Virulence and rep-PCR analysis of Pyricularia grisea isolates from two Brazilian upland rice cultivars

Abstract

The phenotypic and genetic diversity of 77 isolates of Pyricularia grisea collected from two upland rice cultivars, Maravilha and Primavera, was studied. Isolates exhibiting compatible reaction to cv.Primavera were incompatible to cv.Maravilha and vice versa, with the exception of six isolates that were compatible to both cultivars. The virulence of isolates from cv. Maravilha on 32 test genotypes of rice was significantly higher (t = 9.09, p ≤ 0.0001) than the isolates from cv.Primavera. A phenogram constructed from virulence data showed two main groups, one constituted mainly of isolates from cv.Primavera (97.6%) and the other of isolates from cv.Maravilha (91.17%). Rep-PCR analysis of isolates using two primers designed from sequences of Pot2 showed that isolates could be clustered broadly into two groups. The average similarity within a cluster of isolates from cv.Primavera was significantly greater than the average similarity among the isolates of cv.Maravilha (t = 5.37, p ≤ 0.0001). There was close correspondence between clusters based on PCR and virulence data (r = 0.48, p ≤ 0.011). The results showed that isolates of P. grisea were cultivar specific and had low phenotypic and genetic diversity.Additional keywords: Oryza sativa, rice blast, Magnaporthe grisea, pathotypes, genetic diversity. RESUMO Análise de virulência e rep-PCR de isolados de Pyricularia grisea de duas cultivares brasileiras de arroz de terras altasA diversidade fenotípica e genética de Pyricularia grisea foi avaliada em uma amostra de 77 isolados coletados das cultivares de arroz de terras altas Maravilha e Primavera. Isolados que apresentaram reações compatíveis em cv. Primavera foram incompatíveis em cv.Maravilha e vice versa, com exceção de seis isolados que foram compatíveis nas duas cultivares. A virulência de isolados provenientes da cv. Maravilha, em 32 genótipos de arroz foi significativamente maior (t = 9,09; p ≤ 0,0001) que dos isolados da cv. Primavera. O fenograma construído a partir dos dados fenotípicos mostrou dois grupos, um constituído principalmente por isolados da cv. Primavera (97,6%) e outro de isolados da cv. Maravilha (91,17%). A análise de rep-PCR dos isolados, utilizando os primers Pot2., revelou dois grupos distintos. A similaridade média dos isolados da cv. Primavera dentro de grupo foi maior do que a similaridade média dos isolados da cv. Maravilha (t = 5,37; p ≤ 0,0001). Observou-se uma correspondência entre a análise de agrupamento baseada em PCR e virulência fenotípica (r = 0,48; p ≤0,011). Os resultados mostraram ainda uma alta especificidade de isolados de P. grisea para cada cultivar e baixa variação fenotípica e genética.

Comparative Pathogenicity and Host Ranges of Magnaporthe oryzae and Related Species

“…Sequential hierarchical agglomerative non-overlapping clustering was applied for this similarity matrix using the unweighted pair group method with arithmetic averages. The coefficient of similarity was 0.68 ( Goh et al, 2013 ; Park et al, 2008 ; Prabhu et al, 2007 ).…”

Genetic structure and mating type analysis of the Pyricularia oryzae population causing widespread epidemics in southern Brazil

“…Earlier studies in Brazil reported low genotypic variability among P. oryzae isolates from states of Tocantins (Prabhu et al 2002), Rio Grande do Sul (Maciel et al 2004), Santa Catarina (Scheuermann, unpublished), and Goiás/Mato Grosso (Prabhu et al 2007). These studies used DNA fingerprinting by Pot2 rep-PCR for estimate the variability of isolates, which limit a direct comparison with the results of the current study.…”

“…Rice blast may lead to severe crop losses and is widespread in both upland and lowland Brazilian rice regions (Maciel et al 2004;Prabhu et al 2007). Disease management relies on a combination of strategies that include cultural practices and fungicides, but the most effective approach is to use cultivars possessing genes that confer complete resistance (Skamnioti and Gurr 2009).…”

“…In Brazil, earlier studies on the molecular variability of P. oryzae populations used fingerprinting data from Pot2 or MGR 586 transposable elements (Prabhu et al 2002(Prabhu et al , 2007Maciel et al 2004). In general, low variability was found in populations from the states of Tocantins (Prabhu et al 2002), Goiás (Prabhu et al 2007) and Rio Grande do Sul (Maciel et al 2004). More recently, microsatellite (SSR) has been used to assess the genetic variability of P. oryzae populations from Brazil (Maciel et al 2014;Gonçalves et al 2016).…”

Phylogenetic diversity and sensitivity to MBI and QoI fungicides of <i>Magnaporthe oryzae</i> in Taiwan

“…3,4) Recent studies also showed that pathogenicity of P. oryzae to different rice cultivars or lines differs in different countries, including Argentina, 5) Brazil, [6][7][8] China, 9) USA, 10) Thailand, 11) and Vietnam. 12) In Taiwan, more than 78 races of P. oryzae had been identified using 8 standard lines of rice as differentials.…”