Submitted to: Plant Breeding
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/15/2003
Publication Date: 8/15/2003
Citation: ZHO, W.C., KOLB, F.L., BAI, G., DOMIER, L.L., BOZE, L.K., SMITH, N.J. 2003. Validation of a major QTL for scab resistance with SSR markers and use of marker-assisted selection in wheat. Plant Breeding. Interpretive Summary: Scab is a destructive disease of wheat that is caused by a fungus named Fusarium graminearum. In addition to wheat, this fungus infects barley, oats, and rye, and causes stalk rot in corn. 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 grain 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 variability of environmental conditions that influence the development of the disease. In a previous study, we produced markers linked to a gene that provides most of the scab resistance from a Chinese wheat line. In this study, we demonstrated the usefulness of these markers as tools in accelerating the development of new scab resistant wheat lines. The results of these studies will be of interest to researchers who are working to produce new scab resistant wheat varieties, which should reduce economic losses to wheat producers and reduce the levels of mycotoxin in harvested grain.
Technical Abstract: The objectives of this study were to validate the major quantitative trait locus (QTL) for scab resistance on the short arm of chromosome 3B in bread wheat and to isolate near-isogenic lines for this QTL using marker-assisted selection (MAS). Two resistant by susceptible populations, both using 'Ning7840' as the source of resistance, were developed to examine the effect of the 3BS QTL in different genetic backgrounds. Data for scab resistance and simple sequence repeat (SSR) markers linked to the resistance QTL were analyzed in the F (2:3) lines of one population and in the F (3 :4) lines of the other. Markers linked to the major QTL on chromosome 3BS in the original mapping population ('Ning7840'/'Clark') were closely associated with scab resistance in both validation populations. Marker-assisted selection for the QTL with the SSR markers combined with phenotypic selection was more effective than selection based solely on phenotypic evaluation in early generations. Marker-assisted selection of the major QTL during the seedling stage plus phenotypic selection after flowering effectively identified scab resistant lines in this experiment. Near-isogenic lines for this 3BS QTL were isolated from the F (6) generation of the cross 'Ning7840'/'IL89-7978' based on two flanking SSR markers, Xgwm389 and Xbarc147 . Based on these results, MAS for the major scab resistance QTL can improve selection efficiency and may facilitate stacking of scab resistance genes from different sources.