Effects Of Male Ploidy On The Fruit Set And Fruit Characteristics In Kiwifruit

Kiwifruit(Actinidia Lindl.) is dioecious and the choice of male plants always affects the fruit characteristics. In kiwifruit(Actindia), ploidy varies among species or cultivars. It’s necessary to explore the relation between male ploidy and the fruit set or fruit characteristics which may offer useful instructions for choosing suitable male plants.In this study, the female cultivars ‘Ruby star’(a tetraploid A. arguta cultivar), ‘Hongyang’(a diploid A. chinensis cultivar) and ‘Jintao’(a tetraploid A. chinensis cultivar) were pollinated respectively by males with different ploidy at Zhengzhou and Chengdu in 2014 and 2015. Male plants we used included three diploid A. chinensis male selections(‘9-16’♂, ‘2-69’♂, ‘2 hao’♂), a tetraploid A. chinensis male cultivar(‘Moshan4’), a tetraploid A. arguta male selection(‘11-17’♂), a tetraploid A. arguta male cultivar(‘Kuilü’♂), two hexaploid A. deliciosa male selections(‘6-20’♂, ‘6-65’♂), and a hexaploid A. deliciosa male cultivar(‘Tomuri’). Fruit setting rates of all combinations were measured 30 days after pollination. After harvest, fruit characteristics were investigated. Finally, we tried to find why effects of different male plants on fruit characteristics varied and to relate the variation to the difference of ploidy between the female and male. The main results are as follows:1. High fruit setting rate could be attained when the flowers of female cultivars pollinated by males with a higher ploidy. Following pollination using tetraploid A. arguta pollen, the fruit setting rates of ‘Ruby star’ were 40.5%~92.7%. The fruit setting rate dropped to 18.6% when a tetraploid A. chinensis male cultivar was used as the pollen donor. Two diploid A. chinensis male selections showed incompatibilities to ‘Ruby star’, as a result, the fruits fell down seriously and the fruit setting rates were 4.7%~6.1%. But ‘Ruby star’ set well while their flowers were pollinated by different hexaploid A. deliciosa males with the rates of 52.4%~86.3%.When a tetraploid A. chinensis male cultivar or tetraploid A. arguta male selections or different hexaploid A. deliciosa males were chosen as the pollen donors, fruits of ‘Hongyang’ all set well with the rates of 60.4%~89.1%. While following pollination with the pollen of ‘Tomuri’, fruits of ‘Jintao’ set well with the rates of 61.3%~85.8%, which was similar to that a tetraploid A. chinensis male cultivar caused. So, males with a higher ploidy could be used for pollination of ‘Ruby star’, ‘Hongyang’ or ‘Jintao’ as high fruit setting rates could be attained.2. Effects of male plants with different ploidy on the fruit characteristics of ‘Ruby star’(A. arguta) Fruits derived from pollination with pollen of ‘Moshan4’ or ‘Tomuri’ had lower hue angle, lighter fruit weight which indicated that the fruits became smaller but the flesh had a darker red colour. The fruit-shape index and soluble solid contents of fruits significantly increased when ‘Moshan4’ was used as the pollen donor. Following pollination of ‘Ruby star’ with pollen from ‘Tomuri’, the soluble solid contents of fruits decreased.Following pollination using the pollen of ‘Moshan4’, both the total number of seed and the number ofdevelopped seed in per fruit decreased but were still close to the normal level. The 1000-seed weight obviously decreased to 57.6% of that ‘Kuilü’♂ caused. When ‘Tomuri’ was used as the pollen donor, the total number of seed decreased by 30% and the number of developped seed decreased to 21.2%. The 1000-seed weight decreased to 85.7% of that ‘Kuilü’♂ caused.3. Effects of male plants with different ploidy on the fruit characteristics of ‘Hongyang’(A. chinensis) When a tetraploid A. chinensis male cultivar or hexaploid A. deliciosa males were used as the pollen donors, the fruit weight of ‘Hongyang’ was close to the open pollination treatment. The fruit weight decreased by 5.17g(10.88%), when the flowers of ‘Hongyang’ pollinated by tetraploid A. arguta male ‘11-17’♂. Fruits derived from pollination by tetraploid A. chinensis male ‘Moshan4’ had longer transverse diameters. Both the longitudinal and transverse diameters of fruits decreased when ‘Hongyang’ was pollinated by male ‘11-17’♂. The longitudinal diameters of fruits increased when A. deliciosa pollen was used. The fruit-shape index were not significantly influenced by the pollination treatments.The color of inner pericarp of ‘Hongyang’ was obviously influenced by the ploidy of males. In the open, compared with the open pollination treatment, the hue angle of inner pericarp increased when tetraploid male ‘Moshan4’ or hexaploid male ‘Tomuri’ was used as the pollen donor for ‘Hongyang’ at Zhengzhou and Chengdu. At Zhengzhou, the higher the ploidy of male was, the red color of inner pericarp became lighter. But inconsistent with that, in the greenhouse, at Zhengzhou, the hue angle of inner pericarp of fruits never decreased following pollination by tetraploid male ‘Moshan4’ or hexaploid male ‘6-65’.When the tetraploid A. chinensis male cultivar‘Moshan4’or hexaploid A. deliciosa male‘Tomuri’were used as the pollen donors, SSC of fruits changed unregularly, total acids changed little and content of Vc increased. Following pollination by ‘Moshan4’ or ‘Tomuri’, total number of seed tended to significantly reduced or somewhat changed, the number of developped seed reduced and 1000-seed weight decreased. When A. chinensis males or hexaploid A. deliciosa males were chosen to pollinate the flowers of ‘Hongyang’, the 1000-seed weight became lighter when the males were in a higher ploidy level. 1000-seed weight decreased significantly with weight 0.25 g following pollination by tetraploid A. arguta male ‘11-17’.4. Effects of male plants with different ploidy on the fruit characteristics of ‘Jintao’(A. chinensis) The fruit weight, longitudinal diameters, fruit-shape index, hue angle of the outer pericarp and inner pericarp, SSC, total acids, Vc of fruits derived from pollination by males of ‘Tomuri’ all had no distinct differences to that ‘Moshan4’ caused. But the fruit-shape index decreased and the hue angle of the outer pericarp and inner pericarp increased. The total number of seed and the number of developped seed significantly decreased while 1000-seed weight increased.