Reproductive biology.

Abstract

Many factors may be responsible for the low average avocado yield in most countries, and for the wide fluctuations in yield from year to year. Low yield in healthy trees, which are not subjected to water or nutritional stresses, occur mainly as a result of inadequate fruit set, or excessive fruit drop. This chapter discusses the successive stages of fruit formation in relation to initial and final fruit set.

NUTRITIONAL AND HORMONAL FACTORS AFFECTING FRUIT SET IN AVOCADO (Persea americana Mill.)

“…Subtropical avocados cultivars, that are developed with success in the tropics at high altitudes and in the subtropics with cold winters, can produce floral buds only if they are kept under regimes of cold temperatures (Gazit and Degani, 2002), a requirement that is not, however, essential to the cultivars of avocados that grow in cold climates, in semi-arid and tropical and semi-tropical climates. …”

“…Romero (2011) found that in a year of high production, more than 100x10 3 flowers produced only 168 became a fruit. In other cases, such as adult trees Guatemalan race, fruit set barely reached between 0.001% and 0.23% of a total of more than 1.5 x 10 6 flowers (Gazit and Degani, 2002), and Lahav and Zamet (1999) indicates, for the cultivar Fuerte, that only 0.015% of flowers become ripe fruits. In short, the avocado is a species with very intense flowering in subtropical conditions where it may exceed 2 x 10 6 flowers of which only between 0.001% and 0.1% reach the fruit set (Salazar-García and Lovatt, 1998;Dixon and Sher, 2002;Can-Alonzo et al, 2005;Cossio-Vargas et al, 2007b, Garner andLovatt, 2008).…”

“…The second fruit drop has been attributed to rapid utilization of carbohydrate reserves in the tree, so that the necessary photo-assimilated exceed the photosynthetic capacity of leaves and sink growth is limited by availability of metabolites (Gazit and Degani, 2002). Under these conditions only the fruits of greater vigor may persist on the tree (Laskowski, 2006).…”

“…Flowering contributes with a 8% to the total production of dry biomass in a complete growth cycle of an avocado tree and the process mobilizes nonstructural carbohydrates, reserves, and nutrients from leaves (Gazit and Degani, 2002). Romero (2011) found that in a year of high production, more than 100x10 3 flowers produced only 168 became a fruit.…”

“…The first abscission, i.e, which occurs once the fruits begin the fruit set, can be attributed to fruits with faults in the development of the seed, embryo abortion or death of the seed coat (Dixon and Sher, 2002;Kohne, 2004;Alcaraz et al, 2011), and the effect of environmental stress, particularly cold or heat (Gazit and Degani, 2002). The second fruit drop has been attributed to rapid utilization of carbohydrate reserves in the tree, so that the necessary photo-assimilated exceed the photosynthetic capacity of leaves and sink growth is limited by availability of metabolites (Gazit and Degani, 2002).…”