VARIATION AND INHERITANCE OF ISOZYME LOCI IN CONTROLLED CROSSES OF SALIX ALBA AND SALIX FRAGILIS

The expression of polymorphism in different enzyme systems was investi gated in clones of Salix alba and Salix fragilis. Dormant buds and spr outing leaves were used but only few consistent enzyme patterns could be revealed and were retained for further testing. When considering al l obtained enzyme profiles, a total of 43 genes could be scored, of wh ich 15 may show polymorphism within S. alba or S. fragilis. Polymorphi sm was observed in aconitase, alcohol dehydrogenase, phosphoglucomutas e, leucine aminopeptidase, glutamate oxaloacetate transaminase, beta-e sterase, isocitrate dehydrogenase, glutamate dehydrogenase, peroxidase , superoxide dismutase and xanthine dehydrogenase. The genetic basis o f phosphoglucomutase, leucine aminopeptidase glutamate oxaloacetate tr ansaminase and shikimate dehydrogenase could be inferred directly from intraspecific and interspecific controlled crosses. Full-sib progeny showed mendelian segregation for lap-1 and most of the pgm-2 alleles, whereas in other genes such as beta-est-1 and adh-2, there was only fi xed heterozygosity. Most of the isozymes can not be used directly as g ood markers at species level. Differences between S. alba and S. fragi lis are mainly in the allele frequencies. The number of genes and alle les of the polyploid S. alba and S. fragilis were compared to those of earlier reports on diploid Salix species. The polyploids contain less genetic diversity in their soluble enzymes than the diploids. Duplica ted genes did not led to a substantial increase in the heterozygosity levels in the S. alba-S. fragilis complex.