β-Cryptoxanthin is a critical carotenoid component and a major contributor to the flesh coloration of yellow-fleshed kiwifruit cultivars

• The depth of yellow coloration was significantly influenced by both total carotenoid content and the carotenoid-chlorophyll ratio in flesh of 32 yellow-fleshed kiwifruit cultivars. • Twenty-seven individual carotenoid compounds were identified in flesh of the pale yellow-fleshed Actinidia chinensis ‘Fenghuang 2’ and the intense yellow-fleshed A. chinensis ‘Wanding 1’. • β -Cryptoxanthin was the critical component in determining total carotenoid content and a major contributor to the flesh coloration in yellow-fleshed kiwifruits. • AcBCH1 was identified as the key structural gene responsible for β -cryptoxanthin biosynthesis in fruit of the carotenoid-rich A. chinensis ‘Wanding 1’. Carotenoids are a class of pigments widely distributed in nature. They serve as essential nutrients for humans and play a critical role as pigment substances in red- and yellow-fleshed fruits. However, the carotenoid composition and the key carotenoids responsible for flesh coloration in kiwifruit remain poorly understood. Here, we systematically evaluated the fruit quality of 32 yellow-fleshed kiwifruit cultivars at maturity. Results indicated that both total carotenoid content and the carotenoid-chlorophyll ratio were significantly and positively correlated to the b * value of the flesh. A pale yellow-fleshed cultivar ( Actinidia chinensis ‘Fenghuang 2’) and an intense yellow-fleshed cultivar ( A. chinensis ‘Wanding 1’) were selected for further integrated metabolomic and transcriptomic analysis. Our findings revealed that 27 individual carotenoid compounds were detected across these cultivars, 12 of which were identified as differentially accumulated metabolites (DAMs). Additionally, 26 structural genes related to carotenoid metabolism were found to be differentially expressed genes (DEGs). Further analysis demonstrated that β -cryptoxanthin was the most abundant carotenoid in ‘Wanding 1’, with a content 75.84 times higher than that in ‘Fenghuang 2’, accounting for more than 55 % of the sum content of all the detected carotenoid compounds in ‘Wanding 1’. These findings revealed the significant role of β -cryptoxanthin in the formation of intense yellow flesh coloration in kiwifruit. Moreover, a β -carotene hydroxylase gene, AcBCH1 , was identified as a key regulator of β -cryptoxanthin biosynthesis. This study provides valuable insights for improving fruit quality and commercial value in kiwifruit and other fruit crops.