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were transferred to minimal plates from two radii. From the remaining six radii three mycelial blocks from the outer, middle and central portions of the colony were .transferred to minimal media and minimal media supplemented with one of the parental require- ments. Results indicate that heterokaryotic regions do not extend beyond the central portion of the colony In sane cases both auxotrophic canponents were uni- formly distributed in the outer region of the colony. In other heterokaryons only one parenk was found at the periphery of the colony. 'Ihis study suggests that the auxotrophic portion of the colony is nutritionally supplemented by a smaller prototrophic region at the center of the colony. T.E. CHASE. J. TAYLOR. F.W. COBB. JR.. P.T. SPIETH, and W.J. OTROSINA. University of California. Berkeley 94720 and USDA-Forest Service Pacific Southwest Forest and Range Experiment Station. Berkeley. CA 94701. Mitochondria1 DNA differences among biological species of Heterobasidion annosum. H. annosum, a basidiomycete root- and butt-rot fungus of conifers. contains several biological species (intersterility groups). Previous mating tests and isozyme studies (which assess primarily nuclear encoded genes) indicate that the S and P groups in the western United States have undergone a high degree of genetic divergence and that there is no gene flow between them. In order to assess the cytoplasmic genome, we analyzed mitochondria1 DNA restriction fragment length polymorphisms (mtDNA RFLPs) with a rapid screening method employing the Hae 111 restriction endonuclease. RFLP patterns for S group strains from North America were clearly different from P group strains from North America. In addition. differences in Rm9 patterns exist between European and North American S group strains. These results are consistent with our earlier studies based on nuclear genes. both of which demonstrated that the biological species of K. annosum represent well separated gene pools. T.E. CHASE and R.C. ULLRICH. Plant Pathology Dept.. University of California, Berkeley 94720 and Botany Dept.. University of Vermont. Burlington 05405. "Illegitimate" mating in Heterobasidion annosum. In previous studies we showed that intersterility in H. annosum is regulated by five genes. designated Vl+/Vl-. V2+/V2-. V3+/V3-. S+/e, P+/k. Any two homokaryotic strains are interfertile (able to form dikaryons) if they are homoallelic for + alleles at one or more of these loci and also carry compatible mating-type alleles. Cases in which intersterile pairings give rise to putative dikaryons are reported here. Such "illegitimate" mating occurs inconsistently, but is more frequent when pairings are incubated for a prolonged (30 day) period rather than the normal 10 day period prior to the routine subculturing step which is part of the mating protocol. Analysis of progeny derived from an illegitimate mating suggest a genetic model in which parasexuality may play a role in generating nuclei containing recombinant genotypes which are interfertile and compatible with one of the progenitor nuclei. Illegitimate mating thus represents a special case of intersterile and interfertile mating behavior. because the dikaryons resulting from such events contain two genomes with + alleles in common at at least one of the five loci. Ability to engage in illegitimate mating is a strain-specific characteristic but does not appear to be inherited as a simple Mendelian trait. A. W. CHEN. Russell Res. Ctr. PPRU. P.O. Box 5677. Athens, CA 30613. Transition to reproduction in Fanodema Jucidum and other basidiomycetes. Six stages (grovth in vegetative medium, grovth in fruiting medium, transition to basidiocarp primordium formation, stipe formation, growth of pileus, and tube & spore formation) are identified in G. lucidum during transition to sexual reproduction. Cultures continue to grow vegetatively, or only abortive fruiting bodies (vithout tube & spore formation) will be obtained if proper cultural parameters are not maintained. These parameters include medium components (carbon source, C/N ratio, thia- mine, pH and texture), and abiotic factors for incubation (temperature, light/darkness. COJventi- lation, and moisture). Methodology on fruiting induction in s. lucidum is reviewed. Usually shifting from groving inoculum or spawn in vegetative medium to fruiting medium containing more complex carbohy- drates is involved. Of critical importance are: 1) transition to basidiocarp-primordium formation, and 2) transition to tube h spore formation. Damaging or killing cells in fruiting cultures can induce pri- mordia or tube & spore formation. When vorking vith un-defined and heterogenous fruiting media, such as vood or sawdust, and bran or corn meal, or using induction techniques vith no specific effects, the results are not always consistent. The underlined processes during transition to basidiocarp formation (storage and utilization of energy sources, change of mycelial growth pattern, light induction, lipid synthesis, enzyme activities and ultra-structural studies on tube and spore formation) are selectively reviewed including other basidiomycetes. CHD-CHOU, 2. -Q. AN, J. 1. HENDRIX, Q. ZKAI, and H. R. BIEGEL. Department of Plant Pathology, University of Kentucky, Lexington 40546. Effect of the Acremonium endophyte on endogonaceous mycorrhizal fungi reproducing on tall fescue. Soil samples taken from field plots planted to tall fescue (cv. Ky 31) with low or high levels of the hcremonium coenowhialum endophyte were assayed for endogonaceous propagules by an MPN bioassay procedure. Soil from low-endophyte plots contained more propagules and species than soil front high- endophyte plots. Pure cultures of one isolate of Glomus mosseae and two isolates
of E. macrocarwum were used to inoculate endophyte-infected or -free fescue seedlings growing in the greenhouse in sand fertilized with a high or low rate of slow-release fertilizer. Colonization and reproduction by E. rosseae, but not the E. pacrocamum isolates, was inhibited by the high rate of fertilizer. The G. mosseae and one of the - G. pacrocarwum isolates reproduced better on the endophyte-free fescue than on endophyte- infected. The other isolate of E. macrocarwum did not reproduce well on either fescue seed source, although roots were colonized. J.D. CLARK School of Biological Sciences, University of Kentucky, Lexington, KY 40506. Didymium iridis mating systems: partial compati bi li t y between mating series. k Oidymium iridis isolate (GB 1) from Bristol England was crossed to Colllns' standard mating allele testers to determine its relationship to the mating series. When paired to the Central American series only a few plasmodia were produced in repeated crossings i n 4 of the 28 possible combinations. These plasmodia produced sporangia containing many non-viable spores which displayed skewed mating type segregation ratios. When paired with clones from the 3 non-interbreeding isolates, the GB 1 clones did not cross with the Ga 1 and Fla 1 isolates but did produce plasmodia i n 3 of the 4 possible combinations with the Pan 4c isolate. These plasmodia also produced spores with low viability and poor segregation ratios. On the other hand, pairings with the Appalachia series produced plasmodia in most replica crosses of all 8 possible combinations. These plasmodia generally produced viable spores and normal segregation ratios. Most g. iridis heterothallic iso- ilates have mating type alleles which are compatible with only a single geographically restricted mating series. The GB 1 isolate, however, is partially compatible with 3 separate series although it is closest to the Appalachia series in terms of compatibili ty. S. A. CLARY and M. E. S. HUDSPETH. Dept. Biological Sciences, Northern Illinois University, DeKalb, IL 60115-2861 Nucleotide sequence of Phytophthora mitochondrial DNA: Sequence of the apocytochrome b and ATP sy- thase subunit 9 region. Seven mitochondrial genic loci have been previously established in Phytophthora megasperma 695T. These include subunits for cytochrome c oxidase ( ~ 1 2, . 3), apocytochrome b (cob), subunit 9 of AT? svnthase (atp9), and the small and large ribosoza: RNAs (E, s). The validity of the -9 locus was questionable as, unlike the other loci, it failed to hybridize with ascomycetous probes, and was localized by an unsequenced Saprolegnia probe. Prior DNA sequence data of cox1 and 3 2 have indicated the probable use of the universal genetic code in Phvtophthora. We have cloned and sequenced a 3.9Kb g R I fragment of the 6951 mtDKA containing the cob and' - atp9 loci. This region contains four open reading frames (ORFs). Two ORFs shox high degrees of predicted amino acid homology with ascomycetous cob and 9 9 loci. Whether the mitochondrial =9is functional, as in Saccharomyces, or silent, as in filamentous ascomycetes is undetermined. One of the remaining ORFs is an inverted copy of a sequence directly upstream of ~ 2 All . four ORFs are transcribed from the same DNA strand, but opposite to that of ~ l ~ , 2 and , the other copy of the repeated ORF. A search for homologies of the unkno.wn ORFs to other mitochondrial genes is underway. u. Department of Biology, Indiana University, Bloomington, IN 47405. Population Genetics and Host Range Expansion of Atkinsonella hv~oxvlon (Clavicipitaceae). Shifts in host range represent the ultimate starting point for most host-parasite associations yet this important process has received little attention compared to research on variation in compatibility within prexisting species combinations. ptkinsonella hv~oxvloq, classified with endophytic fungi in the tribe Balansieae, has extended its host range from two species of panthonia over much of eastern North America to two additional panthonia species occurring on montane granitic outcrops in the southern Appalachians near Highlands, NC where all four host species occur. Preliminary data from seedling inoculations indicate that the basis of host range expansion is genetic changes in fungal populations. Isozyme studies have revealed that isolates of the fungus from the new hosts represent only a few genotypes. Relative fitnesses of infected versus uninfected host plants suggest that Atkinsonella is more pathogenic on the new hosts. Evolutionary changes in isolates from the new hosts are facilitated by differences in host flowering times, minimizing gene flow between isolates from the new and old hosts. Crosses between isolates from the new and old hosts have been attempted to elucidate the nature of genetic control of host range. Evolutionary changes in Atkinsonella populations infecting the new hosts may represent incipient speciation. BRUCE J. COCHRANE, REX T. NELSON, BIENVENIDO G. YANGCO, AND DIANE TE STRAKE. Department of Biology and College of Medicine, Univ. of S. Florida, Tampa. FL. 33620. rDNA polymorphisms and phylogenetic relationships in Baridiobolus. The genus Basidiobolus (Zy~omycotina; Entomophthorales) is a widespread saprobe that ou;rsionally causes mycoses in man and other vertebrates. While as many as ei~ht species of the genus have been proposed, our analyses of both isozye and rDNA polyfnorphisms
Page 1 and 2: ROGER D. SOiW ISSN 0541 - 4938 Myco
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Page 5 and 6: Abstracts of Papers and Posters S.
Page 7 and 8: isolates each Of NABS 1 and 111. tw
Page 9 and 10: J. li BHAlTACHAWJEE. Department of
Page 11: B. E. CALLAK. Pacific Forestry Cent
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Page 19 and 20: continents. Conidia and conidiophor
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