|Gonzalez, M. Belen|
Submitted to: Federation Of European Microbiological Societies Yeast Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/1/2012
Publication Date: 12/13/2012
Citation: Vero, S., Garmendia, G., Gonzalez, M., Bentacur, O., Wisniewski, M.E. 2012. Evaluation of yeasts obtained from Antarctic soil samples as biocontrol agents for the management of postharvest diseases of apple (Malus x domestica). Federation Of European Microbiological Societies Yeast Research. 13:189-199. Interpretive Summary: Most temperate fruit crops are highly susceptible to postharvest rots and appear to have very little resistance. While the use of chemical fungicides is presently the method of choice to prevent the economic losses that occur due to postharvest diseases, consumers would prefer alternative management practices to the use of fungicides. The use of antagonistic microorganisms as biocontrol agents to inhibit postharvest pathogens has shown considerable potential; however, the antagonists must be effective when apples are placed in cold storage. This research describes the isolation, identification, and evaluation of a strain of yeast isolated from Antarctic soils and reports on experiments that were conducted to examine what mechanisms allow the yeast to act as a biocontrol agent. The yeast, Leucosporidium scottii, isolate At17, produced both soluble and volatile antifungal substances and was also able to effectively sequester iron from its environment which is a key micronutrient needed for fungal growth. This would give the biocontrol agent a competitive advantage when rot fungi and the yeast were present together in the same environment. The biocontrol agent was also resistant to chemical postharvest fungicides indicating that it could be used in combination with a low-dose of these chemicals or would not be adversely affected by chemical residues potentially present in a commercial environment. At17 was also capable of forming a biofilm when cultured in apple juice, a trait that would greatly contribute to biocontrol activity. This research lays the foundation for the development of an alternative approach to managing postharvest diseases of apple in Uruguay. This accomplishment was a direct result of collaboration established in a non-funded cooperative research agreement (58-1931-9-001FN) between the University of the Republic, Uruguay and USDA-ARS.
Technical Abstract: Psychrotrophic yeasts isolated from soils collected in Antarctica and selected by its capacity of growing in apple juice at low temperatures were evaluated for their potential as biocontrol agents for the management of postharvest diseases of apple during cold storage. Among the species recovered, an isolate of Leucosporidium scottii, designated At17, was identified as a good biocontrol agent for blue and grey mold of two apple cultivars. Regarding the mechanisms of action, the selected isolate produced soluble and volatile antifungal substances that were inhibitory to apple pathogens. Siderophore production was also demonstrated, but it did not seem to play a role in pathogen inhibition. The selected yeast could form biofilms when grown in apple juice which can be considered an important attribute of postharvest antagonists to successfully colonize wounds and intact fruit surfaces. At17 was resistant to commonly used postharvest fungicides so a combination of them could be used as part of an integrated management practice.