Preliminary Analysis Of QTL For Fusarium Head Blight Resistance In Wangshuibai×Nanda2419 Population

Fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (telomorph: Gibberella zeae), is a major disease of wheat. Outbreak of FHB can result in devastating economic losses to wheat production, since it not only lowers the yield but also deteriorates the quality of wheat grains. Deployment of scab-resistant varieties is the most economical measure in controlling this disease. However, the paucity of germplasms and lack of knowledge about the resistance genetics have greatly limited the progress in scab resistance breeding. To identify genes for scab resistance, a population of F6 recombinant inbred lines (RILs) from a cross 'Wangshuibai'(resistant) x 'Nanda 2419'(susceptible) was produced. The population was evaluated in a greenhouse and a field for FHB resistance through single floret inoculation of the conidia at flowering stage. Mist system was used to maintain the moisture suitable for disease development. Fifteen days after the inoculation, data werecollected for number of diseased spikelets, number of diseased internodes and length of diseased rachis. SSR and RAPD markers were screened for polymorphisms between the parents and between the resistant and susceptible pools. The polymorphic markers were applied in genotyping of the populations. Using one-way ANOVA and regression analysis, ten markers were found to be significantly associated with FHB resistance (p<0.05), including 6 with the number of diseased spikes, 10 with the number of diseased internodes and 8 with the length of diseased rachis. Because of the trait correlation, some of the markers were shared among the three traits. Among the ten markers, four which showed association with the number of diseased internodes and the length of diseased rachis were consentaneous in the greenhouse and field test. These ten markers were mapped to chromosomes 2B, 3A, 3B and 5B, respectively.By interval analysis, three intervals showed significant association with FHB resistance. Two of them were located between Xnau23 - Xnau22 and between Xnaull. 1 - Xnau24. The resistance alleles of both loci derived from the resistant parent 'Wangshuibai'. The third interval was located between SSR1021 and Xnaul4.1. The resistance allele of this QTL derived from the susceptible parent 'Nanda 2419'. The one between Xnau23 - Xnau22 has the largest effect, explaining 20.1% and 15.9% of the phenotypic variance for thenumber of diseased internodes and the length of diseased rachis respectively in the greenhouse test, and 11.2% and 11.6% of the phenotypic variance respectively for these two traits in the field test. The identification of QTLs for scab resistance paves the way for discovery of scab resistance genes and marker-assisted selection of scab resistance.