Cytogenetic Studies in Cyrtanthus I. Segregation in an Allotetraploid

UKING the last ten years the author has been working on different D cytological and genetical problems in the genus Cyrtanthus.The main problems under investigation were the following:(1) Gene and chromosome segregation in artificial auto-and allotetraploids.(2) The relation between multivalent formation and chromosome morphology in triploids and tetraploids.(3) The inheritance of flower number, perianth length and flower colour in a cross C .parviflorusXC.Mackenii var.Cooperi.(4) Vitality of aneuploids in relation to chromosome constitution.( 5 ) The effect of polyploidy, aneuploidy and translocations on fertility.(6) Type and origin of structural chromosome changes arising during mitosis in some, usually aneuploid, individuals.(7) Karyotype analysis of different species.The present paper is concerned with the cytological and genetical analysis of a triploid F,, two triploid backcrosses, and a tetraploid F, from one single tetraploid F, plant.This tetraploid is in reality a segmental allopolyploid from the cross C. parviflorusX C .Mackenii var.Cooperi.Indirect information concerning chromosome segregation and multivalent formation in this tetraploid is obtained from the cytological constitution of the triploid progeny.For the genetical analysis a dipIoid F, and a diploid backcross from the same cross are also presented.Preliminary data from some of these crosses were treated in the paper "Chromosome balance in Cyrtanthus" (ISING, 1962).Some of the present tables include data given in that paper (pp.108-1 11 ) .In the paper "Chromosome balance in CyrtantZd' C. Hackenii var.Cooperi was incorrectly called C. Zutescens.