Abstract :
Pre-penetration and early penetration phases of two
pathogenic strains of Colletotrichum gloeosporioides (HM
502, HM 514) from Zaire were investigated quantitatively
on four Stylosanthes guianensis genotypes (cv. Schofield,
cv. Graham, Cl AT 184 and C! AT 10136) of various levels
of susceptibility.
The results demonstrated control of the rates and type
of conidial germination by the fungus, influenced to a
lesser extent by the host genotype. Cell reactions were
visible as papillae and cytoplasmic aggregations closely
associated with the penetration peg. No fungal growth
was observed when deposits of papillae occurred under
appressoria-forming infection pegs, whereas the effect of
the cytoplasmic aggregations varied according to the host
genotype. In the interactions with strain HM 502, the
highest rates of plant reaction were recorded on the resistant
CIAT 184 genotype, while the highest level of penetration
without reaction was observed on the most
susceptible cv. Schofield. Cytoplasmic aggregations were
also observed under a few ungerminated appressoria on
this genotype. Differences were thus detected in the rates
and types of conidial germination, in the rates and types
of cell reactions under appressoria and in the appressorial
penetration rates without cell reactions. However, these
differences did not completely explain the range of macroscopic
symptoms observed on the various genotypes
