Effects Of Bagging, SA And INA On Postharvest Quality And Disease Resistance Of Mango (Mangifera Indica L.) Fruit

Effects of bagging and salicylic acid (SA) treatment during fruit growth on postharvest characters and disease control, effects of SA treatment on postharvest physiological responses, qualities and disease resistance, and effects of 2, 6-dichloroisonicotinic acid (INA) treatment on postharvest disease resistance and qualities of mango fruits (cv. Zihua) were studied in this paper. The mechanisms involved in increasing disease resistance of mango fruit after SA and INA treatment were also investigated. The results provided some useful information on how to effectively delay the senescence of mango fruits after harvest, on how to improve the quality of mango fruits, and on how to control the postharvest disease of mango fruits without pollution to environment and harmfulness to human healthy. The results also provided some clues to reduce the amount of chemical fungicide on horticultural crops.Bagging during mango fruit growth significantly decreased rust incidence of peel, latent infection and decay incidence of fruits while accelerated peel degreening of fruits. It was found that bagging had little effect on ripening and storage quality of postharvest mango fruit. 0.1 mmol/L SA spray during mango fruit growth slightly retarded peel degreening of postharvest fruits and inhibited respiration rate of fruits during storage, whereas adverse effect of 1 mmol/L SA treatment was found. 0.1 mmol/L SA and 1 mmol/L SA treatment significantly inhibited increasing of natural or inoculated disease incidence of fruits.Mango fruits were dipped into 0.5 mmol/L SA, 1 mmol/L SA and 5 mmol/L SA solution under a low pressure, part of fruits were inoculated with Colletotichum gloeosporioides Penz. and then stored at 20℃ or 13℃. The results indicated that 0.5 mmol/L SA, 1 mmol/L SA and 5 mmol/LSA treatment inhibited the decreases of fruit firmness, content of ascorbic acid (AsA) and titratable acidity (TA), and the increases of total soluble solids (TSS) and rate of peel degreening. SA treatment also inhibited respiration rate of fruits and reduced the cell membrane permeabilit and malondialdehyde concentration during fruits storage. 0.5 mmol/L SA and 1 mmol/L SA treatment effectively reduced fruits decay and inoculated disease incidence, whereas 5 mmol/L SA accelerated fruits decay. Furthermore, 1 mmol/L SA effectively enhanced activities of peroxidase (POD), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), chitinase (GHT) or β-1, 3-glucanase (GLU) and levels of hydrogen peroxide (H2O2) or superoxide radicals (O2-), and inhibited the decrease of superoxide distmuase (SOD) activity in mango fruits pulp and peel.The results of postharvest INA treatment in mango fruits showed that 20 mg/L INA and 100 mg/L INA effectively reduced fruits decay incidence and inoculated disease diameter, inhibited decreases of fruits firmness and TA level, retarded peel degreening of fruits while had little effect on TSS level of fruits. 100 mg/L INA treatment effectively enhanced the activities of POD and PPO of mango fruits during last 8 days of storage. 100 mg/L INA also enhanced the activities of PAL, GLU and CHT and levels of H2O2 and O2-, inhibited the decreases of SOD activity and AsA content, andinhibited the activities of catalase (CAT) and ascorbate peroxydase (APX) of mango fruits during storage. However, 100 mg/L INA treatment had little effect on glutathion reductase (GR) activity and glutathione (GSH) content.