GENETIC-CONTROL OF PLASTIDIC L-GLUTAMATE DEHYDROGENASE ISOZYMES IN THE GENUS CAPSELLA (BRASSICACEAE)

Leaf extracts of three Capsella species (Brassicaceae), two diploids and one tetraploid, have been analysed for isozymes of L-glutamate dehydrogenase on polyacrylamide gels. A plastidic GDH (EC 1.4.1.4.) consisted of at least seven bands. Progeny analyses and crossing experiments revealed that within the two diploid species two genetic loci code for this pattern. One of the loci, Gdh1, appeared to be monomorphic. The other locus Gdh2, is polymorphic and segregates for three alleles determining allozymes in accordance with Mendelian inheritance. Estimates of outcrossing rates based on segregation at the Gdh2 locus support the view that one of the diploid species is highly inbred whereas the other is an obligate outbreeder. In the tetraploid species, both loci are apparently duplicated so that four instead of two genes determine the polypeptide structure of plastidic GDH. These loci share the same alleles with the diploid species and no additional allozymes have been detected.