ARS | Publication request: Whole genome QTL analysis of Stagonospora nodorum blotch resistance and validation of the SnTox4-Snn4 interaction in hexaploid wheat

Submitted to: Phytopathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 29, 2011
Publication Date: February 1, 2012
Citation: Abeysekara, N., Faris, J.D., Chao, S., Mcclean, P., Friesen, T.L. 2012. Whole genome QTL analysis of Stagonospora nodorum blotch resistance and validation of the SnTox4-Snn4 interaction in hexaploid wheat. Phytopathology. 102:94-104.

Interpretive Summary: Necrotrophic effectors (also known as host-selective toxins) are important determinants of disease in the wheat-Stagonospora nodorum pathosystem. To date we have identified five necrotrophic effector-host gene interactions. The Snn4-SnTox4 interaction was originally identified in a Swiss winter wheat population using a Swiss S. nodorum isolate. Here, we used a wheat population consisting of 121 lines developed from a cross between the hexaploid land race Salamouni and the Canadian bread wheat cultivar ‘Katepwa’ (SK population). The SK population was used for the construction of genetic maps and the detection of the chromosome locations of loci involved in Stagonospora nodorum blotch (SNB) resistance. Genomic regions on chromosome arms 1AS and 7AS were associated with disease caused by the Swiss S. nodorum isolate used previously. The region associated with disease on chromosome 1A was the same region associated with sensitivity to the necrotrophic effector SnTox4 and this region accounted for 23.5% of the disease. A second region associated with disease was identified on chromosome 7A and accounted for 16.4% of the disease. Together the 1A and 7A loci accounted for 35.7% of the disease. The results of this research provide information that can be used to improve SNB resistance in wheat germplasm.

Technical Abstract: Abeysekara, N.S., Faris, J.D., Chao, S., McClean, P.E., and Friesen, T.L. 201_. Whole genome QTL analysis of Stagonospora nodorum blotch resistance and validation of the SnTox4- Snn4 interaction in hexaploid wheat. Phytopathology Necrotrophic effectors (also known as host-selective toxins) are important determinants of disease in the wheat-Stagonospora nodorum pathosystem. To date, five necrotrophic effector-host gene interactions have been identified in this system. Most of these interactions have additive effects while some are epistatic. The Snn4-SnTox4 interaction was originally identified in a recombinant inbred population derived from a cross between the Swiss winter wheat varieties ‘Arina’ and ‘Forno’ using the S. nodorum isolate Sn99CH 1A7a. Here, we used a recombinant inbred population consisting of 121 lines developed from a cross between the hexaploid land race Salamouni and the hexaploid wheat cultivar ‘Katepwa’ (SK population). The SK population was used for the construction of linkage maps and QTL detection using the Swiss S. nodorum isolate Sn99CH 1A7a. The linkage maps developed in the SK population spanned 3228.0 cM and consisted of 441 SSRs, 9 RFLPs, 29 EST-STS markers and 5 phenotypic markers. The average marker density was 6.7 cM/marker. Two QTL, designated QSnb.fcu-1A and QSnb.fcu-7A on chromosome arms 1AS and 7AS, respectively, were associated with disease caused by the S. nodorum isolate Sn99CH 1A7a. The effects of QSnb.fcu-1A were determined by the Snn4-SnTox4 interaction and accounted for 23.5% of the phenotypic variation in this population whereas QSnb.fcu-7A accounted for 16.4% of the phenotypic variation for disease but was not associated with any known effector sensitivity locus. The effects of both QTL were largely additive and collectively accounted for 35.7% of the total phenotypic variation. The results of this research validate the effects of a compatible Snn4-SnTox4 interaction in a different genetic background, and it provides knowledge regarding genomic regions and molecular markers that can be used to improve SNB resistance in wheat germplasm.