Status, scope and strategies of arid legumes research in India-A review

Arid legumes are adjudged for sustaining growth and production, especially in drier eco-systems encountered with harsh and hostile growing environments. Sustained breeding efforts have been made to improve these crops so as to make them more productive. In guar [Cyamopsis tetragonoloba (L.) Taub.], early maturing (85–90 days) varieties like, ‘RGC-936’, ‘HG-365’ and ‘HG-563’ suited to 300–400 mm rainfall, medium maturing(90–105 days)varieties like,‘RG-1002’, ‘RGC-1003’, ‘RGC-1038’, ‘HG-870’ and ‘HG-884’ suited to 400–450 mm rainfall and long duration (110–120 days) varieties like, ‘H-220’ and ‘RGC-986’ suited to 500–550 mm rainfall have been developed. Guar cultivar ‘RGC-1066’ is also suitable for mechanical harvesting. In cowpea [Vigna unguiculata (L.) Walp.], varieties with improved plant types and early maturity (60–62 days) like, ‘RC-101’, mediummaturitylike, ‘Co (CP-7)’ (67–73 days) and ‘GC-3’ (90–95 days and adapted to whole country) and late maturity (>95 days) like, ‘V-585’, ‘V-240’ and ‘KBC-2’ withdualpurposehave alsobeendeveloped.Inmothbean[Vigna aconitifolia (Jacq.) Marechal], varieties with erect upright growth(‘FMO-96’maturedin58-60 days),erect growth(‘RMO40’, ‘RMO-225’ and ‘CAZRI-Moth-3’ in 60–63 days), semi-erect growth (‘CAZRI Moth-2’ in 66–68 days) and semi-spreading growth (‘CAZRI Moth-1’ in 72–74 days) suiting to 150–400 mm rainfall have been developed. In horsegram [Macrotyloma uniflorum (Lam.) Verd], promising varieties maturing in 85–90 days (‘AK-21’ and ‘AK-42’), 90–100 days (‘PHG-9’, ‘CRIDA-118R'and‘BJPL-1’)and105-111 days (‘VLG-15’and‘VLG-19’) have also been released. Besides this, protocols for rapid callus induction and regeneration systems have also been developed in arid legumes. QTLs for resistance to thrips damage have been identified in cowpea. Efficient cropping sequences like, guar-mustard and guar-wheat are widely followed in northern India. In southern states, growing short duration horsegram with rice by replacing cowpea is beneficial. In Orissa and parts of Andhra Pradesh, horsegram is successfully cultivated in rice/maize/sorghum sequences. Beneficial effects of intercropping guar with pearl millet/sorghum/maize/castor have also been observed. Moth bean+pearl millet (3:1) intercropping system is effective in arid situations. However, cowpea+castor (6:1) is found to have the highest monetary return over other intercropping systems. Foliar application of ZnSO₄ @ 0.5% at 25 or 45 days of sowing (DAS) has been useful with 15–20% higher seed yield in guar, cowpea and moth bean. Basalin @ 1.0 kg a.i./ha in moth bean and guar; and pendimethalin @ 0.75 kg a.i./ha + one hand weeding in cowpea are useful for effective weedcontrol withleast weedindex. Organic, inorganic, biocontrol management and IPM strategies have also been developed against major pests and diseases. Guar gum (galactomannan) - a polysaccharide organic compound - is used in a number of industrial products where water is an important factor. However, varieties having more than 32.0% gum content and higher viscosity of guar gum (4000–5000 cP) are more preferred for export. Guar meal (a by-product of guar gum industries) can also replace edible oil cakes due to its higher crude protein (40–45%). Future strategies for these arid legumes are also discussed.