2015
Role of ethylene on soybean SDS: Potential use for disease management
Contributor/Checkoff:
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Lead Principal Investigator:
Leonor Leandro, Iowa State University
Co-Principal Investigators:
Silvia Cianzio, Iowa State University
Gustavo MacIntosh, Iowa State University
+1 More
Project Code:
450-45-15
Contributing Organization (Checkoff):
Institution Funded:
Brief Project Summary:

Ethylene is a biological hormone that regulates physiological processes in plants, such as seedling emergence, fruit ripening and senescence. Ethylene is also a major component of plant defenses, and elevated ethylene has been shown to increase plant resistance to several pathogens, including bacteria, fungi and viruses. Ethylene-insensitive soybean mutants showed reduced disease in response to Pseudomonas syringae pv. glycinea and Phytophthora sojae, suggesting that ethylene-insensitivity decreases susceptibility to disease. This project investigates the possible role of ethylene in enhancing resistance and/or decreasing the susceptibility to sudden death syndrome.

Key Benefactors:
farmers, agronomists, Extension agents

Information And Results
Project Deliverables

• Tested the effect of three ethylene suppressors (cobalt chloride, MCP and STS) and one ethylene enhancer (ethephon) on SDS severity and Fv population in soil, in greenhouse conditions.
• Measured the change in expression of ethylene response genes and defense response genes in plants treated with ethephon, cobalt chloride, or MCP, before and after Fv inoculation.
• Determined the rate and timing of ethephon that is most effective at reducing SDS in two soybean cultivars, in the greenhouse.
• Conducted field trials in three Iowa locations to test the effectiveness of ethephon in suppressing SDS and protecting yield in field conditions.
• Presented research results at the scientific conferences, departmental seminars and industry meetings

Final Project Results

Objective 1
Exp 1: We found that application of the ethylene inducer ethephon as a soil drench was effective at reducing SDS foliar symptoms compared to the water control, in greenhouse conditions. In contrast, MCP and cobalt chloride treatments did not significantly affect SDS severity. Treatment with ethephon did not affect Fv populations in soil, indicating that the suppression of SDS is not mediated by a direct effect on the pathogen.

Exp 2: Seedlings treated with ethephon (4mM) showed up-regulation of all defense-related genes tested (PR1, PR2, PR3, PR10, and chalcon synthase), compared to cobalt chloride or water treated seedlings, at all time points. This increase of expression of defense genes is the likely cause of SDS suppression after ethephon application. Cobalt chloride did not affect expression of defense related genes.

Objective 2.
Exp 3: All ethephon rates tested caused a reduction in SDS foliar disease severity compared to the water treated control, independently of time of application, but the higher rates caused a significantly greater reduction in SDS. For this reason, the rate of 4mM was used for field experiments.
Field experiment: At the Hinds farm location, ethephon applications at planting and at emergence reduced SDS severity and incidence compared to the water-treated plants. Foliar applications at V2 did not affect SDS. The impact on yield was not significant but there was a numerical trend for higher yield in plots treated with ethephon at planting. Results at the other two locations were inconclusive due to low disease pressure.
Triple response tests: the assay tested was not sensitive enough to detect differences in sensitivity to ethylene among soybean genotypes. A new approach will be tested in the next funding year.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.