Use of indices based on consumption and utilization of food as a criterion to evaluate putative transgenic pigeonpea plants for resistance to pod borer Helicoverpa armigera

The increasing need for food can be met through an increase in crop productivity and reduction in pest associated losses. Recombinant DNA technology has created new avenues for genetic enhancement of crops through the development of transgenic plants with resistance to insects. Bacillus thuringiensis (Bt) genes have been widely used as candidate genes for genetic transformation of crop plants for resistance to insect pests (Hilder and Boulter 1999, Sharma et al. 2004). In addition, non-Bt genes such as soybean trypsin inhibitor (SBTI), cowpea trypsin inhibitor (CpTI) and lectin genes have also been exploited to produce insect-resistant plants. Soybean trypsin inhibitor and plant lectins have been found to reduce larval growth and disrupt normal development of H. armigera in artificial diet (Johnston et al. 1993, Shukla et al. 2005). Transgenic pigeonpea (Cajanus cajan) plants with Bt and SBTI genes have been recently developed to reduce the losses due to H. armigera (Sharma et al. 2006). There is a need to develop standardized protocols for evaluation of transgenic plants for resistance to insect pests, and their interaction with other non-target herbivores, and the natural enemies of crop pests. The present studies were therefore conducted to assess the usefulness of indices based on consumption and utilization of food and diet incorporation assay to assess the usefulness of putative transgenic plants of pigeonpea for resistance to H. armigera.