Virulence Spectrum of Mycosphaerella graminicola Isolates on Wheat Genotypes Carrying Known Resistance Genes to Septoria tritici Blotch

Abstract

The virulence spectrum of 23 monopycnidiospore isolates of Mycosphaerella graminicola was determined using wheat genotypes that carried different resistance genes (Stb1-Stb8 and Stb15). Disease severity was measured as the percentage of necrotic leaf area. The isolates used in the experiments were of diverse origin: eight from Poland, seven from Germany, and eight from other countries around the world. Analysis of variance revealed significant differences in the virulence of the isolates. Using multiple regression and CookÕs D statistic, 26 significant cultivar · isolate interactions were detected. The Israeli isolate IPO86036 showed the widest spectrum of specific reactions. It expressed specific virulence on at least four cultivars and specific avirulence on at least three. The other isolates showed specific interactions with 1-6 different cultivars. Despite the limited number of isolates that were tested, we recommend that a number of resistant lines, namely cultivars Veranopolis (Stb2), Cs ⁄ Synthetic 7D (Stb5), Arina (Stb15, Stb6 and partial resistance), and Liwilla (unknown resistance factors), could be incorporated into central European wheat breeding programmes that are aimed at developing resistance against septoria tritici blotch. In contrast, resistance gene Stb7, which is carried by cultivar Estanzuela Federal, was ineffective against most of the isolates that were used. These results on the virulence spectrum of M. graminicola isolates provide valuable information for effective wheat breeding programmes to develop resistance to the pathogen.

Spring air temperature accounts for the bimodal temporal distribution of Septoria tritici epidemics in the winter wheat stands of Luxembourg

“…Even though differences between winter wheat genotypes concerning their leaf blotch susceptibility were shown and proposed for use in breeding programs (Czembor et al, 2011), we did not find a significant effect of the cultivar on T 50 values. It should be noted, that the differences in susceptibility towards S. tritici were rather small (ranking of 4e6 on a 1e9 scale, Table 1) among the cultivars used here, probably too small to result in a significant difference.…”

Resistance spectra of wheat genotypes and virulence patterns of Mycosphaerella graminicola isolates in Iran

“…Therefore, these genes may not be effective in controlling the disease in Iran. The wheat genotypes Oasis, Vernapolis, Tadinia, Synthetic 6X, and Kavkaz-K4500 have been considered as effective sources of resistance to STB in United States and Europe and the Stb genes in some of them were transferred to some commercial wheat cultivars (Eyal 1999;Arraiano et al 2001;Brown et al 2001;Adhikari et al 2004a, b, c;Chartrain et al 2004a, b;Tabib Ghaffary et al 2008;Czembor et al 2010). However, virulence of fungal isolates to Stb genes in these genotypes as well as Israel 493 and Synthetic W7984 was observed with high frequency, as 12-13 isolates were virulent to these cultivars and lines.…”

“…In a similar study conducted using a global set of M. graminicola isolates, Synthetic 6X, TE 9111, and Arina were found to be the most resistant wheat differentials studied (Tabib Ghaffary et al 2008). Moreover, in a recent research in which virulence of 23 European M. graminicola isolates on a set of differential wheat genotypes was evaluated, Arina, Liwilla (with unknown resistance genes), Vernapolis, and Synthetic 6X were the most resistant wheat differentials (Czembor et al 2010). …”

“…In contrast, regional populations of M. graminicola from western Canada showed very low virulence diversity as only two virulence groups were identified among 74 isolates tested on six cultivars indicating that pathogen populations from western Canada are not as diverse as those found in other wheat producing regions (Grieger et al 2005). Although the majority of virulence studies have indicated the presence of virulence diversity among isolates of the pathogen, it is only recently that differential wheat genotypes, carrying known Stb genes, are being used for determining virulence diversity of M. graminicola populations (Tabib Ghaffary et al 2008;Czembor et al 2010). We have previously shown that M. graminicola populations collected from Iran possess a moderate to high genotypic diversity, but to date no information on the virulence diversity of these populations towards differentials is available (Abrinbana et al 2010).…”

“…Partial or quantitative resistance is incomplete, isolate-nonspecific and considered as a polygenic trait controlled by minor genes (Zhang et al 2001;Eriksen et al 2003;Simon et al 2004;Chartrain et al 2004b), whereas isolate-specific resistance is complete or near-complete and usually considered as mono or oligogenic controlled by major genes (McCartney et al 2002). Up to now, 15 genes (Stb1-Stb15) Brading et al 2002;Adhikari et al 2003Adhikari et al , 2004aMcCartney et al 2003;Chartrain et al 2005a, b;Cowling 2005;Arraiano et al 2007;Chartrain et al 2009) and a few quantitative trait loci (QTL) (Eriksen et al 2003;Chartrain et al 2004b) conferring resistance to STB have been identified and mapped in different wheat genotypes.…”