Abstract

In this study, two genus of biocontrol yeasts were isolated from healthy apple fruits surface. Three strains of Candida membranfaciens (A₂, A₄ and A₅) and two strains of Rhodotorula mucilaginosa (A₁ and A₇) were evaluated for the control of the blue mold of apple caused by Penicillium expansum. One isolate of P. expansum was used in these experiments. Dual culture, cell free metabolite and volatile test were used for in vitro assays. Yeast strains of two genus inhibited growth of P. expansum, inhibition varied from 20.6 - 61.4%, in dual culture, in volatile metabolite from 57.2 - 89.1% and from 54.6 - 86% in cell free metabolite test. Apple fruit wounds were inoculated with 40 µl of yeast cell suspension (10⁷cell ml^-1), and after 24 h, inoculated by P. expansum (10⁵ conidia ml^-1). Inoculated apples were incubated at room (20°C) and cold (5°C) temperature. All strains of two genus reduced lesion area at two temperatures. The A₂ (C. membranfaciens)was the most effective strain at both temperatures, significantly. Effect of CaCl₂mixed with yeast (A₁), was evaluated at 20°C. The different concentration of CaCl₂reduced the lesion area from 185.07 - 1738.037 mm² reduction compared to 2452.84 mm² in control after incubation for 15 days at 20°C. At the same time, the other antagonistic yeast conditions such as yeast concentration and inoculation time were studied, and the best conditions for antagonistic yeast were determined.

Key words: Apple, biocontrol, blue mold, Candida membranfaciens, Rhodotorula mucilaginosa, Penicillium expansum.