RELATIONSHIP BETWEEN SYLLEPTIC BRANCHING AND COMPONENTS OF PARENT SHOOT DEVELOPMENT IN THE PEACH-TREE

Sylleptic branching of main axes was investigated in three peach tree cultivars ('Armking', 'Flavorcrest' and 'Silvergem') during the first year of growth. An axis was considered as made up of a series of metamers (internode, node, leaf and associated bud) and its growth was divided into two components: the increase of the number of metamers and the lengthening of the metamers themselves (elongation). The relationship between branching; probability, type of cultivar, growth components and date of metamer production was studied by logistic regression. Branching probability varied according to the cultivar, increased when the growth components did, and decreased if metamers appeared late in the season. The logistic model fitted the data closely and was validated on a data set that had not been used for estimating the parameters. Ninety-four percent of branched and 70% of unbranched metamers were correctly predicted by the logistic model. For any given growth rate and date of metamer production, the main axes branched most and least often in the 'Flavorcrest' and 'Silvergem' cultivars, respectively.