Effect of pre- and post-harvest water stress on the potential for fruit quality defects in avocado (Persea americana Mill.)

Abstract

Physiological and pathological disorders of avocado fruit are a limitation to export sales. The influence of pre-harvest water stress on post-harvest quality was studied using a long-term irrigation trial, i.e., re-wetting in the root zone when soil water tensions reached 35 kPa, 55 kPa and 80 kPa. Fruit quality from two harvest dates was expressed in terms of the browning enzyme polyphenol oxidase (PPO). The effect of post-harvest fruit moisture loss on pathological and physiological disorders was investigated using increased humidity in the storage container to minimize fruit water loss. Pre-harvest water stress played a role in determining post-harvest browning potential. Fruit calcium concentration changes were also affected. For early (autumn) harvested fruit, highest PPO activity was found in the 80 kPa (most stress) irrigation treatment and lowest in the 55 kPa (intermediate stress) treatment for both stored and unstored fruit. Stored fruit had higher PPO values than unstored fruit. Winter harvested fruit showed the same trend. This delayed harvesting greatly increased levels of soluble PPO. Decreased post-harvest moisture loss resulted in a lower incidence of both pathological and physiological disorders.