A chromosome atlas and interspecific – intergenic index for Lotus and Tetragonolobus (Fabaceae)

Abstract

Basic chromosome numbers in Lotus are x = 5, 6, and 7. It is considered that evolution has proceeded in the genus by means of a descending aneuploid series from an eight-chromosomed ancestor. Chromosome numbers for species of Tetragonolobus are based on x = 7. Somatic chromosome numbers are reported for 108 species and 38 varieties. The chromosome numbers for five species (L. hamatus Greene, 2n = 14, L. haydonii (Orcutt) Greene, 2n = 14, L. hintoniorum B.L. Turner, 2n = 14, L. mearnsii Britton, 2n = 14, L. utahensis Ottley, 2n = 14) and seven varieties (L. argophyllus (Gray) Green var. argenteus Dunkle, 2n = 14, L. dendroideus var. traskiae (Eastwood ex Noddin) Isely, 2n = 14, L. heermanii (Durand et Hilgard) Greene var. orbicularis (Gray) Isely, 2n = 14, L. junceus (Benth.) Greene var. biolettii (Greene) Ottley, 2n = 14, L. strigosus var. hirtellus (Greene) Ottley, 2n = 14, L. strigosus var. tomentellus (Greene) Isely, 2n = 14, L. uliginosus ssp. vestitus (Lange) A. Pedersen, 2n = 12) are reported for the first time. Natural diploid, tetraploid, and hexaploid plants are reported for L. alpinus. Several species are reported as possessing B chromosomes. Mixoploidy is reported to occur in three species (L. alpinus, L. glacialis, L. glareosus). In addition, chromosome numbers are given for plants regenerated from calluses grown in tissue culture having both heteroploidy, euploidy, and mixoploidy. Root nodules are reported with tetraploid and octoploid cells in addition to the normal number of chromosomes. Trisomie series have been partially developed in L. tenuis and L. uliginosus. Polytene chromosomes were observed in suspensor cells of three species of Lotus. Feulgen cytophotometric measurements, to determine the DNA nuclear content, were made for 16 species of Lotus and one species of Tetragonolobus. The majority of the studies in Lotus concern the economic species L. corniculatus, L. tenuis, and L. uliginosus. Interspecific hybridization was carried out in different combinations between diploids, autoploids, and amphidiploids. Intergeneric hybrids were attempted by somatic hybridization, protoplast fusion, and asymmetric hybridization between Lotus and other species (Glycine max, Medicago sativa, Oryza sativa). Key words: chromosome numbers, DNA values, Fabaceae, Lotus species, interspecific hybrids, intergeneric hybrids, Tetragonolobus.