| Altogether 216 basidiocarp specimens of Armillaria, mostly from northern and south-western China, were identified with the aid of mating tests using tester strains of the European and North American Armillaria species. The incompatibility system of 45 specimens representing different species or intersterile groups was also determined. Seven specimens proved to be homothallic and the others were heterothallic. Twelve species or intersterility groups were found: A. sinapina, A. gallica, A. ostoyae, A. tabescens, A. mellea, A. borealis, and six so far unnamed intersterility groups called Chinese Biological Species (CBS) C, F, G, H, J and L. Based on the morphology of fruiting bodies, CBS F may be the Japanese species A. singula. Homothallic forms were related to the heterothallic A. mellea; they are included in the CBS G, but it is unclear if this is a homogeneous group. The Chinese Biological Species C, H, J and L seem to be specific to Asia and should be considered new species.Two new species Armillaria korhonenii sp. nov. and A. luteopileata were described on the based of biological species G and CBS C, respectively. Former species distributed over Southwestern China and related closely to heterothallic species A. mellea s.str. and later one was suggested as a member of A. gallica cluster.One hundred and seven isolates belonging to 12 Chinese Armillaria species and their relatives occurring in Japan, Europe and North America were subjected to a restriction analysis of intergenic spacer region (IGS-RFLP) using four restriction enzymes. The analysis revealed a total of 36 different RFLP patterns. Among them six previously unknown patterns of four Chinese Biological Species (CBS C, CBS F, CBS H, and CBS J) and nine new patterns of five species withworldwide distribution (A. sinapina, A. gallica, A. ostoyae, CBS G, A. cepistipes) were observed. The IGS-RFLP patterns were effective for distinguishing A. tabescens, A. ostoyae, CBS G and A. mellea. The species of the "gallica cluster" were, however, only partially separated as Chinese Armillaria possessed high genetic diversity. For example, although A. sinapina and A. gallica, as well as CBS F and CBS H could be divided by the IGS-RFLP patterns, the differentiation between A. sinapina, CBS C and CBS H was not possible. In the dendrogram based on the IGS-RFLP data, the 43 patterns of 11 species were divided into nine groups. Only homothallic CBS G possessed a single independent lineage. Both A. mellea and A. tabescens appeared in two groups. The two clusters of A. mellea correlated to the geographical origin of the isolates, one is the North American lineage and another is the European lineage. The two groups of A. tabescens were distantly separated which may indicate the occurrence of two taxonomic units. Three clusters of A. ostoyae indicated that the species is more variable than found before. The "gallica cluster" appeared as a mixed lineage in the dendrogram.The relatedness of 29 specimens of Armillaria ostoyae originating from China, 33 from Europe, and 8 from North America was investigated with the aid of mating tests and DNA fingerprinting. Mating reactions were recorded in 974 inter-continental pairing combinations between single-spore isolates. A. ostoyae populations originating from different continents showed reduced sexual compatibility. Whereas the mating frequency within a continental population was close to 100 %, it was only ca. 57 % between the Chinese and North American populations, 55 % between the Chinese and European populations, and 46 % between the European and North American populations. These figures are smaller than those reported earlier in the literature. In spite of the reduced compatibility, true hybridization of populations can take place: two compatible matings betweenEuropean and North American isolates fruited and the single-spore offspring showed normal tetrapolar mating pattern. Eighty presence-absence DNA characters were generated by Randomly Amplified Microsatellite (RAMS) and Ml3 fingerprinting analyses an...
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