Abstract: 【Objective】 As the first new variety of macadamia nuts independently selected and bred in Guangxi, Guire No. 1 is themacadamia variety with the largest cultivation in Guangxi at present, accounting for about more than 65% of the planted area. However, it has been found in some local orchards that when other varieties are planted in the vicinity of ‘Guire No.1’, the fruiting rate and yield are higher than those in areas where ‘Guire No.1’ is planted in a row. Through the survey, it was found that ‘695’, O.C, ‘JW’ and A16 are four varieties that widely planted Guangxi with less area as comparing with ‘Guire No.1’. Using these varieties as the pollen sources and ‘Guire No.1’ as the female parent, artificial pollination was conducted to determine which variety had the best effect on improving the yield and fruit quality of ‘Guire No.1’. And self-pollination and open pollination were set as controls. 【Methods】The ‘Guire No.1’ macadamia nut was used as the mother and 4 varieties with less planting area were used as pollen sources for hand pollination. In 2021, three plants (12 a) each of the mother and father were selected, and the experim- ent was set up with complete self-pollination as the control (CK) and six pollination groups, totaling seven treatments, with 10 bunches of inflorescences per plant in each of the treated mothers in the pollination groups, for a total of 30 bunches of inflorescences in the three trees. Fruit was harvested on September 3, 2021, and fruit set surveys were conducted using the final number of fruit set/initial number of flowers. In 2022, five plants (5 a) each of the mother and father were selected, and 40 bunches of inflorescences per plant were pollinated from each treatment mother in the pollination group, for a total of 200 bunches of inflorescences from the five trees. Flowers were taken after 24 h of pollination and counted for pollination efficiency = (number of flowers with pollen germinating at the stigma / total number of flowers examined by microscopy). The fruit was harvested on August 31, 2022, and the fruit setting situation was investigated using the number of fruits set per inflorescence. The fruit setting situation was recorded 14 days after pollination. Pollination group yield was the total mass of 40 bunches of fresh fruits per plant artificially pollinated by the mother plant, while ‘Guire No.1’ naturally pollinated (CK) was the yield of the whole tree. Fruit appearance traits and kernel quality were determined and comprehensively evaluated using principal component analysis. 【Results】‘Guire No.1’ macadamia nut has obvious self-incompatibility. In 2021, the fruiting rate of pollination with ‘695’, ‘JW’ and ‘A16’ were 28.86‰, 18.62‰ and 12.85‰, and the fruiting rate of pollination with ‘Guire No.1’ was 11.39‰, and heterogamous pollination could significantly improve the fruiting rate. The 2022 trial site experienced inverted spring weather and the overall orchard yield was reduced by about 1/3 from last year. However, the yield of 40 bunches of flowers of different varieties pollinated artificially in the experiment (about 300~400 bunches of macadamia inflorescences of the whole plant of 5-year-old ‘Guire No.1’) was not only significantly higher than the yield of the whole tree pollinated naturally, but also the yield of 40 bunches of flowers pollinated with ‘695’ was up to 6.42 kg, which was comparable to the yield of 5-year-old ‘Guire No.1’ under conventional climatic conditions. In terms of fruit appearance, pollination of different varieties showed no significant difference in peel color, papillary process at the top of the fruit, suture at the belly of the shell and fruit, and markings on the shell, which all showed the biological characteristics of the female parent of ‘Guire No.1’, but showed pollen xenia Effect in the vertical, horizontal, single fruit weight and fruit shape index of green peel and shell. In terms of fruit quality, pollination of different varieties showed pollen xenia effect in terms of single kernel weight, kernel setting rate, crude protein, total sugar, mineral P, Fe, Ca elements, and palmitic acid, palmitic acid, 10-heptacenoic acid, linoleic acid in fatty acids. Correlation analysis revealed that the mineral Fe element was significantly positively correlated with the monounsaturated fatty acid MUFA and highly significantly positively correlated with the polyunsaturated fatty acid PUFA, while on the contrary it was highly significantly negatively correlated with the saturated fatty acid SFA. The results of the comprehensive evaluation by principal component analysis showed that ‘695’ pollination had the highest composite score of 0.720.【Conclusion】Artificial pollination can significantly increase the yield of ‘Guire No.1’ macadamia nuts, and at the same time, it can mitigate the adverse effects of special climate to a certain extent. The presence of xenia in ‘Guire No.1’ macadamia nuts in terms of fruit set, yield, longitudinal and transverse meridian and single fruit mass of green and shelled fruit, green fruit shape index, individual kernel mass, kernel yield, crude protein, total sugar, mineral P, Fe, and Ca elements, as well as palmitic acid, palmitoleic acid,10-heptacenoic acid, and linoleic acid in fatty acid. Through the comprehensive evaluation of yield and fruit quality, it was concluded that 695 was the most suitable pollination variety for Guangxi ‘Guire No.1’.
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