Résumé
Genotypic variations in growth and fruiting patterns were investigated in various apple (
Malus ×
dormestica Borkh.) cultivars belonging to different ideotypes by analysis of chains of functions of laterals on fruiting branches. Yearly changes in each axillary bud (latent, vegetative, non-bearing or bearing inflorescence and scar) were described over 5 or 6 years, depending on the cultivar. Sequences obtained for the various cultivars were analysed through calculations of three indices: fruit-richness (ϱ), alternation-to-fruit (α) and, among the alternating subsequences (i.e. bourse-shoot without a terminal fruit), alternation synchronism (σ). The results showed that genotypes could be distinguished by two sets of characters. Some cultivars, such as ‘Red Winter’, balance vegetative and reproductive growth by reducing the number of growing points through an extinction mechanism (essentially the abortion of potential bourse-shoots on non-bearing inflorescences), and through a high functional autonomy (low α and high ϱ values) of the remaining sequences, corresponding to high bourse-over-bourse potentials. Spurred cultivars, such as ‘Oregon Spur Delicious’, were characterized by a low extinction value and, in a complementary way, did not seem able to fruit terminally on bourse-shoots (high α and low ϱ values). The overall results of the study of σ showed that the alternation-to-fruit pattern (high α values) could be completely hidden when alternating sequences are desynchronized (low σ values). The links between extinction and alternation-to-fruit, as well as the physiological significance of alternation synchronism, are discussed.