Interactions between vegetative and generative growth and between crop generations in fig tree (Ficus carica L.)

Yield in fruit trees strongly depends on the balance between vegetative growth and fruiting. This balance is particularly complex in fig tree (Ficus carica L.), in which two generations of figs (Breba and Main crop) develop along an annual shoot and compete with two consecutive growth seasons. For better understanding the interaction between vegetative growth and fruiting in this species, we studied their dynamics throughout three growth seasons on five fig cultivars grown in center-east Tunisia. Shoot elongation was measured at regular intervals from mid-March until mid-December and the number of reproductive buds and fruits were counted at four dates each year.In all cultivars, annual shoot extension exhibited two consecutive phases with unequal duration, separated by a growth cessation. Reproductive buds and fruits number were closely dependent on shoot length. Significant positive correlations were found between Breba crop figs number of current season and shoot length of previous season (0.83 <= r <= 0.98) and between Main crop figs number of current year and shoot length of current season (0.83 <= r <= 0.95). The Main crop amount exerted a strong influence on the current shoot growth as well as on fruiting in the following year: a heavy Main crop load of current season reduces vegetative growth and crop load of Breba for the next year. Similarly, high Breba crop load negatively affected the Main crop load for the current year. The results support the idea of the close interaction between vegetative and reproductive growth in each fig generation and growth flush. By contrast, the strong competition between fig generations appears to be indirect and mediated by the competition between vegetative and reproductive growth. A synthetic scheme of the complex interactions that govern fig generations and vegetative growth rhythmicity in the fig tree is proposed. The data are discussed in terms of the opportunities to manipulate tree growth to enhance fruiting efficiency of fig tree. (C) 2011 Elsevier B.V. All rights reserved.