Identification of quantitative disease resistance Loci towards four Pythium species in soybean

Authors: CLEVINGER, ELIZABETH - Virginia Tech; BIYASHEV, RUSLAN - Virginia Tech; LERCH, ELIZABETH - Iowa State University; YU, HAIPENG - Iowa State University; Quigley, Charles - Chuck; Song, Qijian; DORRANCE, ANNE - The Ohio State University; ROBERTSON, ALISON - The Ohio State University; MAROOF, SAGHAI - Virginia Tech

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/8/2021
Publication Date: 3/30/2021
Citation: Clevinger, E., Biyashev, R., Lerch, E., Yu, H., Quigley, C.V., Song, Q., Dorrance, A., Robertson, A., Maroof, S. 2021. Identification of quantitative disease resistance Loci towards four Pythium species in soybean. Frontiers in Plant Science. 12:514. https://doi.org/10.3389/fpls.2021.644746.
DOI: https://doi.org/10.3389/fpls.2021.644746

Interpretive Summary: Soybean seed and seedling diseases caused by pathogens Phytophthora sojae and Pythium spp are prevalent in the United States and can be a constraint to growers. These pathogens were estimated to reduce yields in the United States by >90 million bushels each year. Pythium species are difficult to manage because they have a wide range of hosts including corn, wheat and cotton and produce oospores that persist in the soil for years. In addition, most fungicide seed treatments cannot efficiently protect developing roots due to their short lasting time in the soil. Developing varieties highly resistant to the disease becomes the most cost effective approach for producers to combat the diseases. Several previous studies have measured resistance towards different Pythium species and have identified mostly minor quantitative disease resistant loci. In this study, we evaluated four new sources of resistance to four Pythium species and created advanced populations with each of the new sources for gene identification. The study identified multiple loci resistant to each species of Pythium, including two with large resistant effect to multiple species of Pythium. These loci could be incorporated into existing elite lines of soybean to provide resistance to a wide range of Pythium species. The research provided new resources and information for breeders to improve soybean seed and seedling disease resistance.

Technical Abstract: In this study, four recombinant inbred line (RIL) populations were screened for their response to infection by Pythium sylvaticum, Pythium irregulare, Pythium oopapillum and Pythium torulosum. The parents, PI 424237A, PI 424237B, PI 408097 and PI 408029, had higher levels of resistance to these species in a preliminary screening and were crossed with ‘Williams’, a susceptible cultivar. A modified seed rot assay was used to evaluate RIL populations for their response to specific Pythium species selected for a particular population based on preliminary screenings. Over 2500 single nucleotide polymorphism (SNP) markers were used to construct chromosomal maps to identify regions associated with resistance to Pythium species. Several minor and large effect quantitative disease resistance loci (QDRL) were identified including one large effect QDRL on chromosome 8 in the population of PI 408097 x Williams, which was identified by two different disease reaction traits in P. sylvaticum, P. irregulare and P. torulosum.Another large effect QDRL was identified on chromosome 6 in the population of PI 408029 x Williams, and conferred resistance to P. sylvaticum and P. irregulare. These large effect QDRL will contribute towards the development of improved cultivars with higher levels of resistance to these common soil-borne pathogens.