Keywords

1 Introduction

The world population may exceed to nine billion in 2050 (Godfray et al. 2010), resulting in a great pressure on agriculture to produce more food, feed, biofuel and industrial raw materials on limited land resources. To meet these demands of growing world population, agricultural productivity has to be enhanced by >70% by 2050 (Bruinsma 2009). According to another report (Tilman et al. 2011), the global crop demand will be increased by 100–110% from 2005 to 2050 that can only be met if underutilized crop, fruit and vegetables are brought under cultivation . Most of the deficiency in food and raw materials is expected to be fulfilled by increasing crop intensity and introducing high-yielding stress-tolerant agricultural crop varieties while the rest of which has to be filled by unutilized agricultural crops. However, food security can be maintained using underutilized, undervalued or neglected crops (Kahane et al. 2013) or minor crops that are cultivated regionally, but some of them are grown globally with relatively low market value (Jain and Gupta 2013; Ochatt and Jain 2007; Stamp et al. 2012). Some of these crop species are widely distributed globally, but are restricted to a more local production and consumption system. Many of these minor crops grown for food, fibre, fodder and oil and as traditional medicine play a major role in the subsistence of local communities and most of them have a special social, cultural and medicinal value. These plant species have good adaptation to marginal degraded lands. Furthermore, these plant species are very important constituent of local diet of communities because they have valuable nutritional components, which are often lacking in staple crops (Jain and Gupta 2013).

Many underutilized indigenous vegetables have higher nutritional values than global vegetables like tomato and cabbage (Keatinge et al. 2011). These vegetables are important sources of nutritional dietary components (Sheela et al. 2004) and are protective foods containing not only protein and carbohydrates but also essential minerals and vitamins necessary to maintain human health and enhance resistance against disease and infection (Nnamani et al. 2009). A variety of the phytochemicals having anticarcinogenic, antioxidant, antifungal, antibacterial and antiviral properties (Gruda 2005) are found in vegetables. Cultivation of underutilized vegetables is the effective source to improve the income of farmers owing small lands. They are mostly of short duration, thus improving the profit and income of the growers. Overall use of underutilized vegetable plants helps to fight malnutrition and associated problems and increase the health status of the rural population, and helps in poverty alleviation by improving grower’s income and food security through providing enough food for global increasing population.

2 Scope of Underutilized Vegetables

The principal source of energy and protein is diets, which are obtained from cereals and pulses. However, less consumption of vegetables and fruits causes deficiency of micronutrient. The available fruits and vegetables are expensive and beyond the purchasing power of poor peoples. To fulfil this gap underutilized vegetables and fruits can be the best solution to fight this hidden hunger. All over the world many vegetable species are available that are not commercially cultivated but have significant potential to contribute proteins, energy, vitamins, minerals and other organic compounds necessary to maintain the livelihood and health of poor people and rural communities. Besides their importance for their nutritional value and as a source of household income, this vegetable diversity also has a cultural and social value and contributes to the stability of ecosystems (Arora 1998). The world over available information showed that a treasure of underutilized vegetable crops is present by exploring which poverty alleviation and food security can be achieved (Nandal and Bhardwaj 2014).

On the other hand, climatic changes, degradation of arable land and scarcity of water resources are reducing the food crop production and it is urgent need of the present era to cultivate those plant species that are having better adaptability to difficult environments. Most of the underutilized vegetables have wide adaptability to various environments and their different parts are being utilized for food, fodder, industrial raw materials, and medicinal purpose, thus can be helpful in reducing poverty and assuring food security . A list of some potential underutilized vegetables is summarized in Table 1, which provides some information about their role to adapt them as future food crops.

Table 1 List of some underutilized vegetables with their potential uses
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3 Nutritional Issues

Nutrient deficiency, malnutrition, and underweight of children are great challenge in third world courtiers of the world. In these countries most of the population has protein–energy malnutrition and micronutrient deficiencies (Ebert 2014). Malnutrition not only affects physical appearance and energy levels, but also directly influences many aspects of the children’s mental growth and functioning, which adversely affects the ability to learn and grow into adults (Mayes et al. 2012). Malnutrition also reduces immunity against the diseases and inhabitants become more susceptible to infection or diseases (Oguntibeju et al. 2013). An adequate intake of vegetables is necessary for a healthy diet which reduces the risk factor for chronic diseases like cancer, heart diseases and strokes (Van Duyn and Pivonka 2000).

Most of the underutilized vegetables are rich sources of nutrients and bioactive compounds. They contain protective nutrients like antioxidants, dietary fibres, vitamins, minerals and folic acid. The diversified and highly nutritive vegetables are affordable and cost-effective solution to hidden hunger and malnutrition. On an average daily diet of a person should be comprised of 2800 calories, 55 g protein, 450 mg Ca, 20 mg Fe, 3000 mg β-carotene, 50 mg vitamin C, 100 mg folic acid, 1.0 mg vitamin B, 1.4 mg thiamine, 1.5 mg riboflavin, 19 mg niacin and 5 mg vitamin D. Sharma (2009) suggested that vegetables are good source of all these nutrients (summarized in Tables 2 and 3).

Table 2 Nutritional composition of some underutilized vegetables per 100 g edible portion (source: Sharma 2009)
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Table 3 Vitamin composition of underutilized vegetables per 100 g edible portion (source: Sharma 2009)
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4 Phytochemicals

Underutilized vegetables are rich in bioactive phytochemicals which provide desirable health benefits beyond basic nutrition to reduce the risk of the development of chronic diseases (Liu 2004). They are non-nutrient compounds present in traditional as well as underutilized vegetables, and in other plant foods, which reduce the risk of major chronic diseases. More than 5000 individual dietary phytochemicals have been identified in vegetables. These phytochemicals need to be isolated and identified before we can fully understand the health benefits of bioactive compounds in whole foods (Liu 2003). Recent research findings indicate that the benefits of bioactive compounds present in vegetables and other plant foods may be even more than is understood. In vitro and animal studies suggest that they have multiple mechanisms of action beyond antioxidant activity (Liu and Finley 2005). Because bioactive compounds differ widely in composition and ratio from fruits to vegetable to grains and often have mechanisms complementary to one another, it is suggested that, to receive the greatest health benefits, one should consume a wide variety of plant-based foods daily (Joshipura et al. 2001). The most important groups of dietary phytochemicals can be divided into general categories as phenolics, alkaloids, nitrogen-containing compounds, organosulphur compounds, phytosterols and carotenoids (Fig. 1) (Liu 2004). The most studied groups of dietary phytochemicals related to human health and well-being are phenolics, carotenoids, vitamins and flavonoids required for plants as well as human beings to fight against diseases and infection and to maintain optimum health (Table 4).

Fig. 1
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Classification of dietary phytochemicals (Liu 2004)

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Table 4 Necessary phytochemicals required for plant body and human being to maintain optimum growth and protection against diseases
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5 Underutilized Vegetables and Health Care

Underutilized vegetables are rich sources of nutritional bioactive compounds. They are important sources of protective nutrients like vitamins, minerals, antioxidants, folic acid and dietary fibres. A person on average needs a daily diet which should provide 2800 calories, 55 g protein, 450 mg Ca, 20 mg Fe, 3000 mg β-carotene, 50 mg vitamin C, 100 mg folic acid, 1.0 mg vitamin B, 1.4 mg thiamine, 1.5 mg riboflavin, 19 mg niacin and 5 mg vitamin D. Vegetables are good source of all these nutrients (Table 4) (Sharma 2009). It is further suggested that higher intake of vegetables lowers the chances of developing  cardiovascular disease. It is also reported that persons having low intake of vegetables (less than 1.5 servings a day) have higher risk for heart attack or stroke than those who have higher intake (eight or more servings a day) (Hung et al. 2004). All types of vegetables are effective but leafy vegetables such as lettuce, spinach, Swiss chard and mustard greens and cruciferous vegetables such as Brussels sprouts, bok choy and kale are more  beneficial (Hung et al. 2004; He et al. 2006, 2007).

Similarly, high intake of vegetables is effective in controlling the high blood pressure (Appel et al. 1997, 2005; Bazzano et al. 2008). Many studies revealed that there is a strong link between eating vegetables and protection against cancer (Hung et al. 2004; Wiseman 2008; Giovannucci et al. 2007; Kavanaugh et al. 2007 ). Additionally, in a study of over 70,000 female nurses aged 38–63 years who were free of cardiovascular disease, cancer, and diabetes, research showed that consumption of green leafy vegetables was associated with a lower risk of diabetes (Bazzano et al. 2008; Mursu et al. 2014).

Vegetables contain indigestible fibre, which absorbs water and expands as it passes through the digestive system. This can calm symptoms of an irritable bowel and, by triggering regular bowel movements, can relieve or prevent constipation (Lembo and Camilleri 2003). The bulking and softening action of insoluble fibre also decreases pressure inside the intestinal tract and may help prevent diverticulosis (Brown et al. 1999). Eating green vegetables can also keep your eyes healthy, and may help prevent two common ageing-related eye diseases (cataracts and macular degeneration) which afflict millions of Americans over age 65 (Brown et al. 1999; Moeller et al. 2004; Cho et al. 2004). Lutein and zeaxanthin, in particular, seem protective against cataracts (Christen et al. 2008).

6 Coloured Vegetables

Colour in vegetables is due to some organic compounds present in that particular vegetable such as ascorbic acid (reduces tocopherol radicals to their active form) (Lobo et al. 2010). Those compounds are vitamins, flavonoids and micronutrients (Slavin and Lloyd 2012 ). The consumption of coloured vegetables enhances the human body’s ability to prevent and fight against diseases and infections (Pandey and Rizvi 2009). The phytochemicals present in vegetables act as antioxidant, anti-allergic, anti-carcinogenic, anti-inflammatory, antiviral and anti-proliferative (Zhang et al. 2015). Pigments from paprika are used as natural colourants in medicines and food items (Arimboor et al. 2015). Some of the nutraceutically rich vegetable crops are red and black carrot, beetroot, tomato, chilli and broccoli. Based on colour vegetables are grouped in Table 5 (Singh 2012).

Table 5 Coloured vegetable crops (source Singh 2012)
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7 Ethanobotany

Vegetables are an integral part of world especially Indian subcontinent system of medicine (Leonti and Casu 2013). The whole plant or plant parts of vegetables are used as crude drugs or drug formulations in naturopathy, Ayurveda and homoeopathy (Pandey et al. 2013). Vegetables like brinjal, ash gourd, snake gourd, drumstick, curry leaf, onion and garlic are used in Ayurveda. Watermelon seeds, seeds of summer squash, ivy gourd, etc. are used in homoeopathic medicines (Indira and Peter 2013; Pandey et al. 2013). Bitter gourd plus and Momordica spp. are used for curing diabetes and hypertension (Haines et al. 2017). Bitter gourd plus is a health supplement which increases glucose metabolism and maintains a healthy blood sugar level (Modak et al. 2007). Ivy gourd extract capsule is used against diabetes. Moringa body butter from moringa seeds and moringa leaf powder capsule are catching the market recently (Indira and Peter 2013).

According to recent research, diet is responsible for 20–30% of all cancers occurring in economically developed countries. Excessive consumption of green and yellow vegetables is associated with decreased susceptibility to some forms of cancer, although the mechanism for their protective action has not been fully understood (Pal et al. 2012).

A diet rich in cruciferous vegetables are associated with inhibition of chemically induced carcinogenesis in laboratory animals and humans. These vegetables are rich in sulphur-containing glucosides called glucosinolates. About 100 different forms of glucosinolates were identified in the cruciferous family. Broccoli, Brussels sprouts and Chinese cabbage are the main sources of glucosinolates in human diet. The dominant glucosinolates in cabbage, Brussels sprouts, cauliflower and kale are sinigrin and glucobrassicin (Singh 2012). The medicinal values of some underutilized vegetables are summarized in Table 6 (Mhaiskar et al. 2014).

Table 6 Underutilized vegetables and their medicinal uses (source: Mhaiskar et al. 2014)
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8 Toxic Metabolites and Anti-Nutritional Compounds

Though vegetables are rich in many nutrients and vitamins, there are many toxic substances and anti-nutritional compounds in them, which restrict their use in animal nutrition (Tadele 2015). However, they can be used as insecticides/pesticides. Some of these wild vegetables contain cucurbitacins, glycoalkaloids, glucosinolates, lathyrogens, saponins, trypsin inhibitors, tannins, phenols and non-amino organic acids (Saxena et al. 2013). These chemicals cause gastric and neurological disorders, kidney stone and high blood pressure (Coşan et al. 2015).

The contents of some of the underutilized vegetables like phytate, tannins, oxalates, nitrates and glucosinolates have toxic effects (Gupta et al. 2005). Tannins and phytate interfere with iron bioavailability, oxalates present in leaf vegetables and legumes interfere with calcium absorption and nitrate accumulation leading to harmful effects (Sotelo et al. 2010). In the gastrointestinal tract, nitrate (NO3) is reduced to nitrite (NO2) which is absorbed in the blood stream and bind with haemoglobin and multifarious disorders appear (Weitzberg et al. 2010). Therefore, before promotion of any underutilized vegetable complete biochemical analysis is necessary .

9 Poverty Reduction

All over the world most of the agricultural land is covered by major/staple food crops and very limited area is available for vegetables and other crops. Per capita consumption of vegetables is 88–90 g/day, whereas World Health Organization (WHO) recommends a minimum of 450 g of vegetables and fruits per person per day for a healthy human diet . So there is a potential demand of 164 kg of vegetables/fruit per capita per annum (Food and Agriculture Organisation [FAO] 2015). Therefore, to reduce the poverty following strategies should be followed.

10 Introduction of Underutilized Vegetables Having Commercial Values

Underutilized vegetables have scope to increase the income of poor farmers. Underutilized vegetables like Amaranthus spp., Corchorus olitorius, Solanum scabrum, Solanum melongena, Solanuma ethiopicum, Moringa oleifera, Momordica charantia, Ipomoea aquatica, Brassica oleracea, Brassica napus, Hibiscus sabdariffa, Basella alba, Abelmoschus manihot, Psophocarpus tetragonolobus and many other vegetable species (Table 1) have commercial value and thus can make a significant contribution in increasing household income (Ebert 2014; Hughes and Ebert 2013) and be helpful in poverty reduction .

11 Improvement in Job Opportunity

Cultivation of underutilized vegetables provides real opportunities for reducing poverty (Dasgupta 2012). Vegetables require intensive cultivation requiring more labour than needed for the production of staple crops. Because of extra care demanded by horticultural crops from land preparation to sowing of harvest, often about two to four times more labour is required compared to the production of cereal crop (Dawn 2007; Nichols and Hilmi 2009). So cultivation of these crops generates new jobs and the jobless population can earn money that will reduce the poverty in country.

12 Cultivation of Environmentally Adapted Vegetables

Underutilized vegetables have a comparative advantage , particularly under conditions where arable land is scarce, labour is abundant and markets are accessible (Jayne et al. 2012). The average income of farmers who cultivated vegetables is higher than that from the cereal crops (Tadele 2017). Different studies showed that small holding farmers producing vegetables for export had five times higher incomes as compared to those who did not grow these crops (Weinberger and Lumpkin 2007; Navadkar et al. 2005). Since vegetable producers are better integrated into markets, the vegetable crops contribute to commercialization of the rural economy, which is characterized by increased trade and marketing (Hellin et al. 2009; Collier and Dercon 2014). Commercialization uplifts the rural economy and contributes to the growth and development process, through generation of employment and increasing per unit area productivity (Christiaensen and Demery 2007; Christiaensen et al. 2010). With the increase in urbanization, the needs of growing cities to feed their population will require more attention towards urban and peri-urban agricultural production (Satterthwaite et al. 2010; Charles et al. 2014).

13 Provision of Healthy and Certified Seed

Vegetable seed sector is a neglected one in underdeveloping countries, has no any gene bank of underutilized vegetables. Furthermore, a major limitation in vegetables production in many developing and underdeveloped countries is the unavailability of good quality seed and other propagation materials . Farmers themselves often produce seeds of locally preferred or indigenous varieties, as the individual markets are too small to attract the interest of the private sector. So, proper and certified availability of seeds can play a great role in boosting the national economy (Chivenge et al. 2015; Mabhaudhi et al. 2016). In most of the underdeveloping countries seeds of vegetables to have higher yield are imported. A focus on the quality seed development by public and private sectors can help a lot to reduce the poverty by providing employment and reducing cost of production by lowering cost of seed.

14 Manufacturing of By-Products

This sector has great potential for income generation through value addition vegetable products like jam, jelly, pickles and marmalades. Tomato and other vegetables pulp processing units can also take part in poverty reduction. Similarly, vegetables can be cured and processed to earn a large amount of foreign exchange. Glut in vegetables in market like potato, reduces its economic return, resulting loss to farmer which can be minimized by making by-products (starch, chips and crisps). There is a potential for perfumery industry as the climate favours some underutilized vegetables grown for flowering, tuberose and medicinal plants production, which are the backbone of perfumery industry in Asia, Africa and even in Europe. Governments should provide benefits to both the growers and the unemployed youth by providing those jobs in the processing industry.

15 Adaption of Modern Harvest Technology

Post-harvest is an emerging discipline to deal with the harvested vegetable crops because of their perish ability. Harvest and post-harvest operations like field heat removal, cleaning, washing, waxing, grading and packing provide job opportunities to a large number of people increasing participation of women in the labour market of developed economies. Many tasks, such as chopping, washing, labelling, and barcoding, are being transferred to developing countries and are generating new jobs, especially for women.

16 Earning of Foreign Exchange

This sector has a great opportunity to earn foreign exchange by exporting the excess of fresh as well as processed products of vegetables to international markets. For proper health, use of freshly processed products of vegetables are recommended by the doctors/physicians. Therefore, high amount of vegetables is required to prepare these products (salads) demanded all over the world. So, by exporting these vegetables (salad crops) reasonable amount of foreign exchange can be earned, which will reduce poverty of the country.

17 Job Opportunity in Rural Areas

This sector is highly profitable because mostly vegetables are short duration crops. For looking after the crop, handling produce, processing and marketing, manpower is required at every step, which increases employment opportunities up to rural level. Proper training is required to the farmers owing small lands and landless labourers so that they can increase their income and contribute in poverty reduction.

18 Adaptation of Better Production Technology

Modern production technologies like tunnel farming and soil-less vegetable and flower production offer a great scope for farmers with small land holdings. By growing off-season vegetables, they can earn a lot from a small piece of land. However, the heavy initial investment is a hurdle, which can be solved if these farmers are given subsidy by the government. Likewise, nursery business is well flourishing , of both fruit plants and ornamental plants. Unfortunately, for fruit plants still there are limited number of certified nurseries in the underdeveloped and developing countries.

19 Promotion of Floriculture and Nursery Business

Due to change of life styles and traditions, interest in the ornamental plants is growing day by day in almost all the people , especially in cities. So, floricultural crop production can increase the income of the farmers; therefore, promotion to floriculture and nursery business should be given to reduce the poverty.

20 Introduction of Mushrooms Production

Mushrooms have a good scope to improve the income of the farmers. Production of mushrooms requires a small area and waste materials from different crop residues can be used; so it is very cheap to produce these highly nutritive alternatives of the meat. It does not require a highly skilled supervisory staff, even house wives can handle a unit easily. So, rural people can be supported by educating and training them in mushroom production technology.

21 Interior Decoration

Interior plant decoration is also getting momentum due to change in the life styles, and ladies in particular can earn a lot by doing interior designing through plants not only in various parties but also in various offices, hotels, hospitals, etc. All this will be helpful in reducing poverty.

22 Limitations

Unavailability of good quality vegetable seeds, inadequate infrastructure (road and transport facilities), limited access to finance by small farmers, limited facilitation in production commodities, storage and marketing, export market restrictions and competition are acting as limitations. The lack of proper storage facilities often lead to low or uncertain seed viability and vigour of vegetables.

23 Food Security

Conservation and sustainable use of the genetic resources of indigenous underutilized vegetable crops offer a tool for addressing the problem of food security (Ebert 2014; Chivenge et al. 2015). Food security means both inadequate quality and inadequate quantity of food supply at both national and household levels (Perez-Escamilla and Segall-Correa 2008). The food base for the rural population, especially in the marginal and semi-arid areas, has become narrower, leaving communities more vulnerable to food shortages and nutrient-deficiency diseases (Tilman et al. 2011; Ebert 2014). Wild and weedy species, commonly used as vegetables in the past, are disappearing because of changes in customs and land use (Łuczaj et al. 2013). Knowledge about the cultivation and management of underutilized vegetable species is not well established (Baldermann et al. 2016). Farmers also lack knowledge about more efficient, intensive production and management technology (Lencsés et al. 2014). There is also a lack of knowledge about nutritive value and cooking methods that minimize nutrient leaching during food preparation. Creation of proper know-how about the wild or underutilized vegetable is necessary to ensure the food security (Hoffman and Gerber 2015).

A nutritious and varied diet is a critical means by which good health can be maintained (Slavin and Lloyd 2012). Consumption of less than 200 g of vegetables per person per day in many countries today is common and this low amount, often in conjunction with poverty and poor medical services, is associated with unacceptable levels of mortality and malnutrition in preschool children and other vulnerable groups (Rama 2016). An increase in consumption of nutrient-dense underutilized vegetables is helpful to overcome malnutrition in the population, and utilization of these vegetables may ensure food security in developing countries (Ebert 2014). So, by introduction of these underutilized vegetables crops require research for developing good quality seed of these plant species (Allen et al. 2014). Opportunities exist for the poor to improve their access to underutilized vegetables, particularly if they are willing to grow on small farms (Krause et al. 2016). Research continues on defining appropriate high nutrient content underutilized vegetables for such activities, but these efforts may be compromised by failure to adopt good agricultural practices, resulting in contamination and unhealthy produce for producers and consumers (Keatinge et al. 2011). The scientific community is ready to play its role in battling malnutrition and hunger , but unless the political resolve can be found to support the causes of both food and nutritional security together, it is unlikely that the Millennium Development Goals will be achieved in a timely fashion. Redressing the current imbalance in agricultural investment can improve efficiency in food production and ensure that nutritious diets can be a reality for all people.

Wild vegetables are a common and important source of food and nutrition in the rural population and make agricultural fields fertile. These plant species, which were initially primary sources of food in many societies, have been listed, and these plants favoured their cultivation in degraded soils. Micronutrient deficiencies , especially in children, continue to be a global cause for concern and yet numerous reports have revealed the high nutritional value of wild vegetables (Bvenura and Afolayan 2015). Incorporation of these wild vegetables into diet can alleviate some of the micronutrient deficiency concerns. In this chapter, literature on ethnobotanical knowledge of wild vegetables is also reviewed with a view to reveal their potential role in household food security. The outcome of the literature search showed that a lot of plant species are available for this, which are summarized in Table 1. These important plant foods are clearly underutilized although they potentially have a big role to play in food security . Underutilized vegetables need to be revitalized and brought back into the mainstream diet so that they can play their role in food security.