Occurrence of differential meiotic associations and additional chromosomes in the embryo-sac mother cells of Allium roylei Stearn

Abstract

A small population of complex translocation heterozygote plants of Allium roylei from the Bani region of Jammu Province was studied for meiosis in the female track. This study resulted in identification of two variants, having embryo-sac mother cells (EMCs) with more than 16 chromosomes. EMCs of the remaining plants invariably had diploid (2n = 16) chromosome complement. Female meiosis, in general, was found to be abnormal, with nearly 23% and 11% chromosomes associating as quadrivalents or trivalents at prophase I and at metaphase I, respectively. This was followed by irregular segregation of chromosomes at anaphase I. Amongst the variants; one had 38% EMCs with eight bivalents plus two small sized chromosomes. Their small size, dispensable nature and tendency to affect the pairing behaviour of normal complement are some of the features that latter chromosomes share with the B chromosomes. Seventeen to nineteen chromosomes were observed in 35% EMCs of other variant; the remaining cells had 16 chromosomes. Chromosomal behaviour in both kind of cells (euploid and aneuploid) was more or less similar. Unlike female meiocytes, male meiocytes analysed earlier of this strain always had 16 chromosomes which paired to form extremely complex associations involving 3-16 chromosomes. The most likely cause of this asynchrony with regards to number of chromosomes involved in multivalent formation seems to be interaction of genes controlling chiasma formation with the different physiological conditions of male and female meiocytes.

Reduction in chiasma frequency and pollen fertility due to multiple chromosomal associations and univalents inSaxifraga diversifoliafrom alpine regions of northwest Himalayas (India)

“…Heterozygosity for reciprocal translocations, which is generally identified by reduced reproductive capacity and the presence of multivalents during reduction division, has the potential to create and conserve specific gene combinations (Sharma and Gohil 2011). The presence of 1-2 quadrivalents (rings or chains) along with 4-6 bivalents in the PMCs of var.…”

Structural Heterozygosity and Cytomixis in <i>Deutzia staminea</i> R. Br. ex Wall. from Parvati Valley, Himachal Pradesh, India

“…These interchanges are usually associated with semi-sterility of gametes (Biswas andBiswas 1997, Ghaffari et al 2009) or complete sterility Koul 1978, Sharma andGohil 2003, Kohli andGo- hil 2011). Heterozygosity for reciprocal translocations which is generally identified by reduced reproductive capacity and the presence of multivalents during meiosis has the potential to create and conserve specific gene combinations (Sharma and Gohil 2011). Presently reciprocal translocations have been noticed for the first time in some wild individuals of D. staminea.…”

Morphological, Cytological and Embryological Characterization of F1 A. cepa × A. roylei Hybrids

“…Although no irregularities were observed during the division of the megasporocyte, most of them occurred after meiosis, when some abnormal megaspores failed to form typical mononucleate embryo sacs (Liu et al, 2004;Zeng et al, 2009). On the other hand, investigation of female meiosis in A. roylei (Sharma and Gohil, 2011) resulted in identification of additional chromosomes and multivalents in embryo sac mother cells that, as the authors suggest, may adversely affect the reproductive capacity and lead to production of genetically imbalanced gametes. This indicates that atypical female gametophytes and degeneration of embryo sacs in the analyzed F 1 A. cepa × A. roylei hybrids may possibly result from meiotic irregularities.…”