LEVELS OF REGIONAL PHENOTYPIC ADAPTATION (QST) INDICATE THAT NEUTRALITY HAS SHAPED THE POPULATION STRUCTURE OF THE SOYBEAN-INFECTING PATHOGEN Rhizoctonia solani AG-1 IA

CAMILA GEOVANA FERRO,TATIANE CARLA SILVA,PAULO CEZAR CERESINI,SAMARA NUNES CAMPOS VICENTINI,GUILHERME MORAES FERRAUDO

doi:10.1590/1983-21252020v33n304rc

CAMILA GEOVANA FERRO, TATIANE CARLA SILVA + Show 3 more

Open Access

https://doi.org/10.1590/1983-21252020v33n304rc

Copy DOI

Journal: Revista Caatinga	Publication Date: Sep 1, 2020
Citations: 2	License type: CC BY 4.0

Affiliation: Universidade Estadual Paulista (Unesp)

Abstract

ABSTRACT Populations of the soybean leaf blight pathogen (Rhizoctonia solani AG-1 IA) are highly genetically differentiated along a latitudinal gradient in the major soybean growing regions of Brazil. However, the evolutionary processes leading to regional adaptation are still unknown. The objective of this study was to evaluate the relative importance of neutral genetic variation and natural selection on the divergence and regional adaptation of populations of the soybean-infecting pathogen R. solani AG-1 IA. Therefore, we compared the phenotypic differentiation in quantitative traits (QST) and the neutral genetic differentiation (FST, based on microsatellites data) among three pairs of populations. As measures of phenotypic responses of the fungus (quantitative traits), we estimated the tolerance to temperature stress and the tolerance to a broad-spectrum fungicide (copper oxychloride) under optimal (25 °C) and high temperature conditions (33.5 °C). In general there was an increase in genetic variance with a positive effect on the heritability for tolerance to copper fungicide under temperature stress. The genetic differences among populations were the main determinants of thermal adaptation in R. solani AG-1 IA (h2 > 0.70). The analysis of neutral genetic structure (FST) indicated subdivision between the three pairs of populations. Although population pairwise comparisons between FST and QST values did not follow a single pattern, the majority of QST values did not differ significantly from FST, indicating that, for the quantitative characters studied, neutrality (or neutral evolution) had a major role in the regional adaptation of R. solani AG-1 IA populations.

Highlights

Genetic structure is the amount and distribution of genetic diversity or variation within and between populations and can provide the basis for inferences about the life history and evolutionary processes that shaped the structure of these populations in agroecosystems (MCDONALD; LINDE, 2002; TYAGI et al, 2014; IQBAL; RAHMAN, 2017).For the characterization of genetic diversity, phenotypic markers were used for a long time (TOPPA; JADOSKI, 2013)
As a study model to measure the effect of natural selection on the divergence between populations of a plant pathogen, we used the basidiomycete fungus Rhizoctonia solani anastomosis group (AG) 1 IA, the causal agent of soybean leaf blight in the Amazon
In the first part of this study, the three populations of R. solani AG-1 IA from soybean were analyzed for differences in phenotypic responses and heritability for tolerance to temperature stress and copper fungicide under optimal conditions (25.0 °C) and high temperature (33.5 °C)

Summary

Introduction

Genetic structure is the amount and distribution of genetic diversity or variation within and between populations and can provide the basis for inferences about the life history and evolutionary processes that shaped the structure of these populations in agroecosystems (MCDONALD; LINDE, 2002; TYAGI et al, 2014; IQBAL; RAHMAN, 2017).For the characterization of genetic diversity, phenotypic markers were used for a long time (TOPPA; JADOSKI, 2013). Empirical studies related to the genetic structure of fungal populations have focused on the use of discrete genetic molecular markers (BUSH; MOORE, 2012). The association between these two categories of markers allows for inferences about the effect of natural selection on the divergence between populations (ARRAOUADI et al, 2009; WHITLOCK; GUILLAUME, 2009; PRICE et al, 2010; EDELAAR; BJÖRKLUND, 2011). As a study model to measure the effect of natural selection on the divergence between populations of a plant pathogen, we used the basidiomycete fungus Rhizoctonia solani (sexual stage = Thanatephorus cucumeris) anastomosis group (AG) 1 IA, the causal agent of soybean leaf blight in the Amazon. The spread over long distances occurs by infected seeds, contributing to the clonal spread of the fungus (CHAVARRO-MESA et al, 2020)

Objectives

Results

Conclusion