Genetic analysis of Phytophthora sojae populations in Fujian, China

Abstract

Phytophthora sojae is a destructive soilborne pathogen causing seedling damping‐off and root rot of soybean (Glycine max). The goal of this study was to determine the genetic structure of P. sojae populations in Fujian, China. Nine microsatellite markers were used to investigate the genetic variation in 19 P. sojae populations, sampled from Fujian Province and northeastern China (Jilin and Heilongjiang Provinces) between 2002 and 2013. Overall, a low genetic diversity, Hardy–Weinberg disequilibrium, and an r¯d index (an index of association) that was significantly different from zero were detected in populations; these results were consistent with self‐fertilization and clonal modes of reproduction for this pathogen. However, using Bayesian Markov chain Monte Carlo approach, principal component analysis and neighbour joining (NJ) algorithm, the Fujian P. sojae populations clustered into three distinct groups, one of which included most isolates of the northeast populations. What is more, significant estimates of pairwise fixation indices (FST) were detected between most populations, especially in different clusters. It is hypothesized that the cropping system used, the limited dispersal ability, and human‐mediated gene flow may account for the observed genetic structure of P. sojae populations in Fujian, China. In addition, a high virulence frequency of the pathogen on different cultivars carrying known major R genes for resistance, and a rapid increase in virulence frequency, indicated that these major R genes should not be used to manage seedling damping‐off and root rot diseases of soybean (Glycine max).

Genetic Diversity among Isolates of Phytophthora sojae in Anhui Province of China based on ISSR-PCR Markers

“…The high percentage of polymorphic loci showed that 62 isolates of P. sojae had abundant genetic diversity, and the polymorphism rate was 80.6%. The percentages of polymorphic bands in Heilongjiang Province, Fujian Province, Argentina, and the United States were 71%, 60%, 71%, and 84% according to previous reports (Galley et al, 2007;Wu et al, 2013Wu et al, , 2017. Isolates from Anhui Province had higher genotypic diversity than those from Heilongjiang Province, Fujian Province, and Argentina, but this diversity was lower than that of those from the United States.…”

“…may be derived from China. Recently, RAPD, SSR, and ISSR were used to assess the genetic diversity of P. sojae isolates from China and Iran (Mohammadi et al, 2014;Wu et al, 2014Wu et al, , 2017. In Heilongjiang Province, China, 39 P. sojae isolates were collected from soil and soybean and genetic diversity analysis was performed by Wu et al (2013) using two methods: RAPD and SSR.…”

Genetic Mapping and Molecular Characterization of a Broad-spectrum Phytophthora sojae Resistance Gene in Chinese Soybean

“…Many of the currently known Rps genes have been mapped on the short arm of soybean chromosome 3, including some genes that have been finely mapped such as Rps1k , RpsYD29 , RpsQ , RpsHC18 , RpsWY , RpsHN , and RpsUN1 [11,20,24,25,26,27,30]. Moreover, most of these genes were mapped in the interval containing typical plant resistance genes encoding a nucleotide-binding site (NBS) and an LRR domain.…”

“…However, Rps genes are race-specific and conform to the gene-for-gene hypothesis with a P. sojae avirulence gene. Several studies have revealed that the virulence of a P. sojae population rapidly changes, and a single race can generate various pathotypes that can overcome the resistance mediated by the Rps genes [9,26,27,28,29,30,31,32]. Due to the breakdown of resistance caused by the emergence of new P. sojae pathotypes, the durability of an Rps gene is generally only 8–15 years [9,28].…”

Fine Mapping, Candidate Gene Identification and Co-segregating Marker Development for the Phytophthora Root Rot Resistance Gene RpsYD25

“…According to the latest reports, from 2006 to 2014, approximately 340 million bushels of yield losses were attributed to PRR in major soybean production areas of Unite States, and PRR causes economic losses of $1 -2 billion annually worldwide (Tyler, 2007;Koenning and Wrather, 2010). The disease was first reported in Northeast China and has now spread to all major soybean producing areas in China (Zhu et al, 2003;Tian et al, 2016;Wu et al, 2016). Under saturated soil conditions, P. sojae infect soybean plants throughout the growing season, resulting in pre-and post-emergence damping-off, root and stem rot, yellowing and wilting of leaves, and the death of soybean plants (Schmitthenner, 1999;Chen and Wang, 2017).…”