The relationship between hyphal growth and branching of the
grape pathogen Botrytis cinerea was determined on solid media
containing either glucose, fructose, sucrose, tartaric acid or malic
acid. The concentration of the carbon source had little effect on
specific growth rate or the specific rate of tip formation, but growth
was inhibited at high concentrations of tartaric and malic acids.
Hyphal growth unit length and hyphal extension rate increased with
increasing sugar concentration and were always significantly greater
than values on tartaric or malic acids. The data provide an
explanation for colonization patterns of grape berries. Growth will be
poor during the period from setting to the onset of ripening, when
organic acids are the main carbon source produced by the berry.
Following the onset of ripening, the production of sugars provides
more favourable carbon sources for the fungus, enabling achievement of
higher specific growth rates, greater hyphal extension rates and,
hence, greater colonizing potential.