Identification of Candidate Genes in QTL 2DL and Deciphering Mechanisms of Resistance Against Fusarium Head Blight Based on Metabolo-Genomics in Wheat

Wheat (Triticum aestivum L.) is the most important cereal crop cultivated in the world. Fusarium head blight (FHB) caused by Fusarium graminearum is one of the most destructive diseases of wheat. Apart from causing huge yield losses, the FHB also known to contaminate seeds with mycotoxins, that are harmful to human and animal health. Several QTL’s have been identified against FHB in wheat, but the mechanisms of resistance and candidate genes underlying them are still unknown. Therefore in present study high throughput metabolomics was used to decipher the candidate genes and mechanisms of resistance in near isogenic lines (NILs) of 2DL QTL. The high fold resistance related (RR) metabolites, identified in NIL-R following pathogen inoculation, belonged to hydroxycinnamic acid amides, such as p-coumaroylagmatine (28 fold) and p-coumaroylputrescine, and a diacyl-glycerophospholipid phosphatidic acid (52 fold). The candidate genes, p-coumaroylagmatine transferase (TaACT) and diacylglycerol kinase (DGK), were associated with the respective RR metabolites. In addition, theWRKY45 transcription factor was also identified within the QTL region, with the help of QTL specific flanking marker sequences. In-silico promoter sequence analysis of TaACT and DGK showed the presence of WRKY binding sites. Further sequencing of WRKY45 gene in both NILs revealed the presence of one functional SNP at the first intron-exon junctionin NIL-S, causing altered splicing and leading to deletion of putative nuclear localization signal spanning 14 amino acids in predicted protein sequence. Thus, the plausible FHB resistance mechanism governed by this QTL is revealed.