Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 7/27/1996
Publication Date: N/A
Technical Abstract: The fungal pathogen Cochliobolus carbonum race 1 produces HC-toxin, a cyclic peptide that is responsible for increased virulence on susceptible maize. Toxin synthesis requires a peptide synthetase encoded by the HTS1 gene in the Tox2 locus, which is absent from non-toxin-producing races. Hybridization analyses of several race 1 isolates with HTS1 sequences revealed that the Tox2 locus resided on one of two chromosomes, either 2.3 Mb or 4 Mb. These were distinguished from one another with chromosome specific markers from C. heterostrophus. Ascospore progeny from crosses of two isolates having HTS1 on different chromosomes were analyzed for virulence, toxin-producing ability, and chromosomal location of HTS1. All 43 progeny were found to be toxin producers, although they exhibited a range in toxigenic capacity. All progeny were phenotypically race 1, although lesion development was delayed for some of the progeny compared to othe parents. All progeny contained HTS1 sequences based on PCR amplification with gene-specific primers. CHEF gel analyses of several progeny revealed parental types with respect to the location of HTS1, but some showed non-parental chromosomal polymorphisms.