Fungal growth and ergosterol content in tomato fruits infected by fungi

Tomato fruits, cv. Red river, were artificially inoculated under controllod consitions with the aim of testing in vitro the invasive ability of several fungal species and their effect on microbiological quality. Seven species most frequently associated with spoiled tomatoes were used: Alternaria alternata, Botrytis cinerea, Fusarium oxysporum, Geotrichum candidum, Phoma lycopersici, Rhizoctonia solani and Rhizopus nigricans. Fungal effect was checked at days 1, 2, 4 and 8 after inoculation using three methods: volume of spoiled tomato, Howard Mold Count and the anlytical determination of ergosterol. The results showed significant differences in the parameters measured in relation to the fungi considered, the time of incubation and their interaction. A significant correlation was found between the quality parameters measured with the three evaluation methods but, with a percentage of variation explained by the regression of about 50%. This implies that the relationship between qualitative parameters can be computed, but with a high level of uncertainty (a wide confidence interval). Therefore, it seems only theoretically possible to specify an "alert" value with this procedure.