A global-temporal analysis on Phytophthora sojae resistance-gene efficacy

Abstract

Plant disease resistance genes are widely used in agriculture to reduce disease outbreaks and epidemics and ensure global food security. In soybean, Rps (Resistance to Phytophthora sojae) genes are used to manage Phytophthora sojae, a major oomycete pathogen that causes Phytophthora stem and root rot (PRR) worldwide. This study aims to identify temporal changes in P. sojae pathotype complexity, diversity, and Rps gene efficacy. Pathotype data was collected from 5121 isolates of P. sojae, derived from 29 surveys conducted between 1990 and 2019 across the United States, Argentina, Canada, and China. This systematic review shows a loss of efficacy of specific Rps genes utilized for disease management and a significant increase in the pathotype diversity of isolates over time. This study finds that the most widely deployed Rps genes used to manage PRR globally, Rps1a, Rps1c and Rps1k, are no longer effective for PRR management in the United States, Argentina, and Canada. This systematic review emphasizes the need to widely introduce new sources of resistance to P. sojae, such as Rps3a, Rps6, or Rps11, into commercial cultivars to effectively manage PRR going forward.

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

“…There is an essential need for continuing to identify and combine effective Rps genes, which have been highlighted by the fact that the widely used Rps genes, Rps1a , Rps1c , and Rps1k , are no longer effective management tools in the United States, Canada, and Argentina since the diversity of pathotypes has changed significantly over time in these areas ( Dorrance et al., 2016 ; Grijalba et al., 2020a , b ; Matthiesen et al., 2021 ; Tremblay et al., 2021 ; Hebb et al., 2022 ; McCoy et al., 2022 , 2023 ). We were able to map resistance toward one and two genes toward five to seven P. sojae isolates in each of the RIL populations derived from four plant introductions (PI 407985, PI 408029, PI 408097, and PI 424477) previously identified as putative novel sources of disease resistance for P. sojae ( Dorrance and Schmitthenner, 2000 ; Gordon et al., 2007a , 2007b ; Matthiesen et al., 2016 ).…”

“…The severity of loss depends on a wide variety of factors including soil type, compaction, and rainfall ( Schmitthenner, 2000 ). P. sojae is a diverse organism with over 200 pathotypes ( Dorrance, 2018a ; Matthiesen et al., 2021 ; Hebb et al., 2022 ; McCoy et al., 2023 ). This pathogen causes root and stem rot in soybean plants, which can lead to stand and yield reduction in susceptible cultivars.…”

A rapid molecular diagnostic tool to discriminate alleles of avirulence genes and haplotypes of Phytophthora sojae using high‐resolution melting analysis

“…Several recent studies have highlighted growing concerns about P. sojae evolving pathotypes that are steadily overcoming commercial Rps genes around the world (Dorrance, 2018;Tremblay et al, 2021). There is a general consensus that Rps1a and 1c have become mostly inefficient while Rps1k is becoming obsolete rapidly (McCoy et al, 2023). For these reasons, there is an increasing need to properly and rapidly define the pathotype of P. sojae isolates in order to deploy the proper Rps genes.…”

Table_1.xlsx

“…There is an essential need for continuing to identify and combine effective Rps genes, which have been highlighted by the fact that the widely used Rps genes, Rps1a, Rps1c, and Rps1k, are no longer effective management tools in the United States, Canada, and Argentina since the diversity of pathotypes has changed significantly over time in these areas (Dorrance et al, 2016;Grijalba et al, 2020a, b;Matthiesen et al, 2021;Tremblay et al, 2021;Hebb et al, 2022;McCoy et al, 2022McCoy et al, , 2023. We were able to map resistance toward one and two genes toward five to seven P. sojae isolates in each of the RIL populations derived from four plant introductions (PI 407985, PI 408029, PI 408097, and PI 424477) previously identified as putative novel sources of disease *Indicates where the final results from two replications of an isolate were combined into a single dataset.…”