D3274: Effect of external application of phytohormones on resistance of wheat seedlings to Hessian fly (Diptera: Cecidomyiidae) infection under heat stress

Hessian fly is one of the most destructive insect pests of wheat plants. Plants often depend on phytohormones to activate complex signaling networks to protect themselves against diseases and insect attacks. Our hypothesis is that the external application of phytohormones affects the susceptibility of wheat plants to Hessian fly under heat stress. We infested a Hessian fly-resistant wheat cultivar, Molly, and a susceptible cultivar, Newton, with an avirulent Hessian fly biotype GP. The plants were sprayed with 2 mM solutions of Jasmonic Acid (JA), Salicylic Acid (SA), Indole Acetic Acid (IAA), and 12-Oxophytodienoic Acid (OPDA), respectively, prior to heat stress at 30 °C for 24 hours, The resistance efficiency of plants was measured and analyzed by comparing the percentage of susceptible plants and the percentage of live insects between the treatments and control plants, respectively. Our results suggest that the external application of different phytohormones affect wheat resistance differently under heat stress. Specifically, OPDA, SA, IAA decreased, but the JA increased the susceptibility of wheat plants to Hessian fly infestation under 30°C heat stress. Our finding sheds light on the mechanism of heat-induced loss of host plant resistance to insects.