Meiotic correlations and bound arm associations between the diploid and autotetraploid of Withania somnifera (L.) Dunal, and implications on genetic stability

Abstract

Artificial polyploidy could be an important means of genetic enhancement in the species where plant biomass is the source of economic product. However, success of polyploidy approach becomes limited if the seeds are the principal means of reproduction, since the seeds so produced could be genetically imbalanced owing to disturbances in meiosis. The present study provides an illustrated account of successful induction of autotetraploidy, morphometric details of the induced polyploid, and its stability over generations through seed progenies in an important medicinal plant, Withania somnifera (L.) Dunal (fam. Solanaceae). Meiotic analyses of the progenitor diploid and its derived autotetraploid revealed that the induced tetraploid sports high bivalent pairing in the C0 generation and its subsequent enhancement over subsequent generations (C1, C2), coupled with reduced genetic segregation. Detailed analysis of meiotic configurations show that low chiasmate association in the progenitor diploid facilitates high bivalent pairing in the autotetraploid, and thus balanced meiosis and improved seed fertility in the tetraploid. Further, the perennial breeding habit of W. somnifera and tetrasomic pattern of inheritance in the induced tetraploid offer a unique opportunity for fixation of heterozygosity by way of using C0 as a the nuclear stock to realize C1 seeds for propagation without losing polyploid heterosis.