Molecular mapping of Thinopyrum-derived Fusarium head blight resistance in common wheat

Resistance to Fusarium head blight (FHB) caused by Fusarium graminearum Schwabe in wheat (Triticum aestivum L.) was identified in disomic chromosome substitution and translocation lines, into which chromosome 7el(2) had been introgressed from wheatgrass, Thinopyrum ponticum. In this study, two chromosome substitution lines with different origins (designated as el(1) and el(2)) and with different reactions to infection by F. graminearum were crossed to develop a segregating mapping population. The objectives of this study were to determine the effectiveness of this type II resistance and map it on chromosome 7el(2). Type II resistance to FHB was characterized in the F-2, F-2:3 families, F-4:5 plants and F-5:6 recombinant inbred lines developed by single-seed descent; and the population was characterized in the F-2 and F-5 with DNA markers along the long arm of 7el. Composite interval mapping revealed a FHB resistance QTL, designated Qfhs.pur-7EL, located in the distal region of the long arm of 7el(2) and delimited with flanking markers XBE445653 and Xcfa2240. Additive effects of Qfhs.pur-7EL reduced the number of diseased spikelets per spike following inoculation of one floret in four experiments by 1.5-2.6 and explained 15.1-32.5% of the phenotypic variation in the populations. Several STS-derived and EST-derived PCR or CAPS markers were developed in this chromosomal region, and showed the specificity of 7el(2) compared to an array of wheat lines possessing other sources of FHB resistance. These markers are useful in an effort to shorten the chromosome segment of 7el(2) and to use for marker-assisted introgression of this resistance into wheat.