1993 - Mycological Society of America

kangaroo rats and many invertebrate detritivores. Burrows and dens PAGE, employing in sifu renaturation, in order to determine how
of many animals are likely to be important sites of microbial activity many kinds of cellulases Achlya produces and whether the induced
and decomposition, esp&ally in arid environments.
enzykes are different from vegetative ones. Si bands of activity were
detected in filtrates from vegetative culhues. These have approximate
molecular weights of 205,97,74,34,28, and 24 kD, the strongest being
Wednesday, 8:45 am 34 kD. Bands of similar mobility were detected in antheridiol-induced
and peptone-induced cultures, with the strongest being 34 and 24 kD,
Peridipes arachidis, a conidial anamorph
and 97 and 34 kD, respecbvely. The major conclusion is that the celluof
the peanut rust fungus (Uredinales)
lases produced during antheridiol-induced and amino acid-induced
branching are not forms unique to those morphogenetic events, but are
Joe F. Hgmen and Pablo Buriticb. Dept. of Botany and Plant
enzymes also seaeted during vegetative growth. The elevated activity
Pathology, Purdue Univ., West Lafayette, IN 47907-1155 and
of specific enzymes in the induced cultures implies that events of
Institute Colombiano Agropequario, Bogoti, Colombia.
branch initiation in induced and vegetative h$hae may not be as
equal as the apparent similarity of their respective branch initials
might suggest.
The rust disease of peanuts (Arachis hypogaen) is important worldwide
but the proper classification of the causal fungus remains unresolved.
Puccinia machidis is the name universally used but the fungus is not a
Puccinia. Perhaps it is a Soratam? On domesticated peanuts a conidial
anamorph occurs widely but a teleomorph has been found only rarely.
Wild Arachis spp. in Brazil commonly have telia. The hosts that basidi-
ospores infect-(presumably Arachis spp.) and structures produced from
these infections are unknown. A membranous mridium and uedicel-
late spores characterize the conidiomata for which we propose P di-
pes as a new anamorphic genus for Uredinales and Peridipes machidis
for the peanut rust uredinia (conidiomata).
Monday, 8:00 am
Sporocarp ontogeny in Panus:
evolution and classification
. . be& 5. Murakarni, and +A. Tsuneda. Dept. of Biology,
Framingham State College, Framingham, MA 01701,
Tottori Mycological Institute, 211 Kokoge, Tottori 689-11
Japan.
We observed ontogeny of cultured sporocarps of Panus conchnfus, P.
rudis, and P.fulvus using scanning electron microscopy. Early hymenophore
differentiation in Panus is accomplished by periclinal growth of
context hyphae below a dosed pallisade of immature hymenial elements,
leading to a cantharelloih appearance. Development of the
Panw hyrnenophore is qualitatively different from that previously
observed in &tinus. This supports the view that the lamellae of Panus
and Loltinus are not homo1op:ous. Panus conchatus and P. rudis have
short stipes and develop diredly from the block of spawn. In contrast,
P.fUIms has an elongate stipe, develops from a pseudosderotium, and
has the ability to regenerate cut p&rdiurn apices. Panus rudis was
unique among the three species in its possession of an ephemeral
partial veil. Developmental and morphological variation in Panus
results from nonterminal insertions or deletions in developmental
programs, as well as heterochronic changes in stipe development.
Poster A3; Sunday pm
An electrophoretic comparison of cellulases
secreted during sexual morphogenesis
and vegetative growth of Achlya ambisexualis
Terry W. Hill. Dept. of Biology, Rhodes College, Memphis, TN
38112.
Male strains of the water mold Achlya mnbisexdis respond to the
steroidal sex hormone antheridiol by producing an abundance of
antheridial branches. The event is marked by a sharp rise in the rate of
seuetion of endocellulases, to a level some 56 timi that associated
with vegetative growth. Branches of initially similar form and abun-
dance can also be induced by mixtures of amino acids, and this, too, is
accompanied by an increase in cellulase secretion. These observations
have led to a hypothesis that cellulases play a role in localized restruc-
turing of the hyphal wall at sites of branch initiation, and possibly also
in events of tip growth. Secreted cellulases were studied by SDS-
Wednesday, 10:00 am
Increased secretion of endoglucanases during
yeast-like growth of Achlya
Terry W. Hill and Nicholas P. Money. Dept. of Biology, Rhodes
College, Memphis, TN 38112, and Dept. of Biochemistry,
Colorado State Univ., Fort Collins, CO 80523.
Under conditions of chronic osmotic stress, two species of the oomycete
genus Achlya have been shown to grow as hyphae, with less than
10% of their normal turgor pressure. When the osmotic pressure of the
growth medium is raised to almost 2.0 MPa, no turgor can be measured,
and the water mold grows with a yeast-like morphology. The
changes in turgor and growth form are associated with a reduction in
strength of the cell wall. Growth in the absence of measurable turgor is
also associated with an increased rate of secretion of endoglucanases,
assayed using CM-cellulose as a substrate. The behavior is exhibited
when osmotic pressure is controlled with sucrose, sorbitol or polyethylene
glycol-400. By contrast, the related species Saprolegnia fern
maintains a normal tip-growing form, even in the absence of measurable
turgor, and sh&s only a small increase in endoglucanase activity
with increasing medium osmotic pressure. The maximum enzvme
activity in ~ ~ilegnia media is as iittle as 3% of the level in id&tically
grown yeast-like Adrlya cultures;when expressed as units/mg of total
cell protein. Electrophoresis of the endoglucanases secreted by yeastlike
cells of Achlya reveals six major bands with the same mobility as
those found in the medium of tip-growing Achlya hyphae, indicating
that no specialized pattern of endoglucanase secretion is associated
with the morphological change. These 0b~eNations are consistent with
the proposed role of endoglucanases in the control of wall strength.
Poster B10; Sunday pm
Effects of Enterobacter cloaceae infection in corn
Dorothv M. Hinton, Charles W. Bacon, and Rita M. Bennett.
USDA-ARS Toxicology and Mycotoxin Research Unit, Richard
B. Russell Research Center, Athens, GA 30613.
Enterobacter cloacae, a nitrogen-fixing bacterium was found to be a
natural endophybc symbiont in seedling roots of an Italian corn cultivar.
Ultrastructural examination of the roots showed a proliferation of
bacterial cells within intercellular spaces of cells in the Artex and stele.
There was no apparent degeneration of host cells in the presence of the
bacterium. Enterobacter cloacae was shown to inhibit the growth of
Fusarium monilifonne, a seedborne pathogen of corn and one of the
causes of seedling blight of corn. The bacterium exhibited antibiotic
properties in the presence of six isolates of F. monilifonne on nutrient
agar. The bacterium was transferred into corn roots of other corn cultiv
k which were planted in Fusmium-amended soil. These cultivars
exhibited an increase in seed germination and seedling vigor compared
to the control group. The results from this study suggest that E.
cloacne has biocontrol potential for F. monilifm in corn.