Damage caused by Lophodermium needle cast in open-pollinated and control-crossed progeny trials of Scots pine (Pinus sylvestris L.)

The effect of genetics on the level of damage caused by Lophodermium needle cast to Scots pine was assessed in an openpollinated progeny trial (226 families from 12 provenances) and in a control-crossed progeny trial (72 families obtained by diallel crossing of 10 parent trees). Each of the trials was replicated on two test sites. The damage caused by the pathogen was estimated visually in June of the 2^nd and 6^th growing seasons using a five grade scale. Location and genetics were found to be significantly related to the level of needle cast damage. The proportion of severely damaged trees in each family correlated significantly between locations; moreover, the correlation was tighter for the control-crossed than open-pollinated families (r = 0.59 and r = 0.36, respectively), indicating higher stability of resistance level against the disease for the genetically more homogeneous material. The effect of plus tree selection on the proportion of severely damaged trees was similar, regardless of its status (i.e., mother-tree or father-tree) in the family. The progenies of plus trees selected for resin production had the same level of damage by Lophodermium spp. needle cast as the selections made for growth and stem form.