Architectural analysis of tree form in a range of avocado cultivars

Abstract

Shoot growth and tree architecture were examined in five avocado ( Persea americana Mill.) cultivars at two locations. Each cultivar had a characteristic form judged on tree height and diameter, and number, frequency and angle of inclination of major limbs. This form was related to differences between cultivars in the number and length distribution of axillary branches, and of the relative dominance of proleptic and sylleptic axillary shoots. These differences were apparently established by the interaction between apical dominance and apical control (acrotony). Cultivars ‘Fuerte’, ‘Gwen’ and ‘Reed’ displayed weak apical dominance in that they produced large numbers of sylleptic shoots. They also displayed weak acrotony, producing few major limbs, relatively short axillary branching and few proleptic shoots. Cultivar ‘Sharwil’ exhibited strong apical dominance with relatively few sylleptic shoots, but strong acrotonous growth with many major limbs, and long and numerous proleptic axillary shoots. Cultivar ‘Hass’ was intermediate between ‘Sharwil’ and ‘Reed’ at the same location. Major differences in tree vigour and number of proleptic shoots were found between locations with ‘Hass’, although the basic model of tree architecture was similar at both locations. The data are discussed in terms of the opportunities to manipulate tree growth to enhance fruiting efficiency.