Telomere-associated RFLPs and electrophoretic karyotyping reveal lineage relationships among race-specific strains of Ustilago hordei

The inheritance of telomere-associated restriction fragment length polymorphisms (tel-RFLP) and chromosome-length polymorphisms (CLPs) were criteria used for the identification of strains of Ustilago hordei that form a direct lineage. Teliospore collections of race 8 strains and strains reported to be derived from race 8 through inbreeding were used in these analyses. None of the race 8 strains examined in this study, representing three consecutive inbred generations, was polymorphic for any terminal BamHI and Bg/II chromosomal loci, nor did they have any apparent CLPs. Strains from a teliospore collection obtained in 1971 and designated 447, representing the first inbred generation of race 8 strains and a shift to increased virulence on cultivar Hannchen, had tel-RFLP arrays indistinguishable from the race 8 strains isolated in this study; and they had no obvious CLPs. Strains from the presumed second inbred generation, the 1279 teliospore line, which was pathogenic on six additional cultivars, had numerous CLPs and a tel-RFLP array that differed from race 8 strains at more than 50% of the terminal chromosomal BamHI and Bg/II restriction sites. The tel-RFLP array of each 1279 strain was identical and indistinguishable from the arrays of strains representing races 10 and 13, indicating that they share a direct lineage. A race 14 strain, also presumed to be derived from race 8 strains by inbreeding, had a unique tel-RFLP array and an electrophoretic karyotype that distinguished it from all other strains. The tel-RFLP arrays alone eliminate the 1279 and race 14 strains from being direct descendants from race 8 strains by inbreeding and suggest that this approach can identify a strain lineage among other inbred sexually reproducing fungi, or isolates that comprise different asexual clonal populations.