Cytological studies in a pentasomic of 2n = 12 Coix taxon

Abstract

Among a natural population of Coix aquatica Roxb., a pentasomic (2n + 3; 2n = 15) was isolated and studied cytologically for the first time. The extra homologous chromosomes in the plant behaved normally, as they did not disturb the rest of the bivalents through meiosis except for the stickiness and rare occurrence of a few univalents and chromosome fragments. The majority of pollen mother cells (PMCs) showed five bivalents and a pentavalent at diakinesis. The different anaphase segregations led to the formation of hypo- and hyper-ploid male gametes from n-1 (n = 5) to n + 4 (n = 10) chromosomal constitutions. Although the chromosomal configurations towards the later stages were found to be sticky in most of the meiocytes, the meiosis was clean, giving rise to pollens that appeared to be normal. The plant yielded a few fertile seeds also. The origin of this higher polysomic is considered to be through the fusion of male and female super haploid gametes produced by the trisomics that arose from the 2n = 12 Coix taxon.