Resistance of larches of Polish provenances to larch canker Lachnellula willkommii [Hartig.] Dennis under mountain conditions of the Sącz Beskid

This study is a fragment of a long-term research on a genetic-silvicultural value of larches of Polish provenances (Table 1, Fig. 1) tested under mountain conditions of the Sšcz Beskid range within the All-Polish Provenance Experiment of Larch 1967. Investigations were based on numerical data on the degree of infection of trees of analyzed partial larch populations with a pathogen Lachnellula willkommii (Hartig.) Denis during 1984 – 1999, i.e. when trees were 20, 25, 30, and 35 years old. Results showed a significant diversification of tested provenances in respect of resistance to larch canker, and a certain tendency of its decrease with age of trees (Tables 2 and 3). Provenances of various regions of Poland were in the group of populations most susceptible to this disease, i.e. with trees showing symptoms above the experimental average (Fig. 3). The resistance to larch cancer of individual partial populations, under mountain conditions of the study area situated in experimental forests of Krynica, was in the first place determined by the genotype (Fig. 4). While the evaluation of the effect of the interaction genotype (provenance) x years of observation (age) pointed to a high stability of resistance to canker of larch populations of extreme values of this trait (Fig. 5). This creates, especially in the case of this provenance group, the possibilities to conduct the effective resistance selection in the early stage.