Thirteen naturally-occurring isolates of P. oryzae
varied in tolerance to Blasticidin-S. A similar observation
has been reported (8). Since these isolates- were selected
randomly from the blast nursery where fungicides were
not used, it is presumed that variation in tolerance may
occur in natural populations of P. oryzae. This may
reflect the variability of the fungus itself and/ or
mechanisms that operate in nature, regardless of the
presence or absence of the chemical. No correlations were
found between pathogenicity of isolates of P. oryzae and
tolerance to Blasticidin-S, as has been observed in
Rhizoctonia solani tolerant to chemicals (4). However,
Shatla et al. (7) reported some correlation between the
pathogenicity of R. solani isolates and tolerance to penta-