Comparison of Rps loci towards isolates, singly and combined inocula of Phytophthora sojae in soybean PI 407985, PI 408029, PI 408097 and PI424477

Authors: CLEVINGER, ELIZABETH - Virginia Polytechnic Institution & State University; BIYAHEV, RUSLAN - Virginia Polytechnic Institution & State University; SCHMIDT, CARICE - Virginia Polytechnic Institution & State University; Song, Qijian; BATNINI, AMINE - The Ohio State University; BOLANOS-CARRIEL, CARLOS - The Ohio State University; ROBERTSON, ALISON - Iowa State University; DORRANCE, ANNE - The Ohio State University; MAROOF, SAGHAI - Virginia Polytechnic Institution & State University

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/5/2024
Publication Date: 6/30/2024
Citation: Clevinger, E., Biyahev, R., Schmidt, C., Song, Q., Batnini, A., Bolanos-Carriel, C., Robertson, A., Dorrance, A., Maroof, S. 2024. Comparison of Rps loci towards isolates, singly and combined inocula of Phytophthora sojae in soybean PI 407985, PI 408029, PI 408097 and PI424477. Frontiers in Plant Science. 15. Article: e1394676. https://doi.org/10.3389/fpls.2024.1394676.
DOI: https://doi.org/10.3389/fpls.2024.1394676

Interpretive Summary: Root and stem rot are an economically important soybean disease in the United States and worldwide. To date, more than 40 resistant genes and alleles have been mapped in soybean. In studies of pathotype diversity of the disease in the United States, more than 200 unique pathotypes were observed, many of which could cause disease in soybeans carrying any of the commercially available resistance genes. Some soybean resistance genes are less effective than in the past, depending on where they are grown, highlighting the need to continue identifying and combining effective genes during the development of new varieties. Researchers at Virginia Tech, Iowa State University, The Ohio State University, and the USDA-ARS (Beltsville, MD) identified and mapped resistance genes across four offspring populations derived from different resistant parents and over multiple generations. They observed consistency in chromosomal regions associated with disease resistance determined by different mapping methods across generations. Several variant forms of the genes identified in this study are putative novel. The gene containing these variants can be used to integrate resistance into soybean varieties and develop varieties with increased resistance to root and stem rot diseases.

Technical Abstract: For soybeans, novel single dominant Resistance to Phytophthora sojae (Rps) genes are sought to manage Phytophthora root and stem rot. In this study, resistance to P. sojae was mapped individually in four recombinant inbred line (RIL) populations derived from crosses of the susceptible cultivar Williams with PI 407985, PI 408029, PI 408097 and PI424477, previously identified asputative novel sources of disease resistance. Each population was screened for resistance with 5 to 7 isolates of P. sojae separately over multiple F7-F10 generations. Additionally, three of the populations were screened with inoculum from the combination of 3 P.sojae isolates (PPR) which comprised virulence to 14 Rps genes. Over 2,300 single-nucleotide polymorphism markers were used to construct genetic maps in each population to identify chromosomal regions associated with resistance to P. sojae. Resistance segregated as 1 or 2 genes to the isolates and 1 gene towards PPR in each population and mapped to chromosomes 3, 13, or 18 in one or more of the four RIL populations. Resistance to five isolates mapped to the same chromosome 3 region: OH7 (PI 424477 and PI408029), OH12168, OH7/8, PPR (PI 407985) and 1.S.1.1 (PI408029). The resistance regions on chromosome 13 also overlapped for OH1, OH25, OH-MIA (PI424477), PPR (PI 424477, PI 407985, and PI 408097), PPR and OH0217 (PI 408097) and OH4 (PI 408029) but were distinct for each population suggesting multiple genes confer resistance. Two regions were identified on chromosome 18 but all appear to map to known loci, notably resistance to the combined inoculum (PPR) did not map at this locus. However, there are putative new alleles in 3 of 4 populations, 3 on chromosome 3 and 2 on chromosome 13 based on mapping location but also known virulence in the isolate used. This characterization of all the Rps genes segregating in these populations to these isolates will be informative for breeding but the combined inoculum was able to map novel loci. Furthermore, within each of these P. sojae isolates there was virulence to more than the described Rps genes and the effectiveness of the novel genes requires testing to larger populations.