D3270: Auxin and the susceptibility of wheat resistance to Hessian fly under heat stress

Hessian fly is one of the most destructive insect pests of wheat plants. Elevated concentration of phytohormone auxin has been found in susceptible wheat plants upon Hessian fly infestation. Our hypothesis is that the external application of auxin increases the susceptibility of wheat plants to Hessian fly under heat stress. We infested two Hessian fly-resistant wheat cultivars, Molly, Iris, and a susceptible cultivar, Newton, with an avirulent Hessian fly biotype GP. The plants were sprayed with 2 mM SA, JA, OPDA, and indole acetic acid (IAA) solutions and their combinations, respectively, prior to heat stress of 35ºC for 24 hours. The resistance efficiency of plants in each treatment was measured and analyzed by comparing the percentage of susceptible plants and the percentage of live insects among treatments, respectively. Our results suggest that the external application of phytohormones IAA and SA enhances the susceptibility of wheat plants to Hessian infestation. Our finding sheds light on the mechanism of heat-induced loss of host plant resistance to insects.