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ARS Home » Midwest Area » Urbana, Illinois » Soybean/maize Germplasm, Pathology, and Genetics Research » Research » Publications at this Location » Publication #323847
Title: Responses of soybean genotypes to pathogen infection after the application of elicitors

Author
item PAWLOWSKI, MICHELLE - University Of Illinois
item Bowen, Charles
item HILL, CURTIS - University Of Illinois
item Hartman, Glen

Submitted to: Crop Protection
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/19/2016
Publication Date: 6/1/2016
Citation: Pawlowski, M.L., Bowen, C.R., Hill, C.B., Hartman, G.L. 2016. Responses of soybean genotypes to pathogen infection after the application of elicitors. Crop Protection Journal. 87:78-84.

Interpretive Summary: Soybean diseases and pests often affect soybean production. One emerging pest management method is to treat plants with chemical elicitors at nontoxic levels to induce host resistance. The objective of this research was to determine if elicitors, benzothiadiazole, chitosan, phenylalanine, and salicylic acid applied to soybean foliage could alter the response of soybean genotypes to soybean pathogens. In the greenhouse, soybean genotypes were challenged with three pathogens 48 hours after elicitation. Plants of the cultivar Pharaoh treated with salicylic acid, and then inoculated with the fungus causing charcoal rot had shorter stem lesion lengths than the water control. Plants of soybean genotype LD00-2817p treated with benzothiadiazole, phenylalanine, or salicylic acid, and then inoculated with the pathogen causing Phytophthora root and stem rot had survival rates of 41%, 57%, and 32%, respectively, which were greater than the water control plants of which only 4% of the plants survived. The four elicitors and a water control were evaluated on two soybean genotypes in the field. Foliar disease incidence and severity were low for both years, but there were some differences in stem disease ratings. Charcoal rot severity rating was reduced from 2.0 in the water control to 1.1 when plants were treated with a phenylalanine treatment. Both greenhouse controlled experiments and field experiments showed that genotype-specific elicitation reduced diseases in some cases, but the differences were greater under controlled-inoculated conditions in the greenhouse. This information is important to scientists and producers interested in research on managing soybean diseases by stimulating the soybean defense responses to pathogens.

Technical Abstract: Soybean diseases and pests can affect soybean production. One emerging pest management method is to treat plants with chemical elicitors at nontoxic levels to induce host resistance. The objective of this research was to determine if elicitors, benzothiadiazole (BTH), chitosan (CHT), phenylalanine (PHE), and salicylic acid (SA) applied to soybean foliage could alter the response of soybean genotypes to soybean pathogens. Two of the soybean genotypes had been previously shown to produce high or low amounts of reactive oxygen species (ROS) in response to elicitation. In the greenhouse, soybean genotypes were challenged with three pathogens 48 hours after elicitation. Plants of the cultivar Pharaoh (susceptible control) treated with SA, and then inoculated with Macrophomina phaseolina had a shorter (alpha = 0.05) stem lesion length (34 mm) than the water control (55 mm). Plants of soybean genotype LD00-2817p (high capacity to produce ROS) treated with BTH, PHE, or SA, and then inoculated with Phytophthora sojae had survival rates of 41%, 57%, and 32%, respectively, which were greater (alpha = 0.05) than the water control (4% of plants survived). The four elicitors and a water control were evaluated on LD00-2817p and LDX01-1-65 in the field for two consecutive years. Foliar disease incidence and severity were low for both years, but there were some differences in stem disease ratings. For example, for charcoal rot in 2013, the severity rating was reduced (a = 0.05) from 2.0 in the water control to 1.1 with a PHE treatment for LD00-2817p and was reduced (alpha = 0.05) from 3.8 in the water control to 2.6 with SA for LDX01-1-65. Both greenhouse controlled experiments and field experiments showed that genotype-specific elicitation reduced diseases in some cases, but the differences were greater under controlled-inoculated conditions.