ANTAGONIST ACTIVITY BETWEEN AUREOBASIDIUM PULLULANS AND PENICILLIUM EXPANSUM IN PYRUS COMMUNIS L. ‘ROCHA’ – IMPLICATIONS ON THE RESISTANCE TO OXIDATIVE STRESS

Storage diseases, especially those caused by fungal pathogens, are responsible for substantial postharvest losses.
In consequence the use of fungicides became widespread, with health, ecological and economic negative effects.
However, as an alternative to fungicides, the use of antagonist yeasts appears to be a promising control technology.
In this context, the yeast-like fungus Aureobasidium pullulans has been proved to control some fruit postharvest pathogens, namely Penicillium expansum Link (blue mold – the major producer of the mycotoxin patulin) in pears.
This infection, usually initiated in wounds during harvest and packing, is often associated with free radicals synthesis (e.g., semiquinones and lipoperoxyl radicals) and reactive oxygen species (ROS). As reactive oxygen species and free radicals induce oxidative stress that can have many detrimental effects, any microorganism that attempts to colonize fresh wounds has to cope with this stress.
In this work, the action of A. pullulans to control the pathogen P. expansum was investigated, considering the hypothesis that the effectiveness of the antagonist could include the promotion of oxidative stress.
For this purpose ‘Rocha’ pears (Pyrus communis L.), harvested at the commercial maturity and stored for 5 months in cold chambers were used.
In fruits at the commercial maturity it was found that wounds inoculated with A. pullulans and infected with P. expansum showed lower loss of membrane selectivity from 24 h of inoculation onwards when compared with the pathogen alone.
Ethylene production increased after 24 h of inoculation in all treatments, with higher values in the tissues infected by P. expansum. Futhermore, H₂O₂ was higher in the tissues inoculated with both microorganisms in comparison to those infected with the pathogen.
It is suggested that the antagonist A. pullulans might promote a higher oxidative level with implications on the control of the pathogen action.

XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Postharvest Technology in the Global Market

F.J.C. Lidon, J.C. Ramalho, J.D. Arrabaça, I.P. Pais, C.S. Carvalho, M. Santos , M.G. Barreiro

Pyrus communis L. ‘Rocha’, Aureobasidium pullulans, Penicillium expansum

https://doi.org/10.17660/ActaHortic.2012.934.44