A wheat chromosome 5AL region confers seedling resistance to both tan spot and Septoria nodorum blotch in two mapping populations

Tan spot(TS) and Septoria nodorum blotch(SNB), caused by Pyrenophora tritici-repentis and Parastagonospora nodorum, respectively, are important fungal leaf-spotting diseases of wheat that cause significant losses in grain yield. In this study, two recombinant inbred line populations, ‘Bartai’ × ‘Ciano T79’(referred to as B × C) and ‘Cascabel’ × ‘Ciano T79’(C × C) were tested for TS and SNB response in order to determine the genetic basis of seedling resistance. Genotyping was performed with the DAr Tseq genotypingby-sequencing(GBS) platform. A chromosome region on 5 AL conferred resistance to TS and SNB in both populations, but the effects were larger in B × C(R^2= 11.2%–16.8%) than in C × C(R^2= 2.5%–9.7%). Additionally, the chromosome region on 5BL(presumably Tsn1)was significant for both TS and SNB in B × C but not in C × C. Quantitative trait loci(QTL)with minor effects were identified on chromosomes 1B, 2A, 2B, 3A, 3B, 4D, 5A, 5B, 5D, 6B,and 6D. The two CIMMYT breeding lines ‘Bartai’ and ‘Cascabel’ contributed resistance alleles at both 5AL and 5BL QTL mentioned above. The QTL on 5AL showed linkage with the Vrn-A1 locus, whereas the vrn-A1 allele conferring lateness was associated with resistance to TS and SNB.

Genetic sources and loci for wheat head blast resistance identified by genome-wide association analysis

The emergence and spread of wheat blast caused by fungal pathogen Magnaporthe oryzae pathotype Triticum is a threat to global wheat production.The resistance level and genetic loci for blast resistance in Chinese germplasm remain unknown.A panel of 266 bread wheat accessions from China,CIMMYTMexico and other countries was screened for head blast resistance under 12 field experiments in Bolivia and Bangladesh.Subsequently,a genome-wide association study was performed to understand the genetic basis of wheat blast resistance.The average blast index of all the accessions was 53.7%±12.7%,and 10 accessions including Chinese accessions Yumai 10 and Yu 02321 showed moderate to high levels of blast resistance,accounting for only 3.8%in the panel.Fifty-eight significant SNPs clustered in a 28.9 Mb interval on the 2 AS/2 NS translocation region,explaining phenotypic variation between10.0%and 35.0%.The frequency of the 2 AS/2 NS translocation in the Chinese accessions was as low as4.5%.These results indicated that the 2 NS fragment was the only major locus conferring resistance to wheat blast in this panel,and the resistant and moderately resistant lines identified could be deployed in breeding.