Biodiversità matricale di Heterobasidion abietinum Niemelä & Korhonen in abetine dell’Italia meridionale

Among constraints of Silver fir (Abies alba Mill.) in the central-southern Apennine area in Italy, infections by Heterobasidion abietinum Niemelä & Korhonen, a basidiomycete causing root rot and wood decay in adult trees, can also be detected at the collar and roots of the seedlings of the regeneration. In order to verify a possible variability in the pathogenic behaviour of the fungus, axenic cultures of H. abietinum, obtained from basidiomes, and A. alba stumps and seedling roots collected in silver fir stands in southern Italy were tested in artificial inoculations on 6-month- and 1-year-old seedlings, and on 4-year-oldtransplants of A. alba. The isolates originated from seedling roots were more pathogenic than the others only on the youngest tested seedlings. No differences in pathogenicity were scored on 1-year-old seedlings according to isolates. No signs of infections were even observed in most cases on transplants 12 weeks after inoculation. Therefore, it seems that isolates of H. abietinum originating from seedling roots are not necessarily more pathogenic than those from stumps, except on very young seedlings, thus supporting the hypothesis that in southern Italian stands fatal attacks of H. abietinum on silver fir regeneration only occur with the contribution of a number of factors more related to environmental influences rather than to the virulence of the pathogen.