Post-storage quality and physiological responses of tomato fruits treated with polyamines

Two greenhouse F1 tomato cultivars, M19 and M79, were grown hydroponically and the mature green fruits were harvested and subjected to eight polyamine (PA) treatments including 1 and 2 mM putrescine (Put), spermidine (Spd) and their combination before being placed at 3°C for 15 and 25 days. Electrolyte leakage, weight loss, fruit firmness, decay percentage, chilling injury index, titratable acidity, total soluble solid content and ascorbic acid content were then measured after keeping at 20°C for 3 days and compared to control. The Put:Spd (2:2 mM) treatment decreased electrolyte leakage (over 50%), chilling injury index and fruit decay percentage. Combinations of PAs caused greater total soluble solids and greater effect on decreasing weight loss during storage when compared to their sole PA application. PAs caused a net increase in fruit firmness during post-harvest life. Titratable acidity increased with increasing duration of low temperature storage for all treatments. Ascorbic acid in fruits stored at low temperature for 25 days was greater than those stored for 15 days. The effects of exogenous PAs on reducing chilling-related disorders decreased with time. Correlations among weight loss, electrolyte leakage, chilling injury, decay percentage and fruit firmness during low temperature storage were positive and significant, but they were non-significant or significantly negative when compared against ascorbic acid, titratable acidity and TSS.