eChapters

INTRODUCTION

Potato plays a vital rolein foodsecurityworldwide. It is the third most important food crop, afterrice and wheat. It is a nutrient-rich crop which provides more calories,vitamins and nutrients per unit area than any otherstaple crops. FAO declared potato as the crop to address future global food security and poverty alleviation during2008. In Indian agriculture, potatoplays a very important role as it alone contributes about 21 percent of the total vegetable area and 26 percent of total vegetable production of India (DAC&FW, 2017a). As per FAOSTAT data for the year 2017,India with48.6 million t is ranked second in potato productionin the world, onlybehind Chinawith 99.2 million t (Figure 1).

Tomato is relatively recent addition to the world’s vegetable crops. Now became one of the most important vegetable crops and is popular & widely consumed. It is being grown extensively in USA, China, India, France, Israel and Netherland.
 
It is used in fresh and processed form. Among the vegetables maximum attempts have been made to improve this crop because of its short duration, easy cultivation and large number of seeds per fruit and this has made it an ideal crop for many research works. An exclusive Tomato Genetics Co-operative located in University of California, USA, published genetic information on the crop and maintains a large number of     collections which have already been thoroughly catalogued.
 
Origin and Distribution: Native of Peru in South America and spread to North America by migrating birds. Largest number of wild tomato forms is present in Mexico. Spanish Priests introduced it to Europe in around 1550. In Europe it is known as Poma amoris = Amorous apple (Love apple). Wild relatives found in narrow elongated mountainous regions of Andes in Peru, Ecuador and Bolivia and Galapagos islands. Domestication and cultivation of tomato appears to have first occurred outside its centre or origin. Domestication of tomato was first done by Mexican people i.e. Red Indians, which is considered as secondary center of origin. Now cultivated tomato is common in Peru but recently added to their diet.

India is the primary centre of origin of brinjal. Decandolle (1904) reported it as native of Asia. In Europe it is not known earlier (before 17th early). According to N.I Vavilov, the egg plant originated in Indo–Burma region and china and spread to South Europe, china and Japan. Vavilov (1951) suggested China a centre of origin of brinjal. Crop is restricted mainly to South and South-East Asia, Southern Europe, China and Japan. Wild brinjal types are available in Southern Coastal area of Africa.

Botany

Solanum melongena’ L. var. esculentum - round or egg shape 
var. serpentinum – long, slender type 
var. depressum – dwarf brinjal plant 
It is often cross pollinated crop due to heteromorphic flower structure (heterostyle)

‘Chili’ (European literature) word derived from ‘Chile’ which means any pepper in Mexico and Central America. Peppers are an important constituent of many foods adding flavor, colour, vit.C and pungency and therefore indispensable to the world food industries. China, Mexico, Japan, Turkey, Indonesia, Pakistan and India are major producers.
 
Origin:  The cultivated chilli is of South American origin. Authorities generally agreed that capsicum originated in the new world (America) tropics and sub tropics. Pepper pods are there from 2000 year old burials in Peru. Decandolle concluded no capsicum was indigenous to the old world (Europe), peppers unknown in Europe until 16th century. Chilli was introduced into Spain by Columbus on his return trip in 1493 and cultivation spread from Mediterranean region to England by 1548 and to central Europe by close of 16th century. Portuguese carried capsicum from Brazil to India prior to 1885 and cultivation was reported in china during late 1700’s.

All capsicum species have 2n = 24. Polyploids with 2n = 36, 48 and  aneuploid 2n = 25 reported

If there is scarcity of food, potato can come to the rescue because of its virtue of high yielding (40-50 t/ha) and is a staple food. It produces more calories per unit area and per unit time than any other major food crops. Potato which is the staple food of Europeans and Americans belong to the highlands of Andean mountainous regions of Peru and Bolivia where it has been cultivated since 6000 years.
 
Origin: Peru, Bolivia. Many wild species occur at Mexico and Central America. Potato was introduced to Europe in 16th century by Spaniards (Salaman, 1966) and in early 17th century to India most probably by Portuguese. There are some suggestions based on linguistic and botanical evidences that potato might have been introduced in India directly from South America across the Pacific Ocean. Earlier potatoes were grown in hilly areas of North and South since British settlers brought the varieties continuously from UK and these were bred for long day temperate conditions of Europe. But in India potatoes are grown in short day-subtropical plains. The seed stocks used to degenerate due to accumulation of viruses and loose their yield potentiality. Seed potatoes were mainly imported from Europe i.e. U.K., Italy and Netherlands and Burma till the beginning of Second World War and the imports gradually reduced.

Okra has higher average nutritive value (ANV) of 3.21 which is higher than tomato, egg plant and most of the cucurbits except bitter gourd (Grubban, 1977). Its roasted seeds are substitute for coffee. It is one of the export potential crop where it accounts to 60 per cent of fresh vegetables (excluding potato, onion and garlic) exported from India. Importing countries are Middle East, Western Europe and USA.

Origin and Distribution : It belongs to the genus Abelmoschus established by Medikus, 1787, however de Candolle (1824), treated it as section of Hibiscus.   In 1924 Hochreuntiner reinstated the genus Abelmoschus of Medikus stating that calyx, corolla and stamen fused together at the base and fall as one piece after anthesis (deciduous) where as in case of hibiscus these are persistent. Though the genus is of Asiatic origin, the origin of cultigen Abelmoschus  esculentus is variable like India (Master, 1875) Ethiopia {de Candolle (1883) and Vavilov (1957)}, Western Africa (Chevalier, 1940 and Mardorct, 1947) and Tropical Asia (Grubban, 1997) and probably its might have entered India at the end of 19th century. Cultivated okra is of old world origin. It arose as a cultigen in the Abyssinian region (Ethiopia). Wild species are indigenous to Africa.  Three wild species Abelmoschus tuberculatus, A. moschatus and A. ficulneus are native to India. Introduced to Mediterranean region to Europe and Asia. But during Columbian period it was introduced to America.  It still turnout to be polyphyletic (many places) in origin. A. tuberculatus (Indian origin) and an unknown species cross resulted into A. esculentus.

Cucumber

Cucumber (Cucumis sativus) is a warm season vegetable used as salad and for pickling purpose has little or no frost tolerance.  Growth and development favoured  by temperature above 200C.  Cucumber cultivars generally classified as pickling or slicing types. In India often cucumbers (Cucumis sativus) are confused with melons (Cucumis melo ) as morphologically some variants of these species overlap, but they are not cross compatible. Kakri of North India are different from kakri of South India and Maharashtra. In Maharastra and South India cucumbers are referred as kakri but, in North India Kakri means Long melon i.e. Cucumis melo Var. utilissima.

Melons (Cucumis melo) are annuals with climbing, creeping or trailing vines of length up to three meters. The desert types quench thirst and add to the nutrient content of main diet. The non-desert types are used as vegetables. Muskmelon (Cucumis melo., 2n=2x=24) encompasses the netted, salmon -flesh cantaloupe, the smooth – skinned green fleshed ‘Honey Dew’, the wrinkled, white – fleshed, ‘Golden Beauty’ and several other dessert melons in USA.

Origin: Not known with certainty but, 40 or more wild species of Cucumis are found to occur in the tropics and subtropics of Africa. Wild species of Cucumis occur in Africa and it is likely that it originated in African continent. It does not appear to have been known to the ancient Egyptians, not to the Greeks and seemed to have reached Europe towards the decline of Roman Empire. Although melon was introduced into Asia at a comparatively later date there are undoubtedly well developed secondary centers of origin of C. melo in India, China and then Southern USSR. In India Oriental pickling melon (C. melo var conomon) and snap melon (C. melo var momordica) are unique and have considerable variability in Western Ghats of India. They are popular desert and preserving melons cultivated in Warm humid tropical condition of South India. It is also considered that China as primary center of origin and Indo-Burma as secondary center of origin. It has been introduced to Europe and from Europe to the USA by the early travelers. At present muskmelon is being cultivated throughout the world under tropical and subtropical climatic conditions. Polymorphism in leaf, flower, fruit shape and colour (Kirkbride, 1993), allowed the classification of horticulturally important melons into seven groups.

Water melon is tender to frost and most of cultivars require relatively long growing season. Plant growth and fruit development are fallowed by higher temperature and abundant sunlight. Atmospheric humidity greatly regulates fruit and foliage diseases.

Taxonomy and Origin: Ealier it was classified as Citrullus Vulgaris Schrod. But in 1963 Thieret called attention to the correct name, C. lanatus (Thumb) Mansf. Africa is centre of origin of the genus. In 1857 David Living Stone, the famous missionary explorer found both bitter and sweet melons grown together in Africa and native people used them as source of water. Cultivation is prehistoric as there are pictures made in ancient Egypt. Early cultivation occurred in Mediterranean area and as far as India also and It was brought to USA by European colonist as early as 1629.

Ridge gourd or Ribbed gourd (Luffa acutangula Rox b. L) and Sponge gourd or Smooth gourd (Luffa cylindrica) have diploid chromosome number  2n=2x=26. Luffa has old world origin in Subtropical Asian region including India (Kalloo, 1993). These two species are inter-crossable. F1 plants generally, intermediate between the parents and showed various irregularities like, univalants, rings and chains of 4 chromosomes, chromatids bridges and fragments at metaphase and thus the species are not easily crossable and the F1 plants appear to be of not much practical value. The genus is monoecious annual vine, tendrils are branched, flowers are yellow, anthers are free and pistil has three placentas with many ovules and stigma are three and bilobate. Fruits oblong or cylindrical and rind becomes dry on maturity.

It is rich in iron and Vit –C and native of tropical Asia particularly eastern India and Southern China (Sheshadri 1986 Mini Raja et al., 1993).
 
Botany: Monoecious annual, staminate flowers small, yellow and borne on slender pedicel. Pistillate flowers solitary have small pedicel, flowers are yellow, leaves segmented pentamerous. Filaments 3, two are bilocular and one is unilocular. There are three short styles ended with three bilobed or divided stigmas.

Chromosome 2n=22: 6-centromere in middle, 3-submedian, 2-subterminal  (Vargheuse, 1973) 

Momordica dioica: 2n=28

Momordica cochincniensis: Sweet gourd of Assam

Germplasm

KAU-Vellanikara, IIHR-Bangalore, NDUAT-Faizabad, CSAUAT-VRS, Kalyanpur, BPUA&T-Pantnagar and IARI- New Delhi are the major sources of bitter gourd germplasm.

Bottle gourd (Lageneria siceraria) 2n=2x=22 is also known as white flowered gourd. Most important vegetable of ancient China.
 
Origin : According to De Candolle (1882) Bottle gourd has been found in wild form in South Africa and India. However, Cutler and Whitaker (1962) are of the view that probably it is indigenous to Tropical Africa on the basis of variability in seeds and fruits. This species appear to have been domesticated independently in Asia, Africa and the New world (Heiser, 1973).
 
Botany: It is monoecious, annual vine with soft pubescence. Leaves are cordate ovate to reniform-ovate, Flowers are white, solitary, open at night and has hairy ovary. Fruit shape is cylindrical, oval egg shaped, club shaped, round and other shapes also appeared.

Genetics of Important Traits

Bitterness: Single dominant gene (Path and Singh, 1950)

Fruit colour: Monogenically controlled (Kalloo, 1993)

Two major genes are involved for fruit shape (Path and Singh, 1950). Single gene for fruit colour involved (patchy v/s white) and reported by Path and Singh (1950). Monogenic recessive inheritance for andromonoecious sex form is reported by Singh et al. (1996). Hermaphrodite sex form is characterized by long corolla (3.5-4.5cm instead of 2.5-3.5cm in normal). In hermaphrodite condition fruits bears prominent blossom scar.  Long fruit conditioned by AA genotype and Round fruit is due to aa genotype where Partial dominance is reported (Kushwaha, 1996).

Squashes and Pumpkin (Cucurbita, spp, 2n = 2x = 40) are the words quite often used interchangeably. However, the term squash is more commonly used for C. pepo which is consumed as an immature fruit. The term pumpkin is normally applied to the edible fruit of any species of Cucurbita utilized when ripe as a table vegetable or in pies.
 
Origin:  The genus Cucurbita is native to America.  The center of diversity is the tropics near the Mexico- Gauatamla border. The archaeology evidences indicate that these were widely cultivated in South Western United States, Mexico, and northern South America in Pre-Colombian times i.e. prior to 1492 A.D.

C. pepo : Summer squash : Some varieties belong to winter squash, pumpkin and marrows. It has bushy habit, peduncle hard, sharply angular, grooved, leaves broad, triangular in outline, usually with deep lobes little or no expansion of peduncle at fruit attachment. In North America it is commonly found.

C. mixta : Squash, cymlins, cushaws: It is used as summer and winter squash, leaves shallowly lobed, hard corky peduncle. This is also commonly found in North America.

Keys to Genera
Flowers zygomorphic, stamens definite, corolla papillonacious, petals imbricate: 1I, 1O, 3 IO
Group I:    Herbs or shrubs, leaves imparipinnate, leaf lets entire, pods usually dehiscent, or if indehiscent usually small, a few seeded. Cyamopsis
Group II:    Herbs low or climbing, leaves paripinnate, leaflets ending in a tendril or bristle, style bearded, pods dehiscent.
Sub group 1: Staminal tube oblique at mouth, pod compressed. Vicia
Sub group 2: Staminal tube truncate (cutting off) at mouth, pods torpid.  Pisum
Group III:     Climbing or prostrate and rarely erect
Sub group 1: style bearded, stamen diadelphous
Sub-sub group: stigma terminal: Dolichos
Sub-sub group: Stigma oblique: Keel spiral : Phaseolus
Keel not spiral: Vigna
Sub group 2: Style not bearded, stamen monodelphous: Canavalia
Group IV:    Trees or shrubs, some times climbing, pods indehiscent: Psophocarpus

Garden Pea
It is cool season crop cultivated throughout the world. It is extensively grown in temperate zone and is restricted to cooler altitudes in tropics and winter season in sub tropics. It is rich source of proteins (25.6%), amino acids and sugars. It goes well with other vegetables in vegetable dish.

Among beans, the most popular bean is French bean and it has wider distribution and larger gene pool. Various names are associated with cultivars viz., Snap bean, salad bean and green bean and all these names associated are with beans of vegetable types. The names haricot bean, dry bean and navy bean are applicable to pulse types. String bean, dwarf bean and pole bean applicable to growth forms. It is known as Rajmah in Hindi, Tingalawari in Kannada and Fras bean in Punjabi. Cultivars preferred for Canning, frozen and freeze-dried are having round pods. Fresh market cultivars are flat or oval shaped. Yellow pod cultivars are also grown. Generally fresh market cultivar yields higher in temperate region than in tropical region. Beans are said to be antidiabetic and good for bladder burns, cardiac, carminative, diuretic.

Origin and Distribution: Phaseolus vulgaris was domesticated in Central America about 7000 years ago and it is also thought to be domesticated in Brazil and Northern Islands and was introduced to Europe in 16th century. Vavilov (1951) reported that Phaseolus vulgaris originated in South Mexico and Central American centre of origin. The first cultivar has been selected in Peru. From Peru it spread to Europe and to Asia. Wild species P. aboriginus in North West Argentina is considered as the wild progenitor of French bean. Based on growth habit, crop can be classified into pole type, semi pole type and bush type. Former varieties are more string types. American origin of P. vulgaris is questioned by De Candolle (1584). Southern part of Mexico and Central America are considered to be primary centre of origin. While secondary centre lies in Peru-Bolivian-Ecuador of South American continent. In Europe, French bean spread rapidly in 16th and 17th centuries and reached England by 1594. From Europe, it was introduced to India during 17th century (Simmonds, 1976).

Southern pea / black eyed pea are the other names associate with cowpea. It is grown for vegetable and also as pulse crop and varieties are specific for use.

Classification of Cowpea
1.    Vigna unguiculata (L.) Walp. Cv. Sesquipedalis: yard long bean or asparagus bean: Possess long pods and used as vegetable. 
2.    Vigna unguiculata (L.) Walp. Cv. Cylindrica: dual purpose, i.e. vegetable and pulse 
3.    Vigna unguiculata (L.) Walp cv. Radiata: Pulse type.
 
More emphasis is given for pulse types for crop improvement. Less attention is given to vegetable types. Pole and bush types are available in vegetable type. Cowpea improvement is from vine to bushy habit with low fiber content and low glucosides and increased protein content.
Origin and Distribution: Cowpea is in cultivation from ancient times in the tropics of old world. Country of origin is uncertain. In India, it has been known from the vedic times. Vavilov (1939) considered India as the primary centre of origin. But it is now generally agreed that Africa is centre of origin since wild forms are found in Africa and in Asia wild forms are absent (Smartt, 1990). Faris (1965) concluded that, cowpea arose from domestication of wild form Vigna unguiculata ssp dekindtiana in West Africa. But domestication is actually happened in Ethiopia and dissemination was West wards Africa, East ward across the Indian Ocean. It has spread from Africa to Asia and Europe through Egypt. Introduced to West Indies in 16th century by Spaniards and was taken to USA around 1700. Now cowpea is widely distributed throughout the tropics and subtropics.

Dolichos bean is known as Lablab bean, hyacinth bean or sem. Grown as field crop in MP, Maharashtra, AP and TN. Genus Dolichus is renamed as Lablab (Syn. D. lablab, D. purpureus, Lablab niger, L. bvulgaris) and Lablab purpureus name is widely accepted. Dolichos lablab L. (synonyms Lablab purpureus (L.) Sweet.) is leguminous pod vegetable grown in tropics and few temperate countries. Lablab niger var. lablab is synonym to Dolichos lablab var. typicus where long axis of seed is parallel to suture and is vegetable type. Lablab niger var. lignosus synonym to Dolichos lablab var. lignosus where long axis of seed is perpendicular to suture and is pulse type.

Onion

Onion is very popular vegetable crop grown worldwide. Consumption is in the form of fresh, frozen, and dehydrated bulbs and green bunching onion. Origin of Allium cepa is still somewhat mystery. Vavilov (1951) suggested that the onion originated in the area of Pakistan. Others have suggested Pakistan, Iran & the mountain areas to the north (Jone& Mann, 1963). One fact is certain that the onion has been around in its present edible form for thousands of years. Onion recorded in tombs as early as 3200 B.C. It was mentioned as a food in the bible and in the Koran with reference thought to be around 1500 B.C. In addition to being a food considered by people, plant is having certain healing power. Some early drawing indicates that onions were used in spiritual offerings.

Cabbage

Cabbage is an important crop in USA, Northern European countries, Russia, Japan & Australia and its breeding occurs here, but Holland and Japan are the major breeding countries. It is also being cultivated in India and crop improvement work is taken up in India also.

Origin and General Botany: Historical evidence indicates that modern hard head cabbage cultivars descended from wild non headed Brassica originated in the Eastern Mediterranean and in Asia Minor. The Celts and Late Romans are responsible for spread cabbage throughout Europe. Latin name Brassica derived from Celtic word “bresic” meaning cabbage. Over a period hard headed evolved in Northern Europe and loose headed and heat resistant types evolved in South Europe. Cabbage was first introduced to America in 1541 by French explorer Jacques Cartier (planted seeds in Canada) and earlier colonist introduced the crop in to India also. Round headed types-are evolved earlier than flat (evolved in 17th or 18th century).  Broccoli, Cauliflower, Brussels Sprout, Collards, Kale, and Kohlrabi are all readily intercrossed members of this species.

Cauliflower follows cabbage in importance with regard to area and production in the world. However in India Cauliflower is more widely grown than cabbage. This crop grows at a latitude 11°N to 60°N with average temperature ranging from 5- 8°C to 25-28°C. It can stand to the temperature as low as -10°C and as high as 40°C for a few days. Italy and India are the major countries growing CF on large scale. Important cauliflower growing states in India are UP, Karnataka, West Bengal, Punjab and Bihar. It is commonly grown in Northern Himalayas and Niligiri hills in south.

Origin and Distribution: Cauliflower is thought to have been domesticated in the Mediterranean region since, the greater range of variability in the wild types of B.oleracea is found there (Nieuwhof, 1969). Wild Cole warts are still found in wild state in sea cost of England and Denmark and in the North West France and various localities from Greece to Great Britain. The Cole crops, including cauliflower and cabbage have descended from a common Kale like ancestor, the wild cabbage (B.olearcea var. sylvestris L.) which is still found in western and southern Europe and North Africa (i.e, sea coasts of England and Denmark and in North West France and various localities from Greece to Great Britain). Cyprus and area around Mediterranean courts are considered to be the primary centers of origin for Cauliflower. It is also reported that cauliflower is originated from a related species. B.cretica. As per Bosewell (1949), it originated in the islands of Cyprus from where it moved to other areas like Syria, Turkey, Egypt, Italy, Spain and North Western Europe. Cornish types originated in England fallowed by temperate types originated in Germany and Netherlands in 18th century. The present Indian tropical cauliflowers developed as a result of intercrossing between European and Cornish type. In India tropical types with resistance to high temp and high rainfall conditions have been developed. Tropical types are grown in Indian plains from May to September, followed by temperate types known as snowball cauliflower.

Amaranthus is one of the main genera of large and taxonomically diverse group of leafy vegetables. Amaranthus is the cheapest dark green leafy vegetable because of low production costs and high yield. It is often described as poor man’s vegetable.

Origin and Distribution: The main vegetable type Amaranthus tricolor L. originated in South or South East Asia, particularly in India. Budhist monks and Muslim invaders took the crop to neighboring countries. Another vegetable type A. dubius shows diversity in Central America, Indonesia, India and in Africa. A lividus is a popular leafy vegetable in Southern and Central Europe. Amaranthus included 50 to 60 species.

Carrot (Daucus carota L.) is a cool season root vegetable and temperature is the important factor affecting root shape and colour, besides soil type and moisture content of soil. It provides an excellent source of vitamin A and fiber in the diet. The genus Daucus, which include carrot, has many wild forms that grow mostly in the Mediterranean region and South West Asia. Representatives are found in Africa, Australia, & North America. For Daucus carrot L. it is generally agreed that Afghanistan is the primary center of genetic diversity and therefore the primary source for dissemination. Asia Minor, Afghanistan, North West India, Iran and Turkey are the centers of origin of carrot. Banga (1957& 1963) has provided evidence that the purple (anthocyanin) carrot together with a yellow variant spread from Afghanistan to Mediterranean area as early as 10th and 11th century. It is known in Western Europe in 14th and 15th century, China in 14th century and Japan in 17th century. The European carrot (Carotene carrot) derived from the Asiatic (anthocyonin containing) form of carrot (tropical carrot).  Afghanistan is the centre of diversity of the purple coloured carrot (anthocyanin). Integration of Asiatic and European carrots has given the present day forms. The yellow coloured (carotene rich) forms were also thought as mutants of anthocyanin carrots. The yellow mutants were traced in Asia Minor in 10 and 11th centuries, Spain in 12th century, North Western Europe in 14th century and England by 15th century.  The crop was introduced to China during 14th century and to Japan during 17th century. D. carota and D. sativus are only cultivated species of the genera with Chromosome No. 2n = 18. All forms have same chromosome number. 

It is a popular root crop having wide range of adaptability, grown in Japan, Koria, China, India and other European countries.

Origin and Distribution: Radish was an important food in Egypt during 2000 BC.  Fossils study reveals that, it was a food as early as 2700 BC. It spread to China during 500 BC and to Japan during AD 700. Variability of crop decreased from Europe to China and from there to Japan. Recent study indicates that East of Mediterranean, most probably China was the centre of origin of the crop. This means Europe and Asia are the probable places of origin.

Beta vulgaris 2n = 2x=18 is an important vegetable crop in Eastern and Central Europe and it belongs to family Chenopodiaceae. It is of lesser importance in Western Europe and USA where it is known as garden beet. The swollen roots are consumed as vegetable and salad. The other types which are non-horticultural forms are known as sugar beet, mangold and fodder beet.
Origin: Leaf beet is the earliest domesticated form. It is believed to be originated from Beta maritima known as sea beet which is indigenous to Southern Europe. 
Botany: Biennial producing enlarged hypocotyl (roots) and rossette of leaves in first year and flowers and seeds in second year.

Turnip is the root vegetable cultivated in cooler season or temperate regions of the globe. Brassica rapa L 2n = 2x = 20 is formerly known as B. campastris subsp rapifera. Swede (B. napus var. napobrassica) is directly related to turnip.
Origin: It is originated in cooler part of Europe, presumably from biennial oilseed forms. It was known to Greeks and Romans at beginning of Christian era. It was introduced to Britain from France by Romans and into North America by the early European settlers in the 17th century.

Sweet potato Ipomea batatas(L). Lam. is an asexually propagated vegetable. It is grown in most of the tropical and subtropical region of the earth. In USA production extended to temperate regions. Vines as well as roots are eaten or fed to live stock. It is the source of industrial starch and potential source of the alcohol. Among the major tuber crops cultivated in India sweet potato rank third after potato and cassava in area and production.

Origin: Available evidence suggests South Mexico through Central America and Northern South America as the probable center of origin. It is perennial but handled as annual. Its hardiness and drought tolerance are well recognized.

Family: Convolvulaceae, Chromosome number: 2n=90

It is the only known natural hexaploid morning glory. Most of the wild species are diploid (2n=30). Hybridization is restricted with in species because of its hexaploidy nature. Extensive variability with in species is observed. Tuber is the fleshy subterranean stem or shoot but in sweet potato tuber is a root, and hence it cannot be a tuber (common error). It is a perennial, and the storage root is capable of continued enlargement and does not mature in the sense of reaching some final size or stage of development. From the stand point of function, the root system consists of absorbing roots and fleshy storage roots.

Cassava (Syn: Tapioca) Manihot esculenta (Crantz) (2n = 2x = 36) (Hindi : Mravuli) is perennial shrub cultivated in tropics for its starchy tuberous roots. It is one of important tuber crops cultivated in tropics because of its high carbohydrate yield per unit land and labour and its adaptation to poor soil and water stress and its tolerance to dominant pest and diseases. Cassava contains cyanide, the toxic principle which limits food and feed value. In cassava the glycoside linamarin and lotaustralin are converted to hydrocyanic acid, a potent toxin, when come in contact with linamerase, an enzyme that is released from rupture of cells. Tuber peel contain significantly higher amount of glycosides than the pulp. It can be removed by cooking in water for about 5 minutes.

Vegetables are important accompaniments for the main course of meal, which is by and large a carbohydrate-based food (wheat, rice or millets). It not only makes the meal more palatable, but also wholesome with its diverse color, smell and taste. More importantly it facilitates the easy movement of food through the bowel, better absorption by the body and till the elimination. Besides hunger satiation, it helps to maintain the health by providing the essential micronutrients and prevent lifestyle disorders.

As a nutritious food, it provides the vitamins, minerals and phyto-chemicals which are required in small quantities for physiological processes and metabolic activities. They are cheap sources of beta-carotene, vitamin-B complex, folic acid, vitamin C, vitamin E, etc. They are rich in minerals like iron, calcium, magnesium, phosphorus, etc., and dietary fibres. It has now been proved that minerals are better absorbed by the body in presence of several other factors of plant matrix, than as mineral supplements. It also provides small amounts of carbohydrates and proteins. Vegetables are important as protective foods as their consumption prevents many diseases. They are important sources of antioxidants and phytochemicals. Each vegetable has been found to have certain specific phyto-chemical which besides being a free radical scavenger, is also inhibitor of certain conditions responsible for disease development.

Among the vegetables, tubers like cassava, potato and sweet potato being highly rich in carbohydrates, served as staples for several countries for very long time, in the history. For the same reason, there are a variety of food products based on these tubers. Others like carrot, radish, beetroot, and turnip in root vegetables, onion and garlic among bulbous crops; tomato, brinjal (egg plant), okra and capsicum among fruit vegetables serve as sources of phytochemicals (carotenoids, anthcyanins, lycopene, betalain, capsicum, bassiniloids, etc.). Beans, peas, cowpea, and other leguminous vegetables are important sources of proteins and leafy vegetables (greens) contribute to the much-needed minerals, vitamins and fibre (roughages) in the diet. Allicin and diallyl disulphide found in onion and garlic control blood cholesterol besides being anti-bacterial. The diphenylamine in onion is effective against diabetes. The ‘Charantin’ found in bitter gourd have hypoglycaemic activity. Diosgenin in yams are used for manufacture of contraceptive drugs. Cole crops like cabbage, cauliflower, Brussel sprouts and sprouting broccoli have anti-carcinogenic properties mainly due to hydrolysed glucosinolate derived isothiocynates and indoles. Similarly, health benefits and curative properties of many indigenous and exotic vegetables have been mentioned in several classical texts of India and China.

Cucurbits form an important and a big group of vegetable crops cultivated extensively in this country. This group consists of a wide range of vegetables, either used as salads (cucumber) or for cooking (all the gourds) or for pickling (cucumber) or as dessert fruits (muskmelon and watermelon) or candied or preserved (ash gourd). They are of tremendous economic importance as food plants.

2.1. Ash Gourd (Benincasa hispida)

Ash gourd (Benincasa hispida L.) belongs to the family Cucurbitaceae. The winter melon, also called white gourd, ash gourd, or “fuzzy melon”, is a vine grown for its very large fruit, eaten as a vegetable when mature. It is the only member of the genus Benincasa. This is a monotypic genus and the only cultivated species is Benincasa hispida (Thunb) Cogn, commonly known as ash gourd or petha. It has a Sanskrit equivalent ‘Kooshmanda’ indicating its antiquity in India.

Originally cultivated in Southeast Asia, the ash gourd is widely grown in China, India and other parts of East Asia. The immature melon has thick white flesh that is sweet when eaten. By maturity, the fruit loses its hairs and develops a waxy coating, giving rise to the name wax gourd, and providing a long shelf life. The ash gourd is known by many other names in India regional wise like komora (Assamese), pethakaddu (Hindi), boodagumbala (Kannada), Kumbalanga (Malayalam), Kohla (Marathi), neer poosanikai (Tamil) and Boodida gummadikaya (Telugu).

Uses

Ash gourd have enormous medicinal properties as it makes a valuable place as a popular natural cure of ailments in traditional medicinal practice. Being low in calories it is an ideal vegetable for diabetic patients and good for weight control. It also acts as a good detoxifying agent.

As per Ayurveda, ash gourd is used to treat epilepsy, asthma, lung diseases, urine retention, internal haemorrhage, and cough. It is said that the fruit juice is also effective in cases of mercury poisoning and snakebite. It could also treat mouth cancer, protecting teeth and gums when a mouth gargle of the juice is done regularly. It is also effective in bleeding of gums. Ash gourd is easily digestible and keeps the body cool. It is a natural blood purifier.

Cole crops are a group of vegetables belonging to the family Brassicaceae (Syn: Cruciferae) and include cabbage, cauliflower, knoll khol, kale, Brussel sprouts, sprouting broccoli, etc. Cole crops are found spread all over Europe from the Mediterranean region, which is supposed to be the centre of origin. In the ancient Egyptian and Asian civilization, there was mention of cole crops and also by Aristotle in his writings on ‘Enquiry into plants’ there was mention about three types of coles. It is believed that it was first collected for food at the beginning of Neolithic times before being cultivated, and the cultivated forms of cabbage group like, cabbage, savoy, kales, collard, broccoli, Brussels sprouts, cauliflower and kohlrabi gradually originated from wild species through mutation, human selection and adaptation.

Among the cole crops in India cauliflower and cabbage are the two most important crops while Kohlrabi is grown very less. In India it is cultivated in states of Uttar Pradesh, Karnataka, Maharashtra, Bihar, West Bengal, Punjab and Haryana. It is also grown in milder climates in southern India like Ooty, Bangalore, etc.

3.1. Cabbage (Brassica oleracea L.f. alba)

Cabbage, Brassica oleracea Linne (Capitata Group) is a popular vegetable belonging to the family Brassicaceae (or Cruciferae) and is used as a leafy green vegetable. It is in the same genus as the turnip – Brassica rapa. Cabbage leaves often have a delicate, powdery, waxy coating called bloom. The occasionally sharp or bitter taste of cabbage is due to glucosinolate(s). Cabbages are also a good source of riboflavin.

In India cabbage is widely grown in the states of Uttar Pradesh, Orissa, Bihar, Assam, West Bengal, Maharashtra and Karnataka.

Cultivars/Varieties: Cabbage cultivars are classified on the basis of colour of head and maturity. In India white cabbage is important and these are available in pointed, round and flat shapes. Of these round cabbages are preferred. Common cabbage varieties grown are Golden Acre, Pride of India, Copenhagen Market, Red Acre, Pusa Drum Head, Pride of India, Pusa Agethi, Pusa Muktha, KGMR-1, Kateri, Hardam and Nakshatra.

In Solanaceae family there are 85 genera, which includes both tuberiferous and non-tuberiferous plants. Among the non-tuberiferous, tomato, brinjal and chilli are the important fruit vegetables.

4.1. Tomato (Lycopersicon esculentum Mill.)

Tomato has originated in Peru and Mexican region of South America. It got its name form the azetc work “Tomatl”. In India tomato is the second largest cultivated vegetable after potato. Though it is produced in almost entire country, the major producer states are Andhra Pradesh, Karnataka, Orissa, West Bengal, Bihar, Gujarat, Madhya Pradesh and Maharashtra.

Cultivar/Varieties: A large number of varieties/hybrids of tomatoes are under cultivation. The most popular among them are Arka Rakshak, Arka Samrat, Arka Saurabh, Arka Vikash, ARTH 3, ARTH 4, Avinash 2, BSS 90, CO3, HS 101, HS 102, HS 110. Hisar Anmol, Hisar Arun, Hisar Lalima, Hisar Lalit, Krishna, KS 2, Matri, MTH 6, NA 601, Naveen, Pusa 120, Punjab Chhuhara, Pant Bahar, Pusa Divya, Pusa Early Dwarf, Pusa Hybrid 1, Pusa Hybrid 2, Pusa Hybrid 4, Pusa Ruby, Pusa Sheetal, Pusa Uphar, Rajni, Rashmi, Ratna and Rupali.

Uses

Tomato adds richness to any dish it is added. Besides using for culinary purpose tomato is also used as salad and dressings and also as adjuvant in several locally available fresh snacks. It is used for thickening of gravies in many Indian curries. As a processed product tomato sauce and ketchup are on top of favourites. It is not only delicious in taste but also rich in its medicinal value. The pulp and juice are mild aperient, a promoter of gastric secretion and blood purifier. It is also considered to be intestinal antiseptic. It is said to be useful in sour mouth, canker of mouth and chronic dyspepsia.

Carrot, radish, turnip and beet root are major root crops grown in India. In addition, root crops like rutabaga, parsnip, parsley, chervil and celeriac are grown in a limited scale in different parts of the world. There are several other roots and modified underground plant parts that grow in forests and consumed by tribes, but they are not commercially cultivated. Carrot, radish, turnip and beet root are generally consumed as cooked vegetables or fresh salads or as pickled vegetables.

5.1. Carrot

Carrots belong to the Umbelliferae family, named after the umbrella-like f lower clusters that plants in this family produce. As such, carrots are related to parsnips, fennel, parsley, anise, caraway, cumin and dill. Carrot, Daucus carota L. is believed have been primarily originated in Afghanistan, South western Asia and Mediterranean region. Daucus carota ssp. Carota is the most common wild form in Europe and South West Asia, and the present day cultivated carrots have most probably originated from this sub-species.

Haryana, Andhra Pradesh, Punjab and Tamil Nadu, Karnataka, Uttar Pradesh and Assam are the major producers of carrot in India.

Cultivars/Varieties: Varieties with long, orange coloured and smooth roots are preferred in India. Both indigenous and exotic varieties having different root length, shape and colour are grown. Temperate or European type varieties are Nantes, Half long, Early Nantes, Chantenay, Chaman, Pusa Yamadagni and Ooty-1, which require low temperature of 4-8°C for flowering. Tropical or Asiatic type varieties do not require low temperature for flowering and can be grown in plains also. The varieties belonging to this group are Pusa Kesar, Pusa Meghali and Hisar Gairic. Some varieties like Gold King, Indian Kuroda and Super Kuroda are also marketed by private seed companies.

6.1. Potato (Solanum tuberosum L.)

Potato, Solanum tuberosum, is a starchy, tuberous crop belonging to the Solanaceae family. The name potato originally referred to a type of sweet potato, batata, in Spanish. Potatoes are occasionally referred to as “Irish potatoes” or “white potatoes” in the United States, to distinguish them from sweet potatoes. The potato was believed to be first domesticated in the region of southern Peru and extreme northwestern Bolivia between 8000 to 5000 BC. The potato diffused widely after 1600, becoming a major food resource in Europe and East Asia. Greater geographic mobility of farmers led to the rapid spread of potato cultivation throughout China, and India. China is now the world’s largest potato producer and nearly one third of the world’s potatoes are produced in China and India.

Today potato is the fourth major food crop after rice, wheat and maize in the world. In India potato is a very important crop and are mainly produced in the states of Uttar

Cultivars/Varieties: Most of the improved potato varieties were developed by CPRI, Kufri, Shimla. Most of the earlier varieties released as clonal selections derived from foreign varieties have been replaced with high yielding new varieties from the same institute. The popular varieties under cultivation now are Kufri Sindhuri, Kufri Chandramukhi, Kufri Jyothi, Kufri Lauvkar, Kufri Muthu, Kufri Dewa, Kufri Badshah, Kufri Bahar, Kufri Lalima, Kufri Swarna, Kufri Jawahar, Kufri Ashoka, Kufri Megha, Kufri Sutlej, Kufri Pukhraj, Kufri Chipsona-1, Kufri Chipsona-2 and Kufri Giriraj.

Uses

Potatoes are used in different ways like boiled, fried, baked and roasted. Potatoes are used to brew alcoholic beverages such as vodka, potcheen, or akvavit.They are also used as food for domestic animals. Potato starch is used in the food industry as, for example, thickeners and binders of soups and sauces, in the textile industry, as adhesives, and for the manufacturing of papers and boards. Many companies are exploring the possibilities of using waste potatoes to obtain polylactic acid for use in bioplastic products; other research projects seek ways to use the starch as a base for biodegradable packaging. Potato skins, along with honey, are used in folk medicine for burns in India. Burn centers in India have experimented with the use of the thin outer skin layer to protect burns while healing. The potato is best known for its carbohydrate content, which is in the form of starch. Because of its high starch content, it is a staple food in several parts of world including in some parts of India. A small but significant portion of this starch is resistant to digestion by enzymes in the stomach and small intestine, and so reaches the large intestine essentially intact, thereby, increasing its physiological significance. Besides these the potato also provides various other nutritional constituents to the body. Potato is also processed into various products like chips, powder, pappad, savory items.

7.1. Okra or Bhindi (Abelmoschus esculentus L.)

Okra (Bhindi) is a member of Malvaceae family, earlier known as Hibiscus esculentus, and is an annual vegetable crop grown from seeds in tropical and subtropical parts of the world. Okra, also known as “lady finger” or “gumbo”, is a highly nutritious green edible pod vegetable. Botanically, this perennial flowering plant belongs to the mallow family but is grown as an annual. It is named scientifically as Abelmoschus esculentus. Okra originated in tropical and subtropical Africa and India is suggested to be the secondary centre of origin. There are four species under Abelmoschus genus which includes both cultivated and wild forms. They are A. esculentus, A. manihot, A. caillei and A. moschatus. In India, Okra is widely cultivated in states of Andhra Pradesh, West Bengal, Orissa, Bihar Uttar Pradesh, Karnataka, Assam West Bengal, Orissa, Gujarat and Bihar.

Cultivars/Varieties: Okra varieties differ in growth habit, height of plant, presence of purple pigmentation and ridges on fruit. The popular varieties under cultivation in different parts of the country are Arka Abhay, Arka Anamika, Azad Kranti, Co 1, MDU1, Gujarat Bhindi 1, Harbhajan Bhindi, Hisar Unnat, Parbhani Kranti, Perkins Long Green, Punjab 7, Punjab 8, Punjab Padmini, Pusa A 4, Pusa Makhmali, Pusa Sawani, Red Bhindi, TN Hybrid 8 and Varsha Uphar. Besides, a number of hybride from many private sector agencies/seed companies are marketed. Of these, Varsha, Vijay, Adhunik, Panchali, Hybrid No. 6,7 and 8, Nath Sobha, Supriya, Sungro 35, Aroh 1, - 2, -3, -9 and are more popular.

Uses

Different parts of the plant are used for different purposes. Abelmoschus moschatus Medik. Leaves and seeds are considered as valuable traditional medicine. Abelmoschus moschatus is also called ‘musk okra’ a medicinal plant belonging the same family. The leaves and new shoots of this plant is also used as vegetable. The aromatic seeds of this plant are aphrodisiac, ophthalmic, cardio tonic, antispasmodic and used in the treatment of and intestinal complaints and anxiety.

Leguminous vegetables include peas, French bean, Lima bean, broad bean, cowpea, hyacinth bean, winged bean etc. They belong to the family Fabaceae (Syn. Leguminosae). These are cultivated either as sole crop is sometimes as intercrop. In some areas they are used in backyard cultivation also. Most of them are short duration crops and are self pollinated.

8.1. Peas (Pisum sativum L.)

The pea (Pisum sativum L.) is a very common nutritioius vegetable grown in cool season throughout the world. It belongs to the family Fabaceae (Syn. Leguminaceae) and genus Pisum. A pea is most commonly the small spherical seed or the seedpod of the pod fruit Pisum sativum L. The pea cultivars are grouped into several groups based on shape of seed, plant height, maturity and use of pods. This crop is cultivated for its tender and immature pods for use as vegetable and mature dry pods for use as a pulse. In both the cases the seeds are separated and used as vegetable or pulse. The central Asia is regarded as the place of origin for all legumes including pea. Based on the genetic diversity, Central Asia, the Near East, Abyssinia and the Mediterranean is considered to be its centre of Origin. Cultivated garden pea is not seen in wild state and it might have been originated from wild field pea or other related species. In India it widely cultivated states of Uttar Pradesh, Bihar, Haryana, Punjab, Himachal Pradesh, Orissa and Karnataka. Followed by Madhya Pradesh, Himachal Pradesh, Assam and Jharkhand.

Cultivars/Varietie: Peas varieties are grouped based on maturity (early, mid season and late) plant height (Bush or dwarf, medium tall and tall). The major cultivars under cultivation in different parts of the country are Arkel, Bonneville, Harbhajan, FC-1, Arka Ajit, UN 53-6 (whole edible type), Jawahar Matar 1, Jawahar Matar 2, Jawahar Matar 3, Jawahar Matar 4, Jawahar Matar 5, Jawahar Peas 83, JP 4 (JM 6), JP 19, Lincoin, Mattar Ageta 6, Pantnagar Matar 2, Pant Uphar (IP 3), P 88, PRS 4,Ooty-1 and VL 3.

9.1. Onion (Allium cepa L.)

The onion (Allium cepa), which is also known as the bulb onion, or common onion is the most widely cultivated species of the genus Allium. It has been used as food since time immemorial and is an important vegetable all over the world. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion (A. fistulosum), Egyptian onion (A. proliferum), and Canada onion (A. canadense). The vast majority of cultivars of A. cepa belong to the “common onion group” (A. cepa var. cepa) and are usually referred to simply as “onions”. The Aggregatum Group of cultivars (A. cepa var. aggregatum) includes both shallots and potato onions. Onion is suggested to have been originated in Asia, particularly Pakistan and Iran.

China is the largest onion producer in the world followed by India. Largest area under onion is in India followed by China. The major onion producing state are Maharashtra, Karnataka, Madhya Pradesh, Rajasthan, Gujarat, Bihar, Andhra Pradesh, Tamil Nadu and Orissa.

Cultivars/Varieites: Onion varieties differ in size, colour of skin, pungency and maturation. The most popular varieties under cultivation are Agrifound Dark Red, Agrifound Light Red, Agrifound Red, Agrifound Rose, Arka Bindu, Arka Kalyan, Arka Niketan, Arka Pragati, Baswant 780, Brown Spanish, Co-1, Co-2 Co- 3, Co-4, Early Grano, Hisar II, Kalyanpur Red Round, MDU 1 N-2-4-1, N-53, N-257-9-1, Punjab 48 (S 48), Pusa Madhavi, Punjab Red Round, Punjab Selection, Pusa Ratnar, Pusa Red, Pusa White Flat, Pusa White Round, Udaipur 101, 102 & 103.

Leafy vegetables are rich sources of provitamin-A, vitamin C and minerals like calcium, magnesium, iron, etc., They are the riches sources of roughes or fibres essential in human diet. The ICMR recommended dietary allowances of green leafy vegetables for adult women is 100g/day and men are 40g/day while for school children above 10 years it is 50g/day. Greens are rich in vitamins and minerals essential for healthy functioning of organs of body. Amaranth, beet leaf, spinach, fenugreek, etc., are the major leaf vegetables grown in India. In addition, a number of under-utilized annual crops are also grown as leaf vegetables in specific regions. Tender stems and leaves of a number of perennial crops are rich sources of vitamins and minerals and are used for cooking.

10.1. Amaranth (Amaranthus sp)

Amaranth is the most common leaf vegetable grown in India. Amarnath is an annual herb with erect growth and scarce to profusely branching habit. Stem is succulent and green or purple or mixed shades of these two. There are two sections in Amaranthus, viz., Amaranthus and Blitopsis. Majority of leaf cultivars grown in India belong to Amaranthus tricolor. Among the several kinds of greens Amaranthus occupy a special place because it has a large number of species grown in one or the other part of country.

Some of the important improved varieties released are CO-2 and CO-5 from TNAU, Coimbatore, Pusa Kiran, Pusa Kirti and Pusa Lal Choulia from IARI, New Delhi, Arka Arunima and Arka Suguna from IIHR, Bangalore. Amaranth are popular all over India by different names. While in northern parts it is popularly known as choulia, in south it is popularly called as keerai or cheera or koora or soppa. The general composition of amaranth is given below:

1. INFLORESCENCE

An inflorescence is a group or cluster of flowers arranged on a stem that is composed of a main branch or a complicated arrangement of branches.

1.1. Types of inflorescence

Inflorescences can be simple or compound.

1.1.1. Simple inflorescence

Inflorescence of sessile disc florets forming the capitulum

1.1.1.1. Indeterminate

Indeterminate simple inflorescences are generally called racemose. The main kind of racemose inflorescence is the raceme. The other kind of racemose inflorescences can all be derived from this one by dilation, compression, swelling or reduction of the different axes. Some passage forms between the obvious ones are commonly admitted.

1. FLOWERING

The flowering goes through a phase of vegetative growth producing more stems and leaves and a flowering phase where they produce the organs for sexual reproduction.

1.1. Synchronisation in flowering

Synchronous flowering refers to the phenomenon of coincident, simultaneous flowering of all population of a given species in a large region.

1. FRUITS

Fruit is a part of a flowering plant that derives from specific tissues of the flower, mainly one or more ovaries.

1.1. Types

1.1.1. Fleshy

1.1.1.1. Simple fleshy fruits

Develop from a flower with a single pistil.

1. SEED

A seed is defined as a ‘mature ovule’ or a reproductive unit formed from fertilized ovule, consisting of an embryo, reserve food and a protective cover.

Seed is the basic input in agriculture upon which other inputs are applied. A good vigorous seed utilities all the resources and realized as a reasonable output to the grower. It is wealth to the farmer, it is the yesterday’s harvest and tomorrow’s hope. Good seed in good soil realize good yield.

Seeds exhibit a great range of variation in shape, size, colour and behaviour. The most essential factor for the success of plantation is the ready availability of quality seeds. The quality of seed is totally responsible for the future return / performance of each and every seedling.

1. VEGETATIVE PROPAGULE

Vegetative propagation or asexual propagation is the method of propagating plants with the use of organs other than the seed and spore. In contrast to sexual propagation, the union of the male and female sexual gametes (fertilization) is not a requisite to the production of new plants. Hence the word “asexual”, which means “without sex” or “not sexual”.

1. OVULE DEVELOPMENT

The development of ovule occurs within the ovary, which provides a location for nurture and development of the female gametophyte, its sexual fusion with in the male gametophyte, and embryo development, survival, and eventual regrowth (Fig. 1). Ovule growth begins as a small outgrowth within the nucellus. As megasporogenesis and megagametogenesis continue, the region of the nucellus that is to become the ovule enlarges and differentiates into definite morphological characteristics. Secondary outgrowths, or collars (integuments), soon appear around the periphery of the nucellar outgrowths and envelop it. These usually consist of the inner and outer integuments and ultimately become the testa (seed coat) of the mature ovule.

1. APOMIXIS

Development of seed without fertilization. When the seed formation occurs without sexual fusion, the process is known as apomixis. This occurs by several mechanism, however all apomitic seed have genetic material only from the female plant Apomixis may or may not require pollination and pollen tube germination to initiate seed formation, however sexual union.

1. DEFINITION

Artificial seed technology involves the production of tissue culture derived somatic embryos encased in a protective coating. Artificial seeds have also been often referred to as synthetic seeds. However, the term ‘synthetic seed’ should not be confused with commercial seeds of a synthetic cultivar which is defined as an advanced generation of an open pollinated population composed of a group of selected inbred clones or hybrids. The concept of artificial or synthetic seed is shown in Figure 1.

1. SEED MATURITY

Harvesting should be done after the attainment of physiological maturity, when the seeds reached complete maturity to avoid harvesting of immature and ill-filled seeds.

1.1. Physiological maturity

It is the stage of accumulation of maximum drymatter within the seeds. It is expressed by maximum seed weight, germination and vigour potential. The moisture content of the seed at this stage is around 25-30% depending up on the species.

1.2. Harvestable maturity

The physiological maturity is represented to a seed and this maturity will not be the same for all the seeds of a single plant / population, due to continuous differential flowering habit. Hence, the stage of attainment of physiological maturity by 80% of the population is considered as the harvestable maturity stage. The moisture content of the seed will be lesser than the physiological maturity stage (18-20%).

The chemical composition of seeds is basically determined by genetic factors and varies among different species and seed parts (Table 1). However, it is influenced by environmental and cultural practices.

1. INTRODUCTION

In general, seed dormancy refers to lack of growth due to any external or internal cause. It also refers to a state in which viable seeds fail to germinate even when given favourable environmental condition i.e. adequate moisture, appropriate temperature regime, a normal atmosphere and in some cases light.

There are various degrees of dormancy varying from very slight to very strong (deep). Sometimes the development or degree of dormancy changes during the lifetime of the seed, usually as a response to external conditions. Hence, dormancy may be innate, develop, be broken and redevelop in seed.

Several types of dormancy exist, and sometimes more than one type of dormancy occurs in the same seed. In nature, dormancy is broken gradually or by a particular environmental event. The type of event that may break dormancy depends on dormancy type. Dormancy caused by a hard seed coat may be overcome by a gradual or an instant abrasion, and darkness induced dormancy by exposure to light. In seed handling, the natural dormancy breaking mechanism is applied or simulated during the process of pretreatment. “Pretreatment” is a term used for conditions or processes applied to break dormancy prior to germination, while “treatment” is used for application of pesticides for control of pests and diseases.

1. INTRODUCTION

In plants, seed dormancy is controlled by temperature, light and hormones. Unlike animals, which secrete hormones from special glands, hormones are always present in plant cells. Each plant hormone plays multiple roles, depending on the site of action, the life stage of the plant and the hormone’s concentration. A plant hormone is any chemical that is produced in one part of the plant that has a targeted function elsewhere. Certain hormones induce and keep seeds in a dormant state, while others cause seeds to break dormancy and initiate germination They are stored in regions where stimulus are and then released for transport through either phloem or mesophyll when the appropriate stimulus occurs. These are chemical messengers influencing many patterns of plant development

The first theory is that the five classic plant hormones, auxin, cytokinins (CKs), gibberellins (GAs), ethylene, and abscisic acid (ABA), plus the new plant hormones, brassinosteroids (BAs), and salicylates or salicylic acids (SAs) can be gathered into three groups. These are growth hormones, stress hormones and shock hormones. Auxin and CKs are growth hormones. Ethylene, GAs, and brassinosteroids are stress hormones. ABAs and SAs are shock hormones. All three types of hormones are similar in that they fall within the classic definition of an intercellular hormone. They are made by a cell and are meant to affect the behavior of other cells, either in nearby tissue or at the opposite end of the plant.

ABA, also known as abscisic acid plays a direct role in dormancy release and germination. Ethylene and the gibberellins group of hormones are indirectly involved.

1. SEED GERMINATION

The process whereby seeds sprout and begin to grow is known as germination.

Germination is the onset growth of a seed, often following a period of dormancy, in response to suitable environmental conditions. During germination (the growth and development process) of a seed, the water is absorbed through micropyle, and the formerly dormant embryo resumes growth and emerges from the seed.