Identification of novel tan spot resistance loci beyond the known host-selective toxin insensitivity genes in wheat

Abstract

Tan spot, caused by Pyrenophora tritici-repentis, is a destructive foliar disease of wheat causing significant yield reduction in major wheat growing areas throughout the world. The objective of this study was to identify quantitative trait loci (QTL) conferring resistance to tan spot in the synthetic hexaploid wheat (SHW) line TA4152-60. A doubled haploid (DH) mapping population derived from TA4152-60 x ND495 was inoculated with conidia produced by isolates of each of four virulent races of P. tritici-repentis found in North America. QTL analysis revealed a total of five genomic regions significantly associated with tan spot resistance, all of which were contributed by the SHW line. Among them, two novel QTLs located on chromosome arms 2AS and 5BL conferred resistance to all isolates tested. Another novel QTL on chromosome arm 5AL conferred resistance to isolates of races 1, 2 and 5, and a QTL specific to a race 3 isolate was detected on chromosome arm 4AL. None of these QTLs corresponded to known host selective toxin (HST) insensitivity loci, but a second QTL on chromosome arm 5BL conferred resistance to the Ptr ToxA producing isolates of races 1 and 2 and corresponded to the Tsn1 (Ptr ToxA sensitivity) locus. This indicates that the wheat-P. tritici-repentis pathosystem is much more complex than previously thought and that selecting for toxin insensitivity alone will not necessarily lead to tan spot resistance. The markers associated with the QTLs identified in this work will be useful for deploying the SHW line as a tan spot resistance source in wheat breeding.

Evaluation and Association Mapping of Resistance to Tan Spot and Stagonospora Nodorum Blotch in Adapted Winter Wheat Germplasm

“…Based on the approximate chromosomal positions of individual QTL, a number of genomic regions identified in our studies, including chromosomal arms 3BL, 3DS, 4AL, 5DL, and 7DL, could be the same as reported by Kollers et al (2014), who used 358 European winter wheat accessions. These regions may also correspond to major resistance QTL previously identified in segregating biparental populations (Chu et al 2008b, Faris andSingh et al 2008;Tadesse et al 2007). Gurung et al (2011) identified genomic regions on chromosomes 1D, 2A, 2B, 2D, 4A, and 7D for Pti2 and genomic regions on chromosomes 2D, 6A, and 7D for race 5 in a worldwide spring wheat core collection.…”

Genetics of wheat–Pyrenophora tritici-repentis interactions

“…The toxin insensitivity genes previously identified (Anderson et al 1999;Effertz et al 2002) likely underlines these QTLs (Singh et al 2008a). However, Chu et al (2008) identified five genomic regions significantly associated with tan spot resistance. Three of these novel QTLs located on chromosome arms 2AS, 5AL, and 5BL, conferred resistance to multiple races while the fourth QTL specific to race 3 was observed on chromosome arm 4AL.…”

Association mapping for resistance to tan spot induced by Pyrenophora tritici-repentis race 1 in CIMMYTs historical bread wheat set

“…Additional QTLs have been identified and located on chromosome arms 1AL (Effertz et al 2001), 2AS (Friesen and Faris 2004;Chu et al 2008), 3AS (Singh et al 2008b), 4AL (Faris et al 1997;Friesen and Faris 2004;Faris and Friesen 2005;Chu et al 2008), 5AL (Effertz et al 2001;Chu et al 2008), 1BS (Faris and Friesen 2005), 2BL (Friesen and Faris 2004), 3BS (Faris and Friesen 2005), 3BL (Faris and Friesen 2005), 5BL (Faris and Friesen 2005;Chu et al 2008), 2DS (Faris and Friesen 2005), 2DL (Faris et al 1997), and 7DS (Effertz et al 2001;Faris and Friesen 2005).…”