Leaf anatomy and identification of drought-tolerant Coconut (Cocos nucifera L.) varieties in Kerala, India

Coconut (Cocos nucifera L.) is a tropical evergreen palm with high economic value. Drought stress, exacerbated by climate change, poses a significant threat to coconut production, prompting research to develop drought-tolerant varieties. In this study, eight hybrid combinations of Dwarf × Tall were evaluated for their drought tolerance. Among the varieties, the hybrid Chowghat Orange Dwarf (COD) × Laccadive Ordinary Tall (LCT) exhibited the greatest thickness of both upper and lower epidermal layers, as well as higher palisade and spongy mesophyll tissue thickness. Additionally, this hybrid recorded the largest xylem diameter. Malayan Yellow Dwarf (MYD) × West Coast Tall (WCT) showed the lowest stomatal density, whereas MYD × LCT recorded the highest trichome density. The combined analysis of the different parameters evaluated through PCA and thickness of the palisade mesophyll cells, width of the bundle sheath cells, number of nuts, stomatal length and width, thickness of spongy mesophyll cells and width of the xylem could distinguish the tolerant hybrids from others. Cluster analysis grouped the hybrids in to four groups based on the drought tolerant nature. The identified drought-tolerant hybrids could undergo screening for additional crucial drought-resistant parameters, contributing to future research aimed at enhancing the drought resistance of hybrids.