A loss‐of‐function of the dirigent gene TaDIR‐B1 improves resistance to Fusarium crown rot in wheat

The TaDIR gene was identified by GWAS and QTL mapping of Fusarium crown rot (FCR) resistance and was functionally verified by VIGS and analysis of tetraploid and hexaploid wheat mutants. (a): Classification of FCR disease index in the surveyed cultivars. (b) Number of accessions with different FCR DI in the association panel. (c) Manhattan and Q‐Q plots for FCR DI in different environments. (d) Distribution of significant SNPs revealed by GWAS on various chromosomes. (e) Haplotype analysis of significant SNPs on 4B identified at multiple environments. (f–g) Comparison of FCR DI of wheat accessions with different alleles in the block on 4B. (h) QTL mapping for FCR DI in the Bainong64/Jingshuang16 (BJ) population. (i) The schematic range of 6 candidate genes including TaDIR identified by haplotype analysis and QTL mapping. (j) Full alignment of amino acid of TaDIR‐B1 alleles between low DI and high DI accessions. (k) Development of the dCAPS marker to distinguish TaDIR‐B1 alleles. Furthermore, TaDIR‐B1 gene was silenced in the FCR‐susceptible cultivar Pingyuan 50 using virus‐induced gene silencing (VIGS) by barley stripe mosaic virus (BSMV). qRT‐PCR analysis showed significant down‐regulation of TaDIR‐B1 in VIGS‐silenced plants (Figure 1l‐2). Compared to the WT and BSMV0 plants, the lignin content in the BSMVTaDIR‐B1 plants was remarkedly increased, and the activities of superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) were also dramatically increased, but the malondialdehyde (MDA) content was significantly decreased in BSMVTaDIR‐B1 plants (Figure 1l‐4). Physiological analysis showed that lignin accumulation was dramatically increased in silenced‐TaDIR‐B1 plants. [...]improvement of FCR resistance caused by loss of function of the TaDIR‐B1 gene may be attributed to accumulation of lignin in wheat plants.