Dissecting the genetic complexity of Fusarium crown rot resistance in wheat

Fusarium crown rot (FCR) is one of the most important diseases of wheat (Triticum aestivum L.). FCR is mainly caused by the fungal pathogens Fusarium culmorum and F. pseudograminearum. In order to identify new sources of resistance to FCR and to dissect the complexity of FCR resistance, a panel of 161 wheat accessions was phenotyped under growth room (GR) and greenhouse conditions (GH). Analysis of variance showed significant differences in crown rot development among wheat accessions and high heritability of genotype-environment interactions for GR (0.96) and GH (0.91). Mixed linear model analysis revealed seven novel quantitative trait loci (QTLs) linked to F. culmorum on chromosomes 2AL, 3AS, 4BS, 5BS, 5DS, 5DL and 6DS for GR and eight QTLs on chromosomes on 3AS, 3BS, 3DL, 4BS (2), 5BS, 6BS and 6BL for GH. Total phenotypic variances (R²) explained by the QTLs linked to GR and GH were 48% and 59%, respectively. In addition, five favorable epistasis interactions among the QTLs were detected for both GR and GH with and without main effects. Epistatic interaction contributed additional variation up to 21% under GR and 7% under GH indicating strong effects of environment on the expression of QTLs. Our results revealed FCR resistance responses in wheat to be complex and controlled by multiple QTLs.