Population Dynamics and Clonal Comparisons of Cowpea Aphid (Homoptera: Aphididae) on Resistant and Susceptible Cowpea Cultivars

摘要

Survivorship, growth, and reproductive performance of cowpea aphid, Aphis craccivora Koch, were studied on whole plants and excised plant tissues of aphid-resistant (‘ICV-12') and aphid-susceptible (‘ICV-1') cultivars of cowpea, Vigna unguiculata (L.) Walp. In a greenhouse study, clonal populations derived from individuals that were originally collected from 5 different locations were studied on plants of the 2 cultivars to assess possible development of aphid biotypes. In the laboratory, performance of 1 clone was studied on excised leaves, flowers, and pods to assess tissue localization and effect of injury on ICV-12 resistance. Aphid life table parameters measured included survivorship, reproductive period, intrinsic rate of increase, net rate of reproduction, number of generations and generation time. Aphid reproductive performance and life table parameters were significantly reduced on seedlings and excised tissues of ICV-12 plants compared with ICV-1. Survivorship, intrinsic rate of increase and net rate of reproduction of populations were most adversely affected. Antibiosis appeared to contribute to aphid resistance in ICV-12. Effects of excised ICV-12 foliage were stronger than those of flowers or pods. Thus, the resistant factor in ICV-12 apparently was based in seedling foliage. However, there were no differences among excised tissues of ICV-1. Trends in the results indicated that there was no variability among the different populations in their demographic statistics on each cultivar. Thus, there did not seem to be biotype development or breakdown of ICV-12 resistance in any of the A. craccivora populations