Evaluation of tree size and branching responses of breadfruit [Artocarpus altilis Parkison Fosberg] cultivars ‘Yellow’ and ‘Ma’afala’ to different levels of pruning 127

Tree height management is an important cultural requirement for sustainable commercial breadfruit production as a food crop. The efficacy of pruning, which is the traditional approach to controlling tree height, has not been evaluated. This study was conducted in Trinidad and Tobago to evaluate the effect of different levels of pruning on tree size and to determine whether cultivars that differ in form also differ in response to pruning. Thirty 4 year old bearing trees each of the ‘Yellow’ and ‘Ma’afala’ cultivars were subjected to five pruning treatments: no pruning; heading back only; heading back with thinning of small branches only; and with removal of 30% or 50% of the primary branches, in 2013 and 2014. Twelve months after the second pruning, trees showed no significant effects of pruning on tree height and canopy width while the number of primary branches was higher (p<0.001) in the control trees than in those from which primary branches had been thinned ‘Yellow’ and ‘Ma’afala’ trees differed (p<0.001) in mean tree height at 5.2 m and 3.9 m, respectively, while in ‘Ma’afala’, mean canopy width (4.0 m) was greater (p<0.001) than that of ‘Yellow’ (3.2 m). ‘Ma’afala’ produced more branches at all levels than ‘Yellow’. The first pruning increased (p<0.001) the number of tertiary branches on ‘Ma’afala’ 5 year old trees but in the 6 year old trees there were no differences among treatments because of the 407% increase in tertiary branches in unpruned trees compared with the pruned treatments. Location of the pruning cuts, time of pruning and low soil moisture availability in the post-pruning period were the major factors restricting growth and should be considered in strategies to manage tree size but cultivars may differ in water requirements during the dry season.