Shoot Architecture and Morphology of Different Branch Orders in Fig Tree (Ficus carica L.)

Tree architecture describes plant form by defining the spatial organization of different structures. Shoot branching is an important step in understanding the tree architecture. Such studies are required for analyzing phenotypic diversity of plant architecture. Because such studies are rare on fig trees, the architecture diversity among nine Tunisian fig cultivars grown in Chott-Mariem (center-east Tunisia) was explored. Quantitative morphological descriptors were noted on six annual shoots and studied during four yearly growth cycles, from 2007-10. Coding strategy was adopted for fig branch description. Branch growth characteristics, location, and distribution of axillary shoots were determined for three axis orders. Results showed a great variability of fig branches, particularly in terms of branching density and position, branching angle, and shoot dimensions. Shoot length was closely related to its architectural position in the branch, i.e., all low-order shoots in all cultivars had more growth than high-order shoots. The meso-basitony tendency was frequent. Thus, an architectural typology characterizing all cultivars was established and three principal groups were distinguished. The first one (Type I) with orthotropic branches located at the basal and median parts of the bearer axis had dense and continuous ramification. The second group (Type II) with a diffuse branching differed in lateral shoot distribution, and finally, the third group (Type III) had open and diffuse branching located on the basal zone of the carrier axis. This typology could be used in future genetic improvement programs of local fig trees in Tunisia.