranging that should be considered. Once we understand these we can create so many different styles and our floral designs will have that professional look.

All higher plants have some kinds of aroma or flavor in their various parts, which includes roots, stems, leaves, flowers and fruits. This flavor and aroma in a particular plant part due to the presence of some specific essential oils present in special glands in it (Chadha and Choudhury, 1989). Essential oils arethe concentrated liquid, which is highly concentrated and water insoluble liquid (hydrophobic) and it is also known as ethereal or volatile oils, which are fragrant oily liquid that are extracted from the various parts of the plants. Generally they are organic compounds like hydrocarbons likealcohols, aldehydes, esters, ketones and phenols. An essential oil is “essential” in case that it contains the essence of the different fragrance, and the properties of the plants from which they are derived. All though all ornamental plants have some aroma but only few of them are used commercially in perfumes, flavor and cosmetic industries. The essential oil demand by fragrance industry is 60%, flavour industry 20% and pharmaceutical industry 20%. In all the perfumes, rose oil is one of the best and costliest perfume. The first recorded reference of rose perfume is in CharakSanghita. The credit for discovery of rose perfume was given to Queen Noor Jehan mentioned in the book written by Md. Achem of King Jahangir’s regime.

The volatile oils showed the different kinds of biological activities including the antibacterial, antioxidant, antiviral, insecticidal, etc. These oils are also used for cancer treatment, while some other has been used for the food preservations, aromatherapy, and in the perfumery industries. Thus, in the day to day life a large spectrum of usage the essential oil and aroma industry has a bright future. Yet the known applications of essential oilsare opening up ofmore areas which will benefit the industry.

1.1 Introduction

The word ‘horticulture’ was first used in 1600’s, and is derived from two Latin words, ‘hortus’(garden) and ‘cultûra’(cultivation), and it means ‘the culture (cultivation) of garden plants’. Relf (1992) defined “horticulture as an applied science and art of growing fruits, vegetables, herbs and spices, nuts, tubers, aromatic and medicinal plants, plantation crops, mushrooms and ornamental plants which include shrubs, flowering plants and turfs stimulating minds, spirits and emotions of individuals, enriching health and wellness of communities, and linking human beings to nature and its landscaped exteriors for wellness and wellbeing”. Fruits and vegetables are nourishing and protective foods. It has been recognized that fruits are a rich source of antioxidants which protect us from dreadful diseases. Vegetables and fruits contain vitamin E, K, and  carotene in addition to minerals like zinc, copper and manganese. To meet the ever-increasing demand of the country for fruits, vegetables, tubers, spices, flowers, ornamentals etc., we must strive hard to deliver better cultivars in as many aspects as possible to the society so that human beings will be in sound health physically as well as mentally. To achieve this goal plant breeding in general, and horticultural plant breeding in particular will come to our help.

2.1 Introduction

Dear students, you shall be taught plant biotechnology during the third semester in the course ‘Elementary Plant Biotechnology’. But, for understanding of non-conventional breeding methods/techniques you should acquire some knowledge of basic plant biotechnology. Hence, in this chapter plant biotechnology is introduced to you in brief.

2.2 Definition

The term ‘biotechnology’ stems from fusion of ‘biology’ and ‘technology’. It was coined by Karl Ereky, a Hungarian agricultural engineer, in the beginning of 20th century. According to him, all processes used to yield finished products from raw materials with the help of living organism come under biotechnology. It may be defined in number of ways. However, in simple terms, biotechnology may be defined as ‘the controlled use of biological agents, such as microorganisms, or cellular components, for beneficial use’ (U.S. National Science Foundation).

3.1 Introduction

Genetics deals with genes and cytogenetics with chromosomes that harbour genes. On the other hand, plant breeding strives to upgrade the genotypes of crop plants. So, the plant breeding methods should be based on genetic principles. Dear students, you should have clear understanding of genetics in broad sense so that you can appreciate the applicability of breeding methods. As I have already pointed out that you have been taught the course ‘Principles of Genetics and Cytogenetics’ in the first semester, only a brief discussion is followed for your review and better understanding.

3.2 Character

When we call ‘character’ or ‘trait’ in genetics, we mean any morphological, anatomical, biochemical or behavioural feature of an organism. For instance, flower colour, blooming period, leaf size, size of guard cells in stomata, vitamin C content, disease resistance etc. A single gene or a number of genes may govern the development of a character and, often it is influenced by the environment. Characters may be qualitative or quantitative.

4.1 Introduction

Many important traits such as yield, quality and some forms of disease resistance are controlled by many genes and are known as quantitative traits or characters (also called ‘metric’,‘polygenic,’ ‘multifactorial’ or ‘complex’ traits). The regions within genomes that contain genes associated with a particular quantitative trait are known as quantitative trait loci (QTLs). The identification of QTLs based only on conventional phenotypic evaluation is not possible. A major breakthrough in the characterization of quantitative traits that created opportunities to select for QTLs was initiated by the development of DNA (also called molecular) markers in the 1980s.

One of the main uses of DNA markers in agri-horticultural research has been in the construction of linkage maps for diverse crop species. Linkage maps have been utilised for identifying chromosomal regions that contain genes controlling simple traits (controlled by a single gene) and quantitative traits using QTL analysis. The process of constructing linkage maps and conducting QTL analysis–to identify genomic regions associated with traits–is known as QTL mapping (also called ‘genetic,’ ‘gene’ or ‘genome’ mapping). DNA markers that are tightly linked to agronomically important genes (called gene ‘tagging’) may be used as molecular tools for marker-assisted selection (MAS) in plant breeding. MAS involves using the presence/absence of a marker as a substitute for or to assist in phenotypic selection, in a way which may make it more efficient, effective, reliable and cost-effective compared to the more conventional plant breeding methods. The use of DNA markers in plant (and animal) breeding has opened a new realm in agriculture and horticulture called ‘molecular breeding’.

5.1 Introduction

The development of quantitative trait loci (QTL) mapping methods to identify genes or QTLs controlling quantitative traits was a landmark achievement in plant genetics research in the late 1980s. Since then literally thousands of research papers have reported the identification of genes or QTLs for important traits across a diverse range of plant species. This wealth of genetic information was built on the foundation of decades of research in crop molecular genetics and genomics.

The selection and enrichment of QTLs within breeding material was the inevitable next step from QTL discovery to application, and there have been numerous reports of successful tracking of genes and QTLs within breeding programmes. DNA (or molecular) markers have enabled selection of major genes or QTLs for critical or important traits in a process called marker-assisted selection (MAS), which has revolutionized plant breeding. DNA markers are used as tools by breeders to improve the accuracy or efficiency of selection as well cost and time efficiency. Apart from MAS, DNA markers have numerous applications including DNA fingerprinting, genetic diversity analysis and parental characterization.

Recent developments in genotyping platforms and systems to implement molecular breeding schemes offer new tools for modern plant breeders. Single nucleotide polymorphism (SNP) markers are biallelic, co-dominant markers which are abundant in the genome. Insertion-deletion (Indel) markers are also prevalent and can be screened using high-throughput genotyping platforms. These platforms are cost-efficient, can handle large sample sizes and provide fast data turn-around time. The availability of genome sequences and genomic resources continues to provide a wealth of SNP and Indel markers which will undoubtedly be the marker type of choice for decades to come.

The availability of high-throughput SNP platforms in conjunction with advances in computational methods has also led to the molecular dissection of traits using genome-wide association studies (GWASs) across diversity panels and the development of genomics-based molecular breeding strategies. Association mapping (AM) has now emerged as a standard method for gene and QTL discovery for major crops.

6.1 Introduction

The process by which living beings give rise to the progeny of similar kind is called reproduction. Reproduction allows both multiplication and maintenance of a genotype/line/cultivar/species. So, the process of reproduction is also called propagation, and the plant part used for this purpose is called propagule. The way progeny originate is known as mode of reproduction (also called breeding system or reproductive system). The mode of reproduction of a crop determines its genetic composition which, in turn, is the deciding factor to develop suitable breeding methods. Knowledge of mode of reproduction is also essential for its artificial manipulation to breed improved types. The methods to be adopted for multiplication and maintenance of improved cultivars are also governed by the mode of reproduction. Especially in undertaking breeding investigations with new plants the nature of reproduction must be known before efficient breeding plans can be developed. The mode of reproduction has been well established for most of our important crop species.

6.2 Mode of Reproduction

Mode reproduction in crop plants may be sexual or asexual. In sexual reproduction (also called amphimixis), specialized reproductive cells called gametes are formed by the process of gametogenesis. Fusion of the male and female gametes leads to the development of an embryo and eventually the seed. In asexual reproduction, fusion of the male and female gametes does not occur, and new plants arise from unfertilized gametes (but not from zygote), or from specialized vegetative organs such as rhizome, tuber, bulb, corm, runner, sucker, stolon, bulbil etc., or by various artificial means of propagation such as rooting of stem and root cuttings, layering, grafting, gootee, etc., or tissue culturing.

7.1 Introduction

Breeding plans are based on controlled mating (i.e., mating between selected strains) and selfing of selected strains or a combination of both. Continued selfing is practised to isolate purelines and inbreds. On the other hand, crossing (hybridization) is necessary to produce hybrids and synthetics. In crossing, self-pollination is prevented in the female parent. Male sterility and self-incompatibility easily exclude self-pollination, and so they are used in hybrid seed production.

7.2 Male Sterility

Koelreuter (1763) for the first time reported male sterility in flowering plants. Male sterility is a reproductive deficiency of some plants in which male organs in bisexual flowers become defunct. It relates particularly to nonviable pollen grains that are formed through a chain of vital processes during microsporogenesis. These processes are so delicately balanced under genetic control of many loci that mutation of any one locus may lead to the formation of non-functional microspores, and hence male sterility. In male sterility, pollen grains are non-functional (inactive); but the female gametes (egg cells) are normally functional.

8.1 Introduction

In pre-historic times, people lived as hunters and gatherers. Then, gradually they began to produce the crops they ate on piece of land, and farming was born. Wild plants have certain traits that keep them protected and productive without human intervention. However, most of them are not desired for food or other use by humans. By spontaneous mutagenesis and hybridization, occasionally variant plants were found that lacked some of the undesired traits, such as bitter taste, thorns, or had particularly attractive features, such as larger fruits and more regular tuber shape. Consequently, as time passes such variation was picked up by humans by selection of such variants, keeping and advancing them. Thus, plant domestication is the process of bringing wild species under human management. In other words, plant domestication is the process by which genetic changes (shifts) in wild plants are brought about through a selection process imposed by humans. It is a method of plant breeding in the sense that, when successful, it provides domestic types that are superior to ones previously available.

Pre-historic man domesticated virtually all of our present-day crops. But, domestication of wild species continues even today and is likely to continue for a long time in the future. For example, in many countries there is an increasing emphasis on bringing forest trees producing timber, etc. under human management. A similar trend is seen for medicinal plants and plants producing specific compounds of interest, e.g., hydrocarbons, oils, etc. Kala jeera (Bunium persicum), a perennial spice, was domesticated during 1990s in Himachal Pradesh; it is being cultivated as an orchard crop. One important aspect of domestication at present is the use of particular genes from wild relatives in the improvement of cultivated species. When a plant breeder transfers one or a few desirable genes from a wild relative to a cultivated type, he is, in a sense, domesticating the wild species in part.

9.1 Introduction

The sum total of genes in a plant species is called as plant genetic resources (also called germplasm, gene pool, or genetic stock). In other words, plant genetic resources refer to a whole library of different alleles of a plant (crop) species. Germplasm is the lifeblood of plant breeding without which breeding is impossible to conduct. It is the genetic material that can be used to perpetuate a species or population. It not only has reproductive value, but through genetic manipulation (plant breeding), germplasm can be improved for better performance of the crop. Germplasm provides the materials (parents) used to initiate breeding programme. Sometimes, what a plant breeder does is to evaluate plant genetic resources and make a selection out of existing biological variation. Promising genotypes that are adapted to the production region are then released for cultivation by the farmers. Other times, a plant breeder generates new variability by using different methods such as hybridization, mutagenesis and more recently gene transfer. This base population is then subjected to appropriate selection methods, leading to the identification and further evaluation of promising genotypes for release as cultivars. When a plant breeder needs to improve crop plants, he has to find a source of germplasm that would supply the genes needed to undertake the plant breeding programme. To facilitate the use of genetic resources (germplasm), germplasm (gene) banks are given the responsibility of collecting, evaluating, cataloguing, storing and managing large numbers of germplasm. This strategy allows a plant breeder ready and quick access to genetic resources when he needs it. The fact that Sir Otto Frankel coined the term ‘genetic resources’ only in 1968 shows that the plant breeders, though aware of the gradual loss of germplasm, failed to recognize the urgency of protecting the genetic resources of crop plants prior to a point of no return.

10.1 Introduction

Plant breeders come across two categories of characters (traits) for improvement, namely, qualitative characters and quantitative characters. Red vs white flower, round vs wrinkled seed, determinate plant growth vs indeterminate plant growth etc. are examples of qualitative trait differences. There is no overlapping of characters and no confusion during classification. Such trait differences are usually governed by one or two gene pairs, each with large effect that can be measured even in the presence of segregation at other loci and even in the presence of effects of environmental factors. These characters are very less influenced by the environmental factors.

On the other hand, most of the traits of economic importance like yield of fruits of vegetable and fruit crops, yield of vegetative parts in fodder crops, yield of lint in cotton, yield of grains in cereals, pulses, oilseeds etc., plant height, days to maturity etc. are examples of quantitative characters. Variation observed for such traits is continuous. Again, there is overlapping of trait differences. So, one cannot assign individuals to a specific class unambiguously. Such characters are influenced by environmental factors, such that phenotypes are not same when grown over locations and/or seasons.

When different plants/lines of a species exhibit trait differences, it is called variation. Variation is essential for any improvement in a crop. It may be present in the population to be improved or else it may be created by different means such as hybridization, mutation, polyploidy, domestication, plant introduction, somaclonal variation, genetic engineering etc. Now, we shall discuss the types and estimation of variation.

11.1 Introduction

In chapter 10, we have discussed the different types of variation, namely, genetic, environmental and genotype × environment interaction variations. We have also learnt how to estimate the phenotypic variance and its components including genotypic (also called genetic), environmental and g × e interaction variances from trial data. Now in this chapter, we shall discuss on the genetic components of polygenic (quantitative) variation and its implications on breeding strategies.

11.2 Genetic Components of Polygenic Variation

In this chapter whenever we call genetic variation, we mean polygenic (quantitative) variation, and we know that variation is usually measured in term of variance. However, variation, variability and variance are almost used synonymously. The genetic variance has been classified into different components by various workers. Fisher (1918) divided genetic variance into three components: additive, dominance and epistatic (interaction) variances. Wright (1935) classified genetic variance into two components: additive variance and non-additive variance (dominance and epistatic variances). Mather (1949) classified genetic variance into two components: heritable fixable variance (additive variance and additive × additive epistatic variance) and heritable non-fixable variance (dominance variance, and additive × dominance and dominance × dominance epistatic variances). Later, Hayman and Mather further divided the epistatic variance into three categories: additive × additive, additive × dominance and dominance × dominance.

12.1 Introduction

Allowing certain plants from the population to reproduce, while barring others, comprises selection. This permission for reproduction may be granted by nature or by the plant breeder. In the other words, both nature and breeder exert selection pressure. Natural selection operates through differences of fertility among the adult individuals of parent generation as well as through differences of viability among the individuals of offspring generation. Artificial selection, i.e., the selection from action of the plant breeder in the choice of parents, produces its change of gene frequency by separating the adult individuals of parent generation into two groups, viz., the selected and the discarded, that differ in gene frequency. So, selection simply implies the retaining of desirable types or culling of unwanted or undesirable types.

13.1 Introduction

F₁ plants produced by crossing two parents with contrasting characters are called hybrids. Hybrids generally exhibit increased vigour and fitness over the parents. This phenomenon is called hybrid vigour or heterosis. Thus, heterosis is the phenomenon in which the hybrid of two genetically dissimilar parents shows increased vigour at least over the mid-parental value. Heterosis is just the reverse of inbreeding depression, which results after selfing the plants of the cross-pollinated crops. Kolreuter (1761-66) was the first to report hybrid vigour in the hybrids of tobacco, Datura, etc. Most of the early plant hybridizers including Mendel (1865) had noticed this phenomenon. Shull (1914) coined the term heterosis from two Greek words, hetero (different) and osis (condition), to replace his own earlier word ‘stimulus of heterozygosis’. In current usage, heterosis and hybrid vigour are used as synonyms and interchangeable.

13.2 Types of Heterosis

Depending on the nature, origin, adaptability, reproducibility and non-reproducibility, heterosis can be categorized into two: (1) euheterosis (true heterosis) and (2) pseudo-heterosis (false heterosis, i.e., luxuriance).

14.1 Introduction

The mating or crossing of genetically dissimilar individuals is called hybridization. Hybridization results in recombination that in turn widens the spectrum of variation among individuals. So, the reason for genetic diversity in progenies of crosses is the formation of new combinations of genes. This newly created variability is then channelized into development of better cultivars.

The importance of pure line selection as a method of breeding started decreasing when plant breeders felt that the genetic variability existing in the land races of self-pollinated crops had been almost completely exploited and there was little chance for further improvement in these crops by using pure line breeding. Therefore, no option was left for plant breeders except to cross diverse individuals and combine together desirable characters in a single genotype from two or more parents. The planned hybridization which could avoid self-pollination and chance cross-pollination, soon became the main feature of almost all plant breeding programmes.

15.1 Introduction

Plant breeding aims at developing genetically improved crop cultivars with economic benefits for small-scale and commercial farmers. Population growth, dwindling agricultural land and global climate change present increasing risk to crop production. Consequently, plant breeding aims to constantly develop crop cultivars with improved yield and quality and tolerant to drought, diseases and pests. Use of genetically improved crop cultivars and better management practices are among the best strategies to increase food production and meet a projected doubling of food demand in the next 40 years. Both the public and private plant breeding sectors face several constraints, including a shortage of professional plant breeders and breeding technicians, limited budget, inadequate facilities and lack of access to information. Successful plant breeding requires adequate infrastructural investment, in addition to the actual breeding activities. The benefits of plant breeding research and development can only be realized on a long-term basis because of the inherent nature of the crops and the eminent breeding procedures involved. Plant breeding involves two main activities, i.e., pre-breeding/ germplasm enhancement and cultivar development per se. These interdependent activities are the controlling factors that determine the pace at which cultivars are released timeously and consistently to farmers. The two phases, in turn, depend upon various factors, e.g., breeding goals, genetics and agronomy of the crop, breeder’s long-term objectives, availability of testing facilities and national cultivar-registration requirements. Despite these factors, there are certain clear steps and breeding procedures found in any conventional breeding programme. These include choice of parents, making crosses among chosen parents, and selection from recombined parents followed by extensive field testing of the candidate cultivars. Maintenance, multiplication and distribution of the seed are the ultimate stages of a breeding programme. Systematically outlined conventional breeding procedures, timeframes and estimated breeding generations are essential to objectively consider the ultimate timescales required to release new and improved cultivars of all crops. The information may assist plant breeding- students, educators, researchers, project advisors, administrators and funding agencies. Dear students, in this chapter we outline the timeframes of conventional breeding procedures of clonally (also called vegetatively) propagated, self-fertilizing (also called self-pollinated) and cross-fertilizing (also called cross-pollinated) crops.

16.1 Introduction

Plant introduction is the process of introducing plants from their growing locality to a new locality. Introduction of plants from a foreign country is called foreign introduction or exotic collection. Introduction from one state to another within a country is called indigenous collection or indigenous introduction. With introduction, the process of acclimatization is associated. Acclimatization is the adaptation or adjustment of an individual plant or population of plants under the changed climate for a number of generations. Plant introduction is an oldest method of plant breeding. It is used in self-pollinated, cross-pollinated and asexually propagated crops. The material of seed-propagated crops is introduced in the form of seed and that of vegetatively propagated crops in the form of cuttings or propagules. The introduced material may be a new crop, a wild relative or a new cultivar of a crop already grown in the area. There are five important sources of plant collection, namely, (1) centres of diversity, (2) gene banks, (3) gene sanctuaries, (4) seed companies, and (5) farmers’ fields.

17.1 Introduction

Self-pollinated vegetable, spice and ornamental crops may be heterogeneous. It is exemplified by landrace cultivars. They may have originated from single plant selections but have been grown over a long period of time. Landrace cultivars are a mixture of genotypes, perhaps because of breeders’ lack of appreciation of selection techniques to produce a pure line, spontaneous mutations, chance hybridization, or a combination of factors. Natural selection in landraces has resulted in a cultivar that is well adapted to the local environment. Depending on amount of human selection, differences among genotypes in a landrace cultivar may be small and inconspicuous. On the other hand, a lack of human intervention may mean that differences among plants in a landrace cultivar will be conspicuous. After years of self-pollination, individual plants are homozygous. Selection of such individuals would result in a true-to-type reproduction of their phenotype within the limitations imposed by the environment.

18.1 Introduction

The genetic variability present in populations of self-pollinated vegetable, spice and ornamental crops is rapidly exhausted by pureline selection. For further improvement, genetic variability must be created. This is generally achieved by hybridization. After the cross has been made, F₁ is grown and seeds set on it are harvested. This makes the seed source for raising F₂ population, and so on. The segregating populations from crosses are handled according to a suitable method. The three basic methods available for this purpose are: (1) pedigree method, (2) bulk method, and (3) backcross method. There are also certain modifications of these methods.

18.2 Pedigree Method

Pedigree method is developed from the pureline system and widely used method of plant breeding for self-pollinated crops. A main difference between pedigree selection and mass selection or pureline selection is that hybridization is used to create variability for the base population in case of the former, whereas in mass and pureline selections variability is naturally present in the base populations. The pedigree method was first described by H.H. Lowe (1927). This method predominated the crop improvement programme throughout the world until 1980s. Pedigree method is common in horticultural crops, especially where readily identifiable qualitative traits are involved. Vegetable crops in which pedigree system is used include tomato, cucumber, pepper, pea, lettuce, snap and field beans, all self-pollinated crops. In general, selection is done on F₂ plants. Yield is important in many horticultural plants, but quality is equally or even more important. Quality may be associated with identifiable traits, making the pedigree system ideal for self-pollinated vegetable crops.

19.1 Introduction

In self-pollinated crops, the methods of selection aim at improving individual plants. On the other hand, in cross-pollinated crops they aim at improving a population of plants. A population is a large group of interbreeding individuals. Hence, selection is called population improvement in cross-pollinated crops. Selection in self-pollinated crops results in isolation of pure breeding lines which is the end product. But in cross-pollinated crops, it results in an improved population which is used as the commercial cultivar. Improved inbred lines (also called inbreds) for producing hybrids can be obtained from such populations. Again, like many rounds of selection being practised in different inbreeding generations in self-pollinated crops we are also practising many rounds of selection in cross-pollinated crops. But, unlike self-pollinated crops selection in cross-pollinated crops is followed by intermating to develop a new population before starting another round of selection. One cycle of selection consists of selection of individual/family and intermating of the selected units. Such cycle is repeated till we get the improved population. This method of practising the cycles of selection and recombination in a population is called recurrent selection or population improvement. Frey (1983) prefers the use of recurrent selection for closed populations where no new germplasm is added to the population during selection. Population improvement was used for a group of breeding techniques where all aspects are similar to recurrent selection but with the provision of adding new sources of germplasm whenever feasible. It is only a matter of coincidence that past history of application of recurrent selection has been limited to closed populations, but its basic aim has always been the accumulation of favourable genes, without any restriction on the migration of new genes during the course of selection. Apart from a slight nuance, population improvement and recurrent selection are two titles of the same principle and procedure of manipulating the genetic potential of populations. Recurrent selection can also be applied in self-pollinated crops.

20.1 Introduction

A hybrid cultivar (also called hybrid) is the F₁ progeny of a planned cross between inbreds, cultivars, clones or populations. Depending upon the breeding approach, the hybrid cultivar may involve two or more parents. A critical requirement of hybrid production is that the parents are divergent. This divergence is the cause of superior performance of hybrids. The outstanding performance of crops is due to the exploitation of the phenomenon of heterosis (hybrid vigour) which is high when parents are divergent. Much of what we know about heterosis breeding (also called hybrid breeding) came from the work on maize hybrid cultivar development. However, commercial hybrids are now available in many crops including self-pollinated crops.

21.1 Introduction

There are a number of field, vegetable, fruit and ornamental crops that are cultivated using asexual or vegetative parts such as stems, roots, modified flower etc. This is a heterogeneous group of plants and can be further categorized into four groups for ease in understanding the breeding methods applied to them. They are:

Group 1: Flowerless or Sterile

This group either does not bear flowers or if bears, they are sterile and do not set seed, e.g., ginger, mango ginger, turmeric, garlic, betel, many yams, etc.

Group 2: Apomicts

Apomixis has been reported in over 300 genera. But stable apomixis has been reported only in a few cultivated plants like meadow grass, citrus, mango, raspberry, etc.

Group 3: Flowers but Seed-Set Rare

In this group flowering takes place under specific situations but seed-set is limited, e.g., potato, sweet potato, sugarcane, etc.

22.1 Introduction

Mutations are sudden heritable changes in the genotype of an organism. De Vries (1900) for the first time used the term mutation (mutare in Latin means ‘to change’) for the appearance of new types in evening primrose (Oenothera) plant. In 1901 he put forth the idea of producing mutations artificially for use in crop improvement. Alberto Pirovano (1922) was first to use X-rays and ultraviolet rays for inducing mutations in plants, but his work remained unknown. So, Muller (1927) became the first known to induce mutation in Drosophila fly using X-rays. Though Stadler (1928) had started working simultaneously on barley and maize and induced mutations, he was late in reporting mutation due to longer life cycle of these plants compared to Drosophila. Mutation may be gene mutation (the result of change in the nuclear gene or plasma gene) or chromosomal mutation (change in chromosome number, structure or chromosomal aberrations of various types).

23.1 Introduction

An organism or individual having more than two basic sets of chromosomes is called polyploid and the condition is known as polyploidy. Polyploidy is an important tool to increase genetic diversity by altering the chromosome number (2x) and consequently the number of genes within a single cell. Polyploidy has been one of the important mechanisms in the evolution of many cultivated crop plants.

23.2 Types of Polyploidy

23.2.1 Autopolyploidy

The condition that arises due to multiplication of the same chromosomes of a single species is known as autopolyploidy (also called ‘simple polyploidy’ or ‘single species polyploidy’). Autopolyploids have generally larger leaves, stem and other vegetative parts and flower, fruit and seeds than their normal diploids.

24.1 Introduction

When crosses are made between two different species of a genus or between two different genera, they are known as distant hybridization (also called wide hybridization). It includes both interspecific and intergeneric hybridization. Thomas Fairchild (1717) was the first man to do distant hybridization. He produced a hybrid between two species of Dianthus, viz., D. caryophyllus and D. barbatus (Carnation and Sweet William). Intergeneric hybrid produced by Karpechenko, a Russian scientist, in 1928 is Raphanobarssica. It is the amphidiploid of cross between radish (Raphanus sativus) and cabbage (Brassica oleracea var. capitata). Unfortunately, it had roots like cabbage and leaves like radish. Triticale was produced by Rimpau in 1890 itself. It is an amphidiploid obtained from a cross between wheat and rye (Triticum and Secale). Another example is Saccharum nobilisation involving Saccharum officinarum, S. barberi, S. sinensis, S. spontaneum. Wide hybridization has been used in the genetic improvement of some crops. It is an effective means of transferring desirable genes into cultivated plants from related species and genera.

25.1 Introduction

The method of selection in which a gene/QTL (Quantitative Trait Locus) is selected on the basis of the genotype of the molecular marker (also called DNA marker) linked to this gene/QTL is known as marker-assisted selection (also called marker-aided selection). The idea of marker-assisted selection (MAS) was first advocated by Tanksley (1983). MAS can be used in combination with the conventional breeding methods or novel breeding schemes could be devised to take full advantage of the marker data. MAS has been widely used for introgression of the desired genes and QTLs using backcross programmes.

25.2 Marker-Assisted Backcrossing (MABC)

The backcross programme based on molecular marker is usually called marker-assisted backcrossing (MABC). MABC has three activities: (a) foreground selection, (b) background selection and (c) recombinant selection.

25.2.1 Foreground Selection

The use of molecular marker to select the gene/QTL being introgressed is known as foreground selection. The objective of foreground selection is to select the target gene, i.e., the gene being introgressed, without phenotypic evaluation for the trait governed by the target gene. Foreground selection for a gene/QTL will be highly desirable in a variety of situation, some of which are listed below:

26.1 Introduction

We have already discussed the basics of tissue culture techniques in Chapter 2. Plant tissue culture techniques in combination with recombinant-DNA technology are essential requirements for development of transgenic plants (will be discussed in next chapter). However, tissue culture techniques like anther, pollen, ovule and meristem culture can themselves be used for improvement of different traits or as an aid to conventional breeding methods. In recent years, isolated microspore culture has been preferred as a breeding tool and an experiment system for various genetic manipulations. Besides, using protoplast fusion and hybrid embryo rescue, distant hybridization has been successfully achieved in many crops. Protoplast fusion technique can be used for the transfer of cytoplasmic male sterility from one species to another in very short duration. Somaclonal variation generated during tissue culture can also be utilized for recovery of variants showing disease resistance or other desirable characters.

27.1 Introduction

Crop improvement depends on genetic variation present in nature or created by hybridization followed by segregation and recombination. Again, gene transfers are possible only from the lines and species that are sexually compatible with the concerned species. Interspecific gene transfers pose many problems, including the loss of F₁ hybrids during embryo development due to abortion of the endosperm in the developing hybrid seeds. Embryo rescue technique was developed to rescue such interspecific hybrid embryos, and it has been widely used for this purpose. It is to be mentioned that embryo rescue can be used only in such cases where sexual hybridization is successful in producing zygotes that begin to develop into embryos.

Besides, the technique of somatic hybridization by protoplast fusion was developed to enable gene transfer from the species that do not produce zygotes on hybridization. This method has been extensively used and some useful lines have been derived. But this method is limited to utilization of genes present in plant species. Again, the results of somatic hybridization are unpredictable since many somatic hybrids fail to regenerate complete plants and the transfer of specific genes or groups of genes depends entirely on chance.

The recombinant DNA technology (also called genetic engineering) has permitted the transfer of genes from any organism into any organism. Besides, chemically synthesized genes can be transferred and integrated into genomes of various organisms to enable the expression of these genes. A gene transferred into an organism by genetic engineering is called a transgene. 

28.1 Introduction

The stress that is caused by biological agents or factors such as diseases, insect-pests and parasitic weeds is called biotic stress. The term disease can be broken into two words: “dis” (means negative, reverse or opposite) and “ease” (means comfort, or freedom from pain or discomfort). Hence, plant disease can be defined as any harmful alteration from the normal functioning of physiological processes. Diseases may be bacterial, fungal or viral. A wide range of insects infests various crop plants. The extent of damage caused to crop plants by various organisms is usually in the order fungi > bacteria > viruses > nematodes = insects. But the relative importance of these organisms varies to a great deal in different crops. Breeding of cultivars resistant to diseases and/or insect-pests is the cheapest, safest and most dependable means of limiting the losses due to them. Resistant cultivars form an important component of integrated management of diseases and insect-pests.

28.2 Breeding for Resistance to Biotic Stresses-Diseases

Agrios (1970) has defined disease as: “Disease is a series of invisible and visible responses of plant cells and tissues to a pathogenic microorganism or an environmental factor that result in adverse changes in form, function or integrity of plant and may lead to partial impairment or death of the plant or its parts.” The organism causing disease is called pathogen, while the plant affected by the disease is called host.

The principles underlying breeding for resistance to diseases are much the same as for other characters, except for one important difference, i.e., the diseases caused by pathogens are the product of interaction between two genetic systems, that of the host and that of the parasite. Both systems are capable of variation and evolution and affect the interaction between host and pathogen. Here the breeder is required to deal with the heritable traits of both the host plant and the pathogens invading it.

29.1 Introduction

An environmental factor that interferes with the complete expression of genotypic potential of a crop is called stress. The stresses may be biotic (pathogens, insect-pests, etc.) or abiotic. The main abiotic stresses are drought, mineral deficiency/toxicity and heat or cold. The losses due to abiotic stresses can be minimized by:

Crop management: The degree of stress can be reduced by suitable agronomic/soil management practices, e.g., irrigation to relieve drought stress, soil amendments to reduce salinity.

Development of resistant cultivars: This offers the cheapest, easiest to apply and most eco-friendly approach to reduce losses due to any stress.

Indirect breeding: Evaluation of materials under stress often helps in identification of a resistant line that may become an important commercial cultivar.

???????Direct breeding: It is deliberate breeding of materials for stress resistance. When a genetically variable material is grown under the stress environment, selection can be based on survival, yield and other traits contributing to stress resistance.

Introduction

‘Protected cultivation’ is a method of cultivation of plants or crops in artificial environment (Polyhouse/ Greenhouse/Glasshouse) to protect the plants or crops from the natural calamities viz. wind, hailstorm, excessive radiation, temperature extremes, insect-pests and diseases. For matching ever growing needs of human population in the country, it has become imperative to provide the not just cereals but also fruits, vegetables, flowers and other horticultural products to fulfill their requirements. In the present scenario of perpetual demand of horticultural produce in order to increase their production round the year and shrinking landholdings drastically, protected cultivation is the best alternative and drugery- less approach for using land and other resources more effeciently.Protected cultivation comprised of selection of crop and media, climate control,marketing, post harvest technology, plant protection and irrigation/ fertigation.

In India, states like Karnataka, Andra Pradesh, Maharashtra and Tamil Nadu are the best suited for protected cultivation of horticultural crops due to their pleasent climatic conditions. Apart from these states, Himachal Pradesh, Uttar Pradesh, Jammu and Kashmir, West Bengal, Delhi and Jharkhand are also fore runners in adopting protected cultivation. Protected cultivation is a key for sustainable production in the country due to its various ecological regions viz., Western Himalayan region, North eastern Himalayas, Eastern Plateau hill regions, Central Plateau hill regions, Western Plateau hill regions, Southern Plateau hill zone, East coast hill zone, West coast hill regions and Gujarat hill regions (Gupta et al., 2003). Control of light through polycover has become a significant part of horticulture technology because quality, intensity and duration of light is involved in many physiological processes of the plants. A plastic film or fibre glass covering over a green house acts like selective radiation filter which allows solar radiation to pass through but traps radiation emitted by the plants inside the greenhouse which is known as ‘Greenhouse effect’. Carbon dioxide released by the plants at night also trapped, this raises the level of CO₂ there by enhances the photosynthetic activity (Ahmed, 1996).

Introduction

India is a land of diverse agro climatic zones and each of these zones offer a great potential for cultivation of wide range of crops across all seasons. Vegetables form major and important part of our dietary requirements, which are widely grown in the rural and peri-urban areas. Hi-tech horticulture including protected cultivation of high value and exotic vegetables has been on the increase, targeting high end domestic and export market. Of late, due to the population pressure, fragmentation of land holdings and urbanization has led to decline in cultivable area, more so in urban and peri-urban areas. Production of vegetables under protected cultivation system results in effective use of the land resources, besides being able to increase the production of quality vegetables both for the export and domestic markets by offsetting biotic and abiotic stresses to a great extent that otherwise is prevalent in open cultivation. Under protected cultivation, vegetables are widely grown due to higher productivity and economic feasibility.

India is blessed with wide range of diverse agro climatic conditions, making it an appropriate place for vegetable cultivation, resulting in increasing vegetable production from has increased from 63.8 MT in 1993 to 168.5 million tonnes in 2015-16 and productivity from 12.6 MT/ha to 17.8 MT/ha (www.indiastat.com). Although the production has increased but still the technology used and practices followed is predominantly traditional resulting in low productivity and inconsistent quality and quantity of produce supplies to various markets in the country. The per capita consumption of vegetables in India is very low against WHO standards and FAO recommendation (135 g/day <180 g/day (WHO standards) < 300 g/ day capita (FAO recommendation).

Abstract

Natural sunlight is the cheapest source available, but for horticulture it is not always attainable in sufficient quantities. Therefore, the use of artificial light has become very common in order to increase production and quality. Under artificial lighting technologies, LED lighting is one of the technology that can help in producing crops and flowers in a more effective and sustainable way around the world. The benefits of LEDs are that the spectrum and intensity can be selected and adjusted, the energy efficiency is higher than most conventional light sources and their small size, durability, long lifetime, cool emitting temperature, and the option to select specific wavelengths for a targeted plant response make LEDs more suitable for plant-based uses than many other light sources. These advantages, coupled with new developments in wavelength availability, light output, and energy conversion efficiency, can bring about a revolution in horticultural lighting. Light quality plays a major role in the appearance and productivity of ornamental and food specialty crop species. Far-red light, for example, is important for stimulating flowering of long-day plants (Deitzer et al., 1979; Downs, 1956) as well as for promoting internode elongation (Morgan and Smith, 1979). Blue light is important for phototropism (Blaauw and Blaauw-Jansen, 1970), for stomatal opening (Schwartz and Zeiger, 1984), and for inhibiting seedling growth on emergence of seedlings from a growth medium (Downs, 1956). The interactions are complex and continue to be unraveled at the molecular level (Devlin et al., 2007), but much of our understanding of these responses comes from studies with narrow-waveband lighting sources, in which LEDs provide obvious advantages. Thus, one potential role of LEDs in horticulture could be to enhance desired characteristics for specific crops. The artificial LED lightings increase the possibility of year-round production of ornamental plants, which will subsequently increase the income of growers related to ornamental industry. Light-emitting diodes pave the way for a better understanding of the interaction between light and pests, diseases, natural enemies and plants, as they make possible the use of very narrow wavelengths. LEDs as an option for reducing the use of growth retardants and obtaining better product quality in ornamental pot plants. Production of secondary metabolites increase with higher blue light ratio. Secondary metabolites production are increased and act against Reactive Oxygen Species (ROS) and pathogens, precondition the plant for environmental changes so they can cope with stress more efficiently.

Introduction

Gerbera is one of the most important commercial flowering crops growing in the world as a cut flower as well as garden decoration, which belongs to family compositae and native in South Africa and Asiatic region. Presently, its demand and utility are rising up continuously in India both in urban as well as rural areas throughout the year. Peoples prefer this flower, because of its unparallel diversity in colour and long vase life; whereas farmers took this crop in relation to high margin of profit and long post harvest life over some others flower. Now, people are showing their keen interest towards use of this flower in their daily life and for celebrating a colorful festival. As per report of NHB (2014), total crop area is 820 hactors, where flower marketed of 3.96 and 17.84 MT of loose and cut flowers respectively. The prime producing states in India for gerbera flower production are Karnataka, Maharastra, Assam, Uttrakhand, Telangana, Tamilnadu and West Bengal. There are some constrains identified in gerbera cultivation under protected situation, like initial investment is too much, protocol of the technology is very much restricted, regular supervision is an essential and all local festivals regulates quantity of consumption etc. However, before adopting this technology for implementation as taking part of business, users should upgrade their knowledge by seeing and believing at different production centers. Details about latest technology are summarized under mentioned, which may be helpful to the students and farmers to some extent for ready references.

Introduction

Alstroemeria also known as the lily of the Incas, Peruvian lily or Inca lily, has been grown mainly as a cut flower crop. Recently, it has become popular as a garden flower and also as a potted flowering plant. The plants produce beautiful large inflorescence in many different colours viz. lavender, orange, yellow to dark yellow, white, pink, red, purple and bi-colors. Flowers are characterized by black dots at the base of the petals and throats. The cut flowers have a long post harvest life, up-to two weeks. These valuable characteristics have made Alstroemeria one of the top cut flowers at the Dutch Flower Auction Centers. The plants produce high yield and possess an ever blooming habit after flower initiation has occurred but in general most cultivars flower best during spring and early summer. The straight, un-branched shoots emerge from underground rhizomes which also produce enlarged storage roots. It is gaining popularity in Indian flower market due to long stem flowers and prolonged vase life. Recently flower growers have shown great interest about its production as a cut flower crop.

Introduction

Flowers speak millions of unspoken words. Presenting a bouquet and making arrangements with flowers in most of the drawing rooms, offices, hotels and hospitals have become the style of the day in the fast – moving modern world where there is hardly any time for exchange of sweet memories. Since time immemorial, the importance of such a delicate creation of nature has always been appreciated. Tamil Nadu ranks first among the flower producing states of India, contributing 25% of the country’s flower production with an area of 31, 970 ha under flowers. Of this, around 700 ha are under protected cut flower cultivation. In Nilgiri district alone, it has an area of around 70 ha under protected cut flower production which is inclusive of around 11.2 ha of lilium.

The genus Lilium (Lilium spp.) is a herbaceous flowering plant normally grown from bulbs, about 110 species world over belongs to lily family Liliaceae. It is native of the northern temperate regions. The species in this genus are the true lilies while the other plants with lily in the common name are related to the other groups of plants. Lilies are usually erect leafy stemmed herbs. The majority of species form tunicless scaly underground bulbs from which they produce flowers. The large flowers have three petals along with three sepals, look like petals.

Introduction

Rose, acclaimed as the “Queen of Flowers”, is one of the most popular cut flowers in the global floriculture trade. Popularly referred to as ‘Dutch rose’ in the international market, cut rose occupies a prominent place among the cut flowers owing to its exquisite form, size and attractive colours. Apart from cut flower it is used for making various value added products such as rose oil, rose water, garland, gulkhand, rose attar etc and also in landscaping as pot plant and garden plant. The present day rose (Rosa hybrida) combines all desirable qualities such as, productivity, attractiveness of buds, a variety of colours and forms of the typical species of Rosa.

The major cut rose producing countries of the world are the Netherlands, Colombia, Kenya, Israel, Italy, United States, and Japan. In India, roses are mostly grown under cover (poly house) in Nasik, Pune, Hosur, Kalimpong, Darjeeling, Bangalore, Solan, Palampur, Shimla, Srinagar, Delhi, Ludhiana and Calcutta. The roses grown for export should be popular varieties of that region and maintain high quality standards with respect to bud size and stem length and should have lush green leaves and be free of pests and diseases. These high quality standards can be achieved and maintained only when grown inside poly house or greenhouse, which gives protection against inclement weather conditions and pests and diseases.

1.1 Weather

Firstly, what is weather? Simply, the conditions in the atmosphere above the earth is called weather. It refers to the conditions such as wind, rain and temperature, prevailing at a particular location during periods of hours or days. We often ask “what’s the weather like today”? Any individual can answer to this question as it requires only a short term experience or say exposure to the atmosphere. The TV news forecasters predict weather each day and inform about the temperature, cloudiness, humidity, or possibility of storm in the next few days. Weather is localised, say, it’s a hot and cloudy weather in one part of the country and dry and windy on the other part.

1.1.1 What are the factors that influence weather?

Before we try to understand the factors that influence weather, we must understand what the components that describe a weather conditions are? Is it the rains, or the air temperature or both? The answer to this question is not so easy, and it’s a bit complicated. There are many components that constitute weather. Weather components include rain, cloud cover, sunshine, winds, hail, snow, sleet, storms, thunderstorms, heat waves and many more. These components are sometimes referred as weather parameters or climate elements. Each of these components define weather patterns of a particular area. These components determine the status of local atmospheric conditions. Again, as a basic definition, weather is the state of the atmosphere and majority of weather phenomena occur in the lowest layer of the atmosphere, called as the troposphere. Does it mean that ground conditions such as the topography, water bodies and vegetation of a particular area has nothing to do with it? No, it is not so. The state of the atmosphere is subjected to various processes taking place not only in the atmosphere but also in the ocean, the sea-ice, the vegetation, etc. Weather parameters or the components of weather form a sequence of events, and the influences are far reaching and they do not remain solely in the atmosphere. For example, terrestrial radiation impacts the air temperature, air pressure and humidity. The terrestrial location also influences the cloud formation. The clouds may or may not turn into precipitation depending on the outcome (cloud or rain), which is by and large governed by troposphere. Likewise, a lack of precipitation affects not only weather conditions, but also soil moisture conditions that may result in lowering of water levels (ground water table) in soil. Wind speed and direction are governed by the atmospheric pressure and air temperature. So, all these parameters or components are interrelated and the weather conditions are the outcome of their interactions. Therefore, we can say that, the three main components of weather are temperature, precipitation and solar radiation. These components are influenced by different factors.

Climate change is caused by both natural as well as anthropogenic causes and it has been changing since the inception of earth-atmosphere (Figure 2.1). In a broader sense, anthropogenic activities (human activities) also must be considered as natural one in longer time scale as human and their activities are also a part of natural-ecosystem-functions. Among the natural phenomena, volcanic eruptions and continental drifts significantly affect the earth’s precipitation and temperature. A huge volume of CO₂ is released due to volcanic eruption at a little span of time-period which heated up the earth-atmosphere. Climate variability is primarily governed by rise in sea temperature, movement of warm water from the Western Pacific towards Peru, and El Nino which occurs at an intervals of 3-7 years. Climate variability also influenced the alteration in temperature and precipitation world wide. And persistent climate variability cause long term climate change. Therefore, basically three drivers that causes climate change are, the alteration in the energy of sun received by earth-atmosphere (natural causes), variations of ref lectivity of earth-surface- atmosphere system (natural as well as anthropogenic causes) and fluctuations in the greenhouse effect (natural as well as anthropogenic causes).