eChapters

1.1 Introduction

Fruit breeding is an ancient technology with dynamic current technology and an exciting future (Janick and Moore 1975, 1996). In its broadest sense, fruit breeding refers to the purposeful genetic improvement of fruit crops through various techniques including selection, hybridization, mutation induction and molecular techniques. Its origins trace to the domestication process in prehistory and antiquity, where useful species were chosen and cultivated, and improved by continuous selection (Janick 2005, 2011). Through the millennia genetic improvement of these species have been achieved by grower selection, first from natural seedling populations and then from grower field that continued unique genotypes fixed by vegetative propagation. Spontaneous hybridization between wild plants and cultivated clones was critical to the early domestication of fruits.

Botanical Name: Hevea brasiliensis

Family: Euphorbiaceae

Chromosome No: 2n =36

Place of Origin: Amazon basin in Brazil

Common Name: Rubber tree, Rubber plant, Para rubber tree

11.1 Introduction

Rubber is a fast-growing tropical tree and mainly grown for the production of latex. In 1495, Columbus was the first person to report about latex. The latex was used for rub out pencil marks and this gave the product name as rubber. The latex is used for production of various rubber products. The most important application of latex rubber was initially accomplished in the 1880s when the rubber was used for making motor cars tyres. When rubber is heated with sulphur, it retains the physical properties.

Botanical Name: Phoenix dactylifera L.

Family: Arecaceae

Chromosome No: 2n = 36

Place of Origin: Countries around Persian Gulf

10.1 Introduction

Date palm is a nutritive fruit rich in sugar and iron and predominantly seen in desert oasis. It is the main fruit crop in arid and semiarid regions, particularly in the arid regions of western Asia and North Africa. The palm tree is well adapted to desert environments that are characterized by extreme temperatures and water shortage. Beyond the arid climates, date palm can also be grown in many other countries for food or as an ornamental plant including the continents of Americas, Southern Europe, Asia, Africa and Australia. The majority of date palm growing areas are located in developing or underdeveloped countries where dates are considered the primary food crop, thus playing a major role in the nutritional status of these communities. By-products from date palm are used in building structures, animal feed, and also in several items such as baskets and ropes. The date palm tree has been in cultivation since 2400 BC. It is one of the oldest cultivated fruit trees on earth. India is the leading importer of dates. According to FAO statistics, in 2011 India was the largest world importer of dates (256,295 mt) and its neighbour Pakistan, in 2012, was the world’s sixth largest producer (600,000 mt). The major date palm growing areas in India are Kutch (Gujarat), Rajasthan and certain parts of the Punjab, as well as Tamil Nadu state to some extent. In Kutch, there are more than 2 million date palms, the majority of them grown from seeds and offshoots, providing a huge biodiversity for experimentation and improvement of products. Efforts by the Indian government in the last decade have resulted in an increase of date palm cultivation from 8,973 to 16,000 ha and establishment of a prominent effort in Rajasthan (Shah, 2014).

Botanical Name: Camellia sinensis L.

Family: Theaceae

Chromosome No: 30

Place of Origin: China

Common Name: Tea

9.1 Introduction

Tea (Camellia sinensis L.) of family Camelliaceae or Theaceae is the oldest and second most widely consumed beverage in the world following water. Tea is an evergreen plant that mainly grows in tropical and subtropical climates. India is world’s 2nd largest tea producer after China with production of 1.25 million tonnes in 2020. In India it is grown in an area of 6 lakh hectares, contributing one fourth of world total tea production annually. Interestingly, India is also the world’s largest consumer of the beverage and using nearly 30 percent of the world’s tea output. India stands third in terms of tea export after Kenya (including neighbouring African countries) and China. The total tea export was US$ 501.16 million in April 2020 to November 2020 and for November 2020 it was US$ 71.61 million.

Botanical Name: Coffea arabica, Coffea canephora

Family: Rubiaceae

Chromosome No: 44, 22

Place of Origin: Africa

Common Name: Coffee

8.1 Introduction

Coffee is widespread throughout the tropics with more than 70 species. All cultivated species originate from Africa. Economically important today is Coffea arabica (Arabica, 64 % of world production) and Coffea canephora, (Robusta, 35 %). It is cultivated worldwide on approximately 10.3 million hectares and represents the sole economic income for more than 25 million families. The crop is produced and exported by more than 60 nations and ranks as one of the top cash crops in developing countries with 3.19 lakh MT production per annum in India in 2018-19 from more than 459 thousand hectares crop area. The coffee plant is a fast-growing tropical bush tree, with two types of shoots: upright growing orthotropic main shoots (stem), and horizontally growing plagiotropic shoots (branches). Traditionally, coffee trees are cultivated only for the berries, which are processed using dry or wet techniques directly in the growing areas to the final raw product, green coffee; this serves as the basis for various coffee products. Both the coffee species tolerate shade and share quite similar growth requirements with various forest crops and trees, thus predisposing them to be grown in agro-forestry ecosystems.

Botanical Name: Anacardium occidentale L.

Family: Anacardiaceae

Chromosome No: 42

Place of Origin: Brazil

Common Name: Cashew, cashew tree, caju

7.1 Introduction

Cashewnut (Anacardium occidentale L.) is an important tropical tree crop which leads the edible nuts in international trade with 29% market share only after hazelnuts (35%) and followed by walnuts (21%) and almonds (16%). It is one of the major exports earning crops which accounts nearly Rs. 2515 crores contributing about 1.5% of the total Indian exports. It was only during the past two decades it gained the status of horticulture crop. India is the world’s largest producer of cashewnut. The cashew cultivation area in India during 2018-19 was 10.89 lakh hectares with an annual production of 743 thousand metric tons of fruits. Maharashtra is a much-advanced state for horticulture which occupies large area (1.9 lakh hectares) under this crop (Directorate of Cashew & Cocoa Development, Cochin, Kerala). Cashew exports amounted to over 566 million U.S. dollars from India in fiscal year 2020. This included cashew kernels and cashew nut shell liquid. India’s main export markets for this commodity included South Korea, China, Spain, United States and Belgium (Department of Agriculture, Cooperation & Farmers Welfare).

Botanical Name: Theobroma cacao L.

Family: Sterculiaceae

Chromosome No: 20

Place of Origin: Tropical South America

Common Name: Cacao, cacao bean, cocoa, cocoa bean

6.1 Introduction

Cocoa (Theobroma cacao L.) is a perennial plant and is used as beverage crop. The generic name Theobroma means the “Food of the God”. The word cacao refers to the tree, while the word cocoa refers to the drink made from its seeds. The roasted product of the dried beans is called as Cacao nibs that are used for the manufacture of various products. When cacao nibs are ground, the resulting product is called chocolate liquor or mass, which contains around 55% fat. The fat that is pressed from chocolate liquor is termed as cacao butter. It is mainly used for the manufacture of chocolates, in pharmaceutical preparations and soap making. After pressing out the fat the resultant product with reduced fat content is called cacao powder. For preparation of chocolates cacao powder is mixed with cacao butter and sugar with a definite ratio. Milk chocolates are prepared by adding milk to the above mixture. The cocoa powder contains 22- 25% fat, 20.4% protein and 35% carbohydrate with caloric value of 452 cal. Rind or shell of pod is used as a cattle feed.

Botanical Name: Borassus flabellifer L.

Family: Arecaceae

Chromosome No: 36

Place of Origin: Tropical region of Africa, Asia and New Guinea

5.1 Introduction

Palmyrah is a monocotyledon and perennial crop. The word “Borassus” was derived from a Greek word and it means the leathery covering of the fruit and “flabellifer”, means fan-bearer. The distinguishing characters of palm in this genus are their palmate, fanlike leaves and dioecious character, i.e., male and female flowers are borne on separate trees (sex ratio 1:1), allotetraploid (X= 8 or 9, n = 18), the male tree has a heteromorphic XY pair of chromosomes while the female has an XX pair (Sankaralingam et al., 1999). Next to coconut, palmyrah is the most abundant palm found in the world. Palmyrah thrives in arid conditions and is grown extensively in Tamil Nadu. Palakkad district of Kerala is popularly known as land of palmyra trees. Palmyra trees are known as the icon of this district and have a vast cultural, heritage and literary association.

Botanical Name: Elaeis guineensis Jacq.

Family: Arecaceae / Palmae

Chromosome No: 32

Place of Origin: Guinea Coast of West Africa

Common Name: Oil Palm

4.1 Introduction

The cultivated oil palm Elaeis guineensis Jacq. is a native of West Africa and exists in wild, semi- wild and cultivated forms. It was introduced as an ornamental crop in 1860 and planted at National Botanical Garden, Kolkata. Research on oil palm in India started during 1960 with the establishment of a research station at Thodupuzha by the Department of Agriculture, Kerala with Dura and Tenera germplasm imported from Malaysia and Nigeria. National Research Centre (NRC) for oil palm is situated at Elur, Andhra Pradesh. Oil palm crop is one of the highest oil yielding crops among all perennial crops. It gives 4 to 6 tonnes of edible oil/ha from 3 to 25 years of its life span compared to less than one tonne of oil per ha from other cultivated oil yielding crops. This oil palm is considered as golden palm due to its high yielding capacity. Among the 10 major oilseeds, oil palm is accounted for 5.5% of global land use for cultivation, but produced 32.0% of global oils and fats output.

Botanical Name: Areca catechu L. Family: Arecaceae / Palmae Chromosome No: 32 Place of Origin: Philippines, Malay, Indonesia, Cochin, China and Malaya Peninsula Common Name: Betel nut 3.1 Introduction Arecanut (Areca catechu L.), commonly known as Supari or Betel palm or Arecanut palm, is cultivated primarily for its kernel obtained from the fruit which is chewed in its tender, ripe or processed form. It is an important cash crop of India. The economic produce is the fruit called ‘betel nut’ and used mainly for masticatory purposes. Its cultivation is restricted in South Western and North Eastern regions of the country. The chromosome number of Areca catechu L. was first determined as 2n=32 (Venkatasubban, 1945) and it belongs to family Arecaceae. It is one of the important commercial crops grown in parts of Karnataka, Kerala, Assam, Meghalaya, West Bengal, and Andaman and Nicobar Islands. The cultivation of arecanut has also been extended to other states like Tamil Nadu, Andhra Pradesh and Maharashtra. India is the largest producer and consumer of arecanut in the world holding 62% of the area and 60% of the production. The other major arecanut growing countries are Indonesia, Bangladesh, China, Myanmar and Thailand. Arecanut being a profitable plantation crop, it is important to understand the package of practices and seasonal operations to be followed in the nursery, in young gardens and in old plantations to get maximum returns. To get additional income in the adverse periods, concept of cropping system is very important. The exact origin of areca nut is not known till date but, arecanut is a palm which grows in much of the tropical Pacific, Asia, and parts of East Africa (Kumar, 2013).

Botanical Name: Cocos nucifera L. Family: Arecaceae / Palmae Chromosome No: 32 Place of Origin: Malaysia Common Name: Coconut 2.1 Introduction Coconut (Cocos nucifera L.), is widely known as ‘Kalpavriksha’ (i.e., tree of heaven) as each and every part of the palm is useful in one way or the other and is an important perennial oil yielding crop of humid tropics. It provides food security and livelihood opportunities to 20 million people around the globe and 10 million people in India (Chowdappa et al., 2017). Even though India is the largest coconut growing country in the world, its contribution to the export market is not significant. Coconut as an edible oil and food crop, is now slowly transforming into raw material for various pharmaceutical, nutraceutical and cosmetic products. Coconut is rich in fibre, vitamins and minerals. Because of its health benefits beyond its nutritional content, it has been considered as “functional food”. Hence, there exists a huge scope for coconut-based agribusiness in India, which will increase the present 8% level of value addition to 25%. The coconut-based value-added products are desiccated coconut powder, coconut milk, coconut cream, coconut milk powder, coconut flour, coconut water concentrate, coconut jelly (Nata-de-coco), coconut vinegar, virgin coconut oil, coconut chips, coconut pickle, coconut ice cream, neera and neera based value added products such as syrup, squash, honey, jaggery, candy and sugar (Chowdappa et al., 2017).

Threats

There are sixteen threat factors have been identified from Indian mangroves (Kathiresan 2010). However, habitat conversion for agriculture and aquaculture activities, environmental pollution by upstream anthropogenic activities, Climate change processes (e.g. sea level rise; increasing frequency of cylones, etc.) are the major threat factors for mangroves. Mangroves are able to cope up with short-term oscillations and long-term fluctuations of climatic conditions, but the consequences of global climate change, such as increased extreme events, will have unprecedented effects on biota and threaten the resilience and recovery potential of the ecosystems (Harris et al. 2018; Sippo et al. 2018). Despite conservation measures, the mangroves still experience an annual loss of 0.2-0.7% during 2000-2012 and they remain the most threatened ecosystem of the world (Hamilton and Casey 2016).

Mangrove forests are ecologically significant and economically important (Kathiresan 2018). They provide ecosystem services worth at least US$ 1.6 billion each year and support coastal livelihoods worldwide (Costanza et al. 1997). They serve as the nursery, feeding and breeding grounds for crabs, prawns, molluscs, finfish, birds, reptiles and mammals. A large amount of global fish catches (up to 80%) is dependent on mangroves, thereby ensuring the food security of coastal people (Ellison 2008). The mangroves provide firewood, timber, cattle feed, honey, medicines and tourism development. They protect groundwater aquifers from seepage of seawater, thereby ensuring water security for coastal population. Mangrove forests remove coastal pollution particularly toxic heavy metals. They offer coastal protection against the fiery effects of natural calamities such as tsunami, storm surges, cyclone and floods (Kathiresan and Bingham 2001; Kathiresan and Qasim 2005; Kathiresan and Rajendran 2005). The potential of mangroves in carbon capture and sequestration is remarkable in mitigating the impacts of global warming and climate change (Kathiresan et al. 2013, 2014).

West Bengal

In West Bengal, mangroves are present in Sundarbans, the large deltaic complex of three major rivers, the Ganges, Brahmaputra and Meghna, and 62% of total area is shared by Bangladesh and 38% by India. The Sundarban Biosphere Reserve (SBR), at the confluence of the Bay of Bengal covering an area of 9,630 km², lies between 21°40′N and 22°40′N latitudes and 88°03′E and 89°07′E longitudes, spreading in districts of South and North 24-Parganas in West Bengal, India. The major portion of SBR is designated as Reserve Forest, covering nearly 4260 km² and the area under mangrove vegetation is 2112 km² (FSI 2019). Compared to 2017 assessment there has been a decrease of 2 km² area of mangroves. The mangroves and their associates in the SBR exhibit great generic and species diversity and it is abode to rare and highly endangered flora and fauna, as well as, the only mangrove-tiger (Royal Bengal Tiger - Panthera Tigris tigris) kingdom in the world. Recognizing importance and uniqueness, the United Nations Educational, Scientific and Cultural Organization (UNESCO) declared the Indian part of Sundarbans as a ‘World Heritage Site’ in 1987, and also designated the ‘Sundarban Biosphere Reserve’ under the UNESCO Man and the Biosphere (MAB) program in 2001. Recently, Sundarbans has been declared as a Ramasar Site, considering ecological significance. Totally 33 true mangrove species belonging to 21 genera and 13 families have been identified in Indian Sundarbans. Among the mangrove species listed, Rhizophora apiculata, Bruguiera parviflora, Ceriops decandra, Kandelia candel, Aglaia cucullata, Excoecaria indica, Xylocarpus moluccensis, Xylocarpus granatum, Heritiera fomes, Scyphiphora hydrophyllacea, Brownlowia tersa, Nypa fruticans, Acanthus volubilis, Dolichandrone spathacea and Phoenix paludosa are under serious threat in Sundarbans (Kathiresan 2008; Gopal and Chauhan 2006). Particularly Heritiera fomes (locally called Sundari, from which Sundarbans derives its name), Nypa fruticans and Phoenix paludosa are declining rapidly due to the reduction of freshwater input (Gopal and Chauhan 2006).

Distribution of Mangroves in India

Mangrove forests in India are found along the coastline of 9 States and 4 Union Territories (Fig. 5). The mangrove habitats are broadly classified into three namely, Deltaic (Eastern Coast Mangroves), Estuarine & Backwater (Western Coast Mangroves) and Insular mangroves (A & N Islands) (Mandal and Naskar 2008). India has a total mangrove cover of 4975 km²; of which, 57% is present along the east coast (Bay of Bengal); 31% along the west coast (Arabian Sea) and the remaining 12% in the Andaman and Nicobar Islands (FSI 2019).

Origin and diversification of Mangroves

Mangroves are quite old, possibly arising just after the first angiosperms (Duke 1992). Based on the fossil evidence and recent molecular studies, it is believed that mangroves originated along the shorelines of ancient Tethys Sea and there was a dispersal along the Tethys seaway westward into the Atlantic and further into the east Pacific (long before the closure of the Panama Isthmus) and eastward into South east Asia and Australia during the Late Cretaceous or early Eocene around 80 million years ago (Duke 2006). Nypa seems to be earliest fossil evidence. However, prior to closure of Tethys sea, around 40-55 million years ago, the mangrove genera - Nypa, Acrostichum, Rhizophora, Avicennia, Pelliciera, Sonneratia, Bruguiera, Ceriops, Heritiera, and Aegiceras - were present around shoreline (Duke 2017). The closure of Tethys Seaway by the mid-Tertiary (34-50 Million years ago) by northward movement of African landmass, created a physical barrier that completely terminated the Atlantic East Pacific (AEP) and Indo-West Pacific (IWP) exchange route, and resulted in subsequent diversifications within the AEP and IWP regions influenced by region-specific events (Ellison et al. 1999; Duke 2006). The plate tectonics and other vicariant events like Pleistocene sea level rise are attributed to the current distribution pattern and disjunct distributions of species within genera. Duke (2017) hypothesised two separate westward dispersal routes in AEP: (i) a southern path along the coasts of West Africa, South America and, (ii) a northern path along the North American east coast, whereas he hypothesised two isolated pathways in IWP towards eastward dispersal: (i) a northern path along the coast to the Middle East, Southeast Asia and, (ii) a southern path along the coasts of East Africa, India, and Australia. Further he noted that collision of India and Australia with Middle East and Southeast Asia respectively, resulted complication in dispersal route. Based on the available records it is presumed that diversification of mangrove plants has largely been driven by three key processes of speciation viz., Allopatric speciation, Peripatric speciation and Parapatric speciation (Duke 2017).

Mangroves Definition

A mangrove is tree, shrub, palm or ground fern, generally exceeding one and a half meter in height that normally grows above mean sea level in the intertidal zone of marine coastal environment and estuarine regions of the tropical and subtropical coastlines (Duke 1992). The mangrove is also defined as assemblages of salt tolerant trees and shrubs. Mangroves are taxonomically heterogenous and more related to environment than terrestrial or aquatic plants.

The term ‘mangroves’ is used to define both a group of plants and a community. To avoid confusion, Macnae (1968) proposed the term ‘mangal’ for the mangrove forest community, and the term ‘mangroves’ for the plants. Other terms for the mangrove forest community are coastal woodland, oceanic rainforest, intertidal forest, tidal forest, blue carbon forest, mangrove forest, and mangrove swamp.

Generally, mangrove species are grouped into two types: Exclusive and Non-Exclusive. The exclusive species are limited to the mangrove habitat, and they are also referred to as strict mangroves, obligate mangroves or true mangroves. The non-exclusive species are mainly distributed in a terrestrial or aquatic habitat, but they also occur in the mangrove habitats and they are referred to as semi-mangroves, back mangroves or mangrove associates. Tansley and Fristch (1905) are the first to introduce the criteria to classify mangrove species into true mangroves and mangrove associates. Tomlinson (1986) used rigid criteria to distinguish true mangroves from mangrove associates. In his criteria, true mangroves possess all or most of the following features:

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.

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.

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. 

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.

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:

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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’.

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.

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).

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.

This is a great Hahnemannian anti- psoric. Its action is centrifugal - from within outward - having an elective affinity for the skin, where it produces heat and burning, with itching; made worse by heat of bed. Inertia and relaxation of fibre; hence feebleness of tone chracterizes its symptoms. Ebullitions of heat, dislike of water, dry and hard hair and skin, red orifices, sinking feeling at stomach about 11.00am, cat-nap sleep; always indicate sulphur homoeopathically. Standing is the worst position for sulphur patients it is always uncomfortable. Dirty, filthy people, prone to skin affections. Aversion to being washed. When carefully selected remedies fail to act, especially in acute diseases, it frequently arouses the reactionary powers of the organism. Complaints that relapse. General offensive character of discharge and exhalations. Very red lips and face, flushing easily. Often use in beginning the treatment of chronic cases and in finishing acute ones.

Imperfect assimilation and consequent defective nutrition, it goes further and produces neurasthenic states in consequence, and increased susceptibility to nervous stimuli and exaggerated reflexes. Diseases of bones, caries and necrosis. In TB it must be used with care, for here it may cause the absorption of scar tissue, liberate the disease, walled in, to new activities. It is a deep acting remedy and slow in action. It is meant for scrofulous children with large head, open fontanels and sutures, distended abdomen, slow in walking. Ill effects of vaccination. It is related to all fistulous openings. Ripens abscesses since it promotes suppuration.

Silica patient is cold, chilly, hugs the fire, wants plenty warm clothing, and hates drafts, hands and feet cold, worse in winter. Lack of vital heat. Prostration of mind and body. Great sensitiveness to taking cold. Intolerance of alcoholic stimulants/Ailments attended with pus formation.

In inflammation with pus formation, which has become chronic, silicea is of great help. It is equally useful in grandular or bony ulceration. Think of silicea in whitlow, unhealthy skin, smelly feet, mammary abscess, mammary cancer, TB of the skin, the bone or of the abdomen,

Acts especially on the portal system, with venous congestion. Stasis and thereby ptosis of viscera and weariness and misery. Weakness, yellow complexion, bearing-down sensation, especially in women, upon whose organism it has most pronounced effect. Pains extend down to back, chills easily. Tendency to abortion. Hot flashes at menopause with weakness and perspiration. Upward tendency of its symptoms. Easy fainting/ Ball" sensation in inner parts. Sepia acts best on brunettes. All pains are from below up. One of the most important uterine remedies. Tubercular patients with chronic hepatic troubles and uterine reflexes. Feels cold even in warm room.

The most important indications of Sepia are in the problems of women relating to the uterus. It has been called the best uterine remedy available. The patient feels that all her internal organs would come out of the pelvic region. She has to sit with legs crossed to relieve this feeling. Sepia is a chronic remedy. It can take care of long standing problems.

It produces contraction of the unstriped muscular fibers, hence a constringent feeling throughout the whole body. This produces an anemic condition, coldness, numbness, mortification and gangrene. A useful remedy for old persons with shriveled skin- thin, scrawny old women. All the Secale conditions are better from cold; the whole body is pervaded by great heat. Haemorrhages continued oozing, thin, fetid, watery black blood. Debility, anxiety, emaciation, though appetite and thirst may be excessive. Facial and abdominal muscles twitch. Secale lowers the flow of pancreatic juice by raising the blood pressure.

Menstrual colic, with coldness and intolerance of heat. Passive haemorrhages in feeble, cachetic women. Burning pains in uterus, brownish, offensive leucorrhoea. Menses irregular, copious, dark, continuous oozing of watery blood until next period. Threatened abortion about the third month. During labor no expulsive action, though everything is relaxed. After-pains. Suppression of milk; breasts do not fill properly. Dark, offensive lochia. Puerperal fever, putrid discharges, tympanitis, coldness, suppressed urine.