Processes affecting fruit distribution and its quality in the canopy of olive trees.

Olive (Olea europaea L.) fruits do not distribute regularly in the canopy. In this species most of the fruits are formed at the periphery of the tree, while very few fruits develop in the interior. Determining limiting processes and their variation between genotypes is one first step to improve productivity in less favored zones of the olive tree. In this investigation, causes underlying differential fruit distribution and oil production in two oil cultivars differing in growth habit were studied: evenly open ('Picual') and closed canopied ('Arbequina'). Results indicate that multiple sequential processes (sprouting, flowering, and fruit set, growth and oil accumulation in the fruits) account for differences in productivity among canopy zones of both cultivars. Olives from twigs developed at the top of the tree produced more than triple the amount of oil produced from olives from the shaded interior. Analyses of variance and covariance showed that shoot growth, intensity of flowering, and fruit set (for 'Arbequina'), or fruit size (for 'Picual'), were the main factors involved, while flower fertility and oil accumulation were less important in causing those losses of productivity. Some differences were observed between cultivars in flowering and fruiting patterns: 'Arbequina'developed more fertile flowers and fruits per twig but of smaller size, and fruit set rather than fruit size accounted for differential productivity among canopy areas, while the opposite was true for 'Picual'.