Characterization of soybean STAY-GREEN genes in susceptibility to foliar chlorosis of Sudden Death Syndrome

Authors: CHANG, HAO-XUN - Michigan State University; TAN, RIUJUAN - Michigan State University; Hartman, Glen; WEN, ZIXIANG - Michigan State University; SANG, HYUNKUY - Michigan State University; Domier, Leslie; WHITHAM, STEPHEN - Iowa State University; WANG, DECHUN - Michigan State University; CHILVERS, MARTIN - Michigan State University

Submitted to: Journal of Plant Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/27/2019
Publication Date: 4/5/2019
Citation: Chang, H., Tan, R., Hartman, G.L., Wen, Z., Sang, H., Domier, L.L., Whitham, S.A., Wang, D., Chilvers, M.I. 2019. Characterization of soybean STAY-GREEN genes in susceptibility to foliar chlorosis of Sudden Death Syndrome. Journal of Plant Physiology. 180:711-717. https://doi.org/10.1104/pp.19.00046.
DOI: https://doi.org/10.1104/pp.19.00046

Interpretive Summary: A soilborne fungus causes sudden death syndrome (SDS) of soybean in the United States. This fungal pathogen inhabits soil and produces multiple phytotoxins, which are translocated from infected roots to leaves, causing a rapid onset of SDS foliar chlorosis and necrosis. Because SDS foliar symptoms are solely induced by phytotoxins, it represents a unique system to study plant-phytotoxin interactions. Yield reductions caused by SDS have been documented at 5–15% and the economic loss was estimated up to $669 million USD in a single year. One method to control SDS is through the deployment of partially resistant soybean cultivars. In this study we used linkage mapping and a genome-wide association study (GWAS) to dissect soybean resistance to phytotoxin-induced SDS foliar chlorosis. Two soybean STAY-GREEN genes were found to be associated with development of chlorosis, and resistance to SDS foliar chlorosis was attributed to a double mutation of the STAY-GREEN genes. Although the role of STAY-GREEN genes with a loss-of-susceptibility mechanism arrested chlorosis development, the breeding merits of STAY-GREEN genes with a loss-of-susceptibility mechanism may be in question because this trait differs by soybean type (different genotypes or varieties). Engineering soybean STAY-GREEN genes to lose susceptibility may provide resistance to SDS foliar chlorosis without detrimental agronomic traits. This information will be of most interest and use to plant geneticists, soybean breeders and pathologists interested in molecular aspects of host-pathogen interactions.

Technical Abstract: Fusarium virguliforme causes sudden death syndrome (SDS) of soybean in the United States. This fungal pathogen inhabits soil and produces multiple phytotoxins, which are translocated from infected roots to leaves, causing a rapid onset of SDS foliar chlorosis and necrosis. Because SDS foliar symptoms are solely induced by phytotoxins, it represents a unique pathosystem to study plant-phytotoxin interactions. SDS foliar symptoms typically appear near flowering through late reproductive growth stages, with chlorotic spots that gradually develop into interveinal chlorosis and necrosis. Among more than 80 quantitative trait loci (QTLs) reported for SDS, only a few QTLs are reproducible due to the complexity of SDS etiology and environmental interactions. Here, we applied similar experimental approaches, using linkage mapping and a genome-wide association study (GWAS) to dissect soybean resistance to phytotoxin-induced SDS foliar chlorosis. Two soybean STAY-GREEN genes (GmSGR1 and GmSGR2) were found to be associated with development of chlorosis, and resistance to SDS foliar chlorosis was attributed to a double mutation of the STAY-GREEN genes. Soybeans with a double mutation of GmSGR1 and GmSGR2 stayed green but displayed necrosis and reduced photosynthesis in response to phytotoxins produced by F. virguliforme. These results demonstrated that STAY-GREEN, as an R gene with a loss-of-susceptibility mechanism, may have different merits in resistance breeding depending on the allele types or the plant species.