Variation analysis of flower traits in male lines of Jinyi kiwifruit seedling progeny

Abstract: 【Objective】Kiwifruit is a dioecious and self-sterile plant, requiring an appropriate number of male plants or artificial pollination for effective fertilization. Insufficient pollination will result in reduced seed numbers, low endogenous hormone levels, and ultimately, smaller or deformed fruit. Identifying superior male plants with high pollen yield and viability can enhance pollination efficiency, lower production costs, and improve fruit quality. However, there has been limited reports on the varieties of male kiwifruit plants. This study aimed to screen male plants with desirable traits from 120 progeny of Jinyi kiwifruit seedlings in order to provide valuable resources for breeding new male variety.【Methods】The experiment was conducted in April 2022 at the kiwifruit breeding orchard of Shen Shan Xing Nong Science and Technology Co., Ltd., Chibi City, Hubei Province. The experimental materials consisted of 120 four-year-old male seedlings of Jinyi. Traits such as the number of anthers per male flower, pollen quantity per anther, and pollen germination rate were measured. In addition, analyses of variation patterns, outliers, distribution characteristics, and principal components were performed.【Results】 The analysis revealed that the average number of anthers per flower, pollen quantity (10 000 grains) peranther, and pollen germination rate (%) were 45.60±8.30, 10.30±2.33, and 34.66±22.24, respectively. The median values were 44.10, 10.04, and 33.72, and the modes were 44.60, 10.17, and 70.53, with distribution ranges of 31.50-99.40, 6.08×10 000 grains-19.17×10 000 grains, and 1.00%-86.24%, respectively. The coefficients of variation for these traits exceeded 18%, with the highest variation observed in the pollen germination rate (64.17%), indicating substantial variation within the sample population. The maximum-to-minimum ratios for these traits were greatest for pollen germination rate (86.24 times), followed by the number of anthers (3.16 times) and pollen quantity (3.15 times). The outlier analysis identified JY-334 and JY-250 as mild high outliers in anther number, JY-402 and JY-130 as mild high outliers in pollen quantity, and JY-329 as an extreme outlier in anther number. No outliers were observed in the pollen germination rate. After excluding outliers, the distribution analysis showed that the median anther number was 43.80, predominantly ranging from 36.00 to 54.00 (82.50% of samples). The median pollen quantity was 99 800 grains, mainly between 70 000 and 130 000 grains (80.83% of samples). The median pollen germination rate was 33.72%, with the majority of samples (65.83%) distributed between 10.00% and 60.00%. The skewness (Sk) and kurtosis (Su) values for anther number, pollen quantity, and pollen germination rate were 0.514, 0.406, and 0.417 (Sk), and 0.085, -0.28, and -0.74 (Su), respectively. Frequency distribution plots indicated a continuous distribution of these traits, with a larger number of intermediate plants, fitting a normal distribution pattern. The principal component analysis indicated that the eigenvector value of the pollen germination rate was the largest, and the contribution rate was 43.16%. Based on the comprehensive evaluations, the male plants JY-402, JY-275, JY-212, JY- 403, and JY-260 had superior male flower traits.【Conclusion】Significant variation was observed in the male flower traits from seedlings of Jinyin. JY-402, JY-275, JY-212, JY-403, and JY-260 were identified as potential candidates for use in breeding programs, and JY-402 showed the best overall performance.