Search

The main aim of our research was to describe the level and distribution of genetic variability of wild cherry (Prunus avium L.) in Italy, using eight nuclear microsatellite markers. The sampled plants were grouped in 11 internally homogeneous breeding zones, defined according to their ecological and vegetational conditions. The mean observed heterozygosity (Ho) was 0.573, and the expected (He) 0.698. Significant departures from Hardy‐Weinberg equilibrium at each locus were found for all breeding zones (P , 0.01). The mean fixation index, calculated taking into account the estimated null allele frequencies, was 0.075, showing a slight excess of homozygotes. FST (departure of genotype frequencies within populations from Hardy‐Weinberg expectations, commonly used as an estimator of genetic differentiation among populations) showed a mean value of 0.046, indicating a slight, although significant, differentiation among breeding zones. However, in general, it was not possible to observe a structuring linked to the geographical location of the breeding zones. The results of the study contribute to a better understanding of our knowledge of the wild cherry genetic variation in Italy, thus making for more efficient programmes aimed at the preservation of biodiversity and for more rational planning of the management of reproductive material. Since our results do not show a clear structuring of genetic variability within the Italian diffusion area of wild cherry, it is not possible to draw any indications on regions of provenance delimitation based only on genetic data, and the identification of the latter should be based mainly on ecological and vegetational features.

Twenty-one populations of Scots pine sampled over the entire Italian range of the species were analysed for genetic variation scored at nine nuclear SSR markers. The main aim of the work was to find genetic features useful for conservation management, namely allelic composition, gene diversity and differentiation. High levels of intra-population variability were scored. The only population sampled in the Apennines gave the lowest values, confirming the genetic erosion undergone in the Scots pine remnants in this area. A low level of genetic variability was also scored for populations from the Po valley and hills of Piedmont. Most genetic diversity was found within populations, while only a small amount occurred among them (F ST = 0.058). Both Bayesian clustering and sPCA analysis showed a East–West subdivision, notwithstanding the unclear position of populations from the Po valley. The population from the Apennines was always clearly separated from the others. The results are discussed in terms of post-glacial recolonisation, as well as for defining genetically homogeneous regions for Scots pine in Italy. The management of genetic resources could benefit from the identification of such ‘gene zones’, thereby avoiding the use of non-local reproductive material for plantations, which can represent one of the most important reasons for failure of reforestation. In addition, the assessment of the biogeographic genetic structure by neutral markers is a prerequisite for disentangling the influence of selectively neutral and non-neutral processes on the distribution of adaptive genetic variability.

The level of genetic variation throughout the Italian range of common ash (Fraxinus excelsior L.) was estimated using six microsatellite markers. High levels of allelic diversity was detected. The levels of expected heterozygosity for each of the populations ranged from 0.726 to 0.871, with an average of 0.798, and indicated that populations have a high level of genetic variation. A general and significant homozygote excess was found at most loci in all populations, with an overall mean F IS of 0.284. Possible explanations for such situations are discussed. Only 4.9% of the total diversity was attributable to differentiation among populations. Although divergence among pedo-climatic regions explained only a small part of the variance it was possible to observe some partial clustering of populations belonging to the same regions. The contribution of the results in relation to the definition of the most appropriate strategies to collect forest reproductive material is discussed.

Fritillaria tubiformis subsp. moggridgei Rix. is a rare alpine geophyte with shiny yellow flowers. This plant is sporadically distributed across the southwestern Alps where it is biogeographically close to F. tubiformis var. burnatii Planch. The latter has dark purple flowers and ranges in the majority of the Western and Central Alps. In order to develop appropriate strategies of conservation, a RAPD based analysis was conducted to study the genetic status of these taxa and the distribution of genetic variability of the subspecies by sampling seven populations distributed across the subspecies' range. Four populations of var. burnatii were chosen within this range and included in the genetic analysis. Some 264 individuals were analysed and 201 polymorphic loci were scored. Genetic diversity scored in the subspecies was in line with expectations for endemic species (He = 0.194). F. tubiformis var. burnatii showed lower intraspecific diversity (He = 0.173), notwithstanding a wider range than the subspecies. Most of the total phenotypic variation (about 83%) was allocated within populations, and significant lower proportions between taxa (6.45%) and between populations of the same taxon (10.64%). Moreover, PCoA analysis and Bayesian clustering separated populations into two genetically differentiated groups corresponding with the subspecific taxa. However, three populations ascribed to the subsp. moggridgei repeatedly showed genetic admixture with var. burnatii populations. Our findings suggest that: i) although the different flower colour, the two taxa are genetically very similar and share a consistent part of their gene pool, ii) the majority of genetic variability is allocated within populations rather than among them, iii) a representative amount of genetic diversity can be preserved by sampling from a restricted number of populations. The efficacy of RAPD markers in analysing genetic variation, and the contribution of the results to the preservation of biodiversity of the species, are discussed.

Genetic diversity and differentiation of 12 native populations of sycamore ( Acer pseudoplatanus L.) from northwestern Italy were investigated by means of variation detected in 10 polymorphic isozyme systems encoded by 16 loci. The trees showed relatively large genetic variability (mean number of alleles per locus = 2.78, effective number of alleles per locus = 1.47, percentage of polymorphic loci = 96.9, expected heterozygosity = 0.280) but small interpopulational variation (FST= 0.019), suggesting the presence of a single gene pool. A slight excess of heterozygotes was found, and the overall inbreeding coefficient (FIS) was –0.038. There was a positive correlation between the age of the individuals sampled and heterozygosity, suggesting the occurrence of natural selection against homozygotes. No significant correlation was detected between genetic and geographic distances of populations, confirming the lack of any barriers to gene flow. Estimate of the mean effective number of migrants exchanged between populations was 4.399, based on the private alleles method. The contribution of the results in relation to terms of the most appropriate strategies to preserve genetic variability of sycamore and to collect forest reproductive material is discussed.