National Research Council of Italy

Institute of Biosciences and Bioresources

Aspetti genetici del faggio in Italia

Bucci G, Raddi S, Vendramin GG, Leonardi S, Giannini R, Menozzi P

In: “Ecologia strutturale e funzionale delle faggete italiane”. Edagricole, Bologna, pp. 35-69.

Understanding the way the forests adapt to changing environment is just at its beginning. The adaptability of "ecological dominants" like forest trees may affect the structure and organization of the whole forest community. To assess the ability of forest tree populations to face environmental stress, the preliminary step is to understand the relationship among genetic diversity, ecophysiological variation and environmental heterogeneity, aimed to evaluate the adaptability of forest tree populations. In the last years, many genetic investigations on Italian populations of European beech has been carrying out. Thanks to marker-based genetic analysis, information has been obtained on several aspects of its population biology. As for the mating system, high levels of outcrossing rate (96-98 %) has been detected in natural beech stands, slightly higher than what detected for other European populations (94 %). Preliminary evidences on realized gene flow within an Italian natural beech stand revealed a mean pollination distance of about 30 meters. The amount of genetic variability of 21 Italian populations (He = 0.189) was lower than what reported for 140 European stands (He = 0.289). More than 95 % of the whole genetic diversity is due to variation within-populations (FST = 0.046 - 0.043). Levels of inbreeding is also similar to what reported for European stands (FIS = 0.070 - 0.117 vs. 0.065 - 0.120, respectively). Selection against inbred recruits (progeny from inbreeding between relatives) seems to take place after earlier stages (5-15 years). According to what reported for other European populations, spatial autocorrelation analysis on allozymic data revealed only a slight clustering of like-genotypes within several Italian stands. Combining the analysis of allelic frequencies among populations and palinological data, preliminary hypothesis about Eastward recolonization of the Alpine chain and Northward Apennine chain after the last ice-age have been inferred. Small isolated populations located in central Italy showed genetic divergence (FST = 0.02 - 0.05, probably due to genetic drift) correlated with marginality in respect to the main Italian range. This information, though preliminary, provides the baseline for further studies aimed to the conservation of the genetic resources and to develop an helpful strategy of genetic improvement for European beech. Genetic analysis carried out so far has shown the existence of "useful" genetic variability in European beech. Differences among Italian provenances have been detected for both adaptive (like water balance, stress tolerance, etc.) and economical traits. The recent introduction of molecular markers in forest tree genetics allow quantitative traits to be dissected and the molecular basis of quantitative variation in natural populations to be studied. Implications and fall-out of the above techniques on genetic improvement of beech and conservation of its genetic resources has been discussed. Germplasm conservation along with production requirements call for integration of genetic information obtained with management of beech forest aiming to establish "sustanaible silviculture’ criteria. Hypotheses on the effect of silvicultural treatments on forest genetic stocks have been presented. Preliminary data on thinning in two Italian beech stands did not revealed significant variation of major genetic parameters of the adult individuals left after cuttings

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