Introduction

Vegetables are important sources of vitamins and are highly palatable of good taste, increases appetite and supply fibres. They have capacity to neutralize acids produced during digestion of proteinaceous and fatty foods. Some vegetables are good sources of carbohydrate (leguminous vegetable), sweet potato, potato, onion, garlic), vitamin A (carrot, tomato, drumstick, leafy vegetables), vitamin B (peas, garlic, tomato), vitamin C (green chillies, drumstick, leaves, leafy vegetables and leaves of radish) and good sources of minerals (leafy vegetables, drumstick, pods).  A wide variety of vegetables are suitable for human consumption but they vary greatly. The vegetables contain varying amount of vitamins, carbohydrates and fiber. They have high beneficial effects on human health. Fresh vegetables can be added to salads, dips, sauces and can be juiced to a highly nutritious beverage (Maiti and Rodriguez, 2013).

In view of the importance of vegetable crops for human health, enormous research inputs have been directed on various aspects starting from seed physiology, agronomy, production practices and physiology up to pre-and post harvest technology. Maiti and his team have made good progress on various aspects of research on vegetable crops for about 10 years, a brief synopsis of research advances are narrated here.

For effective management of vegetable crops, there is a great necessity to know the botany of vegetable crops. This has been documented with good illustration in a handbook for students and researchers (Maiti et al., 2011). A novel technique has been developed for epidermal morphology of leaf (Maiti, 2010). A good knowledge on principles of seed physiology after harvest and seed technology is essential for seedling establishment of vegetable crops in nursery and in the field. Recent advances in this aspect are documented (Maiti et al., 2012). Similarly research advances in various fields starting from germination, seedling establishment, physiology up to biotechnology have been documented for the benefit of students, researchers and teachers (Maiti and Rodriguez, 2012).On the other hand, lack of knowledge on pre-harvest and post-harvest technology cause loss of vegetable crop production on which various research inputs have been directed globally, but with little success. We have made a comprehensive review on harvest and postharvest technology of vegetable crops. This includes Solanaceous crops (pepper, potato, tomato, eggplant); cucurbit vegetables (squash, pumpkin, cucumber, bottle gourd, bitter gourd, musk melon, water melon); cole crops (broccoli, brussels cabbage, cauliflower); leafy vegetables (spinach, coriander, parseley, celery, lettuce); root and tuber crops (carrot, turnip, beet root, raddish,  turmeric, colocasia, cassava, yam, sweet potato); bulb crops (onion, garlic, leeks); leguminous crops (cluster bean, snap bean, green peas, broad bean); other crops (okra, asparagus, shallot, rhubarb).This book discusses various  factors that affect the vegetable crops during pre- and post harvest and suggest technology for effective management of vegetable crops at global level. Researches have been undertaken in various aspects in general and on individual crops.

Seed Priming

Seed priming (hydro-priming) is a technique involving soaking the seeds in water for some hours followed by drying in room temperature for few days and sowing in seed beds. The seed priming improved seedling vigour and yield of few vegetable crops (Maiti et al., 2009; Maiti et al., 2011). The standardization of technique involves at first soaking the seeds in petridishes to determine the time required for germination. Then the time calculated for each species for 1) half the time required for germination and 2) another time suboptimum below full germinations. Thus seeds of each species having 2 treatments (half the time of germination, another suboptimum) are dried in room temperature for seven days and sown in seed beds. We selected the treatment which have given maximum germination. We used this modified priming technique for various vegetable crops such as tomato, chilli, water melon, bitter gourd and few cucurbits. We found that this technique enhances flowering and the productivity of these vegetable crops which need to be confirmed in future researches.

In addition to general aspects mentioned above, we contributed to various aspects of vegetable crops.

Potato: Research advances in various aspects in potato are documented (Maiti and Singh, 2002).

Tomato: Research advances on various aspects on tomato are well documented.

Various reviews have been undertaken on tomato. The physiological basis of crop growth in tomato (Maiti et al., 2008 a), tomato biotechnology (Maiti et al., 2008b), factors affecting tomato productivity (Maiti et al., 2008 d), and advances in tomato technology (Maiti et al., 2009).

Common bean: Research advances on common bean and related species are well documented in two books (Maiti, 1997; Maiti and Singh, 2007).

Capsicum: In a book, research advances in Capsicum has been documented and similar in Capsicum and other crops such as pearl millet and other species (Maiti et al., 2007).

Water melon: Various aspects of water melon technology starting from germination up to biotechnology are documented (Maiti et al., 2011).

Bitter gourd: Bitter gourd has high demand for edible and high medicinal values. We narrated advances in bitter gourd technology (Maiti et al., 2009), biochemistry and food values (Maiti et al., 2008) and also therapeutic and food value (Maiti et al., 2009b).

Egg plant: Research advances on biotechnology of eggplant (Solanum melongena L.) have been documented (Maiti et al., 2008).

Okra: A review has been undertaken on research advances in okra (Abelmoschus esculentus L.) (Singh et al., 2007).

Abiotic Stress Resistance

Abiotic stress: Vegetable crops owing to its great demand and high economic importance are generally grown under high input situations with careful management. In African countries and Europe the crops are grown in green house condition for maximum production. But farmers cannot grow under high input conditions. In semiarid conditions they grow under rainfed situations where abiotic stresses like drought, salinity affect vegetable production. Most of them are irrigated with water from wells which are saline. Therefore, there is a necessity to select vegetable species with resistance to drought and salinity. In India farmers grow vegetables like okra, chilli, tomato under rainfed situations.

About 2/3 world arable land is affected with salinity. Salinity affects crop productivity at a global level. A comprehensive review has been undertaken on perspectives ofsalinity tolerance of some crops (Gozalez-Rodriguez and Maiti, 2010).

A review has been undertaken on research advances in salinity tolerance in vegetable crops (Maiti et al., 2006).

We developed novel strategy to screen crop cultivars (field and vegetable crops) for selecting cropcultivars resistant to salinity, drought, heat stress (Maiti, 2011 a; b). Using a simpe low cost technique, the pipe line of high yielding cultivars and selected crop species/varieties were screened for tolerance to salinity and drought. The crop cultivars, selected were found to perform well in saline or drought prone areas and well accepted by farmers.

We developed a simple inexpensive technique to screen pipe line crop cultivars or varieties for tolerance to salinity. This involves sowing the seeds of each crop cultivars in plastic pots filled with neutralized coconut pits with different concentrations of NaCl-solution (0.50 to 2 mL) and then selecting optimum concentration for evaluating the crop cultivars of a vegetable species for salinity tolerance level (for examle 1.50 M NaCl) (Maiti et al., 2008a, b). Using this simple technique we evaluated different vegetable crop species for tolerance to salinity.  We found large variability in salinity tolerance among different vegetable drops (Maiti et al., 2010). We also found genotypic variability in salinity tolerance of some vegetable crop species at germination and seedling stage (Maiti et al., 2011; Maiti, 2012). Root responses are indicators for salinity and drought stress in crop (Maiti, 2012).

Therefore, there is a necessity to select vegetable crops such as chilli, or okra/tomato tolerant to salinity for farmers fields under sustainable agriculture. We also utilized simple technique for evaluating crop cultivars for tolerance to drought under limited water supply.

References

Gonzalez-Rodriguez H., and Maiti R.K., 2010, Perspectives of salinity tolerance of some crops: a review, International Journal of Agriculture, Environment & Biotechnology, 3(1): 45-82

Maiti R.K. and Singh V.P., 2007, Research advances in common bean (Phasolus vulgaris L.) and related species, Agrobios (International) 81-904309-5-5, pp.197

Maiti R.K., 1997, Bean Science, Science Publishers, Lebanon, USA. and Oxford & IBH Co Pvt. Ltd., New Delhi, India, 534

Maiti R.K., 2011b, A Viable strategy for improving crop productivity under sustainable agriculture, International Journal of Bio-Resource and Stress Management, Editorial column, 2 (4): i-ii

Maiti R.K., 2011c. Genotypic variability in salinity tolerance of some vegetable crop species at germination and seedling stage, International Journal of Bio-resource and Stress Management, 1(3): 204-209

Maiti R.K., 2012b, Root responses are indicators for salinity and drought stress in crops, International Journal of Bio-Resource and Stress Management, Editorial, 3(3): i-iii

Maiti R.K., and Rodriguez H.G., 2008, Research advances in tomato biotechnology: a review, International Journal of Agriculture, Environment & Biotechnology, 1: 129-149

Maiti R.K., and Rodriguez H.G., 2008, Research advances in tomato biotechnology: a review, International Journal of Agriculture, Environment & Biotechnology, 1: 129-149

Maiti R.K., and Rodriguez H.G., 2012, Research advances in vegetable crops, Puspa Publishing House, Kolkata, India

Maiti R.K., and Rodriguez H.G., 2013, Production and post-harvest technology of world tuber and vegetable crops, Puspa Publishing House, Kolkata, India, 642

Maiti R.K., Gupta A., Umasahankar P., Raj K.D., and Vidyasagar P., 2009, Effect of priming on seedling vigour and growth and productivity of few vegetable species: Tomato, Chilli, Cucumber and Cabbage, International Journal of Agriculture, Environment & Biotechnology, 2(4): 368-374

Maiti R.K., Rodriguez H.G., and Sahib H., 2008, Development of a novel technique for evaluation of crop cultivars for salt tolerance: a new strategy for improvement of salt tolerance in crop plants, International Journal of Agriculture, Environment & Biotechnology, 1: A1- A-12

Maiti R.K., Rodriguez H.G., Sarkar N.C. and Vidyasagar P., 2009, Advances in tomato technology, New Delhi publishers. ISBN: 978-81-907421-2-2, PP.361

Maiti R.K., Sarkar N.C., Singh V.P. and Purohit S.S., 2007, Research advances in capscicum-pepper (pearl millet (Pennisetum glaucum L. Br.) and other species. Agrobios (International), ISBN 81-904309-3-9, 218

Maiti R.K., Vidyasagar P., PatilB.S., and Singh V.P., 2006, Research advances on salinity tolerance in vegetable crops- a review, Researchon Crops, 7(1): 44-54

Maiti R.K., Vidyasagar P., Umashanker P., Rajkumar D., and Ramaswamy A., 2011a, Botany of vegetable crops, Puspa Publishing House, ISBN 978-81-920073-1-1, PP 104

Maiti R.K. and Singh V.P., 2002, Advances in potato science, Crop Research, Vol. 23, Agricultural Information Centre, Hisar, India, ISBN 81-85290-07-5 India, pp.401

Maiti R.K, Rakshit A., and Sarkar N.C., 2008, Abiotic factors affecting Tomato productivity, mechanism of adaptations and management strategy, International Journal of Agriculture, Environment & Biotechnology, 1(2): 9-35

Maiti R.K., and Padmavati V., 2008, Research advances on physiological basis of crop growth in tomato, International Journal of Agriculture, Environment & Biotechnology, 1: 89-93

Maiti R.K., Vidyasagar P., Rajkumar D., Ramaswamy A., and Rodriguez H.G., 2011, Seed priming improves seedling vigour and yield of few vegetable crops, International Journal of Bio-resource and Stress Management, 2(1): 125-130

Padmavathi V., Maiti R.K., and Sudha R.T., 2008, Therapeutics and food value of bittergourd, International Journal of Agriculture, Environment & Biotechnology, 2(3): 310-314

Singh V.P., Maiti R.K., Kalpan K. and Hernandez-Pinero J., 2007, Research advances in okra or bhendi (Abelmoschus esculentus L.) –a review, Research on Crops, 8(2): 261-291