An Increase in the Proportion of β-Diketone Epicuticular Wax Is a Beneficial Variant Trait for Drought Tolerance in Leymus chinensis.

Leymus chinensis is a perennial grass with remarkable adaptability and forage quality. It is the dominant species on the saline-alkali land in the Songnen Plain in Northeast China, where two ecotypes naturally grow: the grey-green (GG) and yellow-green (YG) genotypes, named after the leaf color. However, the differences in morphology and adaptability between the GG and YG ecotypes are not elucidated. In this study, we investigated and compared GG and YG ecotypes' cuticular wax and its composition. Furthermore, the difference in drought tolerance between the leaves of the two ecotypes was analyzed. Our results showed that GG plants have stronger drought tolerance owing to an optimal limiting non-stomatal water loss effect than the YG plants, which is associated with their higher proportion of tubular epicuticular wax. The composition of the tubular wax was mainly β-diketone 14,16-Hentriacontanedione (C31H60O2), and its biosynthesis may be closely related to the endoplasmic reticulum-localized diketone metabolism type-III polyketide synthase (DMP). Our findings suggest that the increased proportion of β-diketone epicuticular wax may be a beneficial variant trait for L. chinensis to optimally adapt to drought environments.