Genetic analysis of citrus fruit-related traits in the progeny of HB Pomelo × Huagan No. 4 hybrids

【Objective】The inheritance pattern of fruit- related traits in the cross progeny population with HB Pomelo as the female parent and Huagan No. 4 as the male parent was determined to provide a theoretical basis for the selection of parents for cross breeding.【Methods】A total of 53 trees of hybrid progeny with stable fruit set were selected. From the middle and lower parts of each tree, 9-10 mature fruit without obvious mechanical damage were selected and pooled into one sample. The trait indexes, including single fruit mass, longitudinal diameter, transverse diameter, peel thickness, total soluble solids, titratable acid, and so forth, were then measured. Three biological replicates were determined for each index. The mean, standard deviation, skewness, coefficient of variation, genetic transmission, and other parameters of these data were calculated to assess the genetic variation characteristics of the hybrid population. In this study, the experimental data were processed using Excel 2016 software, among others.【Results】The hybrid offspring resulting from the cross between HB Pomelo and Huagan No. 4 exhibited a wide range of fruit shapes, primarily including high flat round, round or nearly round, and oval shapes. Additionally, they displayed a variety of skin and flesh colors, with orange and yellow being the most common. The majority of the hybrid progenies matured later than their parents, with the majority matured in January and February. This suggests that there is a polygenic control of maturity, with a tendency of later ripening. Statistical analysis of fruit mass and fruit shape traits in the hybrid population from the cross between HB Pomelo and Huagan No. 4 revealed distinct distribution patterns. Specifically, the transverse diameter and juice recovery followed a normal distribution. On the other hand, the single fruit mass, longitudinal diameter, peel thickness, total soluble solids, solid to acid ratio, and vitamin C exhibited a right-skewed distribution. Furthermore, the fruit shape index, seed number, flesh recovery, and titratable acid showed a left- skewed distribution. The analysis of the hybrid offspring resulting from the cross between HB Pomelo and Huagan No. 4 demonstrated significant phenotypic variation in various fruit traits. The single fruit mass exhibited the highest coefficient of variation (33.15%), indicating a wide range of variation among the offspring. The longitudinal diameter showed a moderate coefficient of variation and a heritability of 79.42%, suggesting a genetic control with some environmental influence. Similarly, the transverse diameter also displayed a moderate coefficient of variation and a heritability of 84.93%, indicating a strong genetic influence. The fruit shape index had the lowest coefficient of variation (9.20%) and the highest heritability (96.97%), indicating that it is a highly heritable and consistent trait. Peel thickness exhibited a high coefficient of variation (27.03% ) and a heritability of 71.54%, suggesting that there is considerable variation and moderate genetic control. Seed number showed a heritability of 81.86%, indicating that seediness trait is largely determined by genetics. Flesh recovery had the lowest coefficient of variation (11.44% ) among the second set of traits with a heritability of 92.45%, indicating it is a stable and heritable trait. Juice recovery displayed a high heritability (94.60%) and tended to be lower than the parents. Total soluble solids had the lowest coefficient of variation (9.26%) among the flavor traits and a heritability of 87.36%, suggesting that it is a stable trait with a strong genetic influence. Titratable acid showed a high heritability (158.97% ) and tended to exceed parental values, indicating a super-parental genetic trend. Vitamin C exhibited a heritability of 105.73% and a tendency to be higher than the mid-parent value, suggesting a super-parental genetic trend. The soluble solid to acid ratio had the highest coefficient of variation (32.87%) and a heritability of 57.80% , indicating that it is a complex trait with a genetic tendency towards lower values. 【Conclusion】The present study undertook a comprehensive assessment of several key fruit traits in hybrid population from the cross between HB Pomelo and Huagan No. 4. In particular, the maturity, single fruit mass, fruit shape, seed number, flesh recovery, total soluble solid, and titratable acid content were evaluated. The findings of this study revealed that the fruit quality in the hybrid population exhibited substantial genetic variation, indicating that these traits are likely quantitative and influenced by multiple genes. This research not only enhances our understanding of the genetic patterns in citrus hybrid progeny but also provides essential data for the selection of parents for future citrus breeding programs.