APS Homepage

Poster: Biology & Disease Mgmt: Genetics of Resistance


QTL Mapping of Resistance to Tan Spot in a Winter Recombinant Inbred Line Population Derived from Cross between Harry and Wesley
G. KARIYAWASAM (1), W. Hussain (2), A. Easterly (2), M. Guttieri (2), V. Belamkar (3), J. Venegas (2), S. Baenziger (2), J. Poland (4), J. Faris (5), S. Xu (5), J. Rasmussen (1), Z. Liu (1) (1) North Dakota State University, U.S.A.; (2) University of Nebr

Tan spot, caused by the Pyrenophora tritici-repentis, is an important disease on both common and durum wheat worldwide. The disease system is known to involve three necrotrophic effectors (NEs) that interact with corresponding host sensitivity genes, including Ptr ToxA-Tsn1, Ptr ToxB-Tsc2 and Ptr ToxC-Tsc1. To investigate the role of NE-host sensitivity interactions in disease, we conducted the QTL mapping of tan spot resistance in a recombinant inbred line population derived from a cross between two US winter wheat cultivars ‘Harry’ and ‘Wesley’. Harry was sensitive to Ptr ToxA and highly susceptible to tan spot while Wesley was insensitive and highly resistant. QTL mapping revealed two major loci: the one corresponding to the Tsn1 locus, and one on 1AS, which likely corresponded to the Tsc1 locus. Both the tsn1 and tsc1 loci were significantly associated with resistance to race 1, but only tsn1 was significantly associated with race 2, and only tsc1 was associated with race 3. Neither locus was significantly associated with disease caused by a race 2 ToxA knockout strain. Additional QTL were also identified in this population, but their effects on disease were relatively minor. This work indicates that the Ptr ToxA-Tsn1 and Ptr ToxC-Tsc1 interactions play important roles in conferring tan spot susceptibility in winter wheat, and breeding programs should remove these susceptibility loci in order to improve tan spot resistance.