Nine black gram genotypes were evaluated against B. tabaci at 3rd trifoliate leaf stage using 100 whitefly adults per plant in multiple-choice test under screen-house during kharif 2009 and 2010. On the basis of whitefly resistance index (WRI) calculated over two years of study, the genotypes KU 99-20 and NDU 5-7 were categorized as moderately resistant as they recorded WRI of 1.50. The genotypes IPU 02-043, KU 7-602, KU 7-605, KU 7-618 and Mash 1-1 recorded WRI ranging from 2.59 to 3.05 and hence were categorized as susceptible. The remaining two genotypes, viz. KU 7-504 and KU 7-505 recorded the highest WRI ranging from 3.66 to 3.70 and thus, were categorized as highly susceptible to B. tabaci. All the genotypes, except KU 99-20 and NDU 5-7, scored leaf injury grade V after 6 weeks. Hence, it can be concluded that the optimum period for the complete differentiation of susceptible and resistant black gram genotypes could be taken between 5th and 6th week after release of whiteflies in multiple-choice test under screen-house conditions.
Crop productivity is greatly influenced by various environmental stresses, of which insect herbivory-induced biotic stress assumes much significance. As a consequence of insect herbivory, a number of plant biochemical processes involved in the tolerance mechanism are affected. Different studies have demonstrated a diverse functional role of various plant oxidative enzymes in protecting plants against biotic stress induced by insect herbivory. Comprehensive profiling of stress-associated plant oxidative enzymes is most relevant to successful molecular breeding of stress-tolerant crop plants. Thus, better understanding of the biochemical basis of plant defense mechanisms is imperative, not only from a basic science perspective, but also for biotechnology-based pest control practice. In this review, we emphasize the potential role of various oxidative enzymes in plant defense against insect herbivory.