Enhancement the biocontrol efficacy of Sporidiobolus pararoseus Y16 against apple blue mold decay by glycine betaine and its mechanism

•S. pararoseus amended with 1 mM GB reduced postharvest blue mold decay of apple.•1 mM GB enhanced population of S. pararoseus in apple wounds.•S. pararoseus plus GB reduced spore germination and germ tube length of P. expansum.•S. pararoseus plus GB affected flavonoid content and pH of the apples. Apple is one of the greatest important fruits which is commonly consumed worldwide. There are several pathogenic fungi which target the apple and cause tremendous economic losses, and many means are being discovered in order to reduce these losses, including biological agents (BACs) used to control postharvest diseases of vegetables and fruits. The aim of this investigation was to determine the effect of the BAC Sporidiobolus pararoseus Y16 amended with a glycine betaine (GB) in the control of apple blue mold decay caused by Penicillium expansum, and the possible control mechanisms involved. The study revealed that, In vitro, S. pararoseus Y16 amended with 1 mM GB significantly reduced the incidence and diameter of lesions caused by P. expansum with respect to untreated control or to apple treated with S. pararoseus Y16 alone. In vitro, study showed that the combined treatment greatly reduced germ tube length and spore germination rate of the pathogen. The results also demonstrated that the population growth of S. pararoseus Y16 amended with GB (In vivo) had a greater increase than S. pararoseus Y16 alone at either 4 °C or 20 °C. Similarly, the results of the In vitro studies showed significant increase by the combination of treatments. Furthermore, the treatments did not have adverse effect on various storage quality parameter of apples. Therefore, S. pararoseus Y16 amended with GB revealed high rate of effectiveness against the blue mold decay of the apples when applied as biocontrol agent, demonstrating a good potential for controlling postharvest diseases.