Cytogenetic characterization of seven different primary tetrasomics in grass pea (Lathyrus sativusL.)

Seven different types of tetrasomics were isolated and characterized in the advanced selfed generations of seven primary trisomics (2n+1; 2n=15) recovered earlier in diploid (2n=14) grass pea (Lathyrus sativus L.) variety BioR-231. The tetrasomic types (2n+2; 2n=16) could be distinguished instantly from one another by contrasting modifications in shape, number, position and arrangement of leaflets at early seedling stage and also by variations in stipules, stem habit, floral morphology and seed coat color. These variations were distinctive and stable in the seven tetrasomics during successive generations. The extra chromosomes were detected either in bivalent or in trivalent-univalent or in quadrivalent condition at metaphase-I. Presence of a ring like quadrivalent in diakinesis as well as in metaphase-I was the regular feature in the tetrasomic plants. Occurrence of linear or Y-shaped trivalent indicated unmodified nature of the extra chromosomes in the different types of them and they were characterized as primary tetrasomics. As compared to trisomic phenotypes, influences of two extra homologous chromosomes were manifested in more exaggerated way on phenotypes of different tetrasomics. Pollen sterility and reduced yield in these tetrasomics might be the outcome of irregularities at anaphase-I manifested as unequal separation, formation of laggards and bridges.