Investigation on inheritance of fruit size and its correlation with corolla and leaf area in blueberry (Vaccinium)

Abstract: 【Objective】Fruit size is a critical agronomic feature of fruit trees that influences yield and plays a significant role in the grading of most fresh fruits. Larger fruit size has a direct effect on the merchantability and consumer’s preference for fruits. Thus, breeding blueberries with large fruit is a criticalobjective for breeders. This study aimed at revealing the genetic inheritance of blueberry fruit size and the relationship between fruit size, corolla and leaf area in order to provide valuable reference for parental selection in breeding.【Methods】In this study, we conducted a thorough investigation of the genetic inheritance of fruit size of blueberry by evaluating 314 genetic populations resulting from reciprocal cross between Berkeley (a large fruit variety) and N6 (a small fruit resource) for three years. We also used 55 varieties/strains to form a natural population and investigated the correlation between fruit weight, corolla size, and leaf area to verify the correlation previously observed in the natural genetic population.【Results】The normal distribution of mean fruit weight in both reciprocal populations indi-cated that the fruit size of blueberry was a quantitative trait influenced by multiple genes. Interestingly, the offspring of N6 × Berkeley had smaller fruit weight distribution, middle value and average value than those of Berkeley × N6, indicating the presence of maternal inheritance in fruit size of blueberry and highlighting the importance of parental selection in breeding programs. Moreover, the average size of blueberry fruit in both reciprocal populations (1.46 g and 1.79 g, respectively) were biased towards the low value parent N6 (1.11 g) rather than the high value parent Berkeley (2.90 g), this phenomenon indicated that there was a significant decrease inheritance in the size of the blueberry fruit. The broad heritability (H2 ) of blueberry fruit weight was over 0.90, indicating that genetic effects were the main contributors to the variation, the environmental effect was rather small. Interestingly, in the natural population, fruit size was significantly positively correlated with corolla size (R=0.81, P=2×10- 12) and leaf area (R=0.85, P=2×10-14). However, these positive correlations were not consistently observed in the genetic population. These findings could aid in the selection of parental varieties.【Conclusion】The fruit size of blueberry was controlled by multiple genes and also influenced by maternal parent and the parent with smaller fruit. However, the positive correlation between blueberry corolla size, leaf area, and fruit size previously observed in a natural population was not found in the reciprocal cross populations.