Genetic Characterization of a Fusarium Head Blight Resistance QTL from Triticum turgidum ssp. dicoccoides

Abstract

Qfhs.ndsu-3AS in wild emmer wheat (Triticum turgidum L. ssp. dicoccoides) is a major quantitative trait locus associated with type II resistance to Fusarium head blight (FHB). It was mapped in a population obtained from durum wheat Langdon (Triticum turgidum L. ssp. durum) and disomic Langdon-T. dicoccoides 3A substitution lines. Langdon(Dic-3A)-10 showed better performance against Fusarium graminearum (Fg) infection than the Langdon variety. To identify the genes underpinning Qfhs.ndsu-3AS, we used RNA-Seq approach in Langdon(Dic-3A)-10 and Langdon at 72 h after inoculation. The reference genomes of Svevo and Zavitan representing ssp. durum and ssp. dicoccoides, respectively, were used in parallel to align the reads and identify the genes expressed during the infection. The size of the Qfhs.ndsu-3AS region spans about 24 Mb and contains about 1000 genes. Fourteen differentially expressed genes (DEGs) were mapped in the delimited region and considered candidates for resistance. Five of them combined a higher expression level in Langdon(Dic-3A)-10 and known function in defense response: three receptor protein kinases, one bZip transcription factor, and one protease inhibitor. The alignment of the reads to the two genomes also allowed the identification of 25 genes expressed but no-DEGs localized in the Qfhs.ndsu-3AS region. Their coding sequences contained 63 non-synonymous changes and one frameshift mutation that could alter the function of the proteins and eventually contribute to resistance against Fg. This list is valuable information towards understanding the mechanism involved in resistance conferred by Qfhs.ndsu-3AS.