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The term hybrid or hybrid variety is used to designate F1 populations that are used for commercial plantings. Such F1 populations are obtained by crossing clones, open-pollinated varieties, and inbred lines that are genetically dissimilar. Historically the first attempts to make practical use of fortunate mating system of maize came late in the nineteenth century by W. J. Beal in Michigan, stimulated by Darwin’s work on inbreeding and outcrossing. Beal suggested use of F1 varietal crosses to exploit heterosis for commercial crop. The hybrid seed was to be produced by detasseling alternate rows. It was George Harrison Shull (1909) who first suggested a pure line method of corn breeding based on inbred lines obtained by continued self-fertilization and the use of F1 hybrids between these inbred lines for the production of commercial crop. His proposal was to make use of single crosses (hybrids between two inbred lines) based on the superior performance of the hybrids in various combinations between the inbred lines.

Backcross breeding is defined as system of breeding whereby recurrent backcrosses are made to one of the parents of a hybrid, accompanied by selection for a specific character or characters. It is basically applicable to self-pollinated crops and is precise way improving varieties that excel in large number of desirable attributes but lack in a few characteristics. This method makes use of a series of backcrosses to the variety to be improved during which character for which improvement is sought is maintained by selection. At the end of the backcrossing, the gene to be transferred remains in heterozygous condition and selfing after the last backcross produces homozygosity for the gene under transfer. As a result, the improved variety will remain like recurrent variety in terms of yield, adaptability, quality features, etc. will be superior for the character which was planned to be transferred from the donor parent.

The application of backcross breeding in plants was first proposed by H.V. Harlan and M.N. Pope in 1922. In principle, backcross breeding does not improve the genotype of the product, except for the substituted gene(s).

Single seed descent (SSD) method of breeding is applicable to self-pollinated crops. The method of single seed descent (SSD) was born out of a need to speed up the breeding programme by rapidly inbreeding a population prior to initiating individual plant selection and evaluation while reducing a loss of genotypes during the segregating generations. SSD procedure is based on advancing generations through single seed from each plant in each generation. This separates the inbreeding phase from the selection phase and the population reaches F6 generation faster. This procedure carries forward maximum number of F2 plants to a stage near homozygosity, i.e. F6. It was first proposed by C. H. Goulden in 1941 when he obtained the F6 generation in two years by reducing the number of generations grown from a plant to one or two while conducting multiple plantings per year using greenhouse and off-season planting. H. W. Johnson and R. L. Bernard described the procedure of harvesting a single seed per plant for soybean in 1962. However, it was C.A. Brim who, in 1966, provided a formal description of the procedure of single seed descent, calling it a modified pedigree method.

Bulk population method of breeding is defined as the growing of genetically diverse populations of self-pollinated crops in a bulk plot with or without mass selection, followed by single plant selection. It is applicable to self-pollinated crops and not applied to cross-pollinated crops. Bulk population breeding is a strategy of crop improvement in which natural selection effect is solicited more directly in the early generations of the procedure by delaying stringent artificial selection until later generations. The Swede, H. Nilsson-Ehle, developed the procedure. H.V Harlan and colleagues provided additional theoretical foundation for this method through their work in barley breeding in 1940s. As proposed by Harlan and colleagues, the bulk method entails yield testing of the F2 bulk progenies from crosses and discarding whole crosses based on yield performance. In other words, the primary objective is to stratify crosses for selection of parents based on yield values. The current application of the bulk method has a different objective.

Pedigree method of plant breeding is defined as a method of breeding in which individual plants are selected in the segregating generations from a cross on the basis of their desirability judged individually and on the basis of a pedigree record. This has been the most widely used method of plant breeding in all the self-pollinated crops and still continues to be so. This method has been first described by H. H. Lowe in 1927. This is the most widely used method to handle segregating generations following crosses between two parents to develop new cultivars combining desirable traits from both the parents. In this method, superior types are selected in successive segregating generations and a record is maintained of all parent-progeny relationships. The records help the breeder to advance only progeny lines with plants that exhibit genes for the desired traits. Selection begins in F2 generation where individual plants are selected which in judgment of breeder will produce the best progeny in F5/F6 when the selection is finally concluded. In F3 and F4 generations, many loci will have become homozygous and family characteristics begin to appear. By F5/F6 generation, most families are expected to be homozygous and uniform and hence selection within such families is no longer effective. 

A line homozygous at all loci, ordinarily obtained by successive self-fertilizations in plant breeding is called a pure line. This concept was proposed by Danish biologist, W.L. Johannsen in 1903 while conducting a series of selection experiments for seed weight in common bean, which is strictly self-pollinated species. This is applied in self-pollinated crops, like wheat, rice, pulses, several vegetable crops, namely, tomato, chilli, eggplant, okra, cucurbits, etc. This is also applied to develop inbred parental lines in maize and several other cross-pollinated crops. However, ultimately these parental lines are used in development of new hybrids. This could be summarized as follows:

• Lines that are genetically different may be successfully isolated from within a population of mixed genetic types.
• Any variation that occurs within a pure line is not heritable but due to environmental factors only. Consequently, as Johansen’s bean study showed, further selection within the line is not effective.

Mass selection is a form of selection in which individual plants are selected phenotypically and the next generation propagated from the aggregate of their seed. It is applicable to both self and cross-pollinated crops. The obvious first step in the improvement of self-pollinated variety is the elimination of undesirable types. This may be achieved by simply roguing them as the variety grows in the field. Sometimes, this is called as negative selection. Another approach is to tag desirable types and to harvest only those at maturity. This is called as positive selection. Either way, results are similar. The best plants in the variety are identified and bulked. A refinement of mass selection is to harvest the best plants separately and to grow them as pure lines for comparison. Only those pure lines that are similar and superior are bulked as an improvement of an established variety. 

Broadly and conceptually breeding methods can be classified into four groups. These are:

• Selection breeding
• Combination breeding
• Hybrid breeding
• Special breeding techniques

There are fluid transitions and similarities between the individual groups of breeding methods. Selection not only takes place in the group termed selection breeding but also in other groups. In breeding varieties by combination, new variation is generated by crossing genetically different parents followed by application of various selection methods and ultimately development of a new recombinant type pure-line. In hybrid breeding, inbred lines of different genetic constitution are produced by selfing, pair crossing and other methods and from these best lines are selected and new hybrids are developed. In addition, breeding methods can also be classified according to other criteria. For example, breeding methods have also been classified according to the manner of propagation of the varieties. These are:

Crop Domestication

Domestication can be loosely defined as the process of bringing of a wild species under the management of man. Domestication is the process by which genetic changes (or shifts) in wild plants are brought about through a selection process imposed by humans. Because of the role of humans, the process results in characteristics that are beneficial to humans but some that would be disadvantageous for plants in their natural habitats. It is an evolutionary process in which selection (both natural (frost tolerance) and artificial (large attractive fruits)) operates to change plants genetically, morphologically, and physiologically. 

To start with let the self-incompatibility be defined.

• Self-incompatibility is the mechanism by which plant can prevent selffertilization.
• Self-incompatibility is defined as inability of a plant producing functional gamete to achieve self-fertilization.
• Self-incompatibility is a genetically based mechanism which controls mating within angiosperm species by imposing a ‘barrier’ between pollination and fertilization.
• The term incompatibility is used to describe the failure of pollen tube to penetrate the full length of the style and to effect fertilization.

Male sterility is a condition in plants whereby the anthers or pollen are nonfunctional. The condition may manifest most commonly as absence of pollen or extreme scarcity of pollen, severe malformation or absence of flowers or stamens, or failure of pollen to dehisce. Just like self-incompatibility, male sterility enforces cross-pollination. Similarly, it can be exploited as a tool to eliminate the need for emasculation and for hybrid seed production on commercial scale in field and vegetable crops. There are three basic kinds of male sterility based on the origin of the abnormality related to functional pollen grain.

Hybrid vigor or heterosis is opposite and complementary to inbreeding depression (reduction in fitness as a direct result of inbreeding). In theory, the heterosis observed after crossing is expected to be equal to the depression upon inbreeding, considering a large number of crosses between lines derived from a single base population. In practice, plant breeders are interested in heterosis expressed by specific crosses between selected parents, or between populations that have no known common recent origin. Furthermore, because heterosis is subject to the interactions between genotype and environment, it is desirable to describe the heterosis of a particular hybrid line for a specific trait at a specific location or under specified environmental conditions.

Inbreeding

Inbreeding means the mating together of individuals that are related to each other by ancestry. This may be defined as any system of mating that will lead to an increase in homozygosity. Selfing is the most intense form of inbreeding which provides the most rapid approach to homozygosity. When selfing is not possible, full-sib and half-sib mating are used to do inbreeding. The progeny of selfed plant is symbolized by Sj and the selfed progeny of the Sj by S₂ and so on. Occasionally symbol  is used to designate selfed seed. The effects of inbreeding are as follows:

Random Mating

Random mating occurs when each female gamete has an equal chance of being fertilized by any male gamete of the same plant or with any other plant of the population and, furthermore, there is an equal chance for seed production. It is not possible to achieve true random mating in plant breeding because selection is involved. Consequently, it is more realistic to describe the system of mating as random mating with selection. Whereas true random mating does not change gene frequencies, existing variability in the population or genetic correlation between close relatives, random mating with selection changes gene frequencies and the mean of the population, with little or no effect on homozygosity, population variance, or genetic correlation between close relatives in a large population.

The response to selection (R) or selection advance or genetic gain is the difference between the mean phenotypic value of the offspring of the selected parents and the whole of the parental generation before selection. The response to selection is simply the change of population mean between generations following selection. Similarly, the selection differential (S) is the mean phenotypic value of the individuals selected as parents expressed as a deviation from the population mean (i.e., from the mean phenotypic value of all the individuals in the parental generation before selection). Response to selection is related to heritability by the following equation:

While dealing with polygenic traits and the continuous variation in plant breeding programs, it is important to know as to what extent the phenotype is decided by the genotype and to what extent by the environment. It is well known fact that what we observe i.e. phenotype is the result of genotype, environment and interaction between the genotype and the environment. The total variance is phenotypic variance or the variance of phenotypic values and various components of variance are as shown in Table 6.1.

Quantitative traits are governed by many genes or polygenes genes with small individual effects. They are often described by their gene action rather than by the number of genes by which they are governed. There are four types of gene action: additive, dominance, epistasis, and overdominance. Because gene effects do not always fall into clear-cut categories, and it should be pointed out that gene action is conceptually the same for major genes as well as minor genes, the essential difference being that the action of a minor gene is small and significantly influenced by the environment. A general way of distinguishing between these types of gene action based on interaction among alleles is as follows:

Qualitative characters are those characters which show discontinuous or discrete differences and are counted into different classes and there is no need to measure them. Typically speaking, characters studied by Mendel in garden pea whose results were published in 1966 as Mendel’s Law were the typical characters that fitted into this class of characters in those days. To recall, these characters were (i) tall vs dwarf plants, (ii) round vs wrinkled seeds, (iii) yellow vs green pods, (iv) violet vs white flowers, (v) flat pods vs constricted pods, (vi), green pods vs yellow pods and (vii) axial flowers vs terminal flowers. Mendel postulated “Factors” responsible for these differences and he could explain his results of F₂ in ratio of 3:1 while dealing with one trait at a time and 9:3:3:1 while dealing with two traits simultaneously and proposed (i) law of segregation and (ii) principles of independent assortment to explain these ratios. Later on the term “factor” was called as gene.

Gametogenesis

Male Gametogenesis: Male gametogenesis is the formation of male gametes and it occurs in the anthers. The end products of meiosis in higher plants are four microspores. Two mitotic divisions occur in microspores. The first division produces a tube nucleus and a generative nucleus. The second mitotic division occurs only in the generative nucleus resulting into production of two sperm cells (Fig. 3.1). The microspore is haploid (n) and develops into pollen grain in the anther, and the pollen grain further develops into a pollen tube on the stigma and in the style. The pollen tube, when it reaches the embryo sac is the fully developed male gametophyte and is trinucleate, two sperm cells and one tube nucleus.

Systematic scientific efforts to improve genetic potential of crops in India were initiated in 1905 at the Imperial/Indian Agricultural Research Institute. In 1929, with the establishment of the Indian Council of Agricultural Research (ICAR), several associated developments took place in the first half of the 20th century leading to establishment of several crop-based institutes (sugarcane, cotton, jute, rice, oilseeds, tobacco, potato) and multidisciplinary institutes such as the Indian Agricultural Research Institute (IARI), Central Arid Zone Research Institute (CAZRI), and Central Plantation Crops Research Institute (CPCRI). Additionally, a Project on Intensification of Regional Research in Cotton, Oilseeds and Millets (PIRRCOM) was implemented during 1950s with establishment of several research stations in different regions.

Several definitions of plant breeding have been put forward. All of these have a core component of the definition that is “the art and science of improving the heredity of plants for the benefit of the humankind” as mentioned by famous plant breeding teacher and a popular plant breeding text book author, J. M. Poehlman. N. I. Vavilov has defined plant breeding as “evolution directed by the will of the man”. The most modern definition of plant breeding by Bernardo (2002) is “plant breeding is the science, art, and business of improving plants for human benefit”. A few more definitions on these lines given by several other famous plant breeders are as follows.

To reduce the dependence on hazardous pesticides in modern agriculture, one of the most promising ways is to use insect-resistant cultivars. When available, planting resistant cultivars is one of our most effective, economically viable and environmentally sound tactics. The underlying concept of using host resistance to our advantage comes from the knowledge that most plants and animals are resistant to most potential insect attackers.

Fresh vegetables are essential part of a healthy diet as it is an important source of vitamins, minerals and fibers. The nutritional content of vegetables varies considerably, though generally they contain little protein, fat and varying proportions of vitamins such as Vitamin A, Vitamin K and Vitamin B6, pro- vitamins, dietary minerals and carbohydrates (Woodruff, 1995; Whitaker, 2001).

Biological control is a strategy which employs utilization of natural enemies to reduce the damage caused by noxious organisms to tolerable levels (De Bach and Rosen, 1991). This is the most benign method for reducing pest population in vegetable ecosystem. It opens an amicable platform for production of organic vegetables with good export value. Since the late 1950s, much of the insect control in vegetables has been based on the use of synthetic chemical insecticides.

Mites are small arthropods belonging to the sub-class Acari (also known as Acarina) and the class Arachnida. The scientific discipline devoted to the study of ticks and mites is called acarology. In soil ecosystems, mites are favored by high organic matter content and by moist conditions, wherein they actively engage in the fragmentation and mixing of organic matter (Nyle and Ray, 2009).

Vegetables are the largest important constituent of our daily diet as well as high value cash crops for small, marginal and large scale growers. These are rich in proteins, vitamins, minerals and dietary fibre which are essential for our normal body functions, prevention of malnutrition and deficiency diseases. Vegetables also play key role in neutralizing the acids produced during digestion of fatty foods and also provide valuable roughages which help in movement of food in intestine.

Endowed with varied agro-climatic situations, topography and soil type, India has been a leading vegetable producing country in the world occupying the second
position in vegetable production after China with an annual production of 87.53 million tonnes from 5.86 million hectares having a share of 14.4 per cent to the world production. With commercial cultivation of as many as 61 annual and 4 perennial vegetables, India is the most diverse vegetable growing country in the world (Prakash et al., 2006).

Protected cultivation practices can be defined as a cropping technique wherein the micro environment surrounding the plant body is controlled partially or fully as
per plant need during their period of growth to maximize the yield and resource saving. Cultivation of vegetables under protective structures such as net houses has become popular in recent years (Kaur et al., 2004; Cheema et al., 2004; Singh et al., 2004).

Elephant foot yam, Amorphophallus campanutatus Blume (= Arum campanulatum Roxb.) belongs to the family Araceae. It is also known as elephant yam, Elephant bread, Suran, Sweet yam etc. It is a native to Tropical Asia and is found throughout the plains of the Indian sub-continent and some other parts of South East Asia and Africa growing both wild as well as cultivated.

Leafy vegetables are the herbs that are grown for their edible greens (leaves). Leafy vegetables are also called pot-herbs, greens, vegetable greens, and leafy greens are plant leaves eaten as a vegetable, sometimes accompanied by tender petioles and shoots. They come from a very wide variety of plants. As per Singh and Arora (1978), about 220 species belonging to the families, Amaranthaceae, Chenopodiaceae, Araceae, Asteraceae, Convolvulaceae, Malvaceae, Nymphalaceae, Papilionaceae etc. occur in India.

Coriander, Coriandrum sativum L. is an erect annual herb belongs to the family Apiaceae. Coriander may also be referred to as Cilantro, Chinese parsley or Dhania. In India it is cultivated in Rajasthan, Gujarat, Madhya Pradesh, Tamil Nadu, West Bengal, Uttar Pradesh etc. The leaves of the plant are variable in shape, broadly lobed at the base of the plant. Leaves are slender and feathery higher on the flowering stems.

Curry leaf, Murraya koenigii (Linn.) is one of the most important plants exclusively known for its culinary and medicinal value. Leaves of the plant are widely used for flavouring food in Indian cookery. Leaves are also used in many Indian Ayurvedic and Unani prescriptions (Joseph and Peter, 1985). The whole plant including leaves, stems, flower, fruits and roots are used as tonic, stimulant, anti-flatulent, anti-diabetic, anti-oxidant (Khan et al., 1997) and anti-carcinogenic (Khanum et al., 2000).

Moringa oleifera Linn. belongs to the family Moringaceae, that consists of only one genus with about 13 species of deciduous trees (Keay, 1989). It is believed to be the native of India-Pakistan-Nepal borders, but now is becoming widely distributed and grown in several countries, particularly in tropical and subtropical regions (Satti et al., 2013).

Sweet potato, Ipomoea batatas (Linn.) originated in northwestern South America around 8000 - 6000 BC. The plant is a dicotyledonous, herbaceous, trailing vine which is the only economically important member of the family Convolvulaceae. The plant is generally characterised by starchy, succulent and tuberous storage roots; alternating palmately lobed leaves and medium sized sympetalous flowers which grow individually and vary in colour from white to varying degrees of purple (Austin et al., 1991).

In countries like India, where majority of the population are vegetarians, leguminous vegetables serve as the major source of protein in the diet. In the developing third world countries, especially for the poor, the major protein source in the diet are vegetable legumes. Most leguminous vegetables are rich in phosphorus, calcium, iron and a number of essential vitamins. Crops like soybean, groundnut and Bamabara groundnut are also rich in fats which are needed by the body to absorb vitamin A.

The green pepper or chilli is reported to be the native of tropical America (Thompson and Kelly, 1957). This was widely cultivated in Central and South America in early times and was unknown in Europe prior to the discovery of America. The chilli belongs to the family Solanaceae and genus Capsicum. Only four species are under cultivation, out of which the cultivation of the two, Capsicum pendulum and Capsicum pubescens, are restricted to South and Central America.

Members of the family Cruciferae commonly used as vegetable include Cabbage, Cauliflower, Broccoli, Brussels sprouts and mustard etc. The genus Brassica is known for its important agricultural and horticultural crops. A dislike for cabbage or broccoli can result from the fact that these plants contain a compound similar to
Phenyl thiocarbamide (PTC), which is bitter or tasteless to some people depending on their ‘taste buds’ (Theresa, 1995).

Tomato, Lycopersicon esculentum Mill. is an important vegetable cultivated throughout the world; both outdoors and under protected structures for fresh market consumption and processing. In India this nutritive rich vegetable is grown over an area of 0.60 m ha with an estimated production of 11.9 mt. Productivity of tomato in India is lower (18.6 t/ha) than the world productivity (27 t/ha) (Anonymous 2009). Tomato is grown in a wide range of climatic conditions across states of Andhra Pradesh, Orissa, Karnataka, Maharashtra, West Bengal, Bihar, Gujarat, Uttar Pradesh and Chhattisgarh.

Okra (Abelmoschus esculentus Moench), otherwise known as Lady’s finger or Bhindi is an annual malvaceous plant and the sixth important vegetable crop cultivated throughout the country mostly in kharif and summer seasons. Though it is reported to be originated from tropical and sub-tropical Africa, but it has gained much importance in India as the secondary centre of origin. India ranked first in okra production in the World and major okra producing Indian states are Uttar Pradesh, Bihar, Orissa, West Bengal, Andhra Pradesh, Karnataka and Assam (Anonymous, 2011).

Potato is one of the major non cereal food crops in the world and ranks fourth after rice, wheat and maize. Due to its high production potential per unit area and time, the crop has been recorded for sustaining millions of lives during the times of war and hunger. Native of South America, this crop was introduced into India in
early seventieth century. Currently India ranks 3rd for area and 2nd for production in the world [AICRP (Potato) Bulletin No. 2].

‘Cucurbits’ is a term coined by Liberty Hyde Bailey for cultivated species of the family Cucurbitacae (Robinson and Decker-Walters, 2004). Presently, the term has been used not only for cultivated forms, but also for any species of the family Cucurbitacae. Among vegetables, the cucurbits form one of the largest groups with their wide adaptation from arid climates to the humid tropics.

Brinjal (Solanum melongena Linn.) is one of the widely used vegetable crops and is popular in many countries viz. Central, South and South-East Asia, some part of Africa and Central America (Gurubban, 1977). It is also known as the aubergine, eggplant, melongene, guinea squash etc. Various data indicate that from the several species that evolved in Africa, one (Solanum incanum), gave rise to a distinct species which spread to South-East Asia as the wild ancestor of Solanum melongena (Lester, 1998).

Taxonomy is the science of identifying (discovering), describing, naming and classifying organisms. It is a complex summing up of knowledge starting with thorough analysis to base the synthesis that will end up in the name of a taxon. Correct identification of biological taxa is a necessary pre-requisite to all other enquiries about the biological world.

1.1. Terms and definitions

1.1.1. Landscape gardening

• Branch of floriculture deals with the study of ornamental gardening or garden features.
• Bringing an area or piece of land into a garden using naturally existing features like undulations, terraces and plain surface to have more naturalistic effect than artificial.

1.1.2. Ornamental gardening

• Place for growing plants which are consciously directed for ornamental or practical use.

1.1. Origin and distribution

• Most species are native to Asia, with smaller numbers are native to Europe, North America and North Western Africa.
• China roses are the ancestor of the present day popular roses.
• Native of Himalayan regions, Asia, China, Japan, Europe and North America.

1.2. Economic importance

• King of flowers
• Symbol of beauty, fragrance and used to convey of love.

1.1. Origin and distribution

• Centres of diversity - Central and South America, India, South East Asia with secondary centres of diversity in West and East Africa.
• Leaf amaranth - native of India
• A. tricolor L. (Syn A. gangeticus L), A. mangostanus, A. polygonoides, A. dubius, A. blitum (Syn: A. lividus)
• A. tristis L., A. viridis L. - Wild leaf types
• A. spinosus L., A. cruentus L., A. caudatus L. - Cultivated grain types

1.1. Origin and distribution

• Centre of origin is Central Asia, the Near East, Ethiopia and the Mediterranean
• There are two sub-species
  • Pisum sativum sub. sp hortense, the garden pea
  • Pisum sativum sub. sp arvense, the field pea

1.1. Origin and distribution

• Centre of origin is Peru, Bolivia, and South America in the Central Andean region.
• Introduced into India in early 17^th Century
• In India, cultivation of potato began first in Nilgiris in 1822.
• Mainly grown in Uttar Pradesh, West Bengal, Punjab, Karnataka, Assam and Madhya Pradesh.
• Commercial potato species - Solanum andigenum - not very common. Plants are thin and long stem, small and narrow leaflets. Flowers more profuse, long stolons and mostly coloured deep eyed tubers.
• Solanum tuberosum: More common, plants shorter and thicker stem,