Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2025
Publication Date: 3/18/2025
Citation: Clevinger, E., Biyhev, R., Schmidt, C., Song, Q., Robertson, A., Dorrance, A., Maroof, S. 2025. Mapping of Phytophthora sojae resistance in soybean genotypes PI 399079 and PI 408132. Crop Science. 65(2). Article e70027. https://doi.org/10.1002/csc2.70027.
DOI: https://doi.org/10.1002/csc2.70027

Interpretive Summary: Root and stem rot is among the most important soybean diseases in the United States after cyst nematode and causes an estimated $1-2 billion in losses globally each year. Multiple recent surveys have shown that the disease pathotypes in the north-central United States are more diverse and complex. This pathogen is a soil-borne oomycete that thrives in warm, saturated soil, promoting zoospore development, motility, and infection of soybean roots. Symptoms of root and stem rot early in the growing season include seed and seedling disease and pre- and post-emergence damping-off. Previous research found that PI 399079 and PI 408132 may contain new genes that resist the disease, but this conclusion has not been confirmed. Researchers at Virginia Tech, Iowa State University,Ohio State University, and USDA-ARS (Beltsville, MD) mapped resistance genes in two descendant populations of PI 399079 and PI 408132. They discovered new resistance genes to the disease on chromosomes 3, 7, 13 and 18 in two accessions. Research shows that PI 399079 and PI 408132 are additional sources of the disease resistance, so the genes from these two materials can be used to integrate resistance into soybean varieties and develop varieties with enhanced resistance to root rot and stem rot.

Technical Abstract: umerous novel sources of resistance to Phytophthora sojae which causes Phytophthora root and stem rot of soybean (Glycine max, [L.] Merr) have been identified, but not all loci have been mapped nor cloned. Two plant introductions (PI)s, PI 399079 and PI 408132, were identified as sources of Rps-gene mediated resistance through inoculations with numerous isolates individually and a combination of 3-isolates of P. sojae. Resistance was mapped in advanced recombinant inbred line (RIL) populations derived from crosses of the susceptible cultivar Williams and the two PIs. Quantitative trait locus mapping identified 4 and 3 QDRL for PI 399079 and PI 408132, respectively; but each locus conferred resistance to a different group of P. sojae isolates. QDRL were identified on chromosome 7, one of which is novel and the second may be an allele of Rps11 previously identified in PI 594527.