Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/2/2002
Publication Date: N/A
Interpretive Summary: Scab is a destructive disease of wheat that is caused mainly by a fungus named Fusarium graminearum. Wheat scab significantly reduces wheat grain yield and quality, resulting in billions of dollars in crop losses annually. The fungus also produces mycotoxins that limit the consumption of infected grains by humans and livestock. While it is sometimes possible to use fungicides to control the disease, the costs are often prohibitive. If scab resistant wheat varieties were developed, they could represent cost efficient and effective means of limiting losses caused by the disease. However, producing scab resistant wheat varieties by traditional breeding methods has been difficult because of the genetic complexity of scab resistance and the special environmental conditions needed to initiate test infections. Our objective was to molecularly tag the genes most important for scab resistance in selected Chinese wheat varieties so they could be rapidly moved into U.S. wheat varieties. In this study, we succeeded in identifying a chromosomal region from a Chinese wheat variety that contains one or more genes that are primarily responsible for limiting the spread of the scab fungus from kernel to kernel within wheat heads. The results of these studies will speed the production of new scab resistant wheat varieties by allowing researchers to quickly determine whether this chromosomal region that confers scab resistance is present within their new wheat varieties.
Technical Abstract: To develop new molecular markers and determine the sub-arm location of a major wheat scab (fusarium head blight) resistance QTL, ninety-three microsatellite markers were analyzed. Of the 93 markers, thirty-four markers were mapped on 133 FI l recombinant inbred lines derived from the cross between Ning7840 and Clark. Three microsatellite markers on the short arm of chromosome 3B were linked with an AFLP linkage group and a major QTL for scab resistance. The order of the three markers from telomere to centromere is Xgwm389-Xgwm533-Xgwm493. The linkage distance between Xgwm389 and Xgwm533, and that between Xgwm533 and Xgwm493 are 5.3 cM and 4.8 cM, respectively. Using single factor analysis of scab resistance data from evaluation in four generations, Xgwm533 is the most closely associated with the scab resistance QTL. Based on F10 scab resistance data, Xgwm 389, Xgwm533, and Xgwm493 explained 36%, 44%, and 34% of the total scab resistance variation, respectively. Combined with AFLP mapping data, an integrated linkage map with AFLP and microsatellite markers was constructed. Interval analysis based on the integrated map showed that Xgwm389 and Xgwm493 are flanking the major scab resistance QTL. Comparative mapping of the three microsatellite markers on eight 3BS deletion lines showed that Xgwm389 is located distally to breakpoint 3BS-3, and Xgwm533 and Xgwm493 are located between two breakpoints, 3BS-3 and 3BS-8. Thus, the chromosome region containing the major QTL is located distally to the breakpoint 3BS-8. PCR products amplified by the three microsatellite markers can be separated and detected clearly on standard agarose gel. They should be applicable in marker-assisted selection of