Barrier against water loss: relationship between epicuticular wax composition, gene expression and leaf water retention capacity in banana.

In the present study we examined 13 banana (Musa spp.) genotypes belonging to different genomic groups with respect to total leaf cuticular wax concentration, chemical composition, carbon chain length and their relationship with leaf water retention capacity (LWRC). A positive correlation between epicuticular wax content and LWRC clearly indicated that the cuticular wax plays an important role in maintaining banana leaf water content. The classification of hexane soluble cuticular wax components into different classes based on functional group and their association with LWRC showed that alcohol and ester compounds have a positive correlation. Further, the compounds with >C28 carbon chain length had a positive correlation with LWRC, indicating the role of longer carbon chain length in maintaining the water status of banana leaves. Also, the gene expression analysis showed higher expression of the wax biosynthetic genes FATB and KCS11 in higher wax load genotypes whereas lower expression was seen in low wax banana genotypes. Here, we report for the first time the compositional variations of cuticular wax in different banana genotypes, followed by their association with leaf water retention capacity. The results were also supported by variation in gene expression analysis of cuticular wax biosynthetic genes - FATB and KCS11.