Phenotypic characterization of a major quantitative disease resistance locus for partial resistance to phytophthora sojae

Authors: STEPHANIE, KARHOFF - The Ohio State University; LEE, SUNGWOO - Chunghnam National University; Mian, Rouf; RALSTON, TIMOTHY - The Ohio State University; NIBLACK, TERRY - The Ohio State University; DORRANCE, ANNE - The Ohio State University; MCHALE, LEAH - The Ohio State University

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/6/2019
Publication Date: 5/16/2019
Citation: Stephanie, K., Lee, S., Mian, R.M., Ralston, T., Niblack, T., Dorrance, A., McHale, L. 2019. Phenotypic characterization of a major quantitative disease resistance locus for partial resistance to phytophthora sojae. Crop Science. 59:968–980. https://doi.org/10.2135/cropsci2018.08.0514.
DOI: https://doi.org/10.2135/cropsci2018.08.0514

Interpretive Summary: Phytophthora stem and root rot, caused by Phytophthora sojae (Kaufmann & Gerdemann) is a major disease of soybean. Major quantitative disease resistance loci (QDRL) are rare in the Phytophthora sojae (Kaufmann & Gerdemann) - soybean [Glycine max (L). Merr.] pathosystem. A major QDRL on chromosome 18 (QDRL-18) was identified in plant introduction (PI) 427105B and PI 427106. QDRL-18 represents a valuable resistance source for breeding programs. Thus, the objectives of this study were to determine its effect on yield and resistance to P. sojae, its isolate-specificity, and effect on Fusarium graminearum and soybean cyst nematode (SCN) resistance. We characterized near isogenic lines (NILs) developed from F7 recombinant inbred lines heterozygous at QDRL-18; NILs represent introgressions from PI 427105B, PI 427106, and susceptible ‘OX20-8’. The introgressions from PI 427105B and PI 427106 increased resistance to P. sojae by 11-20% and 35-40%, respectively, based on laboratory and greenhouse assays and increased yield by 13-29% in field with presence of P. sojae. The resistant introgression from PI 427105B was also effective against seven P. sojae isolates with no isolate-specificity detected. Based on quantitative polymerase chain reaction assays, NILs with the susceptible introgression had significantly higher relative levels of P. sojae colonization 48 hours after inoculation. No pleiotropic effect for resistance to either SCN or F. graminearum was detected. This information improves soybean breeders’ ability to make informed decisions regarding the deployment of QDRL-18 in their respective breeding programs. The DNA markers for marker assisted introgression of this QRDL in elite cultivars is currently under development.

Technical Abstract: Major quantitative disease resistance loci (QDRL) are rare in the Phytophthora sojae (Kaufmann & Gerdemann) - soybean [Glycine max (L). Merr.] pathosystem. A major QDRL on chromosome 18 (QDRL-18) was identified in plant introduction (PI) 427105B and PI 427106. QDRL-18 represents a valuable resistance source for breeding programs. Thus, our objectives were to determine its effect on yield and resistance to P. sojae, its isolate-specificity, and effect on Fusarium graminearum and soybean cyst nematode (SCN) resistance. We characterized near isogenic lines (NILs) developed from F7 recombinant inbred lines heterozygous at QDRL-18; NILs represent introgressions from PI 427105B, PI 427106, and susceptible ‘OX20-8’. The introgressions from PI 427105B and PI 427106 increased resistance to P. sojae by 11-20% and 35-40%, respectively, based on laboratory and greenhouse assays and increased yield by 13-29% under disease conditions. The resistant introgression from PI 427105B was also effective against seven P. sojae isolates with no isolate-specificity detected. Based on quantitative PCR assays, NILs with the susceptible introgression had significantly higher relative levels of P. sojae colonization 48 hours after inoculation. No pleiotropic effects for resistance to either SCN or F. graminearum were detected. This information improves soybean breeders’ ability to make informed decisions regarding the deployment of QDRL-18 in their respective breeding programs.