Unraveling the metabolite signatures of maize genotypes showing differential response towards southern corn leaf blight by 1H-NMR and FTIR spectroscopy

Abstract

Southern corn leaf blight, caused by Drechslera maydis, is the most prevalent fungal disease in maize growing regions of India. This is the first study that identified genotypic variability among maize genotypes, LM 13, CM 140 and LM 15 (highly resistant, moderately resistant and highly susceptible towards infection, respectively) on the basis of metabolite profiling, using 1H-NMR and FTIR techniques. High intensity peaks of quercetin, ascorbic acid, glycine betaine and flavonoids were observed in the inoculated leaves of LM 13 by 1H-NMR spectroscopy. LM 15 showed intense peaks of alanine, γ- amino butyric acid (GABA), fatty acids and threonine in their leaves. FTIR spectral analysis of the inoculated leaves of LM 13 and CM 140 genotypes showed O–H stretching vibrations of carbohydrates and glycoconjugates and the C–O–C bending vibrations of cellulose and hemicelluloses in their cells. These vibrations were absent in the infected leaves of LM 15. Principal component analysis showed that the primary and secondary metabolites contributed significantly towards genotypic variability. It may thus be concluded that the presence of polyphenols, flavonoids and lignin might be responsible for inducing resistance against infection. Threonine, GABA, malic acid, fatty acids and the unassigned metabolite could be regarded as potential biochemical markers for disease susceptibility.