Pyramiding Disease Resistance Genes In Wheat (Triticum aestivum L.)
The major goal of this study was to accumulate plant disease resistance QTL (Quantitative Trait Loci) and genes to Fusarium head blight (FHB), leaf rust (Lr), Septoria tritici blotch (STB) and barley yellow dwarf virus (BYDV) in wheat. Two winter and two spring wheat cultivars were crossed and seven generations of spring wheat were developed in three years. Fifty percent of the F3 and 20% of the F5 population showed low severity to both leaf rust and Septoria tritici blotch. Analysis of QTL tagged by molecular markers showed an epistatic effect of an Xgwm533 allele (associated with type II resistance to FHB) on an unknown allele in the F5 population. The relationships between the leaf rust resistance gene Lr34 and Fusarium toxin deoxynivalenol (DON) were not significant. Biplot analyses of the F3 and derived F5 populations demonstrated that the associations between molecular markers and disease resistance were heritable and that genotypic screening can be used in early generations in a small population. Pre-screening of a doubled haploid (DH) wheat population with molecular markers demonstrated that the resistant Xgwm533 allele from Sumai3 had no negative effect on yield whereas the effects of other QTL on yield remains to be determined. Two sources of FHB resistance (25R51 and RCATL31) were incorporated into the DH population and 6% of DH lines displayed a lower FHB incidence than the parent line 25R51 indicating improved FHB resistance in this population.