The effect of Calcium Chloride Salt on Increasing Biocontrol Activity of Rhodotorula mucilaginosa A3 aganist Apple blue mold by Penicillium expansum

The antagonistic yeast, Rhodotorula mucilaginosa A3 was evaluated in order to control the blue mold of apple caused by Penicillium expansum. Dual culture, cell free metabolite and volatile test were used in vitro assay. Yeast strains of two genus inhibited growth of P.expansum, inhibition was 53.38 %, in dual culture, 84.41% in volatile metabolite and 86.16% in cell free metabolite test. Calcium chloride (2% w/v) significantly inhibited the growth of the pathogen Penicillium expansum, but did not affect the colony-forming units (CFU) of yeast Rhodotorula mucilaginosa A3 in potato dextrose broth. The concentration 107 cell/mL of yeast suspension influenced spore germination and germ tube growth of Penicillium expansum in vitro, as well as disease incidence and lesion development in fruits. There were significant negative relationships between the suspension concentrations of the yeasts and the growth as well as infectivity of the pathogen. The addition of calcium resulted in lower spore germination rates and slower growth of germ tubes in vitro, as well as in lower disease incidences and smaller lesion diameters compared with treatments with yeast antagonists alone. When yeast cell suspensions reached a concentration of 108 CFU mL-1, growth of the pathogen was completely limited in vitro, and no infection was found in apple fruits treated with or without calcium. In addition, the calcium chloride salt could increase the activity of antioxidant enzymes such as peroxidase and polyphenol oxidase, Calcium chloride salt was induced more than of the application of yeast alone.