Pathogenic Variability Among Populations of the Pinewood Nematode, Bursaphelenchus Xylophilus

Abstract

Abstract Virulence of populations of Bursaphelenchus spp. associated with conifers varies throughout the range of this nematode in the United States and Japan. Populations of B. xylophilus (pinewood nematode, PWN) from Japanese black and red pine in the same and distantly separated pine stands in Japan range in virulence from 0-100% and there is a tendency for the most virulent populations to be in the northernmost part of the nematode's range where establishment has been relatively recent. Virulence of PWN populations, however, does not vary within a single pine or vector insect. Isozyme patterns are similar between virulent and avirulent populations and therefore cannot be used to differentiate them. Aspartate transaminase isozyme patterns can be used to differentiate between B. xylophilus and B. mucronatus. Pathogenicity of PWN in the United States depends on the interaction of the pine species with different PWN populations, the physiological status of the infected pine, and environmental conditions. Mating and reproductive potential, virulence, DNA sequence differences determined by restriction fragment length polymorphisms, and isozyme differences are useful criteria for studying population biology and genetics of PWN, and when used together, for describing speciation of Bursaphelenchus associated with conifers. For. Sci. 36(4):1061-1076.