Enzyme variation and inheritance in Glechoma hederacea (Lamiaceae), a diploidized tetraploid

The chromosome number of the polyploid species Glechoma hederacea was found to be 2n = 36 in a sample of 93 ramets derived from 27 sites in N and C Europe. Variation in 10 enzymes was surveyed in material from S Sweden and S Czech Republic. The genetic control of variation was investigated using segregating progeny from crosses and self-fertilized heterozygous plants. The genetic analysis comprised 30 of 32 putative alleles detected in the geographical survey. Five loci (Aat-2, Tpi-1, Tpi-2, Pgd-2 and Mnr) behaved as isoloci with one copy of a locus being monomorphic for a common allele, the other di-allelic for a common allele and a variant allele. In four isoloci (Pgd-1, Pgi-2, Mdh-2 and Adh), both copies of the duplicated locus were polymorphic, with one allele common to both copies and with another allele unique for each copy except for Pgd-1 where both copies were tri-allelic. Three loci, Pgm-3, Skd-1 and Skd-2 were regarded as being non-duplicated. Segregation ratios for all enzyme loci were in close agreement with expectations based on disomic inheritance. Our data suggest that the tetraploid G. hederaca is a diploidized autotetraploid.