Pathotypic and genetic diversity in the population of Rhizoctonia solani AG1‐IA causing rice sheath blight in China

Abstract

Sheath blight, caused by Rhizoctonia solani AG1-IA, is one of the most serious diseases of rice. In this study, a total of 175 isolates of R. solani AG1-IA were collected from five rice-growing regions in China. Pathogenicity tests revealed that all isolates were virulent to five cultivars with different levels of resistance at the rice seedling stage in the greenhouse. There was considerable variation in aggressiveness, and the isolates were classified into three pathotypes based on disease severity, with moderately virulent isolates prevalent in the population. Forty-three haplotypes were identified based on ITS sequencing, and 39 haplotypes were distinct among isolates. There were high levels of haplotype diversity and nucleotide diversity within the populations of R. solani AG1-IA. High gene flow (Nm = 1Á63-5Á22) was detected, consistent with relatively low differentiation between pairs of populations. Five populations were divided into two distinct clusters by the unweighted pair group method with arithmetic mean (UPGMA), and no spatial population differentiation was discernible. The majority (97Á8%) of genetic diversity was distributed among isolates within populations, with only 2Á2% of the genetic diversity attributed to differences among populations. The star-like shape of the haplotype network provided evidence of signatures of population expansion in recent history. No significant relationships were found between the genetic diversity and aggressiveness or geographic origin among populations of R. solani AG1-IA. These results highlight that the population characteristics of R. solani AG1-IA should be taken into account in evaluating the germplasm resistance of rice cultivars to sheath blight.

Genetic structure and population diversity in the wheat sharp eyespot pathogen Rhizoctonia cerealis in the Willamette Valley, Oregon, USA

“…Moderate population differentiation and high gene flow were observed among those populations. These results demonstrate that the population genetic structure of R. cerealis is similar to Rhizoctonia solani AG 3‐PT (Muzhinji et al , ), AG‐4 (Haratian et al , ) and AG‐1 IA (Ciampi et al , ; Wang et al , ) that have a mixed reproductive mode, relatively high variance among subpopulations and moderate gene flow.…”

Comparison of gene co-networks reveals the molecular mechanisms of the rice (Oryza sativa L.) response to Rhizoctonia solani AG1 IA infection

“…Xie et al ( 2010 ) found that overexpression of SIB1 (a VQ motif-containing protein) causes plants to activate defense-related genes following pathogen infection or SA and JA treatments, leading to enhanced resistance to P. syringae infection. Moreover, Wang et al ( 2015a , b ) found VQ12 and VQ29 to be highly responsive to B. cinerea infection, and VQ12 and VQ29 might be partially involved in the JA-signaling pathway, as demonstrated via expression analysis of defense-signaling mutants. In the present study, jasmonate ZIM-domain proteins (JAZs) were found in the core gene network.…”

“…At present, management of this disease mainly involves chemical methods. Despite the importance of rice sheath blight, research in resistance has been slow, partly due to the lack of a standard resistance identification methods and because the disease is easily affected by in-field conditions on small-scale farmland (Wang et al 2015a , b ; Yugander et al 2014 ). To date, few in-depth studies have investigated the molecular mechanism of rice sheath resistant during or after fungal entry into host tissues (Okubara et al 2014 ; Silva et al 2012 ).…”

Molecular Variation of the Phytopathogenic Fungus Sporisorium reilianum in Valle del Mezquital, Hidalgo

“…On this topic, Wang et al (2015) proposed that the longterm management of diseases caused by phytopathogenic fungi should include tolerant hybrids and the controlled use of fungicides to minimize gene flow by limiting the propagation of reproductive structures through shared irrigation systems and machinery. Preventing the transmission of phytopathogenic fungi through infected seeds could require improved hygienic procedures, moderate fungicide applications in soil and on plants, and restrictions on the distribution and sale of contaminated seeds, especially when growers share them in, and between, communities.…”