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Restriction Fragment Length Polymorphisms in the Nuclear Ribosomal DNA of Four Laccaria spp.: L. bicolor, L. laccata, L. proxima, and L. amethystina. M. Gardes, Centre de Recherche en Biologie Foresti?re, D?partement des Sciences Foresti?res, Facult? de Foresterie et de G?omatique, Universit? Laval, Qu?bec (Qu?.), Canada G1K7P4, Present address: Department of Plant Pathology, University of California, Berkeley 94720; J. A. Fortin(2), G. M. Mueller(3), and B. R. Kropp(4). (2)(4)Centre de Recherche en Biologie Foresti?re, D?partement des Sciences Foresti?res, Facult? de Foresterie et de G?omatique, Universit? Laval, Qu?bec (Qu?.), Canada G1K7P4, (2)Present address: Institut de Recherche en Biologie V?g?tale, 4101 est. rue Sherbrooke, Montr?al, (Qu?.), Canada H1X 2B2; (3)Department of Botany, Field Museum of Natural History, Chicago, IL 60605, USA. Phytopathology 80:1312-1317. Accepted for publication 6 July 1990. Copyright 1990 The American Phytopathological Society. DOI: 10.1094/Phyto-80-1312.

Restriction fragment length polymorphisms (RFLPs) were examined in the nuclear ribosomal DNA (rDNA) of 29 isolates of Laccaria bicolor, eight of L. laccata, three of L. proxima, and two of L. amethystina. Whole-cell DNAs were digested with BamHI, Bg/II, EcoRI, HindIII, and PstI and probed with cloned rDNA from Armillaria ostoyae by Southern hybridizations. The observed variability suggests that rDNA restriction fragment phenotypes can be used as additional taxonomic characters for comparing Laccaria spp., since the four Laccaria spp., as well as four biological species within L. laccata, were distinguishable. North American isolates of L. bicolor appear to constitute a relatively homogenous group that is distinguishable from European isolates. Large variations in RFLP patterns are detected among isolates of L. laccata, reflecting the morphological, physiological, and genetic heterogeneity of this species. The nuclear ribosomal repeat unit has apparently diverged in L. bicolor and L. amethystina on the two continents and among biological species of L. laccata. Most of the intraspecific polymorphism in rDNA restriction fragment length was observed after digestion with Bg/II and EcoRI. Mixed rDNA types that differ at least in repeat unit length were also detected with these two enzymes within seven dikaryotic isolates of L. bicolor collected from the field.