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 biosy nthesis of conifers. Because it functions differently in different ont ogenetic stages, tissues and organs of trees, a more in-depth investig ation of this isozyme-gene-system in Norway spruce (Picea abies L.) ap peared worthwhile. As a result of CADH analysis in somatic and gametic (megagametophytes of single trees) tissues of various spruce trees, o ne isozyme zone was detected in dormant buds, megagametophytes and emb ryos, which is controlled by one gene locus (CADH-A). Comparisons betw een a plus-tree and a random tree collection from the same Bavarian No rway spruce provenance showed a higher degree of heterozygosity at thi s gene locus among the plus-trees. A study of isozymes from buds of yo ung trees which suffer from Armillaria infections showed a reduced CAD H activity in zymograms as compared to healthy trees of the same stand . PCR-based amplification experiments of the DNA encoding CADH were pe rformed with needles from the same spruce material. Using a specific p rimer pair designed from a cDNA of this gene, only a single band of 52 0 bp could be detected in agarose gels. Whereas this band was strong i n healthy trees, needles of infected trees showed only a very faint DN A band at this position in agarose gels. Since the DNA of other chromo somal regions in infected trees did not indicate similar reductions of the amplification process, it may be postulated that considerable mut ations or modifications of the CADH open reading frame are correlated with the susceptibility of trees to Armillaria infections.