Effects of fruit thinning on fruit growth and quality in Hanhong pear

Abstract:【Objective】Pear is a kind of fruit crop with many flowers in clusters. Each cluster generally contains more than 5 flowers, and the fruit setting rate is high. If the flower and fruit thinnings are not taken properly in production to bring with overloading, this often causes large differences in fruit size, poor coloring and poor quality, resulting in reduced economic benefits. For the excellent varieties, their own quality may be excellent, but in the large-scale commercial production, if there is no scientific technical guidance for flower and fruit thinning, the high load per plant often results in lower high-qualityfruit rate, poor fruit market competitiveness, and low economic benefit, so as to seriously affect the pear farmers’growing enthusiasm. In order to ensure the sustainable development of the industry, the research and application of fruit thinning technology play an important role in achieving stable and high yield, high quality and high efficiency in the pear industry. As different pear cultivars have various amount of flowers and differential fruit setting rates, it is urgent to determine the appropriate amount of fruit retention in Hanhong pear.【Methods】Thinning treatments were carried out at 7th day after flowering, with no fruit thinning serving as the control. The internal and external qualities of fruits with each fruit thinning treatment were determined, and the effects of each treatment on the external and internalfruit quality were analyzed.【Results】According to the results of fruit growth and quality, different flowers in a cluster had a certain effect on the yield and single fruit weight. With the decrease of the ordinal position in a cluster, the single fruit weight of Hanhong pear showed an upward trend, while the yield showed a downward trend. It showed that fruit thinning could significantly reduce the yield of the corresponding cluster, but it significantly increased the single fruit weight and produced larger fruits. Compared with the control, the ordinal position fruits of G1 and G2 showed larger fruit (vertical and horizontal diameter increased), heavier single fruit weight, and better appearance quality. The fruit retention of G3 treatment was more, but the fruit quality was relatively poor, the fruit was small, and the flavor was poor. However, the excessive number of fruits increased the yield but decreased the single fruit weight, which affected the fruit quality. The contents of reducing sugar, soluble sugar, soluble solids and vitamin C in Hanhongli were higher than those of the control, among which G1 and G2 treatments were higher, and the titratable acid content showed no decrease. The fruit hardness of each treatment was significantly lower than that of the same group, while that of G3 treatment was higher than that of the control. Hardness is an important quality index of fruit. Relatively, the hardness of pear fruit of the same variety with crisp flesh type is better than that with low flesh and crisp taste, indicating that reducing the number of fruit left in a cluster is more beneficial to the growth and quality of fruit in the corresponding cluster.【Conclusion】Appropriate fruit load can improve fruit quality, maintain high excellent fruit rate and a certain yield. Hanhong pear is a new cold-resistant pear variety with the blood of Pyrus ussuriensis varieties. It is a large fruit type with a single fruit weight of more than 200 g. Fruit thinning is beneficial to improve the comprehensive quality of the corresponding cluster retained fruit, especially for the single fruit weight, soluble solids and hardness. The overall performance is that, the less fruit retained in a cluster, the better the quality improvement effect. Based on the comprehensive analysis of this study, it is suggested that the fruit thinning of Hanhong pear should be carried out 7 days after flowering, 1-2 young fruits with good development can be selected for retention, and the best way is to retain single fruit in a cluster. The fruit development of different pear varieties is affected by many factors. The reasonable fruit thinning scheme for the production of high-quality pear varieties can be used as a reference. The specific fruit thinning scheme should be determined according to the actual situation of a pear orchard.