High-temperature, adult-plant (HTAP) resistance to stripe rust in wheat is governed by multiple genes, and is race non-specific and durable. The winter wheat cultivar Stephens has served as the primary source of HTAP resistance in Pacific Northwest region of the U.S. for the last 28 years. The objectives of this study were to: (1) identify and map QTL for HTAP resistance to stripe rust in Stephens through genetic linkage analysis; and (2) develop DNA markers for use in marker-assisted breeding. One hundred and fourteen F8 RILs obtained from reciprocal crosses between Stephens (resistant) and Michigan Amber (susceptible) were used for mapping. Disease severity data (percentage of infected leaf area) recorded on three different dates were used to calculate the area under disease progression curve (AUDPC) for use in QTL mapping. RILs were evaluated with 125 polymorphic DNA (124 SSR and 1 STS) markers, and 12 were significantly (P>0.05) associated with the target trait. We identified two QTL, Q.htap-1 (LOD=7.29, R2=0.257, P<0.0001) and Q.htap-2 (LOD=7.15, R2=0.255, P<0.0001) associated with HTAP resistance. Q.htap-1 mapped within a 23.1 cM region flanked by Xgwm88.2 and Xucw71 on the short arm of wheat chromosome 6B, whereas Q.htap-2 mapped within a 14.9 cM region flanked by Xgwm508.2 and Xgwm132 on the same chromosome. Together, these two QTL accounted for 30.8% of the total phenotypic variation for stripe rust resistance.
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