Postharvest Biological Control Green Mold Of Citrus Fruits By Candida Sp.

Green mold, a major postharvest disease of citrus caused huge losses in citrus production. Biological control of postharvest diseases by antagonist yeast, a safe and efficient approach, is a newly emerging area of research.Six strains of the yeasts isolated from citrus fruits, were effective antagonist for control Penicillium digitatum. Four of the yeast strains were proved to be Candida sp. Berkhot and the rest two Cryptococcus sp. Kutzing. The capability of yeast Candida sp. (CWW-4) on biocontrol efficacy of Penicillium digitatum was evaluated in this study, the mechanisms of antagonisim and the effects of different brothes were also investigated.The concentrations of the yeast cells and pathogen spores obviously influenced disease incidence and lesion development in citrus. There was a significant negative correlation between concentrations of the yeast cells and infectivity of thepathogens. Efficacy of Candida sp. (1 10 CFU/mL) against Penicillium digitatum(1 104spores/mL) was maintainted when applied before pathogens, but when applied simultaneously with or after pathogens, biocontrol efficacy was reduced significantly. At challenge level of 1 104spores/mL for Penicillium digitatum and 1 108CFU/mL for washed cell suspension of Candida sp., totally inhibited decay on citrus fruits at 25 in 5 days when applied before pathogens for 24 and 48 hours. Rapid colonization of citrus from woulds was observed both at 4 and 25 at one day, the population increased more than 20 and 60 folds respectively compared to the start point, whether applied pathogens or not, then stabilized at the same density thereafter. Effects of different treatment of Candida sp. on biocontrol of Penicillium digitatum were studied oncitrus. The washed cells of Candida sp. at 1 10 CFU/mL provided the best biocontrol capacity rot on citrus. The cell free culture filtrate and autoclaved of Candida sp. were not effective in preventing the decay and even aggravated the disease at 25. In vitro, the concentrations of the yeast cells obviously influenced the germination rate of pathogen spores. But the cell free culture filtrate and autoclaved of Candida sp. have no effective in preventing the germination. While the antagonist combining with 10% NYDB broth or components of NYDB were reduced. Beef extract was the most effective among thedifferent components of NYDB to reduce the efficacy of the antagonist, the 10% NYDB broth was the smallest.