Yeast-Based Biocontrol: A Novel Approach to Manage Apple Blue Mold with Candida membranifaciens and Rhodotorula mucilaginosa

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 (107
cell 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
CaCl2 mixed with yeast (A1), was evaluated at 20°C. The different concentration of CaCl2 reduced 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.