Bottom-up effects of plant genetic variation on virus transmission dynamics between an insect host and its pathogen

Background/Question/Methods

Declines in biodiversity leading to altered structure and function of ecological communities have been well documented, while the importance of genetic variation within a single species has been given less focus. Currently, research focusing on the loss of plant genetic variation has often centered on effects among plants while considerably less attention has been given to how a loss in genetic variation can alter community interactions -- particularly, interactions among species at higher trophic levels. While reduction in plant genetic variation can lead to changes in species interactions at higher trophic levels, we know little about the mechanisms responsible for these changes. One possible effect of reducing genetic variation is that it may affect the interaction between host and their pathogens. This may be of notable concern for pathogens that can regulate pests and prevent undesired outbreaks. To examine the effects of plant genetic variation on higher trophic levels, we conducted a series of experiments examining how feeding preferences/rates of soybean looper (Chrysodeixis includes) and the transmission of a lethal baculovirus, Autographa californica multicapsid nucleopolyhedrovirus (ACMNPV), varied across nine different genotypes of soybean (Glycine max).

Results/Conclusions

Plant genetic variation altered disease dynamics in higher trophic levels. The probability of soybean loopers becoming infected varied by as much as 6 times among differing genotypes. There were also differences in feeding preferences (t₁₇₇ = 2.61, p = 0.01) and feeding rates (F_{10, 319} = 6.26, p < 0.001) among plant genotypes. For example, feeding preferences varied by as much as 2 times and feeding rates differed by as much as 2.5 fold among genotypes. Our results suggest that variation in feeding rates and preferences were genotype dependent and may lead to differences in virus transmission dynamics by changing the likelihood of exposure and consumption of the baculovirus. These results highlight the importance of considering genetic variation when implementing conservation strategies or biocontrol efforts. The latter being particularly important given that baculoviruses are often employed as biocontrol agents. In general, developing and evaluating methods that will increase the efficacy of baculovirus use in the future and, thereby, reducing harm to non-target species are of critical concern in conservation.