Functional Elucidation of Wheat QTL Fhb4 for Resistance Against Fusarium Head Blight, Based on Non-Targeted Metabolomics

Wheat (Triticum aestivum) is an important staple food crop which feeds 35% of the world’s population. Amongst several factors limiting wheat production, fusarium head blight (FHB), caused by Fusarium graminearum Schwabe (Teleomorph: Gibberella zeae (Schwein) Petch) emerges as one of the most destructive diseases. In addition to yield loss, the major concern is the accumulation of mycotoxins in grains. FHB resistance in wheat is quantitative in nature and is broadly classified as resistance to infection of spikelets and resistance to lesion expansion. The Fhb4 (Qfhi.nau-4B) is a major quantitative trait locus (QTL) conferring resistance against spikelet infection. It is localized on the long arm of the chromosome 4B, and its presence has reduced the disease incidence by 50%. Recently, the Fhb4 locus has been fine mapped to 1.7cM. Metabolic profiling of wheat near isogenic lines (NILs) harboring contrasting alleles for resistance to FHB at Fhb4 locus revealed several resistance-related (RR) metabolites. The key RR metabolites found belonged to phenylpropanoids and flavonoids biosynthetic pathways. Hydroxycinnamic acid amides (HCAA’s), such as N-Caffeoylputrescine and 4-coumaroylagmatine, accumulated several folds higher in resistant upon pathogen inoculation, are known to be antifungal and also prevent pathogen spread by depositing these compounds on the cell wall. In addition, high fold accumulation of a few flavonoids such as kaempferol 3-glucoside-7-α-L-arabinopyranoside and laricitrin 3-rutinoside-7-glucoside, which are known to have a significant role in plant defense, were also detected. These RR metabolites can be used as candidates to improve resistance to FHB in wheat, following validation.