1993 - Mycological Society of America

Monday, 9.30 am
Life history features associated with the
evolution of mutualism in the genus Omphalina
(Basidiomycota, Agaricales)
COG Lutzoni and Rytas Vilgalys. Dept. of Botany, Duke
Univ., Durham, NC 27708-0339.
Virtually nothing is known about life history features associated with a
transition between a non-mutualistic state and a mutualistic nutritional
mode, and the consequences of mutualism on the evolution of the mycobiont
(fungal partner) and the photobiont (algal and/or cyanobacterial
partners, or vascular plant partner). The genus Omphalina has
many properties which make it an ideal model system to conduct coevolutionary
studies on mycobiont-photobiont mutualistic associations
(lichens and mycorrhizae). The phylogeny of the genus Omphalina, including
non-lichenized and lichen-forming species, was estimated
independently using morphological data and sequences from the
nudear-encoded 25s rRNA gene. The resulting trees support the following
interpretation for the orinin and evolution of lichenization in
Omphnlina: i) the lichenized species of Omphalina and stirps ericetorum
are monophyletic, 2) the lichenized state is derived from a non-lichenized
state, 3) lichenization occurred only once during evolution of
.Omphalina and has been retained by subsequent generations and
species, 4) the first morphological innovation resulting from the mycobiont-photobiont
coevolution was the formation of a globular mtose
thallus followed by the formation of a squamulose thallus. A number
of life history features of Omphalinn species appear to be associated
with the transition to a lichenized state. These include the loss of clamp
connections and tetrasporic basidia, coupled with the lost ability to
grow in axenic culture. Another life history pattern associated with
lichenization is the transition from a typically dikaryotic stage to a
uninudeate state.
Tuesday, 113 am
Observation of fusiform rust galls with magnetic
resonance microscopy
J. S. MacFall, G. A. Johnson, and *P. C. S~aine. Dept. of Radiology,
Duke Univ., Durham, NC 27710 and *USDA Forest
Service, 20 Green Street, Athens, GA 30602.
Ten-month-old sedlings of loblolly and slash pine were artificially
inoculated with Crmarthz quercuum (Berk) Miyabe ex Shirai f. sp.
fusiforme. Stems were excised at the root collar i d placed into either
DI water or water containing gadopentate dimeglurnine. Following
transpirational uptake, galls or healthy stem segments were examined
by high resolution magnetic resonance microscopy. Regions of differential
water distribution and transport could be determined in images
both of healthy and galled stems. In well developed galls, secondary
xylem which appeared functional in water transport was greater in
diameter than in symptomless stems. In the center of well developed
galls tissues appeared highly organized. Disruption of transport could
be observed in the stem transition region from heathy stem into galled
tissue, with disruption of cellular organization. Concurrent with the
disruption of the secondary xylem, the cortical parenchyma appeared
to be pushed out by a rapid proliferation of secondary phloem. Similar
secondary phloem was not observed in symptomless stems of the same
age. the cambial layer appeared fully contiguous between healthy and
galled stem regions. This is a preliminary study describing the use of
magnetic resonance imaging to describe changes in anatomy and
water transport/distribution with development of fusiform rust stems
galls in pine.
Poster C16; Sunday pm
Towards the genetic basis of somatic
incompatibility in Plarrotus ostreatus
MY~QLUXU and Rytas Vilgalys. Dept. of Zoology, Duke Univ.,
D'urham, NC 277084325, and Dept. of Botany, Duke Univ.,
Durham, NC 27708.
The ability to recognize and reject non-self through somatic incompati-
bility has been observed in many basidiomycete populations, and is
thought to allow the persistence of discrete individuals by limiting
vegetative fusions between hyphae of genetically distinct mycelia.
Although the extent to which somatic incompatibility can maintain
individuality should depend in part on the genetic basis of the rejec-
tion response, little is known about the genetics of somatic incompati-
bility in basidiomycetes. To address this issue, we have begun a series
of backcross lines using five dikaryotic isolates of the oyster mushroom
Phrotus ostreatus and a number of monokaryotic from each
line. Prelrrmnary results from one of the sets of backaoss lines has
shown that the first generation backcross dlkaryons fall into at least
five discrete somatic incompatibility groups, one of which is compat-
ible with the parental dikaryon. Work with RAPD markers has shown
that compatible backcross dikaryons within these groups are not
genetically identical. Additional pairings involving the original back-
cross dikaryons and their offspring suggest that these somatic incom-
patibility factors are heritable. Results from the other sets of backcross
lines will also be presented, as well as the implications of these
findings for the study of basidiomycete population biology.
Sunday,ll:15 am
Life histories of three undescribed species
of Pym'diophora occurring on beached marine algae
David Malloch and Meredith Blackwell. Dept. of Botany, Univ.
of Toronto, Toronto, Ontario, M5S 3B2 and Dept. of Botany,
Louisiana State Univ., Baton Rouge, LA, 70803.
Beached marine algae (wrack) present a nutrient-rich substrate for prokaryotes,
fungi and invertebrates. We collected wrack from several
localities in California and New Brunswick and found three hyphomycetes
to be consistently present Acremonium sp., ScoIecobasidium salinum
and Sipidea mnrinn. California material usually supported
Asfemqces mciatus as well. In spite of this low diversity of colonizing
fungi, at least three mycoparasitic species of ~yxidiophoi also commonly
occurred. Cultural studies of the Pyxkiiophora species demonstra&
them to be contact parasites capable of parasitizing all of the
common saprotrophs in their habitat. Although mycoparasitism has
been suspected in species of Pyxidiophora, this is the first time that it
has been confirmed in the laboratory. In common with those of other
species of Pyxidiophora, ascospores of the three new species appear to
be dispexsed by phoretic mites and to germinate by repetition during
transit. The occurrence of three dearly undesaibed species of miophora
on wrack and the similarity between the life histories of these
and other species of this genus suggests that Pyndiophom is a relatively
large genus of ascomycetes occurring in a diversity of habitats.
Poster B5; Sunday pm
Immunocytological localization of chitinase
in mucoraceous host and norhost fungi
of a mycoparasite
M. S. Mmocha and A. S. Sahai. Dept. of Biological Sciences,
Brock Univ., St Catharines, Ont L2S 3A1, Canada.
Antiserum raised against a purified chitinase obtained from the micro-
soma1 fraction of a mucoraceous fungus, Choanephora cucurbitmum, a
susceptiile host, was used to localize chitinase in host (Morfierella
pusilla), resistant host (Phascolomyces articulosus), nonhost (Mortierella