Submitted to: Postharvest Biology and Technology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 1/6/2007
Publication Date: 1/6/2007
Citation: Ryan, F.J., Leesch, J.G., Palmquist, D.E., Aung, L.H. 2007. Glutathione concentration and phytotoxicity after fumigation of lemons with methyl iodide. Postharvest Biology and Technology. 45:141-146. Interpretive Summary: Methyl iodide is a possible alternative to methyl bromide as a fumigant to control pests on fresh postharvest commodities. Although it is efficacious in pest control, it can produce injury in fresh produce, including lemons. This work was undertaken to determine whether post-fumigation aeration at 30º C could reduce the injury caused by fumigation. Both the number of injured fruit and the severity of injury were substantially reduced by a 24 hour aeration in comparison to a two hour aeration. Less injury was observed overall than in previous work with aeration at 25º C, and the amount of injury varied between desert and coastal production areas. Coastal lemons had almost no injury after the longer aeration while approximately 30% of lemons from the desert production region were injured, although the injury was slight. This work provides a basis for methyl bromide alternative treatments that are effective in controlling pests and that maintain high produce quality.
Technical Abstract: Commercial lemons were treated with the proposed quarantine fumigant methyl iodide at 28 parts per million for 2 hours at 21º C then were forcibly aerated for 2 or 24 hr at 30º C. Total and oxidized glutathione concentrations were determined enzymatically immediately after aeration and after three weeks storage at 5º C. Total glutathione content was substantially reduced in comparison to controls after fumigation and 2 hr aeration but recovered considerably during the 24 hr forced aeration. After three weeks storage, fruit subjected to the 24 hour aeration had glutathione levels equivalent to those of the controls while those given the 2 hour aeration had lower levels of total glutathione. Also, after three weeks storage, phytotoxicity in fruit given the two hour aeration was high while fruit given the 24 hour aeration had less injury. A higher temperature during aeration (30º C) reduced the amount of injury in comparison to that observed in earlier work with aeration at 21º C.