RFLP mapping of QTL for fusarium head blight resistance in wheat

Recent epidemics of fusarium head blight (FHB), caused by Fusarium graminea rum Schwabe (telomorph: Gibberella zeae), in the USA and Canada have caused severe yield and quality losses in wheat (Triticum aestivum L.). Developme nt of resistant cultivars has been difficult because of the complex inherit ance of resistance and con founding environmental effects. This study was c onducted to identify and map DNA markers linked to genes associated with FH B resistance. A population of 112 F-5-derived recombinant inbred (RI) wheat lines from the cross 'Sumai 3' (resistant)/'Stoa' (moderately susceptible) was evaluated in two greenhouse experiments for Type II resistance (spread within the spike). On the basis of restriction fragment length polymorphis m (RFLP) marker analyses, five genomic regions were significantly (P < 0.01 ) associated with FHB resistance, three derived from Sumai 3 and two from S toa. Regions on Chromosomes 3BS (from Sumai 3) and 2AL (from Stoa) were ide ntified by interval analysis using a LOD threshold of 3.0. These two quanti tative trait loci (QTL) have been assigned the gene designations QFhs.ndsu- 3B and QFhs.ndsu-2A, respectively. Recombinant inbred lines with these two QTL had a median severity of 20.9%, compared with 36.2% for all RI lines. T he best RFLP marker in the 3BS region explained 15.4% of the variation and a multiple regression model consisting of three QTL explained 29.5% of the variation. These results indicate that resistance to FHB is inherited in a quantitative manner and that marker-assisted selection may aid the developm ent of FHB-resistant cultivars.