Identification of Fusarium Head Blight Resistance Genes from Wheat QTL-Fhb2, through Forward and Reverse Genetics

Fusarium head blight (FHB) caused by Fusarium graminearum not only cause loss in yield but also reduces quality of grain by accumulating mycotoxins in wheat. Breeding for resistance is considered to be the best option to manage FHB. FHB resistance is quantitative in nature, involves “many, many genes,” each with small effect, that confer resistance when combined. The incomplete understanding of genetics and lack of precise phenotyping hindered the development of FHB resistant cultivars. Though, more than 100 QTL's imparting FHB resistance are reported, no study has reported specific genes localized within the QTL locus, nor the mechanisms of resistance. In this study, an attempt was made to dissect second major QTL, imparting rachis resistance (Type-II). The wheat lines carrying resistant and susceptible alleles of QTL-Fhb2 were subjected to metabolic profiling and transcriptome analysis (RNAseq), post inoculation with Fusarium graminearum spores and water (control). Non-targeted metabolite profiling and transcriptome analysis revealed the higher accumulation of metabolites and up-regulation of transcripts belonging to glycerophospholipid, fatty acid, phenylpropanoid, flavonoid, lignin and terpenoid biosynthetic pathways. The dissection of QTL-Fhb2 using flanking marker sequences identified 4-Coumarate-CoA Ligase (4CL), basic Helix Loop Helix (bHLH) transcription factor, Glutathione S-transferase (GST) and ABC transporter as putative candidate genes localized within QTL locus, imparting resistance. Upon further functional characterization these genes would be transferred to susceptible genotypes or the susceptible alleles may be replaced with resistant genes/alleles using CRISPR-Cas genome editing technique, making crop plant resistant to FHB.