Summary Isolation of seven different types of trisomics was possible in the advanced generations of an induced trisomic recovered earlier in grass pea cultivar BioR-231. The trisomic plants were phenotypically distinguishable from the diploid mother cultivar (2nϭ14) by their contrasting morphological characteristics and cytologically by the presence of an extra chromosome (2nϩ1ϭ15). Variations in several morphological traits were distinctive and stable in different trisomic plants during succeeding generations. Among the phenotypic manifestations, modifications in leaflet morphology, stipule character and seed coat colour were specific for each of the seven types of trisomics. The different trisomics could be distinguished instantly from one another by the characteristic shape, number, position and orientation of leaflets as well as stipules. Since leaflet character was specific and distinctly visible at the very seedling stage it could be used conveniently as a marker character for identification and classification of seven trisomics. Moreover, apical modification of leaflet, complete absence or occurrence of stipule in different forms and variations in floral morphology were also conspicuously different in different types. The extra chromosome appeared as univalent or in trivalent association and the trivalents occurring only in linear or frying pan or Y shaped configuration characterized all of the 7 types as primary types. Pollen sterility and reduced seed yield in these trisomic types might be the consequences of unequal separation, formation of laggard and anaphase bridge.Key words Seven primary trisomics, Cytogenetics, Grass pea.A trisomic plant of grass pea detected earlier in the R 2 generation (1997-98) raised through gamma ray irradiation was cytogenetically characterized (Biswas 1998, Biswas and Biswas 2002, 2004. Trisomic plants of grass pea possessing relatively medium sized, low number of chromosome are convenient for evaluation of cytogenetic consequences. Further investigation in the trisomic plants was, therefore, carried out by maintaining them through self pollination and conspicuously different types of trisomics evolved with distinctive phenotypic modifications in succeeding generations were identified by their cytomorphological peculiarities, protein profiles and isozyme banding patterns. In the present text, cytogenetic characteristics manifested in the seven types of trisomics isolated in grass pea have been illustrated.
Materials and methodsFresh seed materials were collected during the winter season 1999-2000 from the trisomic plants of grass pea maintained in the authors' laboratory by growing selfed R 3 progeny of an induced trisomic recovered earlier through irradiation with 35 KR gamma rays (Biswas 1998). Initially the trisomic plants were distinguished from the mother diploid cultivar BioR-231 by their characteristic morphological peculiarities observed at different stages of growth and development from © 2007 The Japan Mendel Society Cytologia 72(4): [385][386][387][388][389][390...