Marker-assisted wheat improvement: Creating semi-dwarf phenotypes with superior Fusarium head blight resistance

The Green Revolution genes considerably increased the yield potential of modern wheat varieties, but also rendered them more susceptible to Fusarium head blight (FHB) causing problems with mycotoxin contamination. In order to study (lie association of "reduced height" (Rht) genes and FHB resistance, Rht-Blb, Rht-Dlb and Rht8 genes were introduced in tall high-yielding wheat cultivars expressing a good level of Fusarium head blight (FHB) resistance via marker-assisted selection (MAS). The F-1 plants of five crosses were backcrossed twice and 189 BC1 lines were genotyped. MAS was performed with Rht-Blb and Rht-Dlb specific markers, with SSR Xgwm261 being diagnostic for Rht8, and with a Ppd-Dl specific marker. During the first phase of selection corresponding chromosomes were screened with 48 SSRs for polymorphisms followed by the use of 3 to 5 polymorphic SSRs for the detection of recombination around these loci. Based on this procedure a total of 42 lines were selected for the selection phase two. 152 genome-wide SSRs had been screened among the parent lines, and from these a set of 80 polymorphic SSRs (4 per chromosome) was chosen for background fingerprinting of the 42 lines. This process is ongoing. We expect that Rht alleles will be quickly integrated into tall and high-yielding cultivars with excellent quantitative FHB resistance carrying only small chromosomal fragments of the Rht donor lines. Finally, in multi-location field trials these new lines will be tested to analyse the association of the three Rht genes and FHB susceptibility.