Biotic stresses affecting legumes production in the Indo-Gangetic Plain

On the basis of current knowledge, an attempt has been made to categorize the biotic constraints of the grain legumes groum in the riceand wheat-based cropping systems of the Indo-Gangetic Plain (1GP) of Bangladesh, India, Nepal, and Pakistan. Diseases and insect pests rank high overall, whereas weeds assume greater importance in the rainy season legumes. Nematodes are reported to affect legumes but information on the losses caused by them is scanty. The major contributors to yield losses are foliar diseases and pod borers. Despite the obvious signs of damage caused by various root diseases, their impact on yield is moderate. The diseases of food legumes are also determined by plant type (specifically the configuration of crop canopy), cropping system, imbalances in soil nutrients, and crop rotation but their detailed effects on the incidence and severity of diseases remains unclear. Similarly, interaction between soilborne diseases and nematodes is obvious, but research on their combined effect on yield losses has rarely been documented. For each legume the important diseases, insect pests, and weeds, with prospects for alleviating the constraints, are discussed. Although availability of host plant resistance to the major biotic constraints have so far proven to be of limited use, we suggest that genetic resistance offers greater opportunities for strategic research investments. Redesigning of crop canopies such that they support a less conducive microclimate for infection and spread of fungal diseases needs greater research focus. Also, development of short-duration cultivars to escape drought and drought predisposed diseases such as fusarium wilt (late) in chickpea and aflatoxin infection in groundnut, and the incorporation of drought-resistance traits is worth pursuing. There is a need to understand the consequences of the intensive rice-wheat cropping system on the changing scenario of pests of legumes