MODELING THE SYLLEPTIC BRANCHING ON ONE-YEAR-OLD TRUNKS OF APPLE CULTIVARS

The structure of 1-year-old trunks resulting from sylleptic branching are compared among apple (Malus domestica Borkh) cultivars with divers e branching and fruiting habits. The 1-year-old trunks developing from a graft are described as a succession of metamers whose structure ref ers to location, distribution, and length of sylleptic axillary shoots . We used a stochastic process called hidden semi-Markov chain to capt ure the embedded structure resulting from mixing of different types of axillary shoots developing along the trunks. The models, correspondin g to the different cultivars, are composed of a first transient nonbra nched state, a succession of transient states that cover the median sy lleptic branching zone, and a final absorbing nonbranched state. They are interpreted with regard to complexity, extent, and branching distr ibution of the median sylleptic zone. Main results deal with the balan ce between long and short sylleptic shoots and the distribution of lon g sylleptic shoots along the trunks. Results suggest that sylleptic br anching could be used as an early characteristic to evaluate the later branching behavior of cultivars.