Cytogenetic analysis of Lathyrus japonicus Willd.(Leguminosae)

Abstract L. japonicus belongs to section Orobus and grows in most of the seashores of the Northern Hemisphere and as adventitious in Chile. In this report a detailed analysis of karyotype and meiotic behaviour was carried out in order to provide data for phylogenetic analysis. This species presented a symmetrical karyotype with 2n=14, 6m+8sm chromosomes. The longest and the shortest chromosomes of the complement were metacentrics while the sm were very similar and medium in size. NORs, determined by argentic staining, were localized in secondary constriction of the long arm of the longest m chromosome. The symmetrical karyotype is in accordance with the ancestral morphological characters showed by L. japonicus. Meiotic behaviour was regular with a chiasma frequency of 2.5 per bivalent at metaphase I. This fact agrees with the 98.2% of pollen stainability estimation. However, in ana-telophase I a bridge and fragment (<1%) were observed, while in interphase only fragments were detected (1%). In addition, out of plate chromosomes appeared in metaphase I and II (2%). These chromosomes segregated independently, formed micronuclei in telophase II and they became micromicrospores at the tetrad stage. These micromicrospores correspond to the micro pollen grains observed in anthesis.