Abstract
Background
The present study aimed to examine the biocontrol efficacy of 28 yeast isolates against
Aspergillus niger
, the common pathogen of onion black mold disease. The antagonistic potential of yeast isolates against
A. niger
growth was investigated using a dual culture technique.
Results
Five yeast isolates, including 8 and 11, showed the highest inhibition effect on the mycelial growth of
A. niger
. Molecular analysis using 16S RNA identified strains 8 (AUN-AH14) and 11 (AUN-AH23) as
Galactomyces geotrichum
(JQ713185.1) and
G. geotrichum
(DQ849321.1), respectively. The culture filtrates of AUN-AH14 and AUN-AH23 at percentage concentrations of 20, 40, 60, and 80 were tested against the growth of
A. niger
. As a result, the lowest dry weight of the pathogen was obtained with culture filtrates of the two strains at concentrations of 60 and 80%.. Treatment of onion bulbs with formulation of antagonistic yeast isolates AUN-AH14 and AUN-AH23 and their corresponding cultural filtrates at 80% concentration significantly reduced the severity of black mold disease relative to the controls.
Conclusions
The most significant reduction in black mold severity was proved in yeast formulations of AUN-AH14 and AUN-AH23, followed by their cultural filtrates (CF-AUN-AH14 and CF-AUN-AH23). The shelf life of formulated yeast isolates began to gradually deteriorate after 5 months of storage at 4 °C.