Allozymes and genetic variability in Medicago turbinata, M. truncatula, and their hybrids

Abstract

The genetic variability in the diploid annual species (2n = 2x = 16) Medicago turbinata L. and M. truncatula Gaernt. was studied at three loci for the enzymes peroxidase, Prx1-1, and leucine-aminopeptidase, Lap1-1 and Lap1-2. Eight accessions of each species, including all the taxonomic forms were surveyed by starch gel electrophoresis. No variation was observed among plants within each accession. Among the M. turbinata forms, four alleles were observed at locus Lap1-2. No variation was detected for the other two loci studied. For the M. truncatula forms, four alleles were found for Prx1-1 and three alleles for Lap1-2. No variation was observed for locus Lap1-1. Form uncinata of M. truncatula, of uncertain taxonomic status, has at least one M. turbinata allele. Both species can be differentiated by their specific allozymes. In general, the alleles of the isozymic loci segregated in a Mendelian fashion in the expected ratios for monomeric enzymes. The presence of chlorophyll-deficient plants on some of the progenies involving different taxonomic forms of the species M. turbinata indicates the presence of isolation barriers between these forms. The lack of segregation at locus Lap1-1 in the tetraploidized interspecific hybrid proves its alloploid nature.