β-Carotene and lutein accumulation, and carotenoid biosynthetic gene expression during fruit development and fruit ripening of A genome banana

Bananas (Musa spp.) are an important source of pro-vitamin A, derived from carotenoids. Some cultivated bananas originated from intra-specific hybridization resulting in genotypes which are diploid (AA) and triploid (AAA) genomes that are the most important bananas for desserts. The accumulation of carotenoids and transcripts of genes related to carotenoid biosynthesis during fruit development and ripening in cultivars carrying the banana A genome (AA and AAA) were investigated. The accumulation of total carotenoids was greatest in ‘Khai Kasetsart2’ (KK2; AA) and ‘Sa’ (SA; AA), and comparatively lower in other cultivars. The predominant carotenoids in this fruit were β-carotene and lutein, with a small amount of α-carotene, which correlate with the orange-yellow pulp color (in particular KK2). In contrast, Leb Mu Nang had the lowest total carotenoids during fruit development while lutein and β-carotene in Hom Thong increased with fruit ripening. MaPSY2a gene expression in KK2 and SA cultivars occurred throughout fruit development but declined during fruit ripening. The expression of MaLCYB, MaLCYE, MaCHYB, and MaCHYE genes increased throughout fruit development and during fruit ripening resulting in β-carotene and lutein high content. In cultivars with low carotenoid levels, MaLCYB gene expression was reduced, while the MaLCYE, MaCHYE, and MaCHYB genes were up-regulated during fruit ripening. Besides, the MaCCD4 gene (a gene associated with carotenoid turnover) had lower expression throughout fruit development and ripening in KK2 compared to the other cultivars. These results suggested that the different carotenoid accumulation patterns in the cultivars could be attributed to differential gene expression and A genome composition.