Effect of shape-based fruit thinning and water regulation on the prevention and control of fruit cracking of ‘Duweiwendan’ pomelo

WANG Xianda;FAN Guocheng;LIU Kunyong;LI Jian;Fruit Research Institute, Fujian Academy of Agricultural Sciences;Xianyou Duwei Xianxi Fruit Industry Specialized Cooperative;

'Duweiwendan' pomelo;;fruit cracking;;fruit shape index;;shape-based fruit thinning;;water regulation

In order to reduce fruit cracking of 'Duweiwendan' pomelo [Citrus grandis(L.) Osbeck. cv. 'Duweiwendan'], comprehensive quality improvement practices which comprised fruit shape index(FSI)-based thinning and water regulation were tested on 'Duweiwendan' pomelo. The relationship between autumn girdling and the pattern of FSI was interpreted. Oblate fruits were thinned out while fruits with the original tall spherical size were retained. Water regulation including practices of plastic mulch coverage and stimulated stormy irrigation after long-time drought were implemented. The results showed that autumn girdling significantly increased the amount of fruit set but had no significant effect on fruit cracking rate(FCR). The FSI remained unchanged after fruit shape stabilized, which meant maintaining the original high or flat shape. FSI had no significant effect on total soluble solids(TSS) contents, however, it was significantly negatively related to titratable acid content. In another word, the quality of flat-shaped pomelo was relatively inferior, and shape-based fruit thinning is expected to improve the quality of pomelo. At early ripening stage, plastic mulch significantly increased fruit TSS by around 0.5%, but it did not influence FCR at harvesting time. Stimulated stormy irrigation after a long drought did not influence FCR per plant, but it significantly increased FCR each population by 45.2%, though the FCR of the control group was as high as 35.9%, implying that water imbalance was not the main cause of fruit cracking. The FCR was overall reduced by 4.28%, reaching 77.8% of the theoretical value.