Influence of flower type, position in the cluster and spur characteristics on fruit set and growth of apple cultivars

Flower and spur characteristics as well as flower position in the cluster were related to fruit set, size, shape and growth of a range of apple cultivars in New Zealand, Maine and Ohio. 'Jonagold' and 'Royal Gala' had more flowers per cluster than 'Red Chief Delicious' at all locations. Flower pedicel length and dry weight as well as flower dry weight were positively related to harvest fruit weight. King (K) and lateral (L) pedicel length and dry weight were positively correlated with fruit set in New Zealand, but not in Maine and Ohio. Spur leaf area, leaf size and bourse leaf area were related to fruit set in New Zealand and Ohio, but not in Maine. Although not significant at all locations, 'Jonagold' and 'Royal Gala' had large and 'Red Chief Delicious' small spur and bourse leaf areas, compared to other cultivars. Bourse leaf areas in New Zealand for all cultivars tended to be larger than Maine and Ohio. Rootstock had no influence on performance of the different positions in the flower cluster. Of the cultivars common to all sites, New Zealand had larger fruit size than Ohio and Maine, respectively 'Jonagold' 25% and 25%; 'Red Chief Delicious' 28% and 12%; and 'Royal Gala' 25% and 10%. Of all the cultivars tested, only 'Royal Gala' in New Zealand had larger K than L fruit and in New Zealand, L fruit were larger than the K in 'Braeburn' and 'Jonagold'. Thus, when flower clusters are thinned to single buds at pink, K dominance was not evident.