The 2009 ASHS Annual Conference

Phenomenon of metaxenia and its impact on apple fruit quality has been known for a long while. Several studies confirmed that hormones produced by seeds are responsible for it. Since seed hormones drive not only the evolution of fruit quality but also other physiological processes that may have an effect on fruit development, we assumed that pollinizers also affect king dominance.  Cross-pollination treatments with pollen of ‘Elstar’, ‘Golden Delicious’, ‘Granny Smith’ and ‘Fuji’ cultivars were made on ‘Gala’ flowers. Open pollination of ‘Gala’ served as control. Fruit set of flowers in a cluster greatly varied with their position, flower number per cluster and pollination treatments; generally, king flower had significantly greatest fruit set regardless of flower number per cluster. Clusters with less than 4 flowers did not show any ability to set fruit. The highest probability was found for all clusters to set one fruit rather than more. Increasing number of flowers per cluster generally increased the number of fruit at harvest, however, close relationship was not found between flower number per cluster at bloom time and fruit number per cluster at harvest. Mean fruit weight decreased with fruit number per cluster. Significantly greatest fruit weight was usually measured for king fruit particularly for crosses of cultivars with strong king dominance (‘Granny Smith’ and ‘Fuji’). Decreasing tendency in fruit weight, however, did not necessarily follow the position of side fruits, i.e. their opening sequence in a cluster. Fruit weight of lateral fruits did not significantly differ from each other. Differences in fruit weight between king fruit and side fruits increased with increasing number of fruit per cluster. L:D ratio was usually the smallest for king fruit and greater for lateral ones in all treatments. Soluble solids, skin color and firmness were not significantly affected by cross-pollination treatments. Viable seed number per fruit, however, was greatly influenced by treatments. Seed count in fruit from ‘Golden Delicious’ pollination was greater than the open-pollinated ‘Gala’ control. ‘Elstar’, ‘Fuji’ and ‘Granny Smith’ had a reducing effect on seed number. Fruit position did not affect seed number, significant differences between king fruit and lateral fruits were not observed. Average seed number increased with increasing number of fruit per cluster. Gibberellic acid content in seeds (GA₃, GA₄, GA₇) was the greatest for king fruit but it was not always significantly different from the second or third side fruit. GA content was not significantly affected by cross-pollinations.