Amplified fragment length polymorphism markers linked to a major quantitative trait locus controlling scab resistance in wheat

Scab is a destructive disease of wheat. To accelerate development of scab-r esistant wheat cultivars, molecular markers linked to scab resistance genes have been identified by using recombinant inbred lines (Ws) derived by sin gle-seed descent from a cross between the resistant wheat cultivar Ning 784 0 (resistant to spread of scab within the spike) and the susceptible cultiv ar Clark. In the greenhouse, F-5, F-6, F-7, and F-10 families were evaluate d for resistance to spread of scab within a spike by injecting about 1,000 conidiospores of Fusarium graminearum into a central spikelet. Inoculated p lants were kept in moist chambers for 3 days to promote initial infection a nd then transferred to greenhouse benches. Scab symptoms were evaluated fou r times (3, 9, 15, and 21 days after inoculation). The frequency distributi on of scab severity indicated that resistance to spread of scab within a sp ike was controlled by a few major genes. DNA was isolated from both parents and F-9 plants of the 133 RILs. A total of 300 combinations of amplified f ragment length polymorphism (AFLP) primers were screened for polymorphisms using bulked segregant analysis. Twenty pairs of primers revealed at least one polymorphic band between the two contrasting bulks. The segregation of each of these bands was evaluated in the 133 RILs. Eleven AFLP markers show ed significant association with Scab resistance, and an individual marker e xplained up to 53% of the total variation (R-2). The markers with high R-2 values mapped to a single linkage group. By interval analysis, one major qu antitative trait locus for scab resistance explaining up to 60% of the gene tic variation for scab resistance was identified. Some of the AFLP markers may be useful in marker-assisted breeding to improve resistance to scab in wheat.