Comparisons among isolates of Gremmeniella abietina by means of growth rate, conidia measurement, and immunogenic reaction

Abstract

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.