Growth records among a worldwide collection of isolates of Gremmeniella abietina revealed wide variation in response at different temperatures. Overall, the fungus was identified as a facultative psychrophile with extended capacity for growth at low temperatures and a thermal-death or growth-suppression point between 25 and 30 °C. The gross appearance of cultures, extent of spore septation, and appearance of heavily sporulating and pionnotal variants provide evidence to support a concept of separate North American and European physiologic races. This concept is further supported by comparisons among soluble proteins using immunologic methods, as a result of which a third (Asian) race is proposed. Gremmeniella abietina is defined as a single species in geographic disjunction with a minimum of three physiologic races. Formal subdivision of the species is discouraged in the absence of overwhelming evidence in support of such a requirement. The use of G. abietina and similar microorganisms with complex host ranges and aerially disseminated spore states as models in biogeographic analyses will be highly problematic if not impossible.

A study was designed to isolate potentially pathogenic, endophytic fungi of red alder (Alnus rubra). Apparently healthy leaves and 2- to 3-year-old twigs were collected at three and eight sites, respectively, surface sterilized, cut into small pieces, and incubated on 2% malt extract agar. Ninety percent of the leaves and more than 80% of the twigs were colonized by endophytic fungi; 40 different fungi were isolated and identified. Fungi previously recorded as plant pathogens dominated the endophyte community of leaves (Gnomonia setacea, Gnomoniella tubaeformis, and Septoria alni) but were only minor components of the fungal population of twigs (Melanconis alni and a Nectria species). Abundance of each fungus species and the species composition depended on the plant organ sampled and collection site. In twigs, three main types of endophyte associations occurred among sites: the first was dominated by the unidentified "Black Mycelium 2," the second by Phomopsis sp. 2, and the third by Ophiovalsa suffusa, Pezicula livida, and Phloeosporella sp. The endophyte community of leaves was dominated by G. setacea except at one site where G. tubaeformis was the predominant fungus. Key words: endophytic fungi, fungal community, Alnus rubra, mycoherbicide.

No abstract

DORWORTH, C. E. 1972. Epidemiology of Scleroclerris 1agcrbel.gii in central Ontario. Can. J. Bot. 50: 751-765. Scleroderris canker (Scl~roclerris Iugerbergii Gremmen) has damaged conifers in Europc for nearly a century. The disease has intensified in the Great Lakes region of North America during the past several decades, and the fungus could spread throughout the North Temperate Zone. Attacks by S. Ia,yerbergii are most severe in topographical depressions and the resulting disease was thought to be associated with frost damage. Observations in depressions that resembled frost pockets indicated that extensive damage to regeneration of Pitz~rs resitrosa Ait. could be attributed primarily to amplified spore deposition in the depressions and rapid intensification of the disease in the presence of prolonged periods of high relative humidity. Topographic projections, photographs, temperature profiles, and spore collection data support this thesis. Vertical restriction to foliage within ca. 1.5 n~ of the ground is attributed to radiation fog that prolongs the incubation period afforded the fungus. Effects of edaphic variation, ground vegetation, and snow cover are evaluated. Snow is accorded importance in ~iiodifying extremes of winter and early spring teniperat~~res to the advantage of the fungus. Frost damage and infection by S. lagerbergii both result in !,!antation failures in topographic depressions. DORWORTH, C. E. 1972. Epidemiology of Sclerorlerris lagerbergii in central Ontario. Can. J. Bot. 50:751-765. Le chancre scleroderris (Scleroderris lagerbergii Grernmen) a endoniniage les conifires en Europe depuis environ un siicle. La maladie s'est intensifiee dans la region des Grands Lacs de I'AmCriq~~e du Nord au cours des recentes dtcennies et le champignon pourrait s'etendre dans toute la zone temperee de l'heniisphire nord. Les attaques par S. lagerbergii sont les plus graves dans les depressions topographiques, et on a cru que la maladie qui s'y developpait etait associee aux donimages causes par le gel. Des observations dans des depressions, qui ressemblaient a des poches de froid, indiquent que les donimages iniportants dans la regeneration de Pitzus resitrosa Ait. pouvaient &tre attribues a une deposition accrue des spores dans les depressions e t a une proliferation rapide de la maladie au cours de periodes prolongees d'huniiditt relative elevee. Des projections topographiques, des photographies, des profils de tempkrature et les resultats de recoltes de spores supportent cette thtse. Le fait que la maladie soit restreinte au feuillage situe a moins de 1.5 m du sol est attribue i la brume de condensation qui prolonge la periode d'incubation offerte au champignon. Les effets de la variation kdaphique, du couvert vegetal et de la couverture de neige sont evalues. Une certaine importance est accordbe a la neige qui modifie les extremes de temperature en hiver et au debut du printemps 5 I'avantage du chanipignon. Le dom~nage cause par le gel aussi bien que I'infection par S. lagerbergii provoquent des echecs ...

Melanconium apiocarpum (anamorph of Melanconis alni), Melanconium marginale (anamorph of Melanconis marginalis), and other Melanconium species isolated from healthy and diseased tissues of Alnus species in Canada, England, and Switzerland were compared by means of morphological, cultural, and biochemical techniques, and the results were analyzed by numerical methods. No differences were recorded between symptomless endophytes and disease syndrome associated isolates of M. apiocarpum, although European and Canadian isolates could be consistently and clearly differentiated by protein profiles and cellulose utilization patterns. On the basis of cultural and biochemical characters as well as conidia morphology, M. apiocarpum and M. marginale are distinct species. Two intraspecific groups of M. marginale, particular to separate Alnus species, were identified. Melanconium isolates from Fagus sylvatica and Quercus robur are clearly distinct from those on Alnus. Key words: Melanconium, Melanconis, Alnus, numerical taxonomy.