Genetic variation among clones of Picea abies in resistance to growth of Heterobasidion annosum

An inoculation experiment with Heterobasidion annosum on 98 four-year-old Picea abies clones was conducted on rooted-cuttings under greenhouse conditions. One isolate of H. annosum and 10 ramets of each clone were used. After 34 days of incubation, fungal growth in sapwood and lesion length in the inner bark were measured. There were significant differences among clones in lesion length in the inner bark and in fungal growth in sapwood. Broad sense heritability was 0.35 for fungal growth and 0.27 for lesion length in the inner bark. Fungal growth and lesion length showed strong genotypic correlation. Bud-flushing index of the clones was correlated with mean fungal growth, whereas the growth termination index was not. Fungal growth in sapwood and lesion length in the inner bark of cuttings were not correlated with the mean height and provenance of 15-year-old ramets of the same clones in previously conducted field tests.