Investigations on Tomato Anthracnose. I. The Influence of Carbohydrates on the Growth ofColletotrichum Coccodes(Wallr.) Hughes

Abstract

The author has studied the influence of seven carbohydrates known to occur in the ripe tomato fruit and of a mixture of two of them on growth in Colletotrichum coccodes. For the investigation five monoconidial isolates from four cultures of different origin have been used. The carbohydrates were tested at indentical carbon levels in a mineral medium buffered at pH ca. 6.0 and mycelial growth was determined at intervals of 5 days after seeding. It has been shown that the five isolates can all utilize the carbohydrates although at a different rate; maximum mycelium growth in each isolate requires different incubation times. In general, d-xylose, d-mannose and d-galactose are promptly utilized (10 days), whilst the remaining sugars and the mixture d-glucose + d-levulose are utilized more slowly. With d-galactose, and probably with d-mannose, a lag phase is observed. As to the pH drop in the substrate during growth, it has been observed that pH drops to ca.3.0 in three strains, which appear to be more virulent on ripe tomato fruits. A discoloration of the medium has also been observed with the same three strains.