Survival of Pichia guilliermondii Yeast Isolate in Powder Formulation and Its Potential for Biological Control of Blue Mold of Apple

Development of resistant strains of pathogens to many fungicides as well as fungicide residues in food stuff have been resulted in attemps to develop biological agents as alternative methods to control post-harvest diseases. Practical use of microorganisms requires formulated products that meet a number of criteria. In this study different carriers for powder formulation of P.guilliermondi were compared. Yeast, grown on a cane molasses-based medium was combined with adjuvants and added to talc, kaolin, rice, and wheat bran. Viability of yeast in 4 formulations was determined over a six month period. Wheat bran based formulation had a significantly higher viable yeast cell content (2.2×1010) over a six month period. Kaolin based formulation had a significantly lower viable yeast cell (7.6×107). Formulations stored at 4°C had a longer shelf life than those stored at 24°C. These formulations were tested on apple control blue mould, although the lesion size of apples treated with fresh cells were significantly less than those on apples trated with formulations stored for six months, but all formulations effectively controlled blue mould on apple.