Variation in seed morphology and selected oil parameters of neem (Azadirachta indica A. Juss.) from different agroclimatic zones in Tamil Nadu, India

Tamil Nadu, in southern India, has the second-largest number of neem trees in the country. The oil from the seeds has high economic significance for cottage industries in the region. This paper examines 28 Candidate Plus Trees (CPTs) selected from six agroclimatic zones in Tamil Nadu which exhibit exceptional traits such as superior growth and other desirable characteristics. We aimed to understand seed morphology variations and physicochemical properties in the oil across different regions. Significant differences were observed for morphometric traits. Fruit production correlated negatively with rainfall. 100-seed kernel weight and seed length correlated with oil percentage. Rainfall influenced seed breadth and pericarp weight. Clustering using morphological characters did not group genotypes from the same region; while soil type could distinguish them. Correlation helped us determine the prominent features which influence the traits of interest, which can be useful for breeding programs, cultivation practices, and the development of neem-based products in Tamil Nadu and beyond.