Combined application of alginate oligosaccharide and marine yeast Sporidiobolus pararoseus to control brown rot of peach fruit

Brown rot caused by Monilinia fructicola is the major fungal disease during postharvest storage of peach fruit. In this study, the effects of marine yeast Sporidiobolus pararoseus and alginate oligosaccharide (AOS) used alone or in combination to control brown rot in peach fruit were investigated. The results showed that AOS and S. pararoseus used alone could reduce the disease incidence and lesion diameter of brown rot, and their combination significantly increased the control effect than either treatment alone. Especially in the early stage of disease, the incidence of the untreated control fruit has reached 90%, while the incidences of AOS and S. pararoseus treatment were 36.7% and 30%, however, the combination treatment only showed 13.3% of incidence. The combination treatment of AOS and S. pararoseus can also reduce the weight loss and maintain fruit quality of peaches. Meanwhile, AOS could promote the colonization of S. pararoseus in peach fruit wounds and improve the survival of S. pararoseus under stresses. The combined treatment of S. pararoseus and AOS significantly increased the activities and gene expression of resistance-related enzymes such as catalase (CAT), phenylalanine ammonia-lyase (PAL), peroxidase (POD), polyphenol oxidase (PPO), β-1,3-glucanase (GNS), chitinase (CHI), promoted the accumulation of total phenols. These findings indicated that the increased biocontrol efficacy of AOS combined with S. pararoseus may be attributed to the promoting growth of S. pararoseus by AOS and the enhanced disease resistance of peaches. Overall, the combined application of AOS and S. pararoseus could be an effective method to control brown rot of peach fruit.