The trials of keeping fresh on-tree storage of citrus fruits were carried out by the treatments of using 2,4 -D and canopy covering with film from the beginning of December to the first ten days of next April during 2004 -2008 in the main citrus areas of Sichuan province. The overwintering technique for the delayed harvest and the changes for the fruit quality were studied. The results showed that the damage of low temperature and rain or snow during winter were effectively prevented by using 20 mg/L 2,4-D combined with canopy covering. During the stages of on-tree storage,for the fruits of navel orange (Citrus sinensis Osb.),blood orange (C. sinensis Osb.)and ponkan (C. reticulate) ,the total soluble solid content (TSS) and total sugar content increased and the total acid contents reduced significantly. Meanwhile the ratios of TSS/acid for the three cultivars were increased to 19.41, 17. 1 and 21. 17 on the average, respectively. It indicated that the fruit quality had been obviously improved due to the delayed harvest. The average fruit drop rates for navel orange,ponkan tangerine and Tarocco orange treated by 2,4-D combined with canopy covering were less than 10％ without the peak of fruit drop. However,for the control fruit drop was more than 70％ and associated with the high peak of fruit drop at the end of Janurary (for ponkan) , earlier 20 days of February (blood orange) and the end of February (navel orange). At present, the technique of on-tree storage of citrus fruit is extensively popularized in citrus production areas of Sichuan.
Fruit quality Harvest On-tree storage
Liu JJ Yang QY Xu HT Huang J Wu BX Xiao WL Chen W Yang ZK Wang RC Chen KL He J Li HW Guan B Wang JH Deng JL Luo N Qing SM
Horticulture Research Institute, Sichuan Academy of Agricultural Sciences, Chengdu 610066, China Agricultural bureau of Jintang County, Chengdu 610400,China Agricultural & Forestry Bureau of Qingshen County, Qingshen 620460, China Agricultural bureau of Rongxian County, Rongxian 643100, China Forestry Bureau of Zizhong County, Zizhong 641200, China Agricultural bureau of Luzhou city, Luzhou 646000, China Agricultural bureau of Guangan City, Guangan 638000,China Agricultural bureau of Gaoping County,Gaoping 637100,China Agricultural Department of Sichuan Province, Chengdu 610041, China