Encoded chlorophyll degradation enzymes and gene expression in the exocarp during ripening of Carica papaya (L.) 'Krung', 'Khak Nual' and 'Khak Dum'

Papaya (Carica papaya L.) is a fast-growing fruit crop originating from Mexico and Central America. It is cultivated in many tropical and sub-tropical regions globally. In Thailand, papaya has been integrated into Thai cuisine and used as an ingredient in many food dishes and cosmetic products. Papaya fruit can be harvested either at mature green (for cooking) or color break (consumed as fresh fruit) stages. Although harvest time can be estimated from planting and bloom periods, harvest time varies due to cultivars and seasons. Thai farmers largely rely on fruit characters, skin texture and color as a harvest index. Papaya skin (peel or exocarp) is generally dark green when mature, indicating high levels of chlorophyll which is lost as fruit ripen. Among commonly grown papaya cultivars, 'Khak Dum', 'Pluk Mai Lie' and 'Khak Nual', the latter is commonly harvested and consumed at the mature green stage. Investigating changes in skin color during ripening, skin color was measured at 3 stages (mature, color break and ripe). Data collected were compared with the quantitative expression of five genes encoded enzymes in the chlorophyll catabolic pathway. The results showed the association of RCCR expression with skin color change. Chlorophyll degradation during ripening suggested skin color to be a good indicator for a fruit harvest index.