Relationships between Lathyrus cassius, L. odoratus, and L. hirsutus Assessed by Experimental Hybridization, Analysis of Meiotic Pairing, and DNA: DNA Hybridization

Relationships between three species of Lathyrus, including L. cassius, L. hirsutus, and L. odoratus, were studied with hybridization, cytogenetic analyses, and DNA dot blots. Broadly similar results were obtained with these methods, showing that L. cassius, L. hirsutus, and L. odoratus are all closely related, with L. odoratus more closely related to L. hirsutus than L. cassius. Hybrids were formed between the three species, but only those between L. odoratus and L. hirsutus show high levels of fertility and more or less regular chromosome pairing at meiosis. Despite having similar karyotypes, L. cassius had large centromeric C-bands that are absent from L. hirsutus and L. odoratus. DNA dot blots showed that the three genomes were equally different from each other. Reciprocal differences in flower morphology and metaphase I chromosome pairing were seen in hybrids between L. cassius and L. hirsutus. A modification of the most recent systematic placement of the species is suggested so that L. hirsutus is allied with L. cassius and L. odoratus with L. chloranthus.