s - Mycological Society of America

G. May and P.3. Pukkila Dept. of Siology,
University of North Carolina, Chapel Hill, NC
27599-3280..
Molecular cloning and functional analyses of the AJ
mating type factor of Coprinus cinereus.
We have isolated a cosmid clone with the entire 3
mating type factor of Coprinus cinere-us.
Subcloninc and transformatlon experiments reveal
that: 1. both the 4 and the 6 subunits are present
on this clone, 2. the d and' the 8 subunits are
functionally redundant but not structurally similar
and 3. that a cell activated for k controlled
sequences is no longer able to accept nuclei in
mating although it can donate nuclei to a strain
.compatible at 8.
We want to understand the evolutionary history of
different a1 leles. Genomic DNAs digested with
various enzymes were blotted to nylon membranes and
Southern hybridizations were made using large
fragment o( and P (3.8 and 5.5 kb. respectively)
probes as well as probes covering the regions
between and outside of the subunits. These
preliminary results indicate that rearrangements
and length mutations are rampant and complex in the
regions of & , b and in the DNA between the
subunits while few such changes occur outside this
area. Suprisingly, though o( and 6 are very
tightly linked, we find very similar u and P
alleles occurring independently of one another in
isolates from different geographic locations (e.g.
Japan and N.Carolina). Results will be compared to
those obtaineG with mating type genes of other
filamentous fungi.
J.k. KcCAIN and C.J. MIROCHA. Dept. of Plant
Pathology, Univ. o! Minnesota, St. Paul, 55108.
Fungi isoiated from computer microdiskettes.
Standard density 5 1/4-inch disk~ttes that
ma1 functioned in the computer were examined for the
cause of failure. Fungal hyphae were found on the
surface of some diskettes obtained from colleagues in
tropical countries. Fungi isolated on agar from the
diskettes included species of Alternaria, As~erqillus,
E~icoccum, Paecilomvces, Penicillium, and lrichoderma.
Diskettes buried for three weeks outdoors in garden
soil were colonized by species of Fusarium,
Niqrosoora, and Trichoderma. These fungi and other
species available in the laboratory were used to
inoculate clean test samples, to approximate Koch's
postul ates. Most species successfully colonized the
diskettes within 3-4 days on agar at 25 or 32 C, 100%
RH. Penicillium species dominated all others in mixed
inoculations, although species of Chaetomium,
Mvrothecium, Stachvbotrvs, and the other listed genera
sporulated heavily in axenic culture on diskettes.
Growth of all fungi was restricted to the 2-3 m thick
surface emulsion of iron oxide with its organic
dispersants and plasticizers, with hyphae not
penetrating the mylar core of the diskettes.
,B. A. MCDOK.4m. Department of Plant Pathology and
Microbiology, Texas A&M University, College Station, TX
77843-2132.
DNA restriction fragment and chromosome polymorphisms
in a Septoria trifiei population.
Ten anonymous DNA probes were used to measure the amount
and distribution of genetic variation in nuclear DNA among
a sample of 93 Septoria tritici iteleomorph Mycosphaerella
graminicola) isolates collected from a single wheat field.
Nine of the probes detected restriction fragment length
polymorphisms (RFLPs) at single-copy RFLP loci. The DNA
fingerprint~ng probe pSTL40, which hybridized to 4-10
hypervarioble RFLP loci, was used to assess clonal
distribution and diversity. Identical clones were clustered in
the field. All probes detected a high level of genetic variation
distributed on a fine scale. Different pycnidia from the same
lesion had different haplotypes in 45% of the comparisons.
Genome rearrangements apparently occurred at a high
frequency. Two of the single-copy probes detected deletions.
Transverse alternating field electrophoresis showed that
differences in chromosome size were common among the
isolates. Data suggest that S. tritici populations possess a high
level of genetic variability distributed in a fine-scaled mosaic
on a microgeographical scale.
D. J. McLwgMn. J. C. Doubl&s, and H. Lu. Dept. of
Plant Biology. University of Minnesota, St. Paul,
MN 55108. Mitosis and the phylogeny of the
basidiomycete Pachnocvbe ferrualnea.
The gasteroid heterobasidiomycete eachnocvbe
ferruainea produces holobasidia. Along with other
simple-septate gasteroid taxa it has been
classified in the Atractiellales, most of which
form auriculariaceous basidia. Its affinities with
these organisms and with ballistosporic species
remains unclear. Ultrastructural analysis of
mitosis and the spindle pole body (SFB) provides
clues to its relationships. Mitosis occurs in an
acropetal wave in multinucleate apical cells of
the mycelium. The interphase SPB consists of
two connected discs. During metaphase the nuclei
undergo a characteristic reorientation, the SPBs
reside in a distinct polar fenestration in the
otherwise intact nuclear envelope, and an ER cap
encloses the pole. At telophase the SPB becomes
displaced from the nucleus and a discrete bundle
of astral microtubules develops. The significance
of these findings will be discussed.
MEREDITH. J. and R.C. ANDERSON. Biology Department.
Illinois State University. Normal. IL 61761.
The influence of varied microbial substrate
conditions on the growth and mycorrhizal
colonization of little bluestem (Schizachvrium
sco~arium) .
Plants were grown in three substrates (1) autoclaved
soil, (2) autoclaved soil to which a VAM fungal-free
filtrate of nonsterile soil was added and (3) non-
sterile so:;. Preliminary studies revealed that