Cytokinins increase fruit size of 'Delicious' and 'Golden Delicious' (Malus domestica) apple in a warm climate

The two main apple cultivars grown in the warm climate of Israel, 'Delicious' and 'Golden Delicious', produce relatively small fruits. Over four consecutive years (2001-2004), application of 10 mg l(-1) N-(2-chloro-4-pyridyl);N'-phellylurea (CPPU) or 50 ing l(-1) benzyladenine (BA), 2 weeks after full-bloom, when fruitlet diameter was 10 mm, caused ail appreciable (>50%) and significant increase in fruit size with only slight (BA) or no (CPPU) effect on fruit thinning. We therefore conclude that the main effect of these cytokinins was via direct stimulation of fruit cell division. Neither cytokinin had any effect on fruit shape or seed number, nor on fruit quality at harvest or in storage at 0 degrees C, nor on return bloom or yield in the following year.