|Abstract or Summary
- Electrophoretic karyotypes were obtained from intact cells of four wild
type strains of Tilletia caries and T. controversa, and 5 inter specific hybrid
progeny using clamped homogeneous electric field, pulsed field gel
electrophoresis (CHEF PFGE). Each karyotype was polymorphic and unique
relative to the other strains. However, the relative size range of all the
chromosomes was consistent and typically ranged from approximately 850 to
4,490 kilobasepairs (Kb) for all strains, accept for two atypically small
chromosomes in one strain of T. caries. The minimum estimated number of
chromosomes was 19 or 20 for strains of T. controversa, 14 to 20 for T. caries, and
from 19 to 22 for the hybrid progeny. The minimum estimated total genome size
ranged from 28 to 39 megabasepairs (mb) for T. caries, 34 to 40 mb for T.
controversa, and 36 to 42 mb for the hybrid progeny.
Southern hybridization analysis performed with cloned, single copy
homologous DNA fragments identified a single similar-sized chromosome in all
strains. The maximum percent variability of the linkage groups defined by the
single copy probes was 10% or less. The rDNA from Neurospora crassa
hybridized with 2 or 3 chromosomes in the wild type stains of T. caries and T.
controversa, and with 1 to 3 chromosomes in the hybrid progeny. The maximum
percent variability among chromosomes that hybridized with the rDNA probe
ranged from 35 to 40%. Either 1 or 2 chromosomes were identified by the single
copy actin gene from Aspergillus nidulans, and the maximum percent variability
ranged from 4 to 14% for these chromosomes. It was not possible to differentiate
between the karyotypes of strains of either T. caries or T. controversa using the
physical appearance of the karyotypes, the number and sizes of chromosomes,
the genome sizes, or by Southern hybridization analysis. Analysis of the
karyotypes of the hybrid progeny revealed that all were unique relative to each
other and the parental stains, providing circumstantial evidence for the presence
of recombinant chromosomes. That the genome size and chromosomes numbers
of the hybrid progeny were similar to their monokaryotic parental strains
strongly argues that the reduction division stage of meiosis had occurred.
Seven teliospore samples from Oregon and Turkey were examined for
their germination and autofluorescence properties. The teliospore samples were
analyzed to determine if low temperature germination (0-4° C) and
autofluorescing spore-wall reticulations associated with spores of T. controversa
were usually linked. Two of the seven teliospore samples showed these
characteristics to be unlinked.
In an attempt to clone the mating type genes of T. caries and T.
controversa, total genomic DNA was probed with a fragment of the b west
mating type gene from Ustilago hordei. Although single 1.4 kb BamHI fragment
from both pathogens was cloned by homology and sequenced, its role in mating
type function remains uncertain.