Soybean Glycine max cultivars display different host resistance to Tetranychus urticae
Scott, I., S. Dhaubhadel, L. Chen, K. Drew, T. McDowell, J. Renaud. 2018. Soybean Glycine max cultivars display different host resistance to Tetranychus urticae. Platform presentation at the 10th Spider Mite Genome Meeting, Logrono, La Rioja, Spain, November 5-8, 2018.
Plain language summary
This presentation provided other spider mite researchers with findings from a Grain Farmers of Ontario funded project that investigated soybean host plant resistance to spider mites. We chose to study Ontario soybean cultivars with known levels of herbivore resistance and isoflavonoid leaf levels in order to determine whether resistance levels are correlated with the plant defense compounds. Greenhouse trials for 4 weeks determined that several cultivars were more resistant to mites than others, however, the correlation with leaf isoflavonoid levels was low. The information on relative resistance among the cultivars tested is useful to Ontario soybean growers. Follow-up studies to identify other leaf metabolites are in progress, and there appears to be a distinct metabolite profiles between susceptible and resistant cultivars, evidence that leaf chemistry underlies the resistance to mites.
In Ontario soybean and corn are the highest production crops. A secondary pest in soybean is the two-spotted spider mite. Due to predicted increase in the environmental conditions that favour spider mite growth under climate change, spider mites are considered an emerging pest in Ontario soybean. A project to investigate genetic resistance to the two spotted spider mite was initiated at AAFC London. Soybean cultivars were selected based on known resistance to insects and the levels of isoflavonoids, the recognized class of secondary plant metabolites for defense against pathogens and herbivores.Several soybean cultivars were determined to differ in resistance to spider mites at the end of the 4 week greenhouse trial. The most resistant cultivar was OAC Avatar. Other cultivars that had fewer mites and eggs in increasing abundance were: OAC Wallace < Pagoda < OAC Lakeview < OT06-22 < OT06-23. The remaining cultivars had on average 1.2 to 2.8x higher numbers of mites and eggs on the younger leaves.
There was a low correlation between isoflavonoid leaf levels and spider mite numbers on 12 cultivars. The findings indicate that other factors including other leaf metabolites may be more closely correlated with the observed mite resistance in certain cultivars.