Geographical variation in Canarium indicum (Burseraceae) nut characteristics across Vanuatu

Abstract Tropical forests in the Pacific region contain many tree species that bear edible nuts (kernels). Canarium indicum (canarium) is an overstorey tree indigenous to Melanesia that produces commercially valuable kernels due to their pleasant taste and high oil content. This study characterises natural variation in fruit, nut-in-shell (NIS) and kernels of C. indicum across eight islands in Vanuatu. Significant tree-to-tree variation in fruit, NIS and kernel characteristics as well as kernel recovery (kernel:NIS) was found. This variation was largely due to tree-to-tree differences and little of this variation could be attributed to location. There were significant linear correlations among fruit, NIS and kernel traits, including kernel mass with fruit mass (R2 0.57) and kernel mass with NIS mass (R2 0.56). Therefore, trees suitable for cultivation may be screened based on fruit and nut characters before making final selections based on kernel mass. Trees sampled over two fruiting seasons showed that kernel mass and kernel number varied significantly between years for 63.6% and 25.9% of the trees respectively. However, those trees that produced larger kernels in the first year of sampling, tended to also produce relatively larger kernels in subsequent years by rank. These results have important implications for further domestication of the species for planting in commercial agroforestry systems.