Effect of Antibiotic Plant Resistance on the Reproductive Fitness of the Russian Wheat Aphid (Homoptera: Aphididae)

Abstract

Laboratory experiments were conducted to examine the effect of antibiosis on the reproductive fitness of the Russian wheat aphid, Diuraphis noxia (Mordvilko). Cumulative nymphal production was modeled for 6 wheat, Triticum aestivum L., plant introductions (PI 47545, PI 94355, PI 94365, PI 151918, PI 225245, PI 225262) and a susceptible standard, 'Stephens' wheat, with a nonlinear regression procedure that used the logistic equation. It was not possible to model the resistant standard, 'Border' oat, because of early mortality and lack of nymphipositional activity. The maximum nymphal production (M) ranged from 68.3 (PI 225262) to 87.2 nymphs per female (Stephens wheat). The rate of increase, or increase in nymphal production rate, ranged from 2.4 (PI 225262) to 3.0 (Stephens wheat). The lag time ranged from 2.5 (Stephens wheat) to 2.7 log (days) (PI 151918). Lag time represented the period before the adult female began to produce nymphs. The original time scale (days), was transformed (natural log) to evaluate the early lag phase in these data. Contrasts of parameters M and K, and joint hypothesis testing (comparison of entire curve) among Stephens wheat and the selected resistant plant introduction lines indicated that there were significant differences between Stephens wheat and all plant introduction lines examined for all parameter comparisons (M, K, and whole curve). Estimated models from trial 1 were applied to data from trial 2 to validate the suitability of the models to describe the nymphal production process. Examination of residuals (defined as the difference between the predicted value and the observed value) suggested that although the models tended to slightly overestimate nymphal production, they adequately represented nymphal production data for all plant introduction lines as well as Stephens wheat.