Variation in spread of Heterobasidion annosum in clones of Picea abies grown at different vegetation phases under greenhouse conditions
1996
Swedjemark, G. | Stenlid, J. (SLU, Uppsala (Sweden). Inst. foer Skoglig Mykologi och Patologi)
Forty-nine Picea abies (L.) Karst clones were inoculated under greenhouse conditions with a Heterobasidion annosum (Fr.) Bref. isolate of the S intersterility group. The cuttings were inoculated at the following vegetation stages; bud-flushing stage, vegetative stage and after bud-set. Fungal growth in sapwood and lesion length in the inner bark were measured after 34 days. The susceptibility of the various clones to H. annosum was strongly correlated among the three vegetation stages, both in terms of mean growth and mean growth ranking. Partitioning of variance components showed that variation in growth was explained by physiological stages and clone to 4% and 24%, respectively, and for interaction between clone and physiological stage to 9%. Corresponding values for lesion length in the inner bark were 3%, 14% and 5%, respectively. Fungal growth in wood and lesion length in the inner bark were strongly correlated (r2 ranging between 0.23 and 0.36). When cuttings were inoculated during bud-flusing, lesion length and fungal growth in wood were both strongly correlated with bud-flushing index of the cuttings (r2=0.03 and 0.04 respectively) but that was not the case for the other stages. The number of active fine-roots and the degree of wilting of the cuttings were negatively correlated with lesion length and fungal growth (r2 ranging between 0.01 and 0.13). Height and diameter varied greatly between the clones and both were negativley correlated with fungal extension (r2 ranging between 0.01 and 0.09).
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