Effects of Pollen Source and Seed Number on Fruit Set, Fruit Quality, and Flower Initiation of Apple

In apple, adequate pollination and fertilization is required for fruit set and subsequent fruit growth. Limitations in fertilization could potentially be due to the rate of pollen tube growth or the interaction of the pollen with the tissues within the ovary. Both these factors are presumed to be influenced by the genetic interaction between male gametophyte and female tissues of the flower. To evaluate the roles of these two factors in affecting fruit set and return bloom, the pollen of three cultivars, Red Delicious, Gala, and Ralph Shay Crabapple, were applied to Honeycrisp flowers. Hand pollinations were performed under bee exclusion tents. Fruit set, seed number, fruit quality and flower development in bourse buds were measured. Preliminary data showed that fruit set and return bloom both increased when Red Delicious and Gala were used as male gametophytes and were lower with crabapple as the pollen source. However, pollen source did not affect fruit quality and maturity. Seed numbers were positively correlated to fruit weight, but not to fruit quality or fruit maturity. Seed number had no significant impact on return bloom. Male gametophyte had positively effect on soluble solid concentration (SSC), the amount of sugar in the apple fruit. These results suggest that prevailing pollen source and seed numbers can increase fruit set, fruit quality and return bloom of apple.