Genetic analysis of resistance to septoria tritici blotch in the French winter wheat cultivars Balance and Apache

Abstract

The ascomycete Mycosphaerella graminicola is the causal agent of septoria tritici blotch (STB), one of the most destructive foliar diseases of bread and durum wheat globally, particularly in temperate humid areas. A screening of the French bread wheat cultivars Apache and Balance with 30 M. graminicola isolates revealed a pattern of resistant responses that suggested the presence of new genes for STB resistance. Quantitative trait loci (QTL) analysis of a doubled haploid (DH) population with five M. graminicola isolates in the seedling stage identified four QTLs on chromosomes 3AS, 1BS, 6DS and 7DS, and occasionally on 7DL. The QTL on chromosome 6DS flanked by SSR markers Xgpw5176 and Xgpw3087 is a novel QTL that now can be designated as Stb18. The QTLs on chromosomes 3AS and 1BS most likely represent Stb6 and Stb11, respectively, and the QTLs on chromosome 7DS are most probably identical with Stb4 and Stb5. However, the QTL identified on chromosome 7DL is expected to be a new Stb gene that still needs further characterization. Multiple isolates were used and show that not all isolates identify all QTLs, which clearly demonstrates the specificity in the M. graminicola–wheat pathosystem. QTL analyses were performed with various disease parameters. The development of asexual fructifications (pycnidia) in the characteristic necrotic blotches of STB, designated as parameter P, identified the maximum number of QTLs. All other parameters identified fewer but not different QTLs. The segregation of multiple QTLs in the Apache/Balance DH population enabled the identification of DH lines with single QTLs and multiple QTL combinations. Analyses of the marker data of these DH lines clearly demonstrated the positive effect of pyramiding QTLs to broaden resistance spectra as well as epistatic and additive interactions between these QTLs. Phenotyping of the Apache/Balance DH population in the field confirmed the presence of the QTLs that were identified in the seedling stage, but Stb18 was inconsistently expressed and might be particularly effective in young plants. In contrast, an additional QTL for STB resistance was identified on chromosome 2DS that is exclusively and consistently expressed in mature plants over locations and time, but it was also strongly related with earliness, tallness as well as resistance to Fusarium head blight. Although to date no Stb gene has been reported on chromosome 2D, the data provide evidence that this QTL is only indirectly related to STB resistance. This study shows that detailed genetic analysis of contemporary commercial bread wheat cultivars can unveil novel Stb genes that can be readily applied in marker-assisted breeding programs.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-011-1623-7) contains supplementary material, which is available to authorized users.

Quantitative inheritance of resistance to Septoria tritici blotch in durum wheat in Tunisia

“…Moreover, the frequency distribution for the 149 RILs was not consistent with a single gene model for STB resistance and was continuous and followed normal distributions. Our results support the polygenic and quantitative inheritance of resistance to STB 1988;Lynch and Walsh, 1998;Tabib Ghaffary et al, 2011b). The relative skeweness toward the resistant parent during both seasons (Figures 1a, 1b, and 1c) would imply that multiple genes with complementary additive effects but with partial dominance toward resistance are conferring resistance derived from 'Salim'.…”

“…The partial resistance is durable under field conditions and is expressed as a reduction in epidemic development (Chartrain et al, 2004). During the last decade 18 major resistance genes (Stb1-Stb18) to STB have been identified and mapped in the wheat genome (Arraiano et al, 2007;Goodwin, 2007;Chartrain et al, 2009;Tabib Ghaffary et al, 2011a;2011b). These developments have greatly improved the efficiency of marker-assisted selection in bread wheat.…”

Adult-plant resistance to Septoria tritici blotch in hexaploid spring wheat

“…The most closely linked locus to Stb11 was once more barc008. An additional Septoria tritici blotch seedling resistance gene on 1BS was reported by Tabib Ghaffary et al (2011) in the French cultivar 'Apache'. Stb11 is treated as an isolate-specific QTL due to a continuous distribution of disease scores in progeny plants after inoculation of the pathogen and was mapped as a seedling resistance gene specific to isolate IPO90012 from Mexico.…”

The Genomes of Mycosphaerella graminicola and M. fijiensis

“…So far, 16 major genes (reviewed in Goodwin 2007Goodwin , 2012Tabib Ghaffary et al 2011, 2012 and numerous Quantitative Trait Loci (QTL) with smaller effects (Simon and Cordo 1988;Jlibene et al 1994;Simón et al 2004) have been identified and mapped in the wheat genome. However, tightly linked molecular markers have not been available until very recently, so relatively few resistance genes have been used in wheat breeding programs.…”