|Cheng, Zhe - Hefei University Of Technology|
|Chi, Mengshan - Hefei University Of Technology|
|Li, Guangkun - Hefei University Of Technology|
|Chen, Huizhen - Hefei University Of Technology|
|Sui, Yuan - Hefei University Of Technology|
|Norelli, John (jay) - Jay|
|Liu, Yongsheng - Hefei University Of Technology|
|Liu, Jia - Hefei University Of Technology|
Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/8/2016
Publication Date: 1/11/2016
Citation: Cheng, Z., Chi, M., Li, G., Chen, H., Sui, Y., Wisniewski, M.E., Norelli, J.L., Liu, Y., Liu, J. 2016. Heat shock improves stress tolerance and biocontrol performance of Rhodotorula mucilaginosa. Biological Control. 95:49-56. Interpretive Summary: Postharvest diseases of harvested fruits cause significant economic losses. Due to increasing consumer demands for organic fruit, stricter regulations on the pesticide residues (especially on fruit exported to Europe), and problems with pathogen resistance to current fungicides, there is a strong need to develop alternative disease management practices. The United States Department of Agriculture (USDA), Agricultural Research Service (ARS) has taken the lead in the past decade in demonstrating the ability to use yeasts as biocontrol agents against postharvest pathogens. While a few yeast-based products are commercially available, industry acceptance has been minimal, mainly due to their erratic performance under commercial conditions. Therefore, there is a definite need to find ways to increase their efficacy and reliability. The present research represents a collaborative effort between Chinese scientists at Hefei University of Technology and USDA-ARS scientists to explore ways to increase the stress tolerance of a yeast biocontrol agent. The collaborative research was conducted under a non-funded cooperative agreement. Results indicated that exposing the yeast biocontrol agent, Rhodoturula mucilaginosa, to a mild heat shock (40 degrees celsius for 30 min.) increases its stress tolerance to a wide array of other abiotic stresses, including high temperatures, oxidative stress, salt stress, and low pH. These stresses represent many of the types of stresses that the yeast might encounter in a commercial packing house processing harvested fruit. Overall biocontrol performance was also increased. These findings can be used to develop formulations of biocontrol agents with enhanced efficacy and reliability.
Technical Abstract: Biological control of postharvest diseases, utilizing wild species and strains of antagonistic yeasts, is a research topic and eco-friendly management approach that has received considerable attention. A few yeast-based biocontrol products are available in the market. Ecological fitness, stress tolerance, and biocontrol performance are the most essential attributes for yeasts used as biocontrol agents. In the present study, a mild heat shock (HS, 40 degrees celsius for 30 min) pretreatment of the biocontrol yeast, Rhodotorula mucilaginosa, increased its tolerance to subsequent high temperature (48 degrees celsius), oxidative stress (70 mM H2O2), salt stress (3 M NaCl) and low pH (pH 4). Antioxidant system, activated by HS, resulted in less accumulation of reactive oxygen species and lower level of oxidative damage to protein and lipid under the abiotic stresses. Additionally, HS-treated yeast exhibited greater control of apple fruit infection by Penicillium expansum and a higher growth rate in apple wounds. These results suggest that stress adaptation may represent a viable approach for improving the performance reliability of yeast biocontrol agents under the variable conditions during practical application.