Growth and branching pattern along the main axis of two apple cultivars grafted on two different rootstocks.

摘要

The growth and branching patterns of annual shoots of apple (Malus domestica [Malus pumila]), allowed to develop with minimum pruning, were studied over six successive years (1991-96) in Montpellier, France. Two cultivars, Rome Beauty (RB) and Starkrimson (STK) were grafted on M.7 and M.9 rootstocks. After six years, the number of leaves, the length and the basal diameter of the successive annual shoots (AS) along the main axis of the trees were measured for each cultivar/rootstock treatment. Laterals, classified into three categories (spurs, medium and long shoots), were counted and the rank of their bearer node was recorded. A rapid decrease was observed in both the number of nodes and the length of the AS for all cultivar/rootstock treatments over the six years. A yearly comparison of all treatments highlighted greater differences in AS length than number of leaves. Rootstock effect was greater with RB than with STK. Differences in the relationships between the number of leaves per shoot and shoot length or diameter were found between cultivars but not between rootstocks. Both the number and the type of lateral shoots depended on the length of the bearer AS in all treatments. Long laterals developed only on the first AS. In the subsequent years, the proportion of spurs and medium shoots was more affected by the cultivar (STK exhibiting more spurs than RB) than by the rootstock. Flowering occurred first in the second or the third year i.e., when the mean AS length reached an asymptotic value.Regular flowering behaviour was then observed in RB whereas STK exhibited a more irregular behaviour. Finally, the results suggest that rootstocks have a cumulative effect resulting in the shortening of AS in each growing period on both the main axis and the laterals.