2013 ASHS Annual Conference

Apple fruit production is highly dependent on flowering frequency. Irregular flowering can lead to irregular crop load and economic loss. Floral induction takes place through the summer; these flowers remain dormant and bloom next spring. Factors such as crop load, bourse length, and seed number influence floral induction. These factors are thought to influence gene expression and contribute to floral induction via affecting endogenous factors such as growth regulators. There are two hypotheses to explain the contribution of these factors on floral induction. The first hypothesis suggests that inhibition signals from seeds and fruits interact with promotion signals from leaves to induce floral induction. The second hypothesis suggests that fruits, seeds, or leaves compete with buds for the floral induction signal. Both hypotheses explain why high crop load leads to low floral induction. In this experiment we are trying to examine both hypotheses and explain how crop load, seed number, and bourse length work altogether to influence floral induction. 'Honeycrisp' apple trees were manually thinned to different flower numbers on the spurs. Fruit weight, seed number, bourse length, and return bloom for these spurs were recorded. One year data showed that both fruit weight and seed number have significant effect on return bloom, but surprisingly bourse length had no effect on flower induction. This evidence might favor the second hypothesis. Creating a better understanding of the interaction of different flowering signals will help us to identify their pattern and identify the genes responsible for flowering initiation.