Submitted to: International Journal of Food Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/7/2011
Publication Date: 3/15/2011
Citation: Liu, J., Wisniewski, M.E., Droby, S., Vero, S., Tian, S., Hershkovitz, V. 2011. Glycine betaine improves oxidative stress tolerance and biocontrol efficacy of the antagonistic yeast Cystofilobasidium infirmominiatum. International Journal of Food Microbiology. 146:76-83. Interpretive Summary: Consumer demands to lower exposure to chemicals and the need to minimize the impact of agriculture on the environment are important drivers for developing alternative approaches to disease control. Development of effective biocontrol strategies is a critical objective of NP-303, Plant Diseases. In the past decade, USDA-ARS has identified several species of yeasts that can be used as biocontrol agents against postharvest diseases of fruit, and one of these antagonists was previously commercialized. Other international research programs and commercial companies have also developed postharvest biocontrol products. Despite these options, use of these products remains limited partly due to variable performance. Therefore, there is a need to find strategies that will increase the efficacy of these bicontrol agents and allow them to perform more reliably under variable, and often adverse environmental conditions. In the present study, we exposed the yeast, Cystofilobasidium infirmominiatum, to the simple sugar/amino acid, glycine betaine, and found that it made the yeast more tolerant to oxidative stress, an abiotic stress often encountered in the wound site where yeast must grow to inhibit rot pathogens. The improvement was partially due to the induction of antioxidant enzymes in the yeast that detoxify the agents (reactive oxygen species – ROS) responsible for creating the oxidative stress. Importantly, yeast cells of Cystofilobasidium infirmominiatum that were exposed to glycine betaine also performed better as a bicontrol agent against a postharvest rot of apple caused by Penicillium expansum compared to untreated cells. The use of glycine betaine treated cells resulted in lower disease incidence and reduced lesion size, apparently due to the ability of these cells to grow more rapidly in the wound site during the first two days after application. The use of this strategy to improve the efficacy of bicontrol agents will be explored for other species and on a larger scale to determine if it can be incorporated into the manufacturing process or at the time of application in a packing house.
Technical Abstract: The effect of hydrogen peroxide-induced oxidative stress on the viability of the yeast antagonist, Cystofilobasidium infirmominiatum, as well as the effect of exogenous glycine betaine (GB) on yeast viability under oxidative stress, was determined. GB treatment improved the tolerance of C. infirmominiatum to oxidative stress. Compared to untreated control yeast cells, GB-treated cells showed less accumulation of reactive oxygen species (ROS) and a lower level of protein oxidation in response to oxidative stress. Additionally, GB-treated yeast exhibited greater biocontrol activity against Penicillium expansum and a faster growth in wounds of apple fruits stored at 25 degrees C compared to the performance of untreated yeast. The activities of antioxidant enzymes, including catalase (CAT), superoxide dismutase (SOD) and glutathione peroxidase (GPX) of C. infirmominiatum, were elevated by GB treatment. Results indicate that the elicitation of antioxidant response by GB may contribute to the improvement in oxidative stress tolerance, population growth in apple wounds, and biocontrol activity of C. infirmominiatum.