In Vitro Regeneration and Genetic Transformation of Cowpea, Mungbean, Urdbean and Azuki Bean

Vigna species contribute a vital component of vegetarian diet of the resource poor population of underdeveloped and developing countries. Focus is to increase its yield by elevating and/or imparting resistance for diseases, insect pests and rescuing from natural genetic inadequacies. Absence of sufficient and satisfactory level of genetic variability within the germplasm has been the major hurdle in their improvement by conventional breeding. The immense potential of biotechnological tools to supplement breeding programmes to bring into elite germplasm of Vigna species is being realized. Much progress has been made in in vitro regeneration of sexually mature plants, in majority of these recalcitrant species, from various tissues and considerable success in generating plants from protoplast of Vigna aconitifolia. While attempts are being made to develop suitable transformation protocols for most of these species, commendable success has been achieved in Vigna angularis by generation of transgenics resistant to storage pests. An overview of the in vitro regeneration and critical analysis of the genetic transformation studies in major Vigna species is presented. The bottlenecks to overcome their recalcitrance vis-a-vis the advantages and limitations of all those transformation techniques applicable, along with future directions in research, are discussed.