Three types of rind coloring in response to fruit bagging in new citrus cultivars

摘要

In some citrus cultivars released from NIFTS, rind color degradation before harvest is a serious problem. Once rind color forms, it degenerates along a decreasing temperature gradient in winter. This phenomenon occurs in cultivars like 'Setoka'. If the rind color degradation occurs, market value is lost. This study investigated the influence of bagging colors on rind color parameters in 10 citrus cultivars recently released from NIFTS. Fruits were bagged with cloth of six different colors in Dec. Afterharvesting at the appropriate time for each cultivar, rind color parameters were surveyed with NF333 (NIPPON DENSHOKU). Using the results of responses of coloring to fruit bagging, cultivars could be classified into three groups. One group includes 'Tsunokaori' etc. In this group, there was no or only a slight difference in the L, a, and b values between treatments. Another group includes 'Setoka' etc. In this group, the a value remained high when fruit was bagged black, green and pink bags, while the effects of white, yellow and gray bagging were slight. This means that the reddish rind color remained vivid when bagged, i.e. rind color degeneration was prevented by fruit bagging. The other group includes 'Amaka'. 'Amaka' was the only cultivar parameter a value was not influenced by bagging, but parameter L and b values were higher when bagged than when not-bagged. This implies that the yellow color was enhanced by fruit bagging. These results suggest that the response of rind color to exposure to sunlight and bagging depends on its genetic features, and that the bag color affects the degree of inhibition of rind color degradation.