Impacts of Polyploidy on Blooming and Flower Morphological Traits of Kiwifruit Cultivars

In this study, 60 kiwifruit cultivars selected from wild accessions in China and abroad were used as test materials, including 20 diploid and tetraploid cultivars of A. chinensis var. chinensis and 20 hexaploid cultivars of A. chinensis var. deliciosa. Flowering phenophase and flowering characteristics over three consecutive years were investigated to determine the correlation between ploidy level of all cultivars and their flowering period and morphological traits. The results indicated: (1) There was a very significant positive correlation between ploidy level of all cultivars and their initial blooming date at a level of 0.01. With the increase in ploidy, the initial blooming date was gradually delayed and showed a continuous distribution. (2) There were no significant differences in flowering duration among different ploidy cultivars of the same gender but there was significant difference in flowering duration between different gender cultivars of the same ploidy. The duration of flowering for male cultivars was 3-10 days longer than that for female cultivars. (3) For flower morphological traits, there were obvious differences in corolla diameter among cultivars with different ploidy, showing positive correlation. There were significant differences in petal number and stamen number (in particular) between diploid and tetraploid A. chinensis cultivars and hexaploid A. chinensis var. deliciosa cultivars. There was a positive correlation between the number of stigma and ploidy of female flower cultivars, with significant differences in stigma number among diploid cultivars and tetraploid and hexaploid cultivars but no differences between tetraploid and hexaploid cultivars. (4) For tetraploid cultivars, A. chinensis var. deliciosa ‘Xiangma No. 6’ showed significant differences in the number of stamens compared to those of A. chinensis at the 0.01 level. However, there were no significant differences in the initial blooming date and flower size between A. chinensis var. deliciosa ‘Xiangma No. 6’ and tetraploid cultivars of A. chinensis. According to analysis of flower morphological traits, A. chinensis var. deliciosa ‘Xiangma No. 6’ clustered with hexaploid A. chinensis var. deliciosa cultivars.