Poster Session: Molecular and Cellular Plant-Microbe Interactions - Plant Defense Responses
748-P
Ethylene elicits soybean defense responses and reduces symptoms of sudden death syndrome.
N. ABDELSAMAD (1), G. MacIntosh (1), L. Leandro (1)
(1) Iowa State Univ, Ames, IA, U.S.A.
The role of ethylene on soybean response to Fusarium virguliforme (Fv), the causal agent of soybean sudden death syndrome (SDS), was investigated in a resistant and a susceptible cultivar. Seedlings were drenched at the first unifoliate stage with either ethephon, an ethylene inducer, or cobalt chloride, an ethylene suppressor. To block ethylene perception, seedlings were sprayed with 1-MCP until runoff. All treatments were applied twice, 24 h before and after inoculation with an Fv infested sand-cornmeal mix. Defense response genes were quantified 0, 2, and 4 days after inoculation (DAI) using qPCR. Foliar and root symptoms, and Fv density in soil were assessed 21 DAI. In both cultivars, SDS foliar symptoms at 21 DAI were lower in ethephon treated seedlings compared to water controls (P<0.05). Ethephon activated expression of the ethylene biosynthesis genes ethylene oxidase (ACO) and ethylene synthase (ACS), while cobalt chloride and 1-MCP treatments had no effect on ethylene levels. Treatment with ethephon increased induction of soybean defense response genes such as pathogenesis related proteins (PR), basic peroxidase (IPER) and chalcone synthase (CHS), compared to the other treatments at all time points (P<0.05). Treatment with ethephon or cobalt chloride had no effect on Fv density in soil. This study suggests that ethephon application induced resistance against SDS, possibly by induction of soybean ethylene levels and defense response genes.