Molecular marker-assisted selection: a novel approach for host plant resistance to insects in grain legumes

Grain such as chickpea, pigeonpea, cowpea, fieldpea, lentil, grams, beans, soybean, and groundnut play an important role in "the daily diets the people worldwide. Being a rich source of protein, they are damaged by. a large number of insect pests such as legume pod borer, corn earworm, pod borer, aphids, white fly, tobacco caterpillar, leafhoppers, thrips and bruchids. of resistance to insects in grain legumes have been identified long ago, but these have not been used. effectively in crop improvement because of the difficulties involved in screening and selection of the test material under conditions. Molecular markers can play an important role in accelerating the introgresslOn of genes conferring to target insects into high-yielding cultivars, understanding the nature of gene action, and reducing the deleterious effects introgressing unwanted genes from wild species through linkage drag. Molecular breeding also offers the opportunity to pyramid different sources of resistance that could not be effectively selected through conventional breeding due to identical phenotypes and thereby accumulate levels of resistance and/or create potentially more durable resistant cultivars. Considerable has been made in developing genetic linkage maps of chickpea, cowpea, and soybean, while much remains to be done in pigeonpea, beans, lentil, and fieldpea. Preliminary identification of molecular markers resistance to insects in soybean, chickpea, mungbean, fieldpea, and cowpea has been reported. However, no distinct advantage has been observed by using assisted selection resistance to insect pests over the conventional approach, and in most cases, the epistatic are also quite high. Thus, a new paradigm approach may be required to combine conventional approaches and marker-assisted selection in such way as to create systems better than either approach. This paper reviews current state-of-the-art concerning conventional and molecular breeding for pest resistance, and highlight the opportunities and con~traints for use of molecular markers for accelerating the pace of development of insectresistant culrivars in grain legumes