Maize and Imperata cylindrica have been utilized globally as a pollen source for induction of haploids in wheat through chromosome elimination technique. Pollen parents with a higher haploid induction rate are desired for recovering the high frequency of haploids in wheat and related species. The present investigation was carried out with the aim to assess haploid induction efficiency of diverse germplasm of maize and I. cylindrica in different generations of intra and intergeneric crosses of hexaploid and tetraploid wheat and triticale-wheat derivatives. Crosses of twenty-six lines (female) with each of two I. cylindrica and twenty-one maize genotypes (testers) were evaluated for four haploid induction parameters viz., pseudoseed formation frequency (PFF), embryo formation frequency (EFF), haploid regeneration frequency (HRF) and haploid formation frequency (HFF). I. cylindrica outperformed maize in haploid induction rate with a frequency of embryos formed with I. cylindrica (18.39%) were significantly higher as compared to maize (4.08%). In the case of I. cylindrica genotype Ic-ye identified best with mean EFF of 30.55, 14.48 and 25.43% for hexaploids, tetraploids and triticale × wheat derivatives, respectively whereas in the case of maize genotype HPMC-60 performed best with EFF of 12.61% for hexaploids, HPMC-58 (12.58%) for tetraploids and HPMC-16 for triticale × wheat derivatives with EFF of 8.91%. I. cylindrica genotype Ic-ye and maize genotypes HPMC-14, HPMC-53, HPMC-60, HPMC-64 with significantly positive GCA for haploid induction parameters may be utilized as efficient pollen parents for recovering higher frequency of haploids in wheat.

Somatic cells derived from zebrafish haploid larval (both androgenetic and gynogenetic) cultures were used as donors for nuclear transplant into non-enucleated oocytes. Nuclei were transplanted either before or simultaneously with oocyte activation in the central region and in the incipient animal pole, respectively. Against expected results, 20% of transplanted embryos during oocyte activation using cells of gynogenetic origin reached the 100% epiboly stage, even two survived for up to 5 days, whereas no development was observed when cells from androgenetic origin were used. Results derived from this work open a novel possibility of studying somatic cell reprogramming and imprinting phenomena in zebrafish.

The objective of this study was to determine developmental pattern, total cell number, apoptosis and apoptosis-related gene expression in haploid and diploid embryos following parthenogenetic activation. In vitro-matured porcine oocytes were activated by electrical pulses and cultured in the absence or presence of cytochalasin B for 3 h. Zygotes with two polar bodies (haploid) and one polar body (diploid) were carefully selected and were further cultured in NCSU 23 medium containing 0.4% bovine serum albumin (BSA) for 7 days. The percentage of development to blastocyst stage was higher (p<0.01) in the diploid than in the haploid parthenotes. In haploid blastocysts, average total cell number was significantly reduced (p<0.05) and apoptosis was increased at day 7. The relative abundance of Bcl-xL and Bak mRNA in the diploid blastocysts was similar to that of in vivo-fertilized embryos. However, Bcl-xL was significantly decreased, and Bak mRNA was significantly increased (p<0.05) in haploid parthenotes compared with the diploid parthenotes. These results suggest that the haploid state affects apoptosis-related gene expression which results in increased apoptosis and decreased developmental competence of haploid parthenotes.

Freshly ovulated mouse oocytes exposed to 5 mM calcium ionophore A23187 for 5 min and controls (not exposed) were cultured in TYH medium with 10 μg/ml puromycin (the puromycin group) or 2 mM 6-dimethylaminopurine (DMAP; the DMAP group) for 4 h. Among the controls, few oocytes were activated even if they were treated with DMAP or puromycin. In the oocytes exposed to A23187, in contrast, the activation rate, i.e. the rate of oocytes showing at least one pronucleus (PN) after the treatment, was 46.2% (48/104) in the DMAP group and 90.0% (118/131) in the puromycin group. Activation rate in the puromycin group was significantly higher than in the DMAP and control groups (p < 0.0001, respectively). Furthermore, 82.4% (108/131) of the activated oocytes in the puromycin group showed one PN with extrusion of the second polar body (PB). In the puromycin group, the DNA content of the PN of parthenogenones with 1PN2PB was half that of a set of metaphase II chromosomes. Chromosomal analysis was possible in 14 parthenogenones with 1PN2PB in the puromycin group. The parthenogenones possessed a normal set (n = 20) of haploid chromosomes. The combination of A23187 and puromycin proved to be an effective method of producing haploid parthenogenones.

Haploid models of genetic drift in populations of constant size are considered. Generalizations of the models of Moran and Wright have been developed by Karlin and McGregor (for multiple alleles and non-overlapping generations), by Chia and Watterson (for two alleles and overlapping or non-overlapping generations) and by Chia (for multiple alleles and overlapping or non-overlapping generations), using conditioned branching processes. A new approach is developed which contains the models mentioned above and provides simpler expressions for the latent roots. A greater dependence between the birth events and death events can be permitted, and non-independent mutations treated.

The paper discusses models for genetic drift in haploid models; non-overlapping models following Wright, and overlapping models following Moran. It is shown that these models, and their extensions by Chia and Watterson, can all be restated as non-overlapping models. This equivalence between the two sets of models greatly facilitates the specification of latent roots and vectors.

This work studies the long-term effects of mutation and selection pressures on a diploid population embracing many genetic types. A number of results previously established for the simpler asexual case (see [4]) are extended to the cases of random mating and complete inbreeding (Theorem 1), and then, under particular conditions, to certain circumstances of mixed random mating and inbreeding (Theorem 3 and Corollary 1). Several implications for sex and diploidity are drawn from Theorem 2 and its corollaries. Further biological interpretations of these findings, especially of Theorem 2, are given in [3].