الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The potential ability of some alternative abiotic means such as salts, chitosan (CH), propolis (PRO), antioxidants and modified atmosphere (MA) to control postharvest decay and rots on melon fruits caused by Fusarium semitectum,Aleternaria alternata, and Rhizopus stolonifer were investigated. In vitro trials, among the tested salts, potassium sorbate showed the highest direct effect against the mycelial growth of all tested fungi followed by sodium bicarbonate. Meanwhile, calcium chloride and sodium acetate had the lowest inhibition effect against the tested fungi at the same concentrations. Both chitosan and propolis natural substances proved significant effect in all fungi where the concentration increased, in which chitosan yielded the highest effect against A. alternate, while propolis proved the highest effect on R. stolonifer. Among antioxidants substances, benzoic acid showed the highest inhibitory action on the mycelial growth of all tested fungi, followed by salicylic acid. However, MA in vitro had a low effect at all tested concentrations among all tested alternatives. In vivo trials were conducted according to three strategies: (a) spraying before harvest, (b) dipping after harvest, and (c) treatments spraying combined with MA. Under artificial inoculation, the alternatives showed a variable effect against the tested pathogens. Mostly, treatments spraying combined with MA showed the high level of protection against the development of postharvest decay of all tested fungi, in which benzoic acid +MA was the most effective treatment, notably on R. stolonifer development which completely inhibited. Preharvest spraying revealed high activity against the tested fungi compared to postharvest dipping at the same treatment in which sodium silicate 3%, potassium sorbate 1%, benzoic acid 0.6 g/l, sodium bicarbonate 3% and chitosan 1.5 g/l were the most effective treatments against postharvest decay development of melon fruits when applied before and postharvest. Meanwhile, propolis was most effective as postharvest dipping than preharvest spraying treatments. The ability of the tested alternatives to trigger defense mechanism reaction in fruit tissues were manifested during the activity assessment of some defense related enzymes in melon fruits i.e. peroxidase (POD) and polyphenol oxidase (PPO). Major treatments showed a high activity of POD enzyme such as potassium sorbate 1%, chitosan 1 and 1.5 %, sodium silicate 3%, sodium bicarbonate 3%, benzoic acid 0.6 g/l and salicylic acid 0.6 g/l respectively, while ascorbic acid treatment strongly reduced the activity of POD compared to control. All treatments significantly increased the PPO activity excepted for sodium acetate 3%, propolis 3mg/ml, ascorbic acid 0.6 g/l. Meanwhile, pretharvest spraying treatments combined with MA approximately showed the lowest level of activity for both POD and PPO enzymes. In addition, the influence of the alternatives on fruits quality (physical and chemical properties) of melon including general appearance, firmness, total soluble solids and titratable acidity percentage was also investigated. Generally, pretharvest spraying treatments combined with MA significantly maintained the physical and chemical properties compared to control, followed by chitosan, sodium silicate, benzoic acid and salicylic acid treatments respectively.