Parastagonospora nodorum leaf and glume blotch (syn. Septoria nodorum blotch, SNB) is a severe disease in many wheat-growing areas worldwide. In a previous study, a mapping population, Liwilla × Begra, was used to detect several resistance quantitative trait loci (QTL) at the seedling stage. In this study the same mapping population was analysed at the adult plant stage under field and polytunnel conditions. After artificial inoculation the disease severity on leaves and glumes was scored as the areas under the disease progress curves for field tests and as the percentage of the leaf and glume area covered by necrosis for the polytunnel test. Three QTL associated with Septoria nodorum glume blotch resistance and two QTL associated with Septoria nodorum leaf blotch resistance were detected on chromosomes 1B, 3A, 4A and 7D. Each of the detected QTL explained only a small proportion of the total phenotypic variation, ranging from 9.1 to 20.0%. None of these QTL co-located with necrotrophic effector sensitivity loci or aligned with previously identified resistance loci at the seedling stage for the Liwilla × Begra population. SNB resistance QTL detected in our study did not overlap with QTL associated with morphological and developmental traits. Therefore they could be involved in the defence reaction and can be considered in wheat improvement for SNB resistance.

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.

No abstract

No abstract

Septoria tritici blotch (STB) is one of the most devastating foliar diseases of wheat worldwide. Host resistance is the most economical and safest method of controlling the disease, and information on resistance loci is crucial for effective breeding for resistance programs. In this study we used a mapping population consisting of 126 doubled-haploid lines developed from a cross between the resistant cultivar Mandub and the susceptible cultivar Begra. Three monopycnidiospore isolates of Z. tritici with diverse pathogenicity were used to test the mapping population and parents’ STB resistance at the seedling stage (under a controlled environment) and adult plant stage (polytunnel). For both types of environments, the percentage leaf area covered by necrosis (NEC) and pycnidia (PYC) was determined. A linkage map comprising 5899 DArTSNP and silicoDArT markers was used for the quantitative trait loci (QTL) analysis. The analysis showed five resistance loci on chromosomes 1B, 2B and 5B, four of which were derived from cv. Mandub. The location of QTL detected in our study on chromosomes 1B and 5B may suggest a possible identity or close linkage with Stb2/Stb11/StbWW and Stb1 loci, respectively. QStb.ihar-2B.4 and QStb.ihar-2B.5 detected on chromosome 2B do not co-localize with any known Stb genes. QStb.ihar-2B.4 seems to be a new resistance locus with a moderate effect (explaining 29.3% of NEC and 31.4% of PYC), conferring resistance at the seedling stage. The phenotypic variance explained by QTL detected in cv. Mandub ranged from 11.9% to 70.0%, thus proving that it is a good STB resistance source and can potentially be utilized in breeding programs.