Phenomic Diversity and Population–Province Variation in Aromatic Coconut in Southern Thailand Revealed by On-Farm Survey

Coconut is an important livelihood and industrial crop for coastal communities in Thailand; however, limited information is available on the phenotypic diversity of traditional aromatic coconut populations cultivated by smallholders in southern Thailand. An on-farm survey was conducted in Phang Nga, Trang, Krabi, and Nakhon Si Thammarat, evaluating 27 palms representing nine populations (three palms per population) for 28 quantitative morphological, reproductive, fruit, yield, and coconut-water quality traits. A hierarchical linear mixed model, with province treated as a fixed effect and populations nested within province, was used to characterize phenotypic variation and obtain adjusted population-level BLUPs. Substantial phenotypic variation was observed among the surveyed populations. Var7 in Krabi recorded the highest fruit weight (2039 g) and kernel thickness; Var6 in Trang had the highest number of fruits per bunch (13.3); Var2 in Phang Nga had the highest water volume (430 mL); and Var9 in Nakhon Si Thammarat had the highest number of female flowers (20). Principal component analysis showed that the first five components explained 72.6% of the total phenotypic variation, with fruit, reproductive, water, and vegetative traits contributing strongly to population differentiation. Correlation network analysis further identified coordinated associations among vegetative vigor, leaf morphology, and fruit and yield traits. The study provides a baseline phenotypic characterization of Nam Hom coconut populations under smallholder conditions and identifies population-province combinations with promising trait profiles for further evaluation.