Melampsora pinitorqua (Braun) Rostr. on progenies of Pinus silvestris L. and in relation to growth regulating substances

Various methods of recording pine twisting rust have been discussed, and attack frequencies on 75 progenies of Pinus silvestris plus trees have been noted. Mention has also been made to the possibility of resistance breeding. Acid ether extracts of annual shoots of Pinus silvestris have been examined by various bioassays. Marked differences in the inhibitor effect between extracts from different pine clones have been established. A possible connection between inhibitor content and resistance has been discussed. Reduction in inhibitor content during axial extension and inhibitors in leachates from pine shoots has been connected with Melampsora occurrence. Gel filtration combined with thin layer chromatography has been used for separating the extract components. Among the inhibitors a number of resin acids have been identified by chemical means