Identification of preharvest factors determining postharvest ripening behaviors in ‘Hass’ avocado under long term storage

A major challenge for the global avocado industry is to provide a homogenous product in terms of fruit-ripening behavior, especially considering the significant variability in quality that can be found within a box or pallet of the fruit. The broad range of conditions under which trees are grown, particularly with regard to climate, soil and agronomical management, can influence this ripening variability. The aims of this study were (i) to determine the variability in fruit ripening among ‘Hass’ avocado grown under different conditions in Chile and (ii) to understand the postharvest fruit-ripening behavior of ‘Hass’ avocado due to the combined effect of several preharvest variables. Preharvest variables were evaluated at 42 experimental sites in Chile during three consecutive seasons. In addition, avocados with over 21% dry matter were collected at each site during each season and stored for 35d at 5°C under normal atmospheric conditions before being ripened at 20°C. Indicators of ripening behavior, such as the softening rate (SOFTRATE), change in peel color (COLO35) and days at 20°C necessary to reach the ready-to-eat stage (RTE35), were evaluated. As expected, high fruit variability in terms of ripening behavior was observed among the experimental sites and seasons. Multivariate analysis showed that the seasonal mean minimum air temperature, seasonal degree-days, trunk diameter and fruit firmness at harvest had a proportional relationship with postharvest SOFTRATE and COLOR35 during storage and a significant inverse relationship with RTE35. Conversely, the leaf area index, number of plants per hectare, and irrigation management at the bloom stage had a proportional relationship with RTE35 and an inverse relationship with SOFTRATE and COLOR35. Moreover, all of the three postharvest ripening behavior indicators were significantly (p<0.05) estimated by predictive models considering preharvest variables. Therefore, attempting to predict postharvest behavior by considering only a single preharvest variable could be a misleading simplification of reality because several factors, including climate/environmental, agronomic management and physiological variables, influence the ripening behavior of ‘Hass’ avocado fruit.