Effect of auxin sprays on 'French Prune' plum fruit size and yield efficiency under different source/sink ratio

摘要

In Chile, Prunus domestica 'French prune' had usually been grown to produce dried fruit, but in recent years, the Asian market for fresh fruit increased the demand for larger fresh fruits. Synthetic auxin sprays have been reported to increase fruit size in different fruit trees, but they have not been validated in this cultivar. The objective of these experiments was to determine the effect of auxin sprays on fruit size and yield of 'French' plum and its interaction with the vegetative growth of the trees. Two trials were carried out during 2018-2019 and 2019-2020 seasons, in orchards located in central Chile (~34-35 S; ~70-71 W), in adult 'French'/'Marianna 2624' trees. Treatments were applied to trees with differentiated pruning and trees with high or low spur load to deduct the effect of crop load on yield efficiency and fruit size. Auxin treatments were done from cluster to pit hardening, based on commercial products available in Chile: Stonegross?, Maxim? (2018), NAA 800?, Propulse? (2019), and Auxym? (2019) and contrasted with not sprayed trees. At harvest, tree leaf area was estimated (2018). Intercepted PAR was significantly reduced when auxin sprays were done before pit hardening. In both seasons, auxin treatments significantly increased fruit size and yield efficiency adjusted by crop load (from 7 to 20). Results suggested that the greater auxin effect was achieved with at least~200 cm~2 of leaf area per fruit; over this leaf area per fruit greater response of fruit size was achieved.