Impact of silvicultural system on Cryphonectria parasitica incidence and on genetic variability in a chestnut coppice in Central Italy

This study was carried out in order to analyze the effect of silvicultural treatment on the structure and productivity of the chestnut stands, on the disease evolution and on the genetic structure of the species. The study co nsidered a coppice stand aged 35 years (1994), growing on Monte Amiata (Tus cany, Italy). In the winter of 1994-1995, a low thinning of moderate intens ity was applied; all suppressed shoots were removed, the intermediate class was partially reduced while the dominant storey was lightly thinned. Befor e, and after thinning, a description of stand structure, evaluation of numb er and typology of cankers caused by Cryphonectria parasitica on each tree and characterization of genotypical profile of all stumps was carried out. The structural and pathological surveys were repeated in February 1997 in o rder to analyze the growth trend of the stand and to verify the incidence a nd the evolution of disease two years after thinning. The results show that the applied silvicultural system neither reduced the generic variability n or influenced the genotypic distribution of the stand. The removal of virul ent cankers and the reduction of the individual susceptibility by the selec tion of the most vigorous trees has a positive effect on pathogen evolution . (C) 2001 Elsevier Science B.V. All rights reserved.