Eur.J.For. Path. 27(1997)273-281 © 1997 Blackwell Wissenschafts-Verlag, Berlin ISSN0300-1237 QQJ ££ 199? PERIODICALS Ds Abies sihirica in the Ural region is attacked by the S ty j Heterobasidion annosum By K. KORHONEN', N. I. FEDOROV^, N. LA PoRTA^and N. P. KOVBASA^ 'Finnish Forest Research Institute, Vantaa Research Centre, PO Box 18, FIN-01301 Vantaa, Finland (for correspondence); ^Department of Forest Protection, Belarussian State Technological University, ul. Sverdlova, 13-a, 220630, Minsk, Belarus; ^Istituto di Patologia e Zoologia Forestale e Agraria, Universita degli Studi, Piazzale delle Cascine 28, 50144 Firenze, Italy Summary Specimens of Heterobasidion annosum were collected in seven mixed stands of Abies sibirica and Picea abies in Yekaterinburg and Perm regions on the western side of the Ural Mountains, Russia. Pure cultures were isolated from 60 collections and identified in mating tests. Only the S intersterility group was found, attacking both fir and spruce. Based on the appearance of clamp connections in matmgs, the compatibility of 12 homokaryons from the Ural area with 14 S group homokaryons from western Europe was 100%, with 13 F group homokaryons from southern Europe 76% and 9 P group homo- karyons from western Europe 3%. The results show that A. sibirica,, in contrast to A. alba, is very susceptible to the S type H. annosum. 1 Introduction Approximately 13 species of Abies have been recognized in Europe and in adjacent areas (BERNETTI 1995). Most of them occur in the Mediterranean region and are relict species with a small distribution area (Fig. 1). Some are considered as being hybrids (LANDRY 1984; FARJON and RUSHFORD 1989). Only two species have a wide distribution: silver fir {Abies alba Mill.) in southern and central Europe and Siberian fir {Abies sibirica Ledeb.) in north- eastern Europe and Siberia. Heterobasidion annosum (Fr.) Bref. is the major agent of root and butt rot of many conifers, including the European .A^ies species. H. annosum is a collective species consisting of three intersterile groups in Europe. Among them, the F intersterility group shows high specialization to Abies. It is common and destructive in silver fir forests of the Apenmne mountains (GAPRETTI et al. 1990 ) and also occurs in central Europe, although there it is less common and aggressive. The northern-most record is from southern Poland, close to the northern limit of the natural distribution of silver fir (LAKOMY 1996). In addition to A. alba, the F group attacks A. cephalonica Loud, and A. borisii-regis Mattf. in Greece (TSOPELAS and KoRHONEN 1996). The occurrence of the F group on the remaining Abies species in southern Europe and adjacent areas is not known. Neither it is known which type of H. annosum attacks Siberian fir, a species that has a distribution area that is very isolated from other European fir species. Norway spruce {Picea abies (L.) Karst., including the eastern subspecies obovata (Ledeb.) Domin.), has a wide natural distribution in northern Europe, in the mountains of central and south-eastern Europe (Fig. 1), in Siberia and in the far east of Russia. The main agent causing root and butt rot on spruce is the S type of H. annosum. In northern and central Europe this fungus is associated almost only with spruce and seldom attacks other native Received: 28.6.1996; accepted: 1^.LI997 ; > v U. S. Copyright Clearance Center Code Statement: 0300-1237/97/2705-0273 $14.00/0