Anthracnose (Colletotrichum gloeosporioides), stem-end rot (Lasiodiplodia theobromae) and Phomopsis rot (Phomopsis caricae-papayae) are major post-harvest diseases in papaya resulting in relatively high postharvest losses, up to 45%, in Sri Lanka. The current consumer preference is for tropical fruits free of synthetic pesticides. The objectives of the present investigation were to identify major post-harvest pathogens in papaya fruits, test in vitro fungitoxic effect of basil oil (Ocimum basillicum) and alum (sodium aluminium sulphate) on major fungal pathogens of papaya fruit and develop a relatively safe, disease control strategy. Alum (1% w/v) and basil oil (0.12-0.16% v/v) in a liquid bioassay, indicated fungistatic and fungicidal efficacy on C. gloeosporioides, L. theobromae and P. caricae-papayae isolated from "Red Lady" and "Rathna" cultivars of papaya. In vivo investigation of fruits of both papaya cultivars harvested from fruit plantations in Sri Lanka ("Red Lady"-Yatawarawatta plantation, Kurunegala, "Rathna" -CIC plantation, Kekirawa and the Agricultural farm, Polonnaruwa) at 25% maturity level indicated that papaya washed in 1% (w/v) alum and subsequently sprayed with an emulsion solution of 0.16% (v/v) basil oil and enclosed in styrofoam sleeves could be stored for 14 days at 12-14 o C. The visual quality rating (VQR) was high (11-13), shriveling and "green islands" were low on fruits with zero disease severity where results were statistically similar to 500 mg/L Bavistin treatment. Physicochemical properties assessed were unaffected by the treatments and were comparable to the controls washed only in water. The organoleptic properties were slightly low in fruits subjected to cold temperature compared to fruits subjected to ambient temperature. No residues of basil oil could be detected on fruit peel by gas chromatography at the end of the experimental period of 14 days. The treatment strategy developed could be adopted for sea shipment or temperature-regulated supermarket storage of papaya fruits where storage life could be lengthened up to 14 days.
1- Methylcyclopropene (1-MCP) has been identified as a safe chemical tested successfully in extending shelf life while maintaining quality of plant products. 1-MCP, at very low concentrations, usually blocks ethylene receptors and then inhibits the action of ethylene delaying further ripening and senescence. Several studies have been conducted elsewhere for delaying ripening of different banana cultivars such as Cavendish, Prata, Tella Chakkerakeli, Beragan and Kolikuttu. Physiological reactions related with ripening of banana are delayed by inhibition of ethylene perception, while ethylene synthesis of banana fruit can be regulated at suppressed levels of ACS and ACO by 1-MCP. The effectiveness of 1-MCP on bananas varies with the maturity of the fruit. Fumigation, the conventional application method, has some limitations, particularly long exposure duration, uneven ripening and green ripening in bananas. Application of 1-MCP in aqueous form is recently developed to minimize these limitations. Micro-bubbling and controlled release packaging technologies are effective tools of application of 1-MCP on bananas. This review compiles and critically analyses the existing knowledge on the technological use of 1-MCP, clarifies inconsistencies in different publications.
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