Comparison of the genome size, endoreduplication, and ISSR marker polymorphism in eight Lotus (Fabaceae) species

Abstract

Several species within the genus Lotus are important forage crops, and many are endangered or rare. Despite the high genetic diversity of the genus, identification of Lotus species is problematic because of the limited number of reliable morphological markers. In search of a quick, inexpensive, and steady method for species identification, genome size and cell cycle/endoreduplication intensity of 14 accessions belonging to eight Lotus species were estimated by flow cytometry. ISSR-PCR was also applied to find sensitive molecular markers for genetic diversity estimation. Genome size estimation revealed that Lotus species possess very small genomes and this characteristic enables the identification of five out of eight species. However, a flow cytometric study of cell ploidy/endopolyploidy in seeds and seedlings enabled us also to distinguish the remaining species. Thus, it is proposed here that combined flow cytometric analyses (the estimation of genome size and cell cycle/endoreduplication pattern) can be applied for screening of Lotus species. Nonetheless, ISSR markers provided a more precise identification of studied accessions, including detection of genetic diversity within a species. Most of the tested primers revealed polymorphism between species, and three primers, (GACA)4, (CA)7G, and (CTC)4RC, also revealed polymorphism between accessions within a species. The ISSR markers revealed high polymorphism between eight Lotus species and low intraspecific variation between accessions within the same species (L. maritimus and L. uliginosus).