Effect of the Rht‐D1 dwarfing locus on Fusarium head blight rating in three segregating populations of winter wheat

Abstract

Fusarium head blight (FHB) is one of the major fungal diseases in wheat throughout the world. To control FHB severity, breeding genetically resistant varieties is thought to be the most promising strategy. In wheat breeding programmes, short cultivars predominantly carrying the Norin 10 derived semi-dwarfing allele Rht-D1b (Rht2) are preferred worldwide because of higher achievable grain yields and lower risk of lodging. This study was conducted to determine the influence of different alleles at the Rht-D1 locus on FHB reaction. Three winter wheat populations were produced by crossing rather susceptible varieties ÔBiscayÕ, ÔPiratÕ and ÔRubensÕ carrying mutant-type allele RhtD1b with the more resistant varieties ÔApacheÕ, ÔRomanusÕ and ÔHistoryÕ containing the Rht-D1a wild-type allele (rht2). The 190, 216 and 103 progeny of the F 4 -derived populations were assayed for the presence of Rht-D1a or Rht-D1b, plant height, and mean FHB rating after spray inoculation at flowering time with a highly aggressive isolate of Fusarium culmorum. Comparably, high mean FHB severities ranging from 28% to 49% for all population · environment combinations were achieved, with significant genotypic variation for FHB rating and plant height within all populations. Both traits were negatively correlated with r ranging from )0.48 to )0.61 in the complete populations. However, within the subpopulations homozygous for one or other height allele these correlations decreased considerably. The Rht-D1b semi-dwarfing allele resulted in 7-18% shorter plants, depending on the population, but a considerably increased FHB reaction of 22-53%. Nevertheless, significant genotypic variance for FHB resistance remained in all tested Rht-D1b subpopulations indicating that selection for moderately FHB resistant genotypes within agronomically beneficial Rht-D1b genotypes is still feasible.

Resistance of winter wheat varieties registered in the Czech Republic to Fusarium head blight in relation to the presence of specific Rht Alleles

“…Selecting taller GA insensitive genotypes is an approach that was found advantageous for the examined Central European conditions (Šíp et al 1988), and it can be feasible also for the high yielding environments of Northwest Europe (Mathews et al 2006), where not using the rht-D1b allele would lead to a considerable yield penalty. The obtained results indicate that it is possible to achieve improved FHB resistance also in genotypes carrying rht-D1b, however, in accordance with the findings of Voss et al (2008) Table 5. Results of testing the differences between mean VSS (visual symptom score on 1-9 scale; 1 = low incidence) of GA insensitive (rht-D1b) and GA sensitive lines in relation to different plant height categories it becomes increasingly difficult (but not impossible) with large height reductions.…”

“…The effect of rht-B1b on FHB resistance could not be evaluated in this variety set, because only one variety (a moderately resistant variety Baletka) was found to carry this gene. The association of FHB susceptibility with the dwarfing allele rht-D1b was recently documented in many publications (Draeger et al 2007;Holzapfel et al 2008;Srinivasary et al 2008;Voss et al 2008) and this association is also supported by the finding that e.g. UK winter wheat varieties, the great majority of which carry the rht-D1b allele, are generally highly susceptible to FHB (Draeger et al 2007;Gosman et al 2007).…”

“…With a high prevalence of relatively shorter rht-D1b genotypes occurring in the randomly selected populations, Voss et al (2008) reported much higher mean FHB ratings (22-53%) compared to mean FHB ratings of the rht-D1a subpopulations. Selecting taller GA insensitive genotypes is an approach that was found advantageous for the examined Central European conditions (Šíp et al 1988), and it can be feasible also for the high yielding environments of Northwest Europe (Mathews et al 2006), where not using the rht-D1b allele would lead to a considerable yield penalty.…”

Cereal resistance to Fusarium head blight and possibilities of its improvement through breeding

“…Similarly, Holzapfel et al (2008) showed on three sets of RILs between European winter wheats that the rht-D1 genomic region is the major source of variation in FHB resistance in the European wheat gene pool. Analogously to Voss et al (2008), they also obtained semi-dwarf lines with acceptable levels of FHB resistance due to the effects of other minor QTLs. rht-B1b allele at rht-B1 locus seems to have a less negative effect, especially on Type II resistance (Srinivasachary et al 2009).…”

“…Similar results were obtained by Buerstmayr et al (2008) from the evaluation of FHB resistance in recombinant lines derived from the crosses Arina/Forno, Arina/Riband, Dream/Lynx, G16-92/Hussar, Renan/Récital, SVP-72017/Capo and Capo/Sumai 3 under natural conditions at different locations in Europe. However, Voss et al (2008) showed on a set of three segregating populations of winter wheat that the correlation between the presence of rht-D1b allele and FHB resistance is not absolute, i.e. lines carrying rht-1Db allele with a relatively high level of FHB resistance can be obtained.…”