RELATIONSHIP BETWEEN THE EARLY DEVELOPMENT OF APPLE FRUITING BRANCHESAND THE REGULARITY OF BEARING - AN APPROACH TO THE STRATEGIES OF VARIOUS CULTIVARS

The growth and fruiting pattern of fruiting branches of apple trees (M alus x domestica Borkh.) was investigated in several cultivars belongi ng to different ideotypes. The development of the laterals was describ ed over several years, investigating the yearly changes in the bud typ e (latent, vegetative, non-bearing and bearing inflorescence, scar) si nce they first developed on one year old wood. The sequences were anal ysed by calculating the transition probabilities between the bud type of a given year and that of the following year, according to the age o f the sequence. In general, the ability to produce a fruit bud after a fruit bud, i.e. the bourse-over-bourse phenomenon (beta), and the abi lity to produce a fruit bud after a non-fruit bud (either vegetative o r non-bearing inflorescence) (phi) tended to increase with time. The t ransition between latent buds and growing buds (vegetative or generati ve) was observed in all cultivars, but at a higher rate for 'Fuji', an d did not vary according to the age of the sequence. The pattern of tr ansition between growing buds and scar (extinction, i.e. physiological cessation of growth of the lateral) was different. First, 68% to 98% of all extinction phenomena appeared before the third year of the late ral. Second, cultivars such as Granny Smith and Red Winter, showed str onger extinction than spur-type cultivars. The balance between extinct ion and awakening of latent buds, called extinction assessment (xi), w as positively related to the bourse-over-bourse, over the first two co uples of years of lateral life-span. The proportions of bud types on o ne year old wood was probably important in orientating the development of the laterals branched on the same parent shoot. Our results showed first that the first 2-3 years had a major effect on the development of the laterals over the following years, and secondly, that cultivar growth and fruiting pattern depended on a number of rather strictly de fined rules (e.g. beta, phi, xi) the combinations of which determine t he proper strategy of each cultivar. A better knowledge of these intri nsic rules should lead to an improvement in the training programme of young trees.