A Shift in Pathotype Diversity and Complexity of Phytophthora sojae in Brazil

Abstract

Soybean root and stem rot caused by the oomycete Phytophthora sojae is a destructive disease worldwide that can affect plants at any growth stage. The use of resistant cultivars is the most effective method of controlling the disease. Therefore, monitoring changes in the population of P. sojae regarding the dynamics of avirulence genes capable of overcoming resistance genes (Rps) is important to reduce yield losses and to enhance the effectiveness of the Rps genes. Forty isolates of P. sojae sampled from a region of high incidence of soybean root and stem rot in Brazil were characterized using 14 soybean differentials and 28 pathotypes were identified. Compared to a study conducted a decade ago there was a major shift in pathotype diversity and complexity towards both higher numbers of different pathotypes and of avirulence genes in a given individual in the current population of P. sojae. Breeding programs aiming at developing soybean cultivars with resistance to root and stem rot should consider the high variability in the population of P. sojae and seek for strategic deployment of genes and germplasm.

An updated assessment of the soybean–Phytophthora sojae pathosystem

“…Indeed, the rapid evolution of the virulence profile of P. sojae populations restricts the utility of a given Rps gene to 8-15 years (Schmitthenner, 1985) et al, 2021). Only Rps1c, 1k, 3a and YD25 remain effective for qualitative control of P. sojae in the agriculturally intensive regions of China Zhong, Sun, Li, et al, 2018;Zhong, Sun, Yao, et al, 2018), whilst all tested differentials (n = 14) were overcome by at least one isolate from P. sojae-infested Brazilian soils (Batista et al, 2022). Moreover, sustained virulence in P. sojae populations suggests Rps gene recycling may not be feasible (Dorrance et al, 2016).…”

“…Both metrics, as well as genotypic diversity, are increasing in field populations of P . sojae (Batista et al, 2022; Dorrance, 2018). For instance, Stewart et al (2016) used genotypic and pathotypic diversity to compare the population structure of P .…”

“…sojae in the agriculturally intensive regions of China (Zhang, Zhao, et al, 2021; Zhong, Sun, Li, et al, 2018; Zhong, Sun, Yao, et al, 2018), whilst all tested differentials ( n = 14) were overcome by at least one isolate from P . sojae ‐infested Brazilian soils (Batista et al, 2022). Moreover, sustained virulence in P .…”

“…Diversity can be defined as the number of pathotypes present amongst a given number of isolates. Both metrics, as well as genotypic diversity, are increasing in field populations of P. sojae (Batista et al, 2022;Dorrance, 2018). For instance, Stewart et al (2016) used genotypic and pathotypic diversity to compare the population structure of P. sojae isolates from Iowa, Ohio, Missouri and South Dakota.…”

Soybean Variety Saedanbaek Confers a New Resistance Allele to Phytophthora sojae

“…Genetic diversity in the P. sojae population is distinguishable among multiple states of the U.S. and the frequency changes of diverse pathotypes were discovered through periodical state-wide studies over decades [3]. Similarly, the diversity and shift of pathotypes of the P. sojae population vary by country and by geographical region within a country based on the phenotypic assays using differential varieties and molecular analyses in China, Japan, and Brazil [6][7][8]. The development of resistant cultivars is the most effective way of preventing PRSR [7].…”