Effect of Dwarfing Rht Genes on Fusarium Head Blight Resistance in Two Sets of Near-Isogenic Lines of Wheat and Check Cultivars

Reduced height (Rht) genes are used in wheat (Triticum aestivum L.) breeding throughout the world. Fusarium head blight (FHB) is one of the most destructive wheat diseases caused by Fusarium graminearum (Schwabe) and F. culmorum (W.G. Sm.) Sacc. Objectives of this study were to analyze the effects of (i) specific Rht dwarfing genes on FHB reaction using two sets of near-isogenic lines (NILs) and (ii) genetic background and environment on FHB reaction. We inoculated NILs carrying Rht-B1b, Rht-B1d, Rht-D1b, Rht8c, and Rht-D1b+Rht8c in the background of the British winter wheat cultivar Mercia possessing medium height and moderate resistance, and NILs carrying Rht-B1b, Rht-B1c, Rht-D1b and Rht-B1b+Rht-D1b in the background of the rather tall, generally more resistant British cultivar Maris Huntsman, as well as three German check cultivars ('Toras', 'Certo', 'Travix') carrying the Rht-D1b allele. Entries were tested in eight (Mercia) and four (Maris Huntsman) environments, respectively, by inoculation with F. culmorum. In the Mercia data set, Rht-B1d and Rht-D1b significantly increased mean FHB rating by 35 and 52%, respectively. Rht-B1b and Rht8c increased FHB rating only by 19%, being not significantly different to the wild-type line (rht). Rht8c affected heading date due to its linkage with the photoperiod insensitive Ppd1 allele. In the Maris Huntsman data set, FHB rating was increased by 22 to 83%, but only the very short Rht-B1c and Rht-B1b+Rht-D1b lines showed significance. Although the mutant Rht alleles increased FHB susceptibility, the checks show that these negative effects can be largely counteracted by a more resistant genetic background.