Avaliaçao de métodos para predição do potencial de ocorrência de bitter pit em maçãs

Abstract

Experiments were carried out with the objective to evaluate the efficiency of methods for prediction of bitter pit occurrence, on Gala , Royal Gala , Fuji and Braeburn apples after controlled atmosphere storage (CA). Fruits from 11 orchards were picked 20 days before and at commercial harvest date. The experimental design was completely randomized. For each method, treatments consist of 4 replicates of 25 fruits. On the other hand, for evaluation of membrane integrity samples had 6 fruits. The predictive methods evaluated were: infiltration of fruits with 0.1M MgCl2 solution containing 0.4M sorbitol and 0.01% Tween-20; immersion of fruits in solution with 2500nL L-1 ethephon at 20°C; the correlation between quality and maturity parameters and; ion leakage of fruit cells at harvest and after 50, 100 and 150 days on CA storage were compared with the real incidence of bitter pit. For estimating the predictive capacity of methods, symptoms induced on fruits sampled 20 days before harvest date and at commercial harvest were compared with real bitter pit present on fruits stored for 5 months on CA plus 12 days at 20°C. The storage conditions were: for Gala and Royal Gala apples 1.5kPa O2 + 3.0kPa CO2 plus +0.5°C; for Fuji apples 1.2kPa O2 + <0.5kPa CO2 plus -0.5°C; and for Braeburn apples 1.2kPa O2 + 3.0kPa CO2 plus +0.5°C. According to results on Gala apples both methods were inefficient, overestimating the real incidence of bitter pit on fruits sampled 20 days before harvest, and underestimating the real incidence when collected at commercial harvest. On Fuji and Braeburn apples both predictive methods were efficient in predict incidence of bitter pit on fruits sampled 20 days before harvest, however, for fruits sampled at commercial harvest both methods were inefficient. No quality parameters or maturity index showed, in general, correlations that justify its utilization as indicate bitter pit occurrence during storage. In relation to membrane permeability, there was in both cultivars, an increase during storage, related to picking time of fruits. For most orchards, no association was observed between the higher incidence of bitter pit with the higher ion leakage at harvest and during storage, with exception for Gala and Braeburn apples picked 20 days before harvest. The relationship between membrane permeability at harvest and after 5 months of CA storage and the real incidence of bitter pit is not valid as a predictive method