Preharvest aminoethoxyvinylglycine plus postharvest heat treatments influence apple fruit ripening after cold storage

The impact of heat plus aminoethoxyvinylglycine (AVG) treatments alone or in combination on ripening of four apple cultivars has been studied. A solution of AVG was applied to 'Lodi', 'Senshu', 'Redchief Delicious', and 'Red Fuji' apple trees ≈4 weeks before normal harvest at 124 g ha^-1 a.i. After harvest, half of each group of control and AVG-treated fruit was heated at 38 8C for 4 days and then stored at 4 8C for 30 days. After cold storage, AVG and heat individually suppressed ethylene production of 'Senshu' and 'Redchief Delicious' but not of 'Lodi' or 'Red Fuji'. The combination of AVG with heat treatment reduced ethylene production the most consistently in each cultivar except 'Lodi', suggesting some additive effect of the treatments. The respiration rate after cold storage was not consistently affected by any treatment. AVG alone and with heat maintained firmness of 'Lodi', AVG plus heat maintained it in 'Senshu', but neither 'Redchief Delicious' nor 'Red Fuji' firmness responded to the treatments. AVG-treated 'Lodi' and'Redchief Delicious' fruit, heated fruit of all cultivars, and AVG plus heat in all had lower titratable acidity than controls after cold storage. Although there were no effects of any treatment on fruit soluble solids concentration, the combined treatment increased the soluble solids:titratable acidity ratio of all cultivars, although heat or AVG alone had no consistent effects. Total ester production by 'Redchief Delicious' peel tissue after cold storage was reduced 44% by AVG and 70% or more by heat and AVG plus heat. There were no differences in peel alcohol acyltransferase activity among the treatments, supporting the hypothesis that substrate availability was the limiting factor for ester synthesis in treated fruit. Overall, heat plus AVG treatment did not provide any advantage over each alone for maintaining apple fruit quality during short-term cold storage.