Medicago sativa’s antixenotic and antibiotic resistance mechanisms differentially impact three members of the Bemisia tabaci species complex

The Bemisia tabaci species complex threatens worldwide agriculture. While host-plant resistance is sustainable and effective, it is a relatively unexplored strategy for whitefly control. Three alfalfa (Medicago sativa L.) populations were developed and used in high-throughput B. tabaci MEAM1 nymph-mortality screens. The phenotypic resistance/susceptibility spectrum in these populations indicated that whitefly resistance to MEAM1 is multigenic. Alfalfa lines highly resistant (R1, R2, and R3) and susceptible (S1) to B. tabaci MEAM1 were identified and further characterized. When life history parameters for three B. tabaci species (MEAM1, MED and NW1) were assessed on the four lines, whitefly species-specific responses to R1, R2 and R3 plants were revealed. While nymph mortality was high for MEAM1 and NW1 on resistant alfalfa, MED nymph development was surprisingly unimpaired. In addition, significant differences in oviposition, host-choice and longevity were observed amongst the three B. tabaci species. Collectively, these data indicated that R1, R2 and R3 plants each express a unique set of antibiotic/antixenotic resistance traits providing a potent multigenic and multi-faceted resistance to whiteflies with each B. tabaci species displaying distinct behaviors on the resistant lines. Our nymph-mortality simulation models indicate that deployment of the nymph mortality-mediated resistance of R1 and R3 alfalfa could substantially suppress whitefly population expansion in the field.