关键词: 桃, 遮光, 套袋, 类胡萝卜素, 叶绿素

Abstract: Effects of shading fruit with opaque paper bag on the accumulations of chlorophylls and carotenoids，as well as on the carotenogenesis related gene expression，were studied in two yellow-flesh peach（Prunus persica L. Batsch）cultivars：‘Babygold 6’and‘Babygold 8’. The results showed that contents of chlorophyll were declined gradually both in peel and flesh，and they were significantly lower in the bagged fruits compared with the non-bagged fruits in each sampling period；The contents of carotenoid were increased during the fruit development and ripening. Compared with the non-bagged flesh tissues，the bagged flesh tissues accumulated less carotenoids at the immature stage，but they accumulated a significantly higher level of carotenoid at the mature stage. HPLC analysis indicated that carotenoids in the immature flesh tissues were mainly composed of lutein and β-carotene，which represented a chloroplast-specific carotenoid biosynthesis pathway；Chromoplast-specific carotenoid biosynthesis pathway was preponderant in the mature flesh tissue，characterized by abundant accumulation of stable estered cryptoxanthin and violaxanthin. In addition，it was noted that there were more carotenoid eaters in the bagged fruits than in the non-bagged fruits. Furthermore，transcriptional analysis revealed that，consistently in the bagged fruit and non-bagged control，genes encoding enzymes for HDR （hydroxymethylbutenyl 4-diphosphate reductase），PSY1（phytoene synthase 1），PSY2（phytoene synthase 2），phytoene desaturase（PDS），and HYD（β-carotene hydroxylase）showed higher expressive levels in the mature flesh than in the immature flesh. It was noted that，compared to the non-bagged control，DXS（1-deoxy-D-xylulose 5-phosphate synthase），PSY2 and PDS genes showed the significantly down-regulated expression in the bagged mature fruit，HYD gene was expressed at a significantly higher level in the bagged mature fruit.

Key words: peach, shading, bagging, carotenoid, chlorophyll