Identification of Quantitative Disease Resistance Loci Toward Four Pythium Species in Soybean.

Elizabeth M Clevinger,Charles Quigley,Ruslan Biyashev,Alison E Robertson,Qijian Song,Elizabeth Lerch-Olson,Anne E Dorrance,M A Saghai Maroof,Haipeng Yu

doi:10.3389/fpls.2021.644746

Abstract

In this study, four recombinant inbred line (RIL) soybean 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 × Williams. It 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 × Williams, and conferred resistance to P. sylvaticum and P. irregulare. These large effect QDRL will contribute toward the development of improved soybean cultivars with higher levels of resistance to these common soil-borne pathogens.

Highlights

Soybean [Glycine max (L.) Merr.] is a major oil and protein crop grown worldwide
Four advanced generation recombinant inbred line (RIL) populations developed from new sources of resistance to Pythium were screened for disease reaction and subsequent mapping of quantitative disease resistance loci (QDRL) toward four Pythium species
We used two disease reaction phenotypes based on a seed rot assay in which the seeds are directly infected by the pathogen to identify the QDRL

Summary

Introduction

In the United States in 2017, soybean was planted on more than 40 million production acres with a value of $41 billion (American Soybean Association, 2017). Seed and seedling diseases of soybean have been reported in all soybean growing regions of the United States and can be a constraint to production (Wrather and Koenning, 2006). Reduced stand, seed rot, and seedling damping-off are symptoms of seedling diseases. If infected plants survive, they may be less vigorous with reduced yield (Broders et al, 2007). From 2010 to 2014, seedling diseases were among the Identification of QDRL Toward Pythium top 10 most yield-limiting diseases of soybean in both the northern and southern United States (Allen et al, 2017)

Methods

Discussion

Conclusion