Genetic mapping of telomeric DNA sequences in the maize pathogen Cochliobolus heterostrophus

Numerous polymorphic bands were observed when genomic DNA of Cochliobolus heterostrophus was cut with restriction enzymes and hybridized with a telomere-specific probe. Bal31 digestion demonstrated that the majority of the bands were from the chromosome termini and thus constitute telomeres. However, numerous hybridizing sequences in the strain B30.A3.R.45 were Bal31 exonuclease-insensitive and thus located at least 600 bases internal to the chromosome ends. Segregation analysis of the polymorphic bands identified nine telomeres; seven were linked to other markers and thus permitted the proper orientation of linkage groups with respect to their chromosome ends. Three internal, telomere-homologous sequences, at least one of which may be subtelomeric, were also mapped.