Genetic characterization of the nonconventional yeast Hansenula anomala

We describe genetic, molecular and taxonomic characteristics of the yeast H ansenula anomala. Pulsed-field gel electrophoresis of chromosomal DNAs from 19 H. anomala strains and related species indicated that H. anomala had a clearly different karyotype. Chromosome length polymorphism of the H. anoma la strains was independent of their geographic origin and source of isolati on. The strains were classified into four groups of similar karyotypes and one strain showed a unique profile. The sizes of chromosomes ranged from 85 0 to 3500 kb in different strains. The haploid chromosome number of H. anom ala is at least nine. We have found RAPD primers discriminating at both the species and strain levels. All the primers tested except the M13 core sequ ence generated unique patterns with most strains. The results indicate the usefulness of PCR analysis with primer M13 for identification of the H. ano mala species. Screening of the CBS (Utrecht) collection strains of H. anoma la showed that they are rather difficult objects for genetic hybridization analysis. The strains have low fertility, viz. very poor sporulation, low m ating type activities and, as a rule, nonviable ascospores. The majority of the hybrids obtained are polyploid, probably tetraploid, as judged by the segregation of control auxotrophic markers. Nevertheless, some monosporic c ultures of the strains studied, including the biocontrol yeast J121, formed diploid hybrids with regular meiotic segregation of control auxotrophic ma rkers. As a rule, H. anomala isolates are homothallic, showing delayed self -diploidization. Rare stable heterothallic strains of H. anomala also occur . (C) 2001 Editions; scientifiques et medicales Elsevier SAS.