eChapters

In tropics, many crops are grown for their edible roots or tubers. Broad group of “tuber crops” encompasses a wide range of starchy food crops, some of which are true botanical roots and some others are stem tubers or corms. In global scenario, they are in a neglected state mainly due to their negative image as poor people’s food. They are highly perishable and are normally consumed locally in fresh or home processed state. It is time to bring out the positive attributes of these important foods and the increased contribution they can make to the nutritional welfare, food security and economic wellbeing of people, especially in developing countries.

After attaining a rich experience over a period of time, our forefathers have developed very pertinent primitive knowledge in a wide variety of fields (Rohilla et al., 1999). These location specific wisdom are known as indigenous traditional knowleges (ITKs). Indigenous traditional knowledge are the upshots of the pragmatic approach by our sons of the soil. As such, there are many ITKs emerged due to the incremental and cumulative learning among societies living in close connection with nature. The traditional communities are often called as indigenous or local or ethinic people. They have accumulated lots of empirical knowledge gained from the day-to-day life. The variations in availability of raw materials and environmental conditions clubbed with time tested traditional knowledge and wisdom, have made people of different regions of the North Eastern hill states to formulate, develop and perpetuate consumption of a wide range of traditional foods and beverages unique to its places since ages (Savitri and Bhalla, 2007).

Tropical root and tuber crops are important staples for food security for about a fifth of the world population. Tropical root and tuber crops like cassava, sweet potato, yams and aroids [taro and elephant foot yam] come under tropical root and tuber crops. Sweet potato, yams and colocasia are processed mainly as fresh vegetable, whereas 75% of the cassava in Africa, 75-80% in Asia and 65% in Latin America are processed either as fermented foods and feeds or as food additives such as starch, starch based sweeteners (glucose and fructose syrups), organic acids (acetic, lactic, glutamic and gluconic), mono-sodium glutamate and microbial polysaccharides (xanthan, pullulan, scleroglucan, etc).

Tuber crops grown in India include Cassava, Sweet potato, Dioscorea, Colocasia, Amorphophallus and minor tuber crops like Chinese potato, Arrowroot, Canna, Yam bean etc. Biotechnology can contribute solution to the major problems and realize greater benefits for tuber crops. Traditional breeding in tuber crops is difficult due to their heterozygous nature, low fertility, out crossing coupled with strong inbreeding depression. Many of the agronomic traits are polygenic and/or recessive which make breeding for such characteristics complicated. Biotechnology is a powerful tool to complement traditional breeding. Developments in the field of tuber crops biotechnology are discussed below.

Tuber crops are rated as one of the richest sources of energy, besides being a treasure house of vitamins and minerals. The highest rate of dry matter production per day per unit area makes tuber crops important in the food economy, especially in meeting rural feed security. The tuber crop produce can also be processed into various food products to suit the taste and need of the urban, semi-urban and rural folk as well. Better post harvest management and diversification for production of value added products is one of the dependable methods to make tuber crops lucrative to both farmers and entrepreneurs.

1. Tuber crops Starches

Tropical root and tuber crops are rich sources of starch (Ghosh et al., 1988; Chadha and Nair, 1994; Moorthy, 1994) besides many vitamins, minerals etc (Table 1). In addition to food applications, they have important industrial uses; especially, cassava in view of the considerable starch content. Cereals form the major source of commercial starches in most developed countries, but cassava (Manihot esculenta Crantz) and to a lesser extent, sweet potato (Ipomoea batatas Lam.) tubers are used for starch extraction in India, Brazil, Thailand, Indonesia, Philippines and China.

The North Eastern region stretches from 21°25' to 29° 28' N and 80° 4' to 97°25' E and covers a total geographical area of 2.55 lakh square kilometer sharing about 8 percent of the country’s geographical area. The NE states, otherwise known as eight jewels, which are Arunachal Pradesh, Assam, Manipur, Meghalaya, Mizoram, Nagaland, Tripura and Sikkim. This region is characterized by inaccessibility, marginality, fragility, cultural heterogeneity, ethnicity, rich bio-diversity, low livestock and crop productivity. These states are the reservoirs for genetic diversity of tuber crops like Colocasia, Xanthosoma, Alocasia, elephant foot yam, Dioscorea and other minor tuber crops. The annual precipitation in the region is about 2450mm and maximum rainfall is received from South West monsoon.

The major tuber crops cultivated in tropical countries are: cassava (Manihot esculenta Crantz), sweet potato (Ipomoea batatas L.), yams (Dioscorea sp.), aroids (Amorphophallus, Alocasia, Xanthosoma, Colocasia ), Canna edulis, arrowroot, Chinese potato, winged bean and yam bean. In addition to this, there are a number of under exploited and under utilized tuber crops grown as wild cultivars having medicinal and pharmaceutical applications. Processing and utilization of tuber crops as food are traditional with both primitive as well as modern equipments being in use (Nanda and Kurup, 1994). One of the oldest traditional processing tools is a stone pounder for making poi from taro in Hawaii.

Tropical tuber and root crops are subjected to the depredation of a number of insect and non insect pests. Comprehensive studies revealed that cassava is attacked by a wide range of arthropod and rodent pests. An exhaustive global account of cassava pests and their management was given by Anon (1978), Bellotti and Schoonhoven (1978) and Bellotti et al. (1999). Lal and Pillai (1982); Pillai and Palaniswami (1984), Pillai (1994) and Palaniswami (1999) reviewed the pests of cassava in India. Anon (1978), Sutherland (1986) and Jansson and Raman (1991) covered world sweet potato pests. Palaniswami (1999) detailed the pests attacking sweet potato in India. Pests of edible aroids, yams and chinese potato were comprehensively reported by Anon (1978); Mitchell and Maddison (1983) and Palaniswami (1994, 1999). In India about 34 species of insects and non-insect pests infest cassava, 80 species attack sweet potato, 46 species on edible aroids, 21 on yams and 10 on chinese potato. One of the main factors for the low productivity of these crops in India is attributed to the pest complex attacking them (Chadha, 2001).

Application of manures and adoption of proper cultivation practices have profound influence in yield and quality of tubers. There crops also need macro nutrients (N,P,K which are primary nutrients and Ca, Mg and S which are secondary nutrients) and micro nutrients (Fe, Mn, Zn, Cu, Mo, B) for their maximum yield potenial.

the package of practices vary with crop and again with soil, climate, edaphic and topographic factors, especially with reference to tropical tuber and root crops. The yield can be maximized through good agronomical practice and by adoption of proven recommended production technologies. Soils, climate, topographic and edaphic factors suitable for each crop alongwith salient cultivation practices and production technologies are enunciated for important tuber and root crops in various parts of India.

In enhancing  the food production there appears to be two solutions, viz., horizontal or vertical increase in production.  In the vertical expansion of production varieties are important. High yielding, high starch and value added varieties suitable to each region/ cropping system play vital role in enhancing vertical production.  Therefore varieties especially value added consumer preferred ecologically adaptable ones hold the key and is very much true in tuber and root crops which have a significant role in supplementing the food and nutritional requirement in rural and semi urban population of India.

A broad class of polypeptides and proteins occur in plants and other life forms, which inhibit the action of proteolytic enzymes and are known therefore as proteinase inhibitors and this includes those which specifically inhibit the important digestive enzyme trypsin. Others inhibit a related enzyme chymotrypsin. The subject of proteinase inhibitors was reviewed by Ryan (1981). The occurrence of these inhibitors has nutritional implications for human and animal feeding as they are found in many important food plants eaten both raw and cooked. The first known plant proteinase inhibitor was the trypsin inhibitor crystallized from soybeans (Kunitz, 1945). Other proteinase inhibitors have since been described in a variety of plants, especially the Graminae, Leguminosae and Solanaceae families. The exact physiological function of proteinase inhibitors in plants is thought to be in plant protection by inhibiting digestive enzymes of invading insect pests or pathogens (Ryan, 1981).

The dry matter production is maximum in cassava (3.0 m t ha^-1) and is followed by yams (2.4 m t ha^-1) and sweet potato (2.1 m t ha^-1) and are higher than rice, wheat, maize and banana (1.3 to 1.9 m t ha^-1). The energy production is maximum in yams (182 M J ha^-1 day^-1) and it is followed by sweet potato (152 M J ha^-1 day^-1) and cassava (121 M J ha^-1 day^-1) (Horton and Fano, 1985).

1. Sweet Potato

Both sweet potato roots and tops are nutritious foods which could be used to advantage in combating nutritional deficiencies in parts of the developing world if means could be found to overcome resistance to their increased consumption. The roots are used primarly as human food and are eaten boiled, steamed, fried or baked. They are not only a moderately good energy source, but also contain significant quantities of the water-soluble vitamins viz., ascorbic acid and thiamin, besides supplying part of the daily requirement for riboflavin and niacin. Their contents of pyridoxine, folic acid and pantothenic acid may be relatively high. Raw leaves and tender tips are also excellent sources of ascorbic acid and some of the B-vitamins, especially riboflavin which is deficient in many Asian diets. However, high percentages of water-soluble vitamins are lost on cooking (Woolfe, 1992).

Plant biodiversity, in particular, is arguably the single greatest resource that humankind has garnered from nature during our long cultural development. Nowhere is the value of biodiversity more evident than in our food supply. Roughly one third of all plant species have edible fruits, tubers, nuts, seeds, leaves, roots, or stems. The World Health Organization estimates that 3.5 billion people in developing countries rely on plant-based medicine for their primary health care, in which tuber crops also play a major role (Tuxill, 1999). There are 25 hot spots of biodiversity of which Western Ghats and Eastern Himalayan are the most important ones in India. About 7% of world flora and 6.5% of world fauna are in India. Indo-Burma region is one of the eight hottest hot spots of the world, and is the centre of origin of tuber crops like Dioscorea, Colocasia, Amorphophallus and Alocasia.

Among angiosperms, there are about 18 families which have more than 30 genera which produce tubers. Most genera have many species which are tuberizing, most of which are unknown to man even now. The history, origin and distribution of only a few species which are economically important root and tuber crops and which are commonly used by men for edible as well as medicinal purpose are elucidated in this chapter.

1. Sweet Potato

Exact centre of origin of sweet potato (Ipomoea batatas), and the routes and times for its dispersal to some of its present locations, are still in dispute and are likely to remain so until further archaeological or ethnobotanical evidence is available (O’Brien, 1972).

As per the projection of International Food Policy Research Institute, Washington, there is likelihood of shortfall of 41% in food production in India by 2020 and need to produce 300mt of food by 2020. India is the seventh largest country in the world with a population of more than 1.03 billion and with 1.93 population growth rate. To overcome such problems we have to go for horizontal or vertical increase in production. As the cultivable area and water resources are limited to bring under cropping, except by way of increasing the cropping intensity/cropping system, horizontal increase has little scope. While the vertical increase in production has tremendous scope with better value added varieties and farmer friendly sustainable management and production technologies.

Gladiolus saundersii

Aerides

Aerides consists of more than 60 species. These are monopodial epiphytic orchids grown on trunks or branches of trees.  The stems are round, leafy and branched with aerial roots. The strap leaves are thick, leathery and bilobed. The inflorescence is auxillary and drooping. The flowers are many and 2cm in diameter closely set on the inflorescence and generally fragrant.

Orchids comprise the largest family of flowering plants with 25,000 to 35000  species belonging to 600-800 genera. They are prized for their incredible diversity in the size, shape and colour and attractiveness of their  flowers and high keeping qualities even upto 10 weeks. In the international trade, among   top ten cut flowers, orchids rank the sixth position and among orchids Cymbidium ranks the first position and in floricultural crops it accounts for 3% of the total cut flower production. In India, it comprises 140 genera and 1300 species which grow upto an elevation of 5000m. Indian terrestrials are located in humus rich moist earth under tree shades in North Western India.  Western Ghats harbour the small flowered orchids. Epiphytic orchids are common in North eastern India which grow upto an elevation of 2000m from sea level.

India is bestowed with varied agroclimate ranging from mild tropical zones to alpine zones and congenial for several types of ornamental plants in different seasons. Worldwide China and India have large total areas under flower cultivation. Among top ten cut flowers, rose ranks the first position followed by spray chrysanthemum, tulip, lily, gerbera, cymbidium, freesia, chrysanthemum, anthurium, alstroemeria and carnation. In view of rapid changing global competition, diversification into lesser known potential new ornamental plants play key role in fetching premium prices. Most of the potential exotic ornamentals plants have been introduced from Australia, South Africa, Israel, New Zealand and Eastern USA. There are about more than 60 types of new ornamentals reported to be hold potential for commercial importance. All these newly introduced ornamental plants require the following stages of research and development.

Cacti

Cacti belong to the family Cactaceae comprising of 130 genera and 2000 species and bear a complex organ, a cushion like structure spirally arranged over the stem called ‘areoles’ from which spines, hairs, flowers and shoots develop. In tribe, Pereskieae, the plants are leafy bushes or shrubby and characterized by areoles on the stem and by the typical flower borne in clusters, e.g. Maihuenia, Pereskia and Rhodocactus.

Bulbous plants are herbaceous perennial or biennial ornamental plants which produce fleshy storage organs including true bulbs, corms, tubers, rhizomes and tuberous roots. These underground organs have capacity to store moisture and nutrients are utilized by bulbous plants to survive winter or other adverse conditions such as summer drought and heat in a dormant state.

Aquatic plants are essential to maintain water balance. They also keep out the dreaded algal bloom. Aquatic plants absorb the minerals and carbon dioxide in the water. Pond plants are classified into four groups: oxygenators, marginals, floaters and aquatic. Oxygenators such as buttercup and water violet supply lots of oxygen in the water. Marginals are ornamental pond plants and planted in pots or baskets in the edge of the ponds to provide space for fishes or frogs, e.g., Primula. Floaters like water hyacinth help in keeping algae at bay and also provide enough cover for tadpoles or small fish.

Foliage or house plants are mostly those with attractive foliages or flowers and are able to survive and grow under indoor conditions. They are mostly used for interior decoration or interior plantscaping. Foliage plants of world’s importance include Aglaonema, Dieffenbachia, Dracena, Epidendrum, Ficus, Peperomia, Philodendron, Sansevieria, Syngonium, Schfflera, ferns, Anthurium, Codiaeum. Florida shares more than 55% in foliage industry.

Shrubs are group of plants having woody stems and multi-branching from the base of the plant. These plants are useful to build up the framework of the planting scheme for screens, ground covers, flowers and hedges. They vary in blooming time, colour, size, growth habit, fragrance as well as situations.

Herbaceous perennial flowers complete their life cycle in more than a year and usually bloom during a specific time period every year during the growing season. These flowers are hardy and herbaceous. They are popular in their dried form for beautiful and exotic dried flower arrangements. Besides, perennials are used as ground covers, mixed with annuals, grown as potted plants and used as accents or specimen plants. Some important perennial flowers are Baby’s Breath, Bells of Ireland, Blue Globe Thistle, Carnation Flowers, Daisy Flowers, Flax, Hibiscus, Hollyhock, Iris, Ladys Mantle,Larkspur, Lavender, Lily Flower, Monkshood, Pearl Everlasting, Rose Flowers, Statice, Sunflower, Yarrow.

Annual plants complete their life cycle within the space of one year are called annuals. They have multipurpose uses like as cut flowers, a wealth of bloom through out the summer and early autumn months; as component in herbaceous border, to make colour scheme, for window boxes and porches, as pot plants in green house or conservatory, for edging, for drying and herbal medicines.

Rose
Rose is a perennial erect shrub, climber or trailing plant  belonging to the genus Rosa within the  family Rosaceae. The plants bear large and showy flowers of white, yellow, red, pink, orange and various shades. Most of the species are native to Asia.

Valuable Genetic Resources

India is bestowed with diverse agroclimatic zones which aids in the cultivation of large number of commercial flowers like rose, gladiolus, chrysanthemum, tuberose, jasmine, marigolds, orchids, lavender, lily, anthurium, gerbera, potted plants, cut foliages, bedding plants etc. In floriculture trade, value addition takes place at every step to create a novel product and to cater the demand of heterogeneous consumers. In the international floriculture trade, besides floriculture and pot plants, many other value added products include artificial colouring of the flowers to create novelty, aqua-packing for better presentation and attraction, three dimensional window packing of flowers for greater visibility, garland, venis, bouquets, flower arrangements etc.

Abstract

Tea [Camellia sinensis (L.) O. Kuntze], of family Theaceae, is an important cash crop  worldwide. It is an evergreen shrub cultivated in humid and sub-humid tropical, sub-tropical, and temperate regions of the world, and grows mainly on acidic soils. Due to limitation of expansion of tea cultivation in new land, import of low cost high quality tea, increasing vertical productivity is the best option of Indian tea Industry. The primary need of the tea industry today is to develop high yielding clones with better quality and stress tolerance potential. Conventional tea research has contributed appreciably to the genetic improvement of tea over the past several decades, but it is time-consuming and labor intensive.

Abstract

Tea is the most consumed, rejuvenating and thirst-quenching beverage. It is bestowed with ‘miraculous’ health benefits which includes promotion of cardio-vascular health, skin protection, antioxidant activity, defence against microbial infection, prevention from cancer, obesity, and many more. Among the four types of tea, green tea has attained much attention of tea consumers due to its magical health potentials.Owing to increased knowledge and marketing of its health benefits, there has been astonishing changes in its consumption pattern and increase in its production. The tea industry drives economies of the tea growing regions and contributes greatly to the country’s GDP growth as well as foreign exchange earnings. However, in recent years, tea farming has become subject to environmental deterioration because of exploitation in cultivation practices.

Abstract 

In this chapter the origin of flavour in tea have been explained under the light of chemistry of green leaves and made tea. The dependency of flavor in the final product on several factors involved in every step of its manufacturing process has been explained briefly to draw a back ground picture of the subject. On the other hand in-depth explanations on the chemical basis of diversity and complex nature of tea flavour have been given following a simple manner.

Moreover, traditional and recently developed analytical methods have also been reviewed critically. Analytical strategies and details of instrumentation involved to study or quantify the flavour in tea have been depicted in details with their prose and cones under the light of complicacy of the subject. Potential and loop holes of the new technology viz. E-Nose have been explained critically. Finally a hypothesis with little experimental proofs has been explained to meet a probable solution to the present problems in flavour analysis of tea.

Abstract
 
Tea (Camellia sinensis L.) is a plantation crop having a wide distribution extending from low elevation to high exceeding 2000 m. The demands and consumption of organically grown residue free Darjeeling tea is increasing day by day due to health consciousness and environmental awareness. The average productivity of Darjeeling tea is far below than the average national tea productivity. Reasons for low productivity of Darjeeling tea may be due to high altitude/elevation; temperature/climate and geographical location in addition to the old age of tea bushes and low plant density. In the past indiscriminate use of synthetic fertilizers has led to the pollution and contamination of the soil, water basins, destroyed micro-organisms and friendly insects, making the crop more prone to diseases and reduced soil fertility. Following Good Agriculture Practices (GAP), sustainable and quality production of Darjeeling tea may be increased through eco-forming without any deterioration of surroundings of plants.

Abstract

Tea, Camellia sinensis (L.) O. Kuntze, is a perennial crop and grown as a monoculture on large contiguous areas in India. Being a plantation crop, tea provides a relatively stable microclimate and food supply for several notorious pests such as insects, mites, nematodes which cause substantial loss of foliage. However, region-wide variation in faunal diversity exists as a result of autochthonous and heterochthonous recruitment and the influence of climate, altitude and age of the plantation. This publication provides the details on pest information (identification, crop damage, alternate hosts, pest life cycle) and their possible management strategies. On account of complex pest situations, total avoidance of pesticides in tea is not possible; although due to the sensitive nature of the crop pesticide use must be minimal. A tentative IPM strategy for tea cultivation in India has been proposed in this paper which may ensure low – cost, eco-compatible, pest management package with minimal residue problems.

Abstract

Tea (Camellia sinensis L. O. Kuntze), a foliage crop of Sub-Himalayan Terai-Dooars has Tea mosquito bug (Helopeltis theivora)(TMB), looper caterpillars [Hyposidra talaca, Hyposidra infixaria, Biston (=Buzura) suppresseria] and Red spider mite (Oligonychus coffeae)(RSM) as major pests. In conventionally managed tea plantations, synthetic pesticides and acaricides are routinely applied. The pesticide-exposed pest populations show higher tolerance level as evident in their increased LC50 values. Augmented activities of detoxifying enzymes viz. general esterases (GE), glutathione S–transferases (GST) and cytochrome P450 mediated monooxygenases (CYP) were recorded in the pesticide-exposed pest populations. Sub–lethal exposure to monocrotophos (36% SL) enhanced the tolerance level in adult TMB by 105 fold through three generations. Increased activity of GE was evident in the pesticide-exposed populations of the tea loopers. Activities of GE and GST  in RSM were significantly higher in acaricide-exposed population. Present studies can help developing enzyme-based assay kit for determining level of pesticide-resistance. Integrated resistance management has become an integral part of modern day IPM practices. Adoption of newer chemicals, and cultural practices can minimise synthetic pesticide applications, thereby help reducing resistance development in pests.

Abstract

Pruning is the most important cultural operations in tea cultivation. Time of pruning affects health of bush, incidence of pests and disease, yield and distribution of crop. Root starch reserve at the time of pruning affects the recovery of bush and hence considered as the most crucial factor for deciding time of pruning. Downward movement of photosynthates was found maximum in December and January, thereby maximizing the starch reserve in roots. Maximum recovery of tea bush and minimum loss in annual crop was found when pruned during December – January. Pruning in remaining months (February – November ) may result in crop loss to the tune of 5 per cent – 37 per cent in plain areas. Clonal varieties differ in root starch accumulation during winter months hence pruning time of individual clone needs to be decided accordingly to enhance recovery of plants.

Abstract

Ensuring the provision of safe and healthy working conditions to all workers and promoting the availability to them of certain minimum welfare amenities are the constitutional obligations of all employers as well as the Indian state. Enlightened employers tend to provide for these facilities on their own, as part of their performance and retention strategies. Others, however, largely consider these obligations as burden. Some recent researches reveal that the pursuit of numerical flexibility policies is becoming rampant amongst employers in the advanced world; they are doing so to cut costs and become more competitive. This means more use of labour-cost-saving devices and neglect of some basic rights of workers. Of course, intense competition amongst companies puts pressure on them to attempt cost-cutting and ignore these legal provisions. It should be noted however, that the law relating to working conditions is perhaps the most basic of labour laws in any country; therefore, its sanctity has to be maintained with an added responsibility by all concerned and as a societal value.

Abstract

“Darjeeling Tea” as a global brand brings attention to the Darjeeling District and creates a global imaginary which obliterates the dark colonial history, existing exploitation of the workers and the natural resources of the region. The global brand name is protected under the certification trademarks which has a geographical indication. Thus only tea from the 87 tea plantations can be called Darjeeling Tea. There is an increasing trend towards Darjeeling Tea going organic and fairtrade. This trend is critiqued with questions of how green and fair can a monoculture plantation get. Within this imaginary, small farmers’ tea offers an alternative paradigm based on equity and diversity. This paper explores the alternative by highlighting the (United Development Organization) journey of a small farmers collective Mineral Spring SanjuktaVikashSanstha.

Abstract

The history of the development of the tea plantation industry in the Darjeeling district dates back to the early fifties of the nineteenth century when the English entrepreneurs took lease of extensive land on the mountain slopes of the Darjeeling Himalaya and started tea plantations. During the formative years of the introduction of the plantation industry the region was sparsely populated so, laborers from various parts of India and her neighboring countries were encouraged to settle in the fringe areas of the Tea gardens. Over the last 160 years many changes have taken place in their lifestyle. The main purpose of this paper is to reconstruct the history of Darjeeling tea and to explore the life of people in the Darjeeling region and also to learn how the local populace adjusted themselves with the given environment with the changing scenario of the area.

Perennial vegetables live/survive in field for several years and go on yielding vegetables without much care and attention.  They are usually planted on the side of kitchen garden without much interference with tillage operations of other annual crops.  Tender leaves, shoots, fruits or tubers of a number of perennial crops are used for vegetable purpose in different agro-climatic conditions. They may be trees or shrubs as in bread fruit, jack fruit, drumstick, etc. or bushes as in colocasia or trailing plants as in yams, chow-chow and ivy gourd.

Vegetables which are consumed raw without cooking are known as salad crops.  In temperate regions, a large number of quick growing cool season crops like lettuce, celery, parsley, endive, chicory, chervil, cress, water cress etc. are consumed as raw. Only lettuce and celery are cultivated on a commercial scale in developed countries.  Growing awareness on nutritional values of raw vegetables and also health consciousness of people resulted in increased consumption of salad vegetables in tropics too.  Vegetables like onion, cucumber, tomato, carrot, radish, beet root, cabbage, capsicum, melon etc. are used as salads without cooking.

Leaf vegetables are rich sources of provitamin-A, vitamin-C and minerals like calcium, iron etc.  They also provide roughage required in human diet.  The Indian Council of Medical Research (1984) recommended a daily intake of 100 g and 40 g of leaf vegetables in the diet of woman and man, respectively. Amaranth, beet leaf, spinach, fenugreek, cabbage etc. are the major leaf vegetables grown in the country. 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.  The major annual leaf vegetables have a few features in common:

Tropical tuber crops are an important group of subsistence crops in tropical and subtropical zones.  Carbohydrates synthesised and stored in the form of starch in underground tubers are used as food by millions in under-developed countries.  It is also used as raw material by many industries.  Cassava, sweet potato, Chinese potato, edible aroids like elephant foot yam, taro, tannia and yams like greater yam, lesser yam and white yam are major tuber crops  grown in India.

Tuber crops are mainly grown as rainfed with minimum cost of production.  All are propagated through vegetative means and require fertile and well drained loose soil for proper root development. All roots crops require high dose of potassium for high productivity.

Potato is fourth major food crop after rice, wheat and maize in the world.  It produces the highest dry matter, well balanced protein and more calories/unit area and time.  Unlike other food crops, potato tubers contain vitamin-c (17 mg/100 g). It provides carbohydrates, minerals, fibre and a number of vitamin-B groups.  Potato protein is comparable to that of milk and egg.  Unlike European countries, in tropics and sub-tropics, the crop is of short duration and fits well in intensive cropping system.  It can be grown in a wide range of climatic and soil conditions and tubers are available throughout the year. Tubers can be left un-harvested in the soil for some time and are also suitable for long distance transport and storage. Several products like chips, flakes, French-fries, finger chips, granule, disc, cubes and flour are made out of potato tubers.

Radish, turnip, carrot and beet root are major root crops grown in the country.  In addition, root crops like rutabaga, parsnip, salsify, chervil and celeriac are grown in a limited scale in different areas. Though the crops belong to different families, their cultural requirements are uniform.  Common features of root crops like radish, turnip, carrot and beet root are:

Bulb crops include onion, garlic, leek, shallot, welsh onion and chive all belonging to the genus Allium.  This genus was earlier included in the family Liliaceae due to its superior ovary.  It was later shifted to Amaryllidaceae as flowers are born in a bracted umbel on top of a scape.  Being the typical genus in the family Amaryllidaceae, a new separate family status was given to all the specious under Allium as Alliaceae.

Vegetables belonging to the family Brassicaceae (Syn: Cruciferae) are known as Cole crops.  These are the most widely grown vegetables in temperate and sub-tropical zones.  The word ‘Cole’ comes from abbreviation of word ‘caulis’ meaning stem.  Cole crops are a group of highly differentiated plants originated from a wild plant Brassica oleracea var. oleracea (=B. sylvestris L.) commonly known as “Wild cliff cabbage” or “colewort”, through mutation, human selection or adaptation. Cole crops include cabbage, cauliflower, knol khol, Brussels sprouts, Chinese cabbage, sprouting broccoli, kale etc. of which cabbage and cauliflower are the most popular and widely grown.

Peas and beans belonging to the family Fabaceae (Syn. Leguminosae) are delicious and preferred vegetables grown throughout the world. These include cool season vegetables like pea, French bean, lima bean, broad bean and tropical vegetables like cowpea, hyacinth bean, winged bean, jack bean, sword bean etc.  These are integral components of sustainable agriculture due to their ability to fix atmospheric nitrogen and to improve soil properties. Legume vegetables are rich in protein and essential amino acids and have significant role in combating malnutrition among poor people and vegetarians.

Okra is predominantly a crop of tropics and subtropics.  It occupies fifth position, next to tomato, in area under vegetables in the country with a production of 33.24 lakh metric tonnes from an area of 3.47 lakh hectares.  The crop is cultivated for its young tender fruits, used in curry and soups after cooking. It is a good source of vitamins A and B, protein and minerals. It is also an excellent source of iodine and is useful for the treatment of goitre.  Fruit is useful against genito-urinary disorders, spermetorrhoea and chronic dysentery. Fruits are also dried or frozen for use during off-season.  Dried fruit contain 13-22% edible oil and 20-24% protein and is used for refined edible oil.  Dry fruit skin and fibres are used in manufacture of paper, card board and fibres.  Root and stem are used for clearing cane juice for preparation of jaggary.

Crops belonging to family Cucurbitaceae are generally known as ‘Cucurbits’. It consists of a wide range of vegetables either used for salad purpose (cucumber) or for cooking (all gourds), pickling (West Indian gherkin) or as dessert fruit (muskmelon, water melon) or candied or preserved (ash gourd).  As a group, cucurbits occupy the largest area in India and in other tropical countries. Its use is not primarily because of calories, minerals or vitamins since they are generally low to moderate in nutrients with a few exceptions like bitter gourd (rich in vitamin C- 96mg/100g), pumpkin (vitamin A 1600 IU/100g ), Kakrol (high protein  3.1g/100g,), parwal and chow chow (calcium- 531 mg and  140 mg / 100 g respectively). From the nutritional point of view, cucurbit seeds are valued for their high oil and protein contents.  Seed proteins of cucurbits are comparable to that of legumes and are richer in methionine.