Effects of grapefruit and pummelo pollens on fruit growth and quality of Dongshizao pummelo

Abstract: 【Objective】Cross- pollination was used to investigate and evaluate the xenia effect on the fruit growth and quality of Dongshizao pummelo in order to screen the optimum pollination parents for improving fruit quality of Dongshizao pummelo.【Methods】23- year- old Dongshizao pummelo trees were used as the female parents. Different cultivars of pummelo and grapefruit were used as pollen parents. The fruit setting rate was investigated at 40 d after flowering. The longitudinal and transverse diameters of the fruit were measured in field at regular intervals after full bloom. After fruit ripened, the hybrid fruits were harvested and taken back to the laboratory to measure their conventional fruit quality indexes. Correlation analysis and comprehensive evaluation were then performed.【Results】During fruit development of Dongshizao pummel, the longitudinal and transverse diameters both showed a single S trend. The results showed that pollinizer varieties had some effects on the fruit setting rate,growth, development and quality of Dongshizao pummelo, and therefore phenomenon of xenia was obvious. The fruit setting rate after cross-pollination was above 60%, while that of natural pollination was only 10.19%. The average single fruit weight had not significant difference between pollination with Flame pollen and natural pollination, while the average single fruit weight of another pollination combination was significantly higher than that of natural pollination. Cross pollination could increase fruit weight by 27.77% to 85.08%. The fruit diameter in natural pollination was the lowest. Among them, the fruit longitudinal and transverse diameters in pollination with Sarawak pollen were significantly higher than the other cross-pollination combinations and natural pollination. Cross-pollination had a marked influence on the numbers of cracked segments and greatly increased the number of seeds, and thus had an obvious phenomenon of seed-xenia. The total soluble solid content in pollination with Oroblanco pollen was also higher than that in the other pollination combinations. The total soluble solid content in pollination with Sarawak, Tahition, Hongbaoshi pummelo, and Vietnam green pummelo was significantly lower and the titratable acidity content was significantly higher than that in natural pollination. Cross-pollination did not show a significant impact on the soluble protein content but had an important influence on the contents of soluble sugars, vitamin C, lignin, and naringin, with a distinguished xenia effect. The correlation analysis indicated that the number of seeds had a significant positive correlation with fruit transverse diameter; the number of cracked segments had a significant negative correlation with the number of seeds and fruit transverse diameter. The main index of fruit external quality had a significant negative correlation with the internal quality. Comprehensive evaluation the fruit quality of the ten pollination combinations were performed using the membership function method and principal component analysis. Genetic Dwarf was chosen as the best pollen parent, which had total a score of 0.68, followed by Oroblanco with a total score of 0.67; while natural pollination had a score of 0.66.【Conclusion】 Cross-pollination could significantly increase the fruit setting rate of Dongshizao pummelo. Xenia significantly influenced fruit growth and fruit quality. The comprehensive evaluation results showed that Genetic Dwarf and Oroblanco could be chosen as the pollen parents for Dongshizao pummelo.