Metabolic profiling and factor analysis to discriminate quantitative resistance in wheat cultivars against fusarium head blight

Metabolic profiles of spikelets of wheat cultivars, Roblin and Sumai3, respectively, susceptible and resistant to fusarium head blight (FHB) were analyzed using GC/MS to develop a technology to discriminate resistance. More than 700 peaks were detected and a total of 55 compounds were tentatively identified, of which 49 were induced/up-regulated following pathogen inoculation, including 23 in Roblin and 26 in Sumai3. However, only five metabolites were significantly different both between cultivars and inoculations. Metahydroxycinnamic acid, though was detected in all four treatments, exhibited a six-fold increase in abundance in Sumai3 following pathogen inoculation, with no corresponding change in Roblin. The abundance of myo-inositol in Sumai3 was higher than that in Roblin, and in both the abundance increased following pathogen inoculation. The compounds common to all treatments were subjected to factor analysis to identify groups of compounds, based on significant factor-loadings, associated with susceptibility or resistance against FHB. The treatment involving pathogen-inoculation of the resistant cv. Sumai3 was associated with the highest scores for the first and second factors that can be used for the discrimination of resistance against FHB. The first factor was associated with higher abundances of several fatty acids and aromatic compounds, while the second factor was associated with metabolites such as p- and m-coumaric acids, myo-inositol and other sugars, and malonic acid. The treatments involving pathogen-inoculation had higher factor scores for the third factor than the water inoculated, the highest being for the susceptible cultivar Roblin, and may be useful in explaining susceptibility/pathogenesis. The third factor had positive correlation with metabolites from different groups, mostly amino acids, fatty acids, and aromatics. The various compounds detected in this study are discussed, in terms of their possible roles in plant defense against pathogen-stress, their metabolic pathways of synthesis, and their potential application for screening cultivars of wheat for resistance to FHB.