Formation of Aneuploid Gametes through Nondisjunction during Premeiotic Mitoses in Coix gigantea

Abstract

Mixoploid plant showing a range of aneuploid PMCs from nullisomic (2n-2, 2n=18) to tetrasomic (2n+2, 2n=22) constitutions was isolated from a population of Coix gigantea. While majority of the PMCs were diploid carrying 2n=20 chromosomes, nearly 24% PMCs in some male racemes showed typical aneuploid chromosome configurations viz., 9^II in nullisomics (2n=18), 9^II+1^I in monosomics (2n=19), 9^II+1^III or 10^II+1^I in trisomics (2n=21) and 11^II or 9^II+1^IV in tetrasomics (2n=22). The chromosome configurational regularity among the aneuploid PMCs indicated that 2n-1 (2n=19) and 2n+1 (2n=21) constitutions probably arose through nondisjunction during one of the premeiotic mitoses in some sporogenous cells. Although difficult to explain the origin of PMCs with 2n-2 (2n=18) and 2n+2 (2n=22) constitutions, somatic pairing followed by nondisjunction during one of the premeiotic mitoses might lead to such situations.