Sandra L. Anagnostakis

The Use of Solid Media for Detection of Enzyme Production by Fungi

SUMMARYSolid media are described on which the production of the extracellular enzymes amylase, lipase, DNA- and RNAase, pectinase, protease, urease, and chitinase were detected. The media were test...

Biological Control of Chestnut Blight

After 77 years of being attacked by the chestnut blight fungus, American chestnut trees continue to sprout from gradually declining root systems. The blight fungus in Italy is now associated with virus-like agents that limit its pathogenicity, and attempts have been made to introduce these controlling agents into the blight fungus in the United States. If a way can be found to help the spread here of strains of the fungus with controlling agents, it may be possible to save the American chestnut trees in our eastern forests.

Chestnut Blight: Biological Control by Transmissible Hypovirulence in Endothia parasitica

Hypovirulence in Endothia parasitica is caused by a cytoplasmic determinant that is transferred by hyphal anastomosis in host tissue and in culture. Transmission of this determinant affects the virulence of the fungus to the extent that host invasion by previously virulent isolates is limited.

Vegetative incompatibility in Endothia parasitica

Endothia parasitica , which causes a canker disease of chestnut trees, has a system of vegetative incompatibility similar to that found in other ascomycetes. Incompatible interaction of strains on agar media leads to a barrage and the formation of pycnidia with conidia. Twenty-eight compatibility groups have been identified among mass mycelial isolates from natural cankers from Italy, France, and North America and single ascospore clones from North America. Single random ascospore and tetrad clones were tested for compatibility and the results provide new evidence that this fungus is homothallic with the ability to outcross. Hypovirulent strains do not behave in a predictable manner in vitro with regard to vegetative incompatibility. There is evidence for anastomoses in the host between hypovirulent and virulent strains in different compatibility groups.

Solid Media Containing Carboxymethylcellulose to Detect Cx Cellulase Activity of Micro-organisms

Solid media containing carboxymethyl cellulose (CMC) were developed to detect CX cellulose-producing micro-organisms. Hydrolysis of CMC was seen as a clear zone around colonies after flooding plates with 1% aqueous hexadecyltrimethyl-ammonium bromide. Tests with ten bacterial and four fungal species showed that the degree of substitution (DS) of the CMC affects both growth and enzyme production. Most of the organisms produced more CX cellulase on CMC with a DS of 0-9, but CMC with a DS of 0-4 was better for one fungus. A qualitative measure of cellulase production may be obtained by calculating the ratio of zone size to colony diameter. Solid media containing CMC provided a more rapid assay of CX cellulose production than a medium containing native cellulose.

The Effect of Multiple Importations of Pests and Pathogens on a Native Tree

Climate changes in the past reshaped the North American native forests as some species increased and others decreased in number and distribution. Native American chestnuts were once abundant, but have been eliminated from the forest canopy by two imported pathogens, and are additionally threatened by an imported pest. The trees survive one of the pathogens, but rarely become larger than understory shrubs. These clumps of sprouts provide a reservoir of genetic diversity for use in reinstating this tree into its forest habitat. An imported parasite can be used to control one pathogen and allow the sprouts to grow large enough to flower. The trees can then be crossed with imported chestnuts of other species with good resistance to both pathogens, and resistant offspring selected. Good progress has been made in coping with these imported problems.

CONVERSION TO CURATIVE MORPHOLOGY IN ENDOTHIA PARASITICA AND ITS RESTRICTION BY VEGETATIVE COMPATIBILITY

Endothia parasitica strains in some vegetative compatibility (v-c) groups barrage weakly when their mycelia meet on agar media. The morphology associated with Italian white curative (hypovirulent) strains of this fungus was used as a marker to detect cytoplasmic transfer between weakly-barraging strains. The (cytoplasmic) determinants for curative morphology were rapidly transferred between most weakly-barraging strains, but transferred infrequently or not at all between strongly-barraging strains.

Oxalate production by virulent but not by hypovirulent strains of Endothia parasitica

Abstract Three virulent strains of Endothia parasitica when grown on potato dextrose agar containing methionine and biotin (PDAmb) or minimal media containing glucose supplemented with either glycolate or glyoxylate produced 10–12, 50–60 and 20–40 mg oxalate g−1 dry weight of fungus respectively. Oxalate accumulation was detected the fourth day after inoculation when the strains were grown on PDAmb or the glycolate medium but not until day 7 on the glyoxylate medium. In the early stages of growth (up to 0·1 g dry weight per colony) the total amount of oxalate excreted into the medium was proportional to the dry weight of the fungus but there was little or no correlation at later stages of growth. Oxalate was detected at the edge of the fungal colony, which is important if oxalate is to play a role in pathogenicity. Under identical conditions three hypovirulent strains, derived from the virulent ones by the introduction of cytoplasmic determinants for hypovirulence, produced no detectable oxalate.

American chestnut sprout survival with biological control of the chestnut-blight fungus population

The American chestnut trees in Connecticut were reduced to understory shrubs by an imported fungus that causes lethal cankers. Chestnut blight disease was first reported in the United States in 1904, and in Connecticut in 1907. Hypovirulence is a virus disease of the fungus that reduces its virulence enough to allow the defense systems of the trees to restrict the fungus to the outer bark. Blight cankers on chestnut sprouts in a 1.4 ha wood-lot in central Connecticut were treated with hypovirulent strains from 1982 through 1986. Stem diameters were measured periodically. Stem size distribution has stayed consistently higher than in a comparable forest area with no treatment.

The Pathogens and Pests of Chestnuts

Publisher Summary The name “chestnut” refers to seven species of deciduous, nut-bearing trees found native and introduced throughout the world. In 1838, a root disease was reported on European chestnut in Portugal, and soon after this “ink disease” was found in several other parts of southern Europe. Ink disease is assumed to have entered the United States in the mid-l800s, and probably accounted for the recession of American chestnut from large areas in the Gulf and Mid-Atlantic states in the United States, and inland to the foothills and mountains of Mississippi, Alabama, Georgia, Tennessee, Maryland, Virginia, and the Carolinas. Chestnut blight, or chestnut bark disease is caused by the fungus Cryphonectria parasitica Barr, formerly called Endothia parasitica And. & And. The fungus enters wounds, grows in and under the bark, and eventually kills the cambium all the way around the twig, branch, or trunk. From 1982 through 1986, the 317 cankers that developed on American chestnut stems in 50 sprout clumps were treated with H strains. European chestnuts (C. sativa) were distributed throughout southern Europe from the Caucasus mountains, and the nuts have become an important food source, both cooked whole and ground into flour. Chestnuts are actually fruits, with shells enclosing cotyledons. Two species of weevils lay eggs in the nuts, and the developing larvae make the nuts unmarketable.