The activity of two biological control agents, strains L1 and L8, previously identified as Aureobasidium pullulans, was tested for the first time in the same experiments on apple, artificially inoculated with Botrytis cinerea (grey mould), Colletotrichum acutatum (bitter rot) or Penicillium expansum (blue mould). The washed cells of antagonists controlled over 86% of three decays and the antagonist L1 seemed more efficient than L8. The cell concentration of both antagonists was highly correlated with their efficacy, the R2 ranging from 0.93 to 0.99. The highest concentration (108 CFU ml-1) of L1 and L8 provided the best control of B. cinerea, C. acutatum and P. expansum, although gray mould was completely inhibited also by a concentration one log lower (107 CFU ml-1). The population dynamic of L1 and L8 strains in ‘Gala’ apple increased almost eightfold during the first 48 h after treatment and remained elevated until 7 days, revealing that, although antagonists were isolated from carposhere of peach fruit, they showed good adaptation in other wound environments such as apple, making them suitable for pathogen control in a wide range of hosts. Preliminary in vitro trials were conducted in order to investigate the mechanisms of action of L1 and L8 strains. Both the washed cells showed a complete control of all three pathogens, while the culture filtrates and autoclaved cells were found to have had no significant inhibition on pathogens. In a dual culture dish assay, where there was neither physical contact between antagonists and pathogens nor fungal diffusion through the culture medium, the antifungal effects observed on pathogen mycelium growth could be attributed to the production of volatile organic compounds (VOCs) generated by the antagonists. The VOCs significantly inhibited the growth of all three tested pathogens compared to the control, albeit with a different rate. L1 strain also showed a curative effect; indeed when an antagonist-based-treatment was carried out twelve hours from inoculum, the incidence of blue mould and bitter rot was reduced by 38% and 50% respectively, while the greatest inhibition of grey mould was observed when fruit were treated with the antagonist six hours from the inoculum. In conclusion, A. pullulans L1 and L8 strains could be considered good candidates for the development of biofungicides for postharvest application in the pomefruit industry.
Mari M., Martini C., Spadoni A., Rouissi W., Bertolini P. (2012). Biocontrol of apple postharvest decay by Aureobasidium pullulans. POSTHARVEST BIOLOGY AND TECHNOLOGY, 73, 56-62 [10.1016/j.postharvbio.2012.05.014].
Biocontrol of apple postharvest decay by Aureobasidium pullulans
MARI, MARTA;MARTINI, CAMILLA;SPADONI, ALICE;ROUISSI, WAFA;BERTOLINI, PAOLO
2012
Abstract
The activity of two biological control agents, strains L1 and L8, previously identified as Aureobasidium pullulans, was tested for the first time in the same experiments on apple, artificially inoculated with Botrytis cinerea (grey mould), Colletotrichum acutatum (bitter rot) or Penicillium expansum (blue mould). The washed cells of antagonists controlled over 86% of three decays and the antagonist L1 seemed more efficient than L8. The cell concentration of both antagonists was highly correlated with their efficacy, the R2 ranging from 0.93 to 0.99. The highest concentration (108 CFU ml-1) of L1 and L8 provided the best control of B. cinerea, C. acutatum and P. expansum, although gray mould was completely inhibited also by a concentration one log lower (107 CFU ml-1). The population dynamic of L1 and L8 strains in ‘Gala’ apple increased almost eightfold during the first 48 h after treatment and remained elevated until 7 days, revealing that, although antagonists were isolated from carposhere of peach fruit, they showed good adaptation in other wound environments such as apple, making them suitable for pathogen control in a wide range of hosts. Preliminary in vitro trials were conducted in order to investigate the mechanisms of action of L1 and L8 strains. Both the washed cells showed a complete control of all three pathogens, while the culture filtrates and autoclaved cells were found to have had no significant inhibition on pathogens. In a dual culture dish assay, where there was neither physical contact between antagonists and pathogens nor fungal diffusion through the culture medium, the antifungal effects observed on pathogen mycelium growth could be attributed to the production of volatile organic compounds (VOCs) generated by the antagonists. The VOCs significantly inhibited the growth of all three tested pathogens compared to the control, albeit with a different rate. L1 strain also showed a curative effect; indeed when an antagonist-based-treatment was carried out twelve hours from inoculum, the incidence of blue mould and bitter rot was reduced by 38% and 50% respectively, while the greatest inhibition of grey mould was observed when fruit were treated with the antagonist six hours from the inoculum. In conclusion, A. pullulans L1 and L8 strains could be considered good candidates for the development of biofungicides for postharvest application in the pomefruit industry.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
