Abstract
Alternaria alternata Japanese pear pathotype produces a host-specific toxin (AK-toxin) as a determinant of host-specific pathogenicity. By employing a competitive hybridization procedure, specific transcripts were detected in a toxin producer, but not in its toxin-less avirulent mutant. Poly(A)+RNA fraction from the toxin producer was cloned as cDNA by Escherichia coli using pBR322 and screened by the competitive hybridization. The cDNA clones were obtained from transcripts which present in larger quantity in the producer than in its toxin-less mutant. Dot blot hybridization analysis by the cDNAs showed that there was a correlation between the amount of the specific RNAs and toxin productivity in several A. alternata isolates.
