Abstract:【Objective】The identification of the S-genotype of the rough-skinned strains of ‘Majiayou’ (Cupi Majiayou), clarification of the pollination compatibility among the main varieties of ‘Majiayou’, and exploration of the comprehensive quality of the main cultivated ‘Majiayou’ under different pollination tree configuration patterns and different pollination distances, provide references and feasible solutions for the quality improvement and pollination tree configuration of ‘Majiayou’.【Methods】Utilize 21 pomelo S gene-specific primers for the amplification and identification of the S-genotype of the rough-skinned strains of ‘Majiayou’. Before the cross-pollination experiments, determine the pollen viability and in vitro germination rate of both rough-skinned and smooth-skinned ‘Majiayou’ to ensure pollen fertility. Observe the growth of pollen tubes from self-pollination and cross-pollination between varieties using the aniline blue staining of the stylet. Analyze the quality of the main cultivated ‘Majiayou’ (Xipi Majiayou) under different pollination tree configuration patterns and different pollination distances by integrating conventional quality, soluble sugar, and the content of various organic acid components.【Results】Using 21 pomelo S gene-specific primers for the specific amplification and identification of the S-genotype of the rough-skinned variety of Majiayou, while also amplifying the S-genotypes of the main cultivated Majiayou and semi-compatible/fully compatible varieties reported previously to verify the accuracy of the method. The amplification results for the smooth-skinned Majiayou were consistent with previous studies, being S10S16, respectively. The S-genotype of the Cupi Majiayou variety was found to be S10S12, sharing one identical S gene with the smooth-skinned variety. Based on the S-genotype, it is predicted that cross-pollination between the two varieties may exhibit semi-compatibility. To further verify the cross-pollination compatibility between the rough-skinned and smooth-skinned strains of Majiayou, pollen viability and in vitro germination experiments were first conducted to confirm the fertility of the pollen. The results showed that the pollen activity of the smooth-skinned and rough-skinned varieties of Majiayou were 98.17% and 97.04%, respectively. The in vitro germination rates of the pollen for the smooth-skinned and rough-skinned varieties were 45.96% and 42.67%, respectively, meeting the conditions for subsequent cross-pollination. The styles of the rough-skinned and smooth-skinned varieties after self-pollination and cross-pollination were used for aniline blue staining to observe the growth status of the pollen tubes. The staining results showed that after self-pollination, the pollen tubes of both the smooth-skinned and rough-skinned varieties stopped elongating at the top and upper part of the style, indicating complete incompatibility during self-pollination. However, after cross-pollination between the rough-skinned and smooth-skinned varieties, some pollen tubes grew normally to the middle and lower parts of the style, while others stopped growing at the top, indicating semi-compatibility between the rough-skinned and smooth-skinned varieties during cross-pollination. To explore the seed set and fruit quality of Majiayou under natural pollination at different distances under semi-compatible pollination father configuration, the seed set of Majiayou under different configuration patterns was investigated. The results showed that under the row-column pollination tree pattern, the seed set of each row from P1 to P8 was above 80.0%, while the seed set of rows P9 to P13 decreased, ranging from 66.7% to 73.3%. Under the central radiation pollination tree pattern, the seed set of rows P1 to P2 was above 87.5%, while the seed set of row P3 decreased to 59.7%. Further comparative analysis of the fruit quality of the smooth-skinned Majiayou under different pollination tree configuration patterns was conducted. With the increase of natural pollination distance, the peel thickness of the main cultivated Majiayou under the row-column pattern showed a trend of decreasing first and then increasing, with the peel thickness of rows P1 and P9 being 23.5 and 27.3 mm, respectively, which were 27.7% and 16% lower than CK's 32.5 mm, and the peel thickness of row P13 was not significantly different from CK. In addition, the number of seeds showed a continuous decrease with the increase of natural pollination distance. In terms of the internal flavor quality of the fruit, the TSS content of the fruit from row P13 was 16.3%, significantly higher than CK's 11.8%; the TA content of the fruit from row P1 was significantly higher than CK, at 0.97%, while the TA content of row P9 was the lowest among all rows, at 0.39%; the TSS/TA ratio was the lowest in row P1, at 14.9, which was 32.0% lower than CK, while rows P9 and P13 increased by 57.1% and 34.7% compared to CK, respectively. The VC content also showed a continuous increasing trend with the increase of natural pollination distance. Under the central radiation pollination tree configuration pattern, the fruit quality data of the smooth-skinned Majiayou with seeds and without seeds at different distances and different fruiting positions were compared. The peel thickness of the pollinated pummelo were significantly lower than CK's 33.7 mm, with an average reduction of 18.7% to 35.0% in peel thickness. In terms of internal flavor quality, the TA content of the seeds in the upper part of rows P1 and P2 was significantly lower than CK, while there was no significant difference between the fruit from row P3 and CK. The solid acid ratio of Majiayou at different fruiting positions showed a clear trend of increasing first and then decreasing with the increase of pollination distance, with the TSS/TA of the seeds in the upper part of rows P1 and P2 increasing by 29.2% and 49.5% compared to CK, respectively; the middle fruit increased by 21.0% and 27.4%, respectively, while there was no significant difference between the seeds in different positions of row P3 and CK.【Conclusion】The scientific configuration of pollination trees using the semi-compatible rough-skinned variety of Majiayou contributes to the production of high-quality commercial fruits of Majiayou.
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