Effects of plant regulators and leaf fertilization on fruit quality, storage ability of persimmon on- tree storage and yield and quality of the fruits next season

Abstract：【Objective】Persimmon is widely cultivated in China, and it has a very large area in Gongcheng County of Guangxi Zhuang Autonomous Region, with one fifth of total yield of persimmon in China. However, in each year, the concentrated maturation of persimmon fruits causes a huge challenge for preserving and merchandising the fresh fruits to the growers and merchants. On-tree storage is an efficient measure to extend the harvest of fruits which has been successfully applicated on orange (Citrus sinensis), apple (Malus domestica), mango (Mangifera indica) and other fruits. In production, growers often use gibberellins to delay the persimmon maturation. However, in appropriate concentrations and times of spray or no extra fertilization would cause the easy softness and yield loss of the persimmon fruits. Therefore, this study aimed to determine the quality changes of persimmon fruits treated with plant regulators and leaf fertilization during on-tree storage period and cold storage period (4 ℃), and also to detect the effects on next-year fruit quality and yield, in order to provide a theoretical basis for persimmon on-tree storage.【Methods】The persimmon fruits were treated by 75% GA3 soluble pow-der (1 in 5000 diluent), 0.01% 2, 4-epibrassinolide missible oil (1 in 2800 diluent), and leaf fertilizer with content of 12% available nitrogen, 12% available phosphorus, 10% calcium and 2% boron (1 in 800 diluent). The experiments were carried out during 170 days to 201 days after anthesis for three times (TreatmentⅠ), during 170 days to 208 days after anthesis for four times (Treatment Ⅱ), and during 170 days to 214 days after anthesis for five times (Treatment Ⅲ). The treated trees used in these experiments were additionally fertilized with 0.5% urea and 0.5% KH2PO4 during post-harvest. The trees with sprays of water and without additional fertilizer were used as control (CK). The difference of fruit color like a*, b* and C value, contents of nutritional substances such as carotenoid, soluble sugar, ascorbic acid and titratable acid, and fruit texture like hardness, springiness, cohesiveness and chewiness were determined during on-tree storage period and storage period. Also, the effects on fruit quality, fruit transverse diameter, fruit longitude diameter, fruit weight, number of fruits per plant, fruit yield and ratio of high-quality fruits of individual plant next year were investigated.【Results】(1) The a* value (color component of red and green), b* value (color component of yellow and blue) and C value (chroma) of fruit peel color gradually increased with the maturing of the fruits. Also, the content of carotenoid, soluble sugar and titratable acid were gradually increased, and the content of ascorbic acid firstly increased and then decreased with the duration of fruit on-tree. The fruit hardness, springiness, cohesiveness and chewiness all decreased with the fruit maturity. The trends of fruit color, fruit nutrition constituent and texture of three treatments were the same as control, but the trends were delayed about 30 days, which indicated that the treatment could retard the downswing of fruit color, nutritional ingredients and texture. (2) The fruit carotenoid and soluble sugar firstly increased and then descend, while ascorbic acid and titratable acid gradually decreased during cold storage period. The fruit hardness, springiness, cohesiveness and chewiness all decreased with the prolonging of storage time. The treatment of plant regulators and leaf fertilization could delay the occurrence of the peak or flatten the decrease trends of the fruit nutritional substance and fruit texture. The storage time of treatmentⅠcould up to 75 days, which was longer than those of the other treatments and control. The storage time of treatment Ⅱ and Ⅲ were the same or shorter than that of the controls. (3) The treatments did not change the fruit transverse length, fruit longitude length, fruit weight, number of fruits per plant, fruit yield and ratio of high-quality fruit compared with the CK. (4) The on-tree storage was an effective method to prolong the supply period of persimmon and treatmentⅠwas more efficient than other treatment.【Conclusion】The spray of plant regulators and leaf fertilization on the trees of perssimon could retard the accumulation of nutritiona substance contents of the fruits on-tree storage , reduce the ageing of the fruits during on-tree storage period and cold storage period and not cause the decline of fruit quality and yield next year. So it would be an effective way to prolong the supply period of persimmon 3 times of spray would be most efficient and economical in practice.