Effect of Gamma-Amino-Butyric Acid (GABA) Foliar Application on Chilling and Postharvest Quality of Tomato (cv. Newton)

Tomatoes are considered the favorite and most widely consumed vegetables in the world since their fruit is rich in minerals, vitamins and antioxidant compounds. Tomato fruit is harvested after physiological maturity at different color stages based on consumption type. Mature unripe tomato fruit could be stored for long time and be ripened according to market demand, but this tropical product is susceptible to low temperature, which imposes serious constraints in postharvest period and supply chains. Several techniques or chemical treatments have been used to decrease low temperature deleterious effects. Gamma-mino butyric acid (GABA), as an efficient tool, could increase plant resistance to chilling injury (CI) during postharvest life. This study was carried out to evaluate the effect of pre-harvest GABA spray on postharvest quality changes and chilling of tomato fruit during cold storage.

In this study, the effect of pre-harvest application of GABA at three concentrations (0, 5 and 10 mM) on postharvest quality and chilling of tomato cv. Newton was evaluated. The spray was carried out 2 weeks before harvest. Fruits were harvested after physiological maturity when the fruit color changed from pink to red. During storage period at 4 °C and 90-95% relative humidity, some fruit quality attributes such as weight loss, firmness, chilling injury of tomato fruit, soluble solid content (SSC), titratable acidity (TA) and fruit bioactive constituent were analyzed at days 0, 5, 10, 15 and 20.

Chilling in control fruit was 25% at final assessment, while in 10 mM GABA treatment it was only 8.33% at the same time. GABA treatments decreased the rate of weight loss and retained fruit firmness during storage. Also, vitamin C and titratable acidity in GABA treatments were higher than those of untreated fruit. Fruit lycopene content increased during fruit storage in both treated and untreated fruit, but the value was greater in GABA treatments than the control. SSC increased during fruit storage, but it was greater in control than the treatments. While superoxide dismutase enzyme activity decreased in both treated and untreated fruit, the rate of decline in control fruit was greater than GABA treatments. Discussion Pre-harvest foliar application of GABA ameliorated chilling injury induced by cold storage, maintained quality properties of tomato fruit, and increased lycopene content. GABA treatments probably lessened deteriorate effect of low temperature through keeping fruit cell integrity and higher bioactive constituent levels.