eChapters

Introduction

Turnip is an important root crop which is very popular particularly in northern India. It is a cool season crop mainly grown as a fall or winter crop in the hills and winter crop in the plains. Turnip (Brassica rapa L. syn. Brassica compestris var. rapa) belong to family Brassicaceae. It has a chromosome number of 2n=2x=20. Two main centers of origin have been indicated. The Mediterranean area is considered to be the primary centre of origin of European type/temperate types. While Eastern Afghanistan with adjoining areas of Pakistan is considered to be another primary centre with Asia Minor, Transcaucasus and Iran as secondary centre. The parents of cultivated turnip are found in the wild form in Russia, Siberia and Scandnavia. It was cultivated by the ancients and ranked next to grapes and cereals in Italy. It was introduced in England probably in 1590 and United States in 1606 (Yawalkar, 1980). Turnips are now cultivated throughout the world.

Turnips are botanically biennial herbs, but are cultivated as annual root crops for both animal and human consumption. The turnip root contains 41.6% moisture, 6.2 g carbohydrates, 0.5 g protein, 0.2 g fat, 0.04 mg thiamin, 0.04 mg riboflavin, 43 mg ascorbic acid, 30 mg Ca, 40 mg P and 0.4 mg Fe per 100 g of edible portion. The turnip green contains 15,669 IU vitamin A per 100 g (Aykroyd, 1963). Turnip is grown for its enlarged root as well as for its foliage. Extra seedlings from thinning are often used as greens. The fresh roots are consumed in salads or cooked as vegetable or used in pickles. The young leaves contain high amount of ascorbic acid and iron, rank second in vitamin A content and are cooked as greens.

The fleshy thickened underground portion of turnip is actually the hypocotyl. The colour and shape of this underground portion vary with the cultivars and the roots are flat globular to top-shaped and long. The colour of under ground portion may be white or yellow, while that of above ground portion may be red, purple, white, yellow or green. A distinct tap root and secondary roots arise from the lower part of the swollen hypocotyl. Thickening begins in the central part of the hypocotyle, followed by the upper and lower parts. Normally, the roots attain edible maturity in 40-80 days depending on cultivar and climatic conditions.

Introduction

Radish (Raphanus sativus L., 2n=2x=18) is a root cum leafy vegetable suitable for sub tropical and temperate climate. Radish probably originated in Europe and Asia. It has been under extensive cultivation in Egypt since long. It was introduced to England and France in the beginning of 16^th century. In 1806, it was introduced to America. Radish does not exist in wild stack. It is believed to have originated from R. raphanistrum which is widely distributed as weed in Europe. Radish is primarily a winter crop but with the development and release of new varieties, it can be grown all the year round. The new varieties can withstand heat and does not bolt in spring. Radish is a favourite crop because of its quick growth and availability in 4-7 weeks.

Its fleshy roots are modified roots, developed from both the primary root and hypocotyl. The leaves and roots are consumed both as salad and cooked. The radish root is a good appetizer; its different preparations are useful in curing liver and gall bladder problems. Roots are also used in treating urinary complaints and piles. The juice of fresh leaves is useful as diuretic and laxative. Pungency in radish is due to volatile isothiocyanates while pink colour is due to pigment anthocyanin.

Radish is a good source of vitamin C containing 15-40 mg per 100g of edible portion. Roots also contain proteins, fat, minerals, fibre and carbohydrates, besides trace elements like aluminium, barium, lithium, manganese, silicon, titanium, fluorine and iodine. Pink skinned radish is generally richer in vitamin C than the white skinned type. Radish contains glucose as the major sugar and also contains fructose and sucrose in smaller quantities. Pectin and pentosans are also reported to be present. The leaves are good source of extraction of protein on a commercial scale and seeds are potential source for non-drying fatty oil suitable for soap making, illuminating and for the edible purposes.

Introduction

Peas (Pisum sativum L., 2n = 2x =14) are consumed as fresh vegetables or dry seeds throughout the world. In India, peas are grown as winter vegetable in plains and as summer vegetable in the hills. As field pea, it occupies about 0.45 m ha area in India, accounting for only about 2% of the total pulse area. About 90% of its area and production is limited to Uttar Pradesh alone. The area under vegetable peas is on increase. The acreage of vegetable pea in India is 2.72 lakhs ha with a productivity of 9.9 tons/ha. Pea is a rich source of protein (7.2% in green pea & 20 % in dry pea) and minerals (0.8%).

The geographical region comprising of Central Asia, the Near East, Abyssinia and the Mediterranean is considered as centre of origin based on genetic diversity. According to Blixt (1970), the Mediterranean is the primary center of diversity with secondary centers in Ethiopia and the Near East.

Garden pea, seeds have been observed in archeological excavations of Mohan Jodaro and Harappa, there are distinct hot weather tolerant and round-seeded varieties which carry high resistance to fusarium wilt and powdery mildew (Erysiphe polygoni). These varieties have a different use as a pulse crop for meeting protein requirements of common people. These are considered as intermediate stages of domestication of the present day vegetable (garden) pea, which is sweet and wrinkled-seeded. In fact, the quick spread of Arkel variety, an introduction from England in seventies, has displaced some of the native round-seeded varieties like Asauji, Hara Bonia, Hoshiarpuri, Kaparkheda, Kalanagni, Lucknow Bonia etc. there is need to conserve these valuable germplasm, before they are swept away by genetic erosion.

Introduction

Indian subcontinent is one of the twelve mega diversity centres for cultivated plants and their wild relatives. More than 15000 species of flowering plants are indigenous to this region, which include 160 species of economic importance, 320 species of wild ancestral forms and approximately 800 species of ethnobotanical origin. Global diversity in vegetable crops is estimated around 400, of which 80 originated in India. These indigenous vegetables have immense potential in meeting the vegetable requirement of the country. They are rich in nutritional value especially in proteins, minerals and vitamins. Many of these vegetables have medicinal uses. Most of them are not used to their potential and their popularisation is needed in meeting the vegetable requirement of the country in coming days.

Ash gourd (Benincasa hispida Cong.)

Ash gourd also known as Wax gourd (Benincasa hispida Cong.) belonging to family Cucurbitaceae, is cultivated for its immature and mature fruits used as vegetable and in confectionery and ayurvedic medicines. A small fruited medicinal ash gourd is also grown in Kerala which is good for people suffering from nervousness. In areas where winter is mild, the crop can be grown throughout the year. The released varieties are KAU Local, Indu, Co.1, Co.2, APAU Shakthi, Karikumbala, Boodikumbala and IVAG -502. In addition, MAH-1 and MAH-2 are F1 hybrids released from private sector. The crop is raised by sowing seeds in pits at a spacing of 2.5 × 2.0 m in Tamil Nadu, 3.4 × 1.8-2.5 m in West Bengal and 4.5 × 2.0 m in Kerala. The seeds can also be sown in channels at a spacing of 2 × 0.5m. The crop is trailed on branches and twigs spread on the ground. The fruits are harvested at immature or fully ripe stage depending on demand. Immature fruits can be harvested 21 days after anthesis. Mature fruits for storage, long distance transport and seed extraction are harvested after full development of waxy coating on fruit surface. The average yield are 30-35 t/ha.

Introduction

Eggplant or aubergine {Solanum melongena L. Solanaceae), is indigenous to a vast area stretching from northeast India and Burma, to Northern Thailand, Laos, Viet nam and Southwest China and wild plants can still be found in these locations. There is a wealth of eggplant common names. Eggplant is a major fruit vegetable with world production exceeding 31 million tonnes (Mt). Leading producers are China (17 Mt) and India (8 Mt), Egypt (1 Mt), Turkey (0.9 Mt), Japan and Italy (0.4 Mt). Eggplant is particularly favoured in Asia where it has been cultivated for millennia, and in India it is considered King of Vegetables. Brinjal, native to India, shares 31 % area (5.1 × 10⁵ ha) and 28% production (82 × 10⁵ t) of the world (Anon., 2003). It contributes 9% of the total vegetable production in the country. Three states/provinces viz. Orissa (1.41 × 10⁵ ha), West Bengal (1.29 × 10⁵ ha) and Bihar (0.72 × 10⁵ ha) cover 67% of total brinjal area in India (Anon., 2006). It is widely adaptive and highly productive (17.78 t/ha) crop of tropical and sub-tropical regions. It is comparable with tomato for nutritional values like vitamin C, iron and fiber, thereby, can play an important role in combating malnutrition in under-nourished regions (Singh et al., 2001). However, genetic improvement, production technology, post harvest handling and plant protection measures are important for increasing the production, productivity and consumption of brinjal.

Plant genetic resources are the most valuable and essential basic raw material to meet the current and future need of crop improvement programme. A wider genetic base assume the priority in plant breeding research aimed as developing new varieties for increased crop production. PGR for food and agriculture are a reservoir of genetic adoptability, which act as buffer against environmental changes and economical challenges. The erosion of these resources results in a severe threat to the world long term food securities. The fundamental objective of the genetic resource conservation is the maintenance of genetic diversity within each of the species. In general PGR include all species which contribute to people by providing food, medicine, feed, fiber etc. PGR is our heritage which needs conservation for prosperity.

Genetic resources management is a complex process starting from the identification of a target gene pool for conservation to the use of genetic resources. Many of these activities not only generate but also require geo-referenced data (Spatial data). Analysis of these data can lead to a greater understanding of the eco-geographic representation of existing collections, increasing the efficiency of conserving and managing genetic resources and broadening our understanding of the distribution of genetic diversity. Genetic resource databases could potentially serve as an information resource to a broader scientific community, providing relatively independent global data sets to meet the unique needs of researcher. GIS can merge genetic diversity information with other georeferenced data such as population density, climate, topography and soils, adding value to genetic resources. GIS analysis can help develop conservation strategies, monitor genetic diversity, select potential collecting sites, design in situ reserves and enhance genetic resources use. Currently, GIS use is constrained by limited georeferenced information.

Phenotypic Diversity

Phenotypic diversity measures the portion of genetic diversity which is expressed phenotypically. So it varies with the character under study and the genetic background and the environment in which it is measured. The measures of genetic diversity based on variance of quantitative traits may be unreliable indicators of diversity in a population at the level of individual gene. But diversity at the molecular level (isozymes, RFLPs) may be a reasonable estimate of phenotypic diversity. The degree of differentiation is related to several biological attributes such as breeding system, mode of pollination and seed dispersal, life history, geographical range, successional stages, etc. The outbreeding populations are much less differentiated whereas the selfers or apomictic are strongly differentiated. Populations of outbreeders contain different alleles especially the rare alleles which contribute little to the diversity. Inbreeders should have greater interpopulations diversity and less intrapopulation diversity than the comparable outbreeders. Further, inbreeders are more prone to show an even distribution of their genetic diversity among populations and this makes their optimum sampling more difficult and any evidence of the geographic pattern of this diversity levels would greatly improve sampling efficiency but geographical and environmental factors rarely explain more than 50% variation.

Introduction

The Indian gene centre has rich diversity in vegetable crops. This diversity includes crops native to India like eggplant, parval, ridge gourd, sponge gourd, Colocasia sp., elephant yam and for centre of diversity for other vegetable crops i.e., Okra, Cucumber, Chayote, Chilli, Cucurbita etc. Rich diversity also occurs in introduced crops such as tomato, french bean, cowpea, leafy brassica, amaranth, yam and in cucurbits, bottle gourd, bitter gourd, coccinea, ash gourd, snake gourd and in bulbous crop like onion and garlic.

Genetic Resources of Vegetable Crops in India

Their diversity and conservation about 400 species constitute the global diversity in vegetable crops. This diversity is mainly distributed in seven-eight geographical regions, which represent the centres of origin and diversity as well. Among these, the regions possessing maximum diversity are the tropical American, Tropical Asian and the Mediterranean (q.v.) regions. In the tropical Asian region, both India and China hold maximum diversity.

Introduction

Germplasm identification as a part of a philosophy of consumer protection extends through the entire seed trade and allied industries, from plant breeders to food consumers. Increasingly, countries are introducing schemes for Plant Breeders (or germplasm) Rights. These reward breeders financially for their efforts and offer protection for their germplasm, but in turn require that new germplasm are distinct from others and also uniform and stable in the expression of their characteristics. Since, the genetic variations in plants and plant populations are of considerable interest to have desirable traits to develop a commercial variety. Biochemical and molecular biology based data and its analysis for information regarding selection have been realized of utmost importance.

Introduction

Global food productivity will have to rise significantly to satisfy an expanding world population. Increased vegetable production is one option towards the efficient conversion of natural resources into food stuffs. As a group, vegetables are a diverse range of herbaceous plants that do not belong to any particular botanical species, genus or family. Individual members may be at various stages of domestication. Vegetables are typically annual herbaceous species, whose plant parts (leaves, stems, flowers, fruits, roots or tubers) are consumed as fresh or as cooked product, and as an additional source of vitamins, minerals, fibre, phytochemicals, protein and/or calories. Health benefits are also claimed for some vegetable species, mainly due to antioxidant activity and capacity to scavenge free radicals.

Domesticated plants have been fundamentally altered from their wild relatives; these species have been moved into and adapted to new environments. They have become dependent on the farmer’s hand and they have been reshaped to meet human needs and wants. Modern crops are the results of thousands of years of these evolutionary processes. Like all biological evolution, crop evolution involves two fundamental process; the creation of diversity and selection (Harris and Hillman, 1989). Crop evolution is distinguished by two types of selection; one natural and another artificial or conscious. These evolutionary processes must continue in order for agriculture, a living and evolving system to remain viable.

In the hands of plant breeder’s sexual hybridization is a powerful tool for producing superior plants by combining characters distributed in different members of a species or different species of a genus. Genetic variability within the species has been efficiently utilized by breeders in their efforts to improve crops. However, the existing variability in a breeding population may not be sufficient for modern plant breeding purposes, and thus great efforts have been made to broaden the existing gene pool of crops through utilization of wild germplasm.

Introduction

Tomato is one of the most important vegetable crops which is grown throughout the world. It is a rich source of minerals, vitamins and antioxidants and considered as a protective food. It is used in several forms ranging from raw to processed one and is widely used as one of the food ingredient. Its popularity is due to its versatility and the variety it lends to the human diet. Tomato leads all other vegetables in terms of total global production except potato which is often classified as starchy staple. India stands fourth in terms of global tomato production after China, USA and Turkey. The total production of tomato in India during 2007-08 was 10.26 million tones which accounted for 8.9 % of total vegetable production. Though concrete historical records of its first introduction into the country from its primary centre of diversity in South America do not exist, tomato is presumed to have been brought here during the second half of the 18^th century through Far Eastern countries. It is believed that tomato was introduced in India during British period in the year 1828 by Royal Agri -Horticultural Society, Calcutta. The story of tomato transformation from an exotic fruit to a popular dietary item and a major item of commerce all over the world is one of the most fascinating events in the saga of crop domestication. As recently as 1900, tomato was avoided in the belief that it was poisonous because of its known relation to the nightshades and other toxic members of the nightshade family. The tomatine is a predominant alkaloid mainly present in foliage and green fruits. However, at the stage of ripening, tomatine is degraded into an inert compound which is not toxic.

Introduction

Cucurbits, belonging to the family Cucurbitaceae are among the most ancient cultivated plants. The term cucurbit was coined by Liberty Hyde Bailey for cultivated species of Cucurbitaceae. Other vernaculars applied to the family and several of its members are ‘gourd’, ‘melon’, ‘cucumber’, ‘squash’ and ‘pumpkin’. The Cucurbitaceae consists of two well defined sub families, eight tribes representing varying degrees of circumscriptive cohesiveness and about 118 genera and 825 species (Jeffrey, 1990). It is mostly tropical and sub tropical in distribution and only a few species occur in temperate regions. Some are semi desert or saprophytic in nature. The Indian sub continent is considered to be the centre of origin for a number of wild and cultivated crops. Chakravorty (1982) reported that 36 genera and 100 species of cucurbits are found in India. Cucurbits are cultivated in 8.5 m ha area in world giving a production of 17.9 mt. While in India a total of 4.5 mt cucurbits are produced from an area of 0.42 m ha area (FAO, 2004).

Cucurbitaceae is one of the most genetically diverse groups of plants in the plant kingdom. As a family and as individual crop, cucurbits epitomize adaptive differentiation and evolutionary divergence. Not only may cultivars within a crop vary significantly in their characteristics, but the same cultivar grown in distinct areas can have different needs in response to disparate local growing conditions. Cultures and ethnic groups may have different cultivar preference and horticultural practices, which also increase morphological diversity within a crop.

Cucurbits are of tremendous economic importance as food plants. They are extensively grown in mixed cropping of more than one kind in long and meandering river beds. Of various improvements approaches possible, breeding of superior pure lines and hybrid cultivars of cucurbits utilizing locally adopted land races are the most important methods which will have far reaching impact on increasing the production and productivity of cucurbits.

Introduction

Cucumber is one of the most popular vegetable of cucurbitacae family and grown worldwide for its freshly harvested fruits. Fruit yield in cucumber is suppressed due to its fruiting habit. Fruits developing from the first pollinated flower inhibit the development of subsequent fruits. This phenomenon is broadly known as crown fruit dominance or first fruit inhibition. Therefore, in mechanical once over harvest of seeded cucumber, only one to two fruits per plant are developed. Fruit set inhibition is less in seedless cucumber when compared to its seeded counter part. Parthenocarpy is the development of fruit without fertilization. This phenomenon was first studied in cucumber byNoll (1902) who introduced the term parthenocarpy. In parthenocarpic lines, a larger proportion of photosynthates could be diverted to fruit tissue instead of producing seeds. Partheonocarpic habit has become indispensable to greenhouse cucumber production because it alleviates the need for bees. Individual plants in the greenhouse produce many fruits simultaneously, with many fold higher yield in comparison to field grown crop.

Greenhouse or parthenocarpic cucumber production is very popular in many areas of the world. The fruits of parthenocarpic cucumber are mild in flavour, seedless and have thin edible skin that requires no peeling. Fruits are generally 10-14 inches in length and 200 g in weight. The parthenocarpic varieties require no pollination for fruit setting. If pollination occurs, the fruit will form seeds, shape of fruit will be destroyed and develop bitter taste. It is therefore essential to prevent bees and other pollinators entering the green houses. Cucumber cultivars are selected for commercial use based on quality and yield characteristics. An important quality factor is the shape of the cucumber referred to as the length to diameter (L/D) ratio. This becomes important to meet specifications of the number of whole cucumber units per container. The cool marine environment causes the L/D ratio of many cultivars to be undesirably long and therefore many of the useful cultivars for other production regions have been eliminate. The presently available parthenocarpic cucumber cultivars have been bred and developed in Europe under similar climatic conditions and produce fruit with desirable L/D ratios. The parthenocarpic cultivars have potential for improvement of both the L/D ratios and fruit interior quality.

Introduction

‘Cole crops’ is a general term used to describe several vegetables in the Brassicaceae family. It is an important and highly diversified group of vegetable crops grown worldwide that belongs to Brassica oleracea (Monteiro and Lunn, 1998) and includes particularly six Brassica crops (cabbage, cauliflower, Brussels sprouts, broccoli, kale and knol kohl). All of these crops can trace their history to a common ancestry of wild cabbage originating in the Mediterranean and Asia Minor regions. Cole crops are one of the oldest cultivated plant groups in the world. They are cultivated in Europe since very ancient time from where they have spread to other parts of the world (Nieuwhof, 1969). All the cole crops (except few cauliflower, broccoli and cabbage types) require chilling temperatures for about two months to transform from vegetative phase into reproductive phase. However, the period of chilling requirement differs according to the kind of crop and varieties. Cole crops are also commonly called as European or biennial vegetables due to their cool temperatures requirements and two season requirement to complete their life cycle.

Major Resources of Cole Crop Germplasm

Germplasm is any form of the hereditary material from an organism. Genetic resources encompass all the various forms of germplasm that are available for collection, storage and use. The genetic diversity of crops, represented by traditional local cultivars and wild relatives has been disappearing rapidly during recent decades. Initial concern was noted by H.V. Harlan in the 1930s (Harlan and Martini, 1936) but by the 1960s, modern plant breeding and land-use changes accelerated loss and stimulated the realization that genetic resources in regions of diversity were being lost at an alarming rate. To conserve the genetic variation within the cole group, a comprehensive base collection of the cultivated forms of Brassica oleracea has been established at the vegetable gene bank of Horticulture Research International (HRI), Wellesbourne, (U.K.). Gene banks have also been established at Instiuut de veredeling van Tuinbouwgewssen, Wageningen, the Netherlands and the Instituto del Germoplasm, Bari, Italy (Van der Meer et al., 1984) for conservation of genetic resources. The International Board for Plant Genetic Resources (IBPGR) has recognized HRI as an international centre for conservation of Brassica oleracea (Innes, 1975). Large number of collections of cole crops is also available with the United States Department of Agriculture, Plant Introduction Service. In India, National Bureau of Plant Genetic Resources (NBPGR), New Delhi has been assigned the duty of conserving the germplasm of all crops, including vegetables. Germplasm of all the cole crops is being maintained at the Indian Agricultural Research Institute, New Delhi (tropical types) and its regional station at Katrain (temperate types). Other major institutes maintaining germplasm of cole crops include Punjab Agriculture University, Ludhiana, G. B. Pant University of Agriculture & Technology, Pantnagar, Indian Institute of Vegetable Research, Varanasi, Dr. Y.S. Parmar University of Horticulture and Forestry, Solan and SKUAS&T, Srinagar.

Introduction

Cowpea, {Vigna unguiculata (L.) Walp.} is an important food legume in the semi-arid tropics covering Asia, Africa, Southern Europe and Central and South America (Henriet et al., 1997; Mortimer et al., 1997; Van Ek et al., 1997). It is a drought tolerant and warm weather crop. Therefore, well adapted to the drier regions of the tropics where other food legumes do not perform as well. It fixes atmospheric nitrogen and grows well even in the poor soils with more than 85% sand and with less than 0.2% organic matter and low levels of phosphorus (Kolawale et al., 2000 and Sanginga et al., 2000). Also, it is shade tolerant and therefore, compatible as an intercrop with maize, millet, sorghum, sugarcane and cotton as well as with several plantation crops (Singh and Emechebe, 1998). Coupled with these attributes, its quick growth and rapid ground cover checks soils erosion and in situ decay of its roots and nitrogen rich residues improves soil fertility and structure which together have made cowpea an important component of cropping system in the dry savannas of the sub-Saharan Africa (Carsky et al., 2001 and Mortimer et al., 1997).

Cowpea is cultivated in about 14 million ha world wide with about 5 million tons annual production. However, a substantial part of the cowpea production comes only from few countries. Nigeria is the largest producer and consumer of cowpea with about 5 million ha area and about 3 million tons production annually. Niger Republic is the next largest producer with 3 million ha and over 1 million ton production. Northeast Brazil grows about 1.5 million ha of cowpea with about 500.000 tons production. In the southern USA about 40,000 ha of cowpea is grown with an estimated 45,000 tons annual production of dry cowpea seed and a large amount of frozen green cowpeas. Even though exact statistics are not available, India is the largest cowpea producer in Asia and together with Sri Lanka, Pakistan, Nepal, Bangladesh, Thailand, Indonesia and other far eastern countries, there may be over 1.5 million hectares under cowpea in Asia.

Introduction

Leafy vegetables belong to an important group of vegetables and are highly nutritious due to their richness in Vitamin A (Carotene), Vitamin C, Folic acid, Riboflavin, Thiamine and minerals like Iron, Calcium and Phosphorus etc. Appreciable quantity of proteins is also found in these crops. They also provide a variety of phyto-nutrients including beta-carotene, lutein and zeaxanthin, which protect cells from damage, age-related problems, among many other effects. Dark green leaves even contain small amounts of Omega-3 fat. They are available at cheaper rate in the market as compared to other vegetables. They provide roughage and have an important place in the balanced diet. It is recommended that a daily intake of 100 g and 40 g of leafy vegetables in the diet of woman and man respectively. India is the 2^nd largest producer of leafy vegetables in the world after China, accounted for about 10% of the world production (Singh et al., 2006) but, the production levels of these leafy vegetables are very low because of lack of availability of high yielding varieties. Leafy vegetables are those crops from which leaves and associated parts are harvested for use as vegetable. The leaves of about 700 different kinds of plants belonging to125 families are consumed in the form of vegetables. The major leafy vegetables grown in the country are amaranth, spinach beet (desi palak), spinach and fenugreek. In addition to this a number of under-utilized annual crops are also grown as leafy vegetables in specific regions. Leafy vegetables are usually grown in kitchen and market gardens. Tender stems and leaves of a number of perennial crops are rich sources of vitamins and minerals and are used for cooking. Though leafy vegetables have high nitrate and oxalate levels, but adverse nutritional effects are not to be feared with a consumption level of 100-200 g per day. The commonly grown major leafy vegetables and their wild relatives are listed below

Introduction

The North-eastern region comprises of eight states viz. Assam, Arunachal Pradesh, Meghalaya, Manipur, Mizoram, Nagaland, Tripura and Sikkim lying between 21.5^o N - 29.5^o N latitudes and 85.5 ^o E - 97.3 ^o E longitudes. It has a total geographical area of 262180 Km² which is nearly 8 % of the total geographical area of the country. In the whole of NE region, about 35 % area is plain and the remaining 65 % area is under hills. Whereas in Assam plains account for 84.44 % of its total geographical area and the remaining 15.56 % area is under hills. Net sown area is highest in Assam (34.12 %) followed by Tripura (23.48 %), however, Arunachal Pradesh has lowest net sown area in the region. Cropping intensity is highest in Tripura (173 %) followed by Manipur (152.1 %), Mizoram (136.36 %) and Assam (123.59 %). About 0.5 million hectare area is under shifting cultivation in the NE region. Out of 4.4 million hectare net sown area, roughly 1.4 million hectare lies in hilly sub region and at least 1.3 million hectare suffer from serious soil erosion problem.

The diverse agro climatic conditions, varied soil type and abundance of rainfall offers immense scope for cultivation of different types of horticultural crops, including fruits, vegetables, flowers, plantation crops, tuber and rhizomatous crops and crops of medicinal and aromatic importance. The region has rich diversity of different vegetable crops and both indigenous tropical vegetables and temperate vegetables are grown to a considerable extent. The major vegetables grown in the region are brinjal, cabbage, cauliflower, okra, onion, pea, potato, tomato, knol-khol, radish, carrot, French bean and different cucurbitaceous crops. Tuber and rhizomatous crops like tapioca (cassava), sweet potato, Dioscorea, colocasia, ginger and turmeric grow abundantly in the region.

Introduction

Genetic resources are the building blocks for new varieties. The Indian gene centre is floristically extremely rich. Most of the tropical and sub-tropical fruits believed to have originated from Hindustan and Indo Malaya-Region. Hindustani gene centre possess a rich diversity of 152 crop plants distributed in different agro-ecological regions of India (Arora, 1985). The Indian sub-continent is one of the centers of origin and diversity of vegetables crops. Around 80 species of major and minor vegetables occur in wild forms (Choudhury, 1967, Seshadri 1987). Among the 118 genera belonging to the Cucurbitaceae family Cucurbita, Cucumis, Citrullus and Lagenaria genera are of great importance. There is tremendous genetic diversity within the family, genera and even within species level. The adaptation range varies from tropical and subtropical regions to extreme arid desert and in temperate regions from Tarai belts to higher altitudes. Extreme germplasm collections are maintained at different centers of the world which represents valuable resources for breeding even in wild form, primitive cultivars, landraces/ folk varieties/ farmer’s selection in a much localized pockets. Now we have very good strains for highly nutritive value, multiple disease resistant and extended shelf lives from our local material through intensive breeding.

Indigenous plant germplasm are adapted component of plant biodiversity. Such adapted components are more valuable resources either as a cultivar or as a parental line in hybridization programme. It might be also a putative material for biotechnological treatment for tolerance to biotic, abiotic factors or nutritional and quality components. Indigenous germplasm can be basically of two types, one which has been domesticated and subjected to human intervention, the other one may be called wild plants or wild relatives and still in the process of evolution without the human intervention. Biochemically the cucurbits are characterized by bitter principles, called cucurbitacins. Great variety of cucurbits contains bitter principle in portion of the plant at some stage of development. Cucurbitacins are tetracyclic triterpenes having extensive oxidation level. Bitter principals found in roots differ from those in fruits. Seedlings specially radicals contains cucurbitacins which are considered primary. The pollen also carries bitter principles and hence when bitter pollen fertilized non-bitter ovule the resulting fruit will be bitter known as metaxenia effect. Cucurbits are consumed in various forms i.e. salad (cucumber, gherkins, longmelon), sweet (ash gourd, pointed gourd), pickles (gherkins), deserts (melons) and culinary purpose. Some of them (e.g. bitter gourd) are well known for their unique medicinal properties. In recent years, abortifacient proteins with ribosome-inhibiting properties have been isolated from several cucurbit species, which include momorcharin (from Momordica charantia), luffaculin (from Luffa operculata), trichosanthin (from Trichosanthes kirilowif) and beta-trichosanthin (from Trichosanthes cucumeroides). Among these, Trichosanthin is of particular interest because its ribosome-inhibiting properties have been found to be effective in inhibiting the replication of human immunodeficiency virus (HIV), indicating its potential as a therapeutic agent for AIDS. In cucurbits three conditions are found (i) fruit and vegetative parts bitter (ii) fruit not bitter but vegetative parts bitter (iii) bitterness absent in both vegetative parts and fruits. Hence some kind of co-evolutionary relationship between cucurbits found and they are very helpful during evaluation of germplasm.

Introduction

Okra, Abelmoschus esculentus (L.) Moench, is annual herb grown in tropical and subtropical parts of world for green tender immature fruits and consumed as cooked mostly fresh but sometimes sun dried or frozen also used as vegetable. Some parts of plant and roots are used for medicinal as well as purification of sugarcane juice. Green fruit contains vitamins, calcium whereas seeds possess 13-22 per cent edible oil and 20-24 per cent edible protein. India is leading producer of okra and exporting fresh as well as processed fruits to other countries and also ranked first in area (0.48 million ha.), production (3.5m tones) and productivity (9.8 t/ha) during 2005 against the world area (0.78 million ha.), production (4.99 m tones) and productivity (6.4t/ha).

Introduction

Cell and tissue culture techniques are becoming increasingly popular as alternative means of plant vegetative propagation. Plant tissue culture involves asexual methods of propagation and its primary goal is crop improvement. The success of many in vitro selection and genetic manipulation techniques in higher plants depends on the success of in vitro plant regeneration. Crop breeding and rDNA technology require the widespread use of reliable true to type propagation and better regeneration methods. Plant regeneration can be grouped in to different categories of enhanced release of axillary bud proliferation, organogenesis and embryogenesis. The oldest practical application of tissue culture techniques is the propagation of disease free plants from meristem tip culture. Meristem tip consisting of dome and one or two subjacent leaf primordial with a size up to 0.25 mm are aseptically cultured in appropriate nutrition media. The resulting plants are disease free because the pathogen is not generally present in the meristematic cells.

The aim of germplasm conservation is to ensure the availability of useful germplasm at any time. Breeding programs rely heavily on locally adapted ancient plant varieties and their wild relatives as sources of germplasm. Further, the continuing search for high yielding varieties of crop plants with resistance to pathogens and pests warrants the availability and maintenance of large collections of germplasm. In species which are propagated through seeds, it is economical to preserve the seeds. These seeds are dried to water content of 5 - 8% and then stored at a temperature of -18° C or lower and low humidity. In case of vegetatively propagated species, preservation of germplasm heavily taxes manpower and land resources. As in vitro techniques are becoming more important in crop improvement through the use of somatic cell genetics, the material produced in vitro will have to be conserved in vitro. The in vitro system is extremely suitable for storage of plant material, since in principle it can be stored on a small scale, disease free and under conditions that limit growth. Germplasm storage in vitro is crucial for the future development and safety of agriculture.