Coniferyl alcohol dehydrogenase, a multifunctional isozyme-gene-system in Norway spruce, affects the Armillaria resistance of young trees

Coniferyl alcohol dehydrogenase (CADH) is a key enzyme in lignin biosynthesis of conifers. Because it functions differently in different ontogenetic stages, tissues and organs of trees, a more in-depth investigation of this isozyme-gene-system in Norway spruce (Picea abies L.) appeared worthwhile. As a result of CADH analysis in somatic and gametic (megagametophytes of single trees) tissues of various spruce trees, one isozyme zone was detected in dormant buds, megagametophytes and embryos, which is controlled by one gene locus (CADH-A). Comparisons between a plus-tree and a random tree collection from the same Bavarian Norway spruce provenance showed a higher degree of heterozygosity at this gene locus among the plus-trees. A study of isozymes from buds of young trees which suffer from Armillaria infections showed a reduced CADH activity in zymograms as compared to healthy trees of the same stand. PCR-based amplification experiments of the DNA encoding CADH were performed with needles from the same spruce material. Using a specific primer pair designed from a cDNA of this gene, only a single band of 520 bp could be detected in agarose gels. Whereas this band was strong in healthy trees, needles of infected trees showed only a very faint DNA band at this position in agarose gels. Since the DNA of other chromosomal regions in infected trees did not indicate similar reductions of the amplification process, it may be postulated that considerable mutations or modifications of the CADH open reading frame are correlated with the susceptibility of trees to Armillaria infections.