The ability of Botrytis cinerea to produce
cutinolytic, pectolytic and cellulolytic enzymes was re-examined
in vivo and in vitro. In
liquid culture, B. cinerea produced both constitutive and
inductive forms of hydrolytic enzymes. The constitutive levels were 44
mU,
720 mU, 1820 mU, 12·0 U and 22·4 mU for cutin esterase,
endopolygalacturonase (endoPG), exopolygalacturonase (exoPG), pectin
methyl esterase (PME) and pectate lyase (PL), respectively. Unlike
the other enzymes, however, carboxymethyl cellulase (CMCase)
production was found to be entirely inducible. The enzymes secreted
at the germination and germ-tube growth stages, and during
subsequent disease development, were quantified simultaneously. Complete
germination was observed within 9 h of incubation of
B. cinerea on the surface of bean leaves and disease symptoms
gradually increased during days 1–6 of the incubation. Significant
amounts of all hydrolytic enzymes studied in the early hours and
monitored during 6 d of incubation were detected, supporting the
possibility of a major role for the enzymes produced by B. cinerea
in the development of disease. The amount of cutinase was found
to be uniform from the beginning, indicating that this enzyme may
have an important role in penetrating the impervious cutin layer.
The exoPG level increased from the beginning of incubation whereas that
of endoPG started to rise later. PL and PME were also
detected on the leaf surfaces. The patterns of in vitro
production of exoPG, endoPG and PL correlated with the in vivo
production of
these enzymes, but there was only partial correlation in the production
of PME and no correlation in the patterns of cutinase and
CMCase production.