Expanding populations are often less genetically diverse at their margins than at the centre of a species' range. Established, older populations of the chestnut blight fungus, Cryphonectria parasitica, are more variable for vegetative compatibility (vc) types than in expanding populations in southeastern Europe where C. parasitica has colonized relatively recently. To test whether vc types represent clones, we genotyped 373 isolates of C. parasitica from southern Italy, Romania, Bulgaria, Macedonia, Greece and Turkey using 11 sequence-characterized amplified region (SCAR) markers. Ten SCAR loci and six vegetative incompatibility (vic) loci were polymorphic in these samples. These populations are clonal by all criteria tested: (i) among 373 isolates, we found only eight multilocus haplotypes, and the same haplotypes were found in multiple countries, sometimes separated in time by as much as 12 years; (ii) the number of haplotypes observed was significantly less than expected under random mating; (iii) populations are in linkage disequilibrium; (iv) the two sets of independent markers, SCARs and vc types, are highly correlated; and (v) sexual structures of C. parasitica were found only in Bulgaria and Romania. One mating type (MAT-1) was found in 98% of the isolates sampled. In contrast, a population in northern Italy, in the central part of the range in Europe, had 12 multilocus haplotypes among 19 isolates. The spread of a few clones could be the result either of founder effect and restricted migration, or these clones have greater fitness than others and spread because they are better adapted to conditions in southeastern Europe.

Summary We surveyed chestnut stands at 18 sites in 11 locations in Bulgaria in 2005 and 2007 for the presence of chestnut blight. We found chestnut blight in seven locations (Belogradchik, Berkovitsa, Brezhani, Barziya, Govezhda, Petrich and Petrovo) but not in four others (Tsaparevo, Kresna, Dupnica and Botevgrad). We successfully isolated Cryphonectria parasitica from cankers on 606 trees with symptoms of chestnut blight and assayed them for vegetative compatibility (vc) types and mating type. Three vc types were identified among the 606 isolates; all three were among the European vc types with known vegetative incompatibility (vic) genotypes. Vc type EU‐12 was the most common, representing 80% of the isolates, and was found at all locations with blight, with the exception of Belogradchik in north‐west Bulgaria, where all isolates were vc type EU‐2. Only one population (Barziya) had more than one vc type, with a combination of EU‐12 and EU‐10 in almost equal frequencies. Similarly, the diversity of mating types was very low. All but three of 536 isolates assayed were in mating‐type MAT‐1; MAT‐2 was only found in one population in the north‐west (Berkovitsa). We inspected 671 bark samples from chestnut blight cankers with stromata of C. parasitica and found perithecia in only 33, of which 28 were from Berkovitsa where MAT‐2 was present. We did not detect hypoviruses in any of the 270 isolates screened using the standard double‐stranded RNA extraction protocol. Similar to results from previous studies in south‐eastern Europe, the diversity of vc types and mating type of C. parasitica in Bulgaria is low, and reproduction of the fungus is mainly asexual. Unfortunately, naturally occurring hypovirulence was not detected. Nevertheless, we observed a small number of superficial cankers typical of those caused by C. parasitica isolates infected with a hypovirus.

The historical development of afforestations in Bulgaria was investigated. Some of the more important decisions and events which determine the correct state policy in the field of afforestations are pointed out. The most significant achievements are in: erosion control, incl. water tank protection from silting up; increasing the tree volume and forest growth; protection of agriculture via forest protection belts; landscape improving. The social importance for more employment and improvement of means of livelihood is mentioned. Proved reasons for decreasing the afforested areas since 1980s are given. The main mistakes and problems are mentioned as well as the changes in the afforestation policy and future challenges.