ALLOZYME VARIATION AMONG EUROPEAN BEECH (FAGUS-SYLVATICA L) STANDS INPIEDMONT, NORTH-WESTERN ITALY

The genetic diversity and the genetic differentiation of 11 native pop ulations of European beech from Piedmont (northwestern Italy) were stu died by means of the allozyme variation at 10 loci. Data obtained also contributed to the identification of the most valuable stands for the production of high quality seed. Horizontal electrophoresis on starch gel was employed to separate the variants of 7 enzyme systems: Got, G 3pdh, Idh, Mdh, Mnr, 6Pgdh and Pgi. The expected heterozygosity ranged from 0.177 to 0.278 with an average of 0.232; the mean number of alle les per locus was 2.12 and 68.18% of loci were polymorphic. Only 4.3% of the total genetic diversity was due to differentiation among popula tions and the mean value of NEI'S genetic distance was 0.013. The shar ing of one gene pool among the studied beechwoods suggests a lack. of barriers to gene flow. It was possible to score a significant correlat ion between the frequency of the allele 6Pgdh-B1 and the altitude wher e the samples were collected, while the north exposure was related to a higher mean heterozygosity. Although no correlation between genotype and geographical distance could be found, the stands from the same pr ovince showed a certain degree of similarity. On the basis of the gene tic distances, the very old stand of Palanfre was clearly distinguisha ble from the others. Moreover, it displayed the highest level of expec ted heterozygosity.