Effective Pollination Period and Influence of Crop Load Management on AU Kiwifruit Cultivars
Type of DegreeMaster's Thesis
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Kiwifruit size and marketability is closely associated with successful pollination and crop load management. Commercial kiwifruit production often involves much effort to enhance pollination due to the inherent difficulties associated with functionally dioecious plants with flowers that do not produce nectar. Determining the length of time that female flowers can be successfully pollinated would aid management decisions. Therefore, the purpose of the first study was to determine the effective pollination period (EPP) for Actinidia chinensis ‘AU Golden Sunshine’ and A. deliciosa ‘AU Fitzgerald’. In 2013, 30 female flowers of each cultivar that were previously isolated/bagged were hand pollinated each day by direct flower to flower contact with the male pollinizer, and re-bagged to prevent open pollination. ‘AU Golden Sunshine’ flowers were pollinated 1, 2, 3, 4, or 5 days after anthesis (DAA) and ‘AU Fitzgerald’ flowers were pollinated 1, 2, 3, 4, 5, or 6 DAA. Anthesis was considered the day the flower opened. In 2014 and 2015, the same procedures were followed as the year before except 32 female flowers were hand pollinated with harvested male pollen each day with a camel hair brush and the flowers were pollinated for 1, 2, 3, 4, 5, 6, or 7 DAA. ‘AU Fitzgerald’ was not tested in 2014. For ‘AU Golden Sunshine’ in 2013, there was no decrease in fruit set over the 5-day period. Differences in fruit weight, fruit size index and seed number for this year were found between 1-3 and 4-5 DAA. For 2014, differences in fruit set were found between 1-5 and 6-7 DAA while differences in fruit weight, fruit size index and seed number were found between 1-3 and 4-7 DAA. In the last year (2015) for this cultivar, differences in fruit set were found between 1-6 and 7 DAA while differences in fruit weight, fruit size index and seed number were found between 1-5 and 6-7 DAA. Based on fruit set percentages for 2014 and 2015, the EPP for this cultivar is 5 to 6 DAA. For ‘AU Fitzgerald’, the EPP was more variable. Fruit set was high for the first 4 DAA and then began to decline 5 DAA for the first year (2013) suggesting that the EPP was 4 DAA. Differences in fruit weight, fruit size index and seed number were found between 1-4 and 5-6 DAA. In the second year (2015) however, fruit set remained constant over the 7-day period with differences in fruit weight, fruit size index and seed number found between 1-5 and 6-7 DAA. Flower production and fruit set was higher for ‘AU Fitzgerald’ in 2015, suggesting that the EPP was affected by the biennial nature of the species. Another production concern for kiwifruit, is that some cultivars produce excessive yields of small unmarketable fruit. For these cultivars, thinning is necessary to produce fruit of good quality and of marketable size. There are several developmental stages where thinning practices can be implemented, particularly bud swell, bloom and fruit set. The objective of the second study was to determine the effects of lateral bud and fruit removal on marketable fruit yield of A. chinensis ‘AU Golden Dragon’ and the prolific ‘AU Golden Sunshine’. Bud-thinning consisted of removing all lateral buds, by hand, leaving only the “king” or terminal bud while fruit-thinning consisted of removing all lateral fruit leaving only the “king” or terminal fruit. Crop load reduction was not advantageous for ‘AU Golden Sunshine’ or ‘AU Golden Dragon’ during this study, as no differences were observed between bud or fruit thinning and no thinning treatments for marketable fruit number or marketable yield. Total fruit yield was also not affected by bud or fruit thinning treatments for either cultivar. Thinning treatments did not affect fruit quality for ‘AU Golden Sunshine’ or ‘AU Golden Dragon’.