Ethylene evolution of flowers of different apple cultivars varies in timing and intensity

Fruit set of some apple cultivars is low despite abundant flowering. This could be, among other things, due to ethylene production of the flowers and or short ovule longevity. ‘Minneiska' apple has been notable for its low productivity if not managed adequately. To better understand the cause of the low fruit set presented by this cultivar, a series of trials evaluating ethylene evolution and fruit set were conducted from 2017 to 2019. Flowers/fruitlets of different apple cultivars showed a distinct pattern in ethylene evolution. ‘Minneiska’ apple cultivar has a high and sustained level of ethylene just after bloom which may be the cause of the lower fruit set of ´Minneiska´ compared to the other cultivars such as ‘Gala’ and ‘Fuji’. The production and maximum peak of ethylene of ‘Minneiska’ flower/fruitlet clusters varied among years. Spray applications of aminoethoxyvinylglycine (AVG) during the bloom and petal fall timing reduced ethylene levels compared to the untreated control. Fruit set and fruit number per tree was also increased with the applications of AVG.