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In order to provide early selection indicators for the breeding of plants used for producing tea seed oil or harvesting tea, we investigated the relationships between flower morphology and fruit yields in tea plants. We analyzed 106 tea varieties to determine the relationships between flower morphological traits and fruit yields. Notably, the homogeneity of flower traits within the same tea plant variety was found to be very high. The average length and width measurements of certain phenotypic traits of tea plants, including pistil length, stamen length, stamen bundle inner width, stamen bundle outer width, and stigma width, were 11.8, 10.9, 2.5, 15.0, 3.7 mm, respectively. In this study, the flower traits that affect fruit yield appear to be related to the difficulty of pollination by insects (e.g., bees), in terms of their contacting the stigma. In 2013, three phenotypic trait variables showed significant effects on yield; namely, the stamen bundle outer width (negative), stigma width (positive), and stigma width minus the stamen bundle inner width (positive). In 2015, only the stamen bundle outer width had a significant negative effect on yield. Regarding pollen viability, in the TTC (2,3,5-triphenyl tetrazolium chloride) staining test, about 84% of the considered tea varieties presented pollen viability exceeding 70%. This indicates that most tea pollen has the ability to germinate normally after contact with the cross-pollinated stigma. The yields of all of the tea varieties exhibited a positively skewed distribution in 2013 and 2015. Although our results indicate that flowers in the anther superior group tend to produce fewer fruits than flowers in the stigma superior group in 2013, in the analysis of the effect of traits on yield, there were no significant differences in the relative positions of stigmas and anthers. In conclusion, we determined that the main trait affecting fruit yield is stamen bundle outer width, while the secondary trait affecting fruit yield is stigma width. However, the efficacy of the stigma width may also be affected by the position of the stigma relative to the anther and the stamen bundle inner width. These two traits have the potential to be used as reference indicators for early selection in future breeding programs.

Background: This study investigated the relationship between the flower morphology and fruit yield of tea plants. Tea plants have late self-incompatibility, and cross-pollination can improve fruit yield. However, fruit yield considerably differs among tea varieties. Other factors might affect pollination and fruit yield. This study analyzed 106 tea varieties to determine the relationship between flower morphology and fruit yield.Results: The average fruit yield per plant of the tea varieties exhibited a positively skewed distribution. The higher the yield was, the lower was the proportion of the varieties. According to the relative position between the anther and stigma, the tea varieties were divided into the stigma and anther superior groups. Multiple relationships were observed between floral morphology and fruit yield. The stigma superior group accounted for approximately 85% of the population, and fruit yield was significantly higher in the stigma superior group than in the anther superior group. The longer the pistil was than the stamen, the higher the fruit yield was. The effect of the style width on fruit yield was opposite between the groups. In the stigma superior group, the wider the style width was, the higher was the fruit yield. By contrast, in the anther superior group, the wider the style width was, the lower was the fruit yield.Conclusion: Flower morphology affects the fruit yield of tea plants. In tea breeding, the stigma being higher than the anther is conducive for harvesting fruit. Moreover, the increase in the style width is beneficial for increasing fruit yield and might help pollinating insects in contacting the stigma.