DISCUSSION
Spore germination and leaf penetration by the various
E. turcicum isolates evaluated in this study were similar
in resistant and susceptible reactions, which confirms
the findings of Jennings & Ullstrup (1957) and Lilian et
al., (2002). Hilu & Hooker (1964) reported that about
90% of all penetrations are direct and typically occur
over the juncture of vertical epidermal walls whereas
10% of penetrations are stomatal. Our study had similar
findings with about 85% of all the isolates penetrating
directly. The pathogen requires an appressorium to be
able to penetrate the host (Jennings & Ullstrup, 1957),
which probably explains why all the isolates were
observed to form appressoria. Other pathogens, e.g.
Leptosphaeria maculans have been reported to have
similar penetration mechanisms (Naseri et al., 2008).
Penetration elicited localized host responses
resulting in macroscopically visible flecks as previously