Chemical and morphological diversity of foliar epicuticular waxes in economically important grain crops.

Global food systems are under pressure to remain stable amidst increasing uncertainty. Plant epicuticular waxes play vital roles in mitigating a range of environmental stressors, hence understanding their diversity can inform practices that sustain the large-scale production of grain crops that underpin human nutrition. This study employs a combination of gas chromatography-mass spectrometry and scanning electron microscopy to chemically and morphologically characterise the foliar epicuticular waxes from economically important monocot and dicot species. Principal component analyses are also performed to identify key wax components that distinguish species apart. Monocot epicuticular waxes were uniform in platelet morphologies and were generally richer in primary alcohols, while dicots were morphologically diverse and were generally richer in alkanes. A clear disconnect between chemical composition and morphology suggests that individual wax components cannot be used to predict leaf surface properties. The wax composition data presented here also suggests that cuticular aldehydes are not exclusive to the decarbonylation pathway, depicting a more complex regulatory framework for cuticular wax biosynthesis. This study offers a broader inter- and intra-species view of foliar wax chemistry, emphasising differences in cuticular wax biosynthetic strategies and their implications for plant-pathogen interactions. The data collected in this study provide a valuable baseline for future studies that link epicuticular wax physicochemical properties to their biological implications.