Cytogenetic characterization, nuclear genome size, and pollen morphology of some Hedysarum L. taxa (Fabaceae) from Algeria, with emphasis on the origin of H. perrauderianum Coss. & Durieu

Four spontaneous diploid taxa (2n = 2x = 16 chromosomes) of the genus Hedysarum L. were studied for the first time using molecular cytogenetic approach and a tetraploid one as an additional comparative control. This study follows the work undertaken on this genus as part of the preservation and valorization of fodder and pastoral phytogenetic resources in Algeria. Fluorescent in situ hybridization (FISH) results revealed the same number of 35S rDNA loci for all diploid taxa, but differences in the number and position of 5S ribosomal genes. Chromomycin fluorochrome banding displayed that all chromomycin positive bands (GC-rich heterochromatin) were colocalized with rDNA signals. 2C DNA values (genome size), estimated by flow cytometry, indicated greater than two-fold difference among diploid taxa where nuclear DNA amount ranged from 2C = 1.26 pg in H. carnosum Desf. to 2C = 3.36 pg in H. naudinianum Coss. Genome size of tetraploid H. perrauderianum Coss. & Durieu (2n = 4x = 32) also estimated for the first time, was 6.64 pg which is almost twice of the value of diploid H. naudinianum 2C = 3.36 pg. Palynological analysis by light microscopy shows two types of pollen grains: prolate and tricolpate for H. naudinianum and H. perrauderianum, subprolate and tricolporate for H. carnosum, H. spinosissimum subsp. capitatum (Desf.) Asch. & Gr. and H. pallidum Desf. These new data enrich the knowledge about relationships among these species and also allow proposing and discussing the possible origin of the tetraploid H. perrauderianum from the diploid H. naudinianum.