SUGAR VARIATION IN ‘ROCHA’ PEARS AND PENICILLIUM EXPANSUM REDUCTION BY AUREOBASIDIUM PULLULANS

In an attempt to clarify the mode of action of the antagonist Aureobasidium pullulans, which is being investigated for its ability to control the postharvest infections of ‘Rocha’ pears by the pathogen Penicillium expansum and considering the possibility of competition for sugars, we studied the quantitative variation of fructose, sucrose, sorbitol and glucose in fruits at 3 harvest dates, cold stored (-0.5 to 0°C, 95% RH) and infected 1, 3 and 5 months after harvest.
The application of the antagonist reduced the infections in 31 and 34% of the fruits inoculated with the pathogen 1 and 3 months, respectively, after harvest, while the infection performed on the 5^th month showed only 20% reduction.
The efficacy of the antagonist, expressed in the reduction of lesion diameters, reached values of 60, 64 and 63% in fruits infected 1, 3 and 5 months after harvest, respectively.
From the 4 sugars analyzed only fructose was apparently reduced in fruits at the 3 infection dates.
The application of Aureobasidium pullulans seems to oppose this reduction.
Similar effects, although with lower values, can be detected in the other sugars but mainly in fruits infected 1 month after harvest.
At this date, fruits from the commercial harvest (3^rd harvest) with application of the pathogen showed a reduction of 22% in fructose, of 26% in sorbitol and of 29% in glucose.
However, the application of the antagonist, prior to the inoculation of the pathogen, changed these values to 9.9 and 8.0%. The results obtained, so far, indicate the possibility of Aureobasidium pullulans controling Penicillium expansum by conditioning its consumption of certain sugars, but this work requires further development.

X International Pear Symposium

I.P. Pais, A.P. Ramos, M.G. Barreiro, M.J. Silva

fructose, sucrose, glucose, sorbitol, biocontrol, antagonist

https://doi.org/10.17660/ActaHortic.2008.800.126