Occurrence of 2n gametes in the F1 hybrids of Oriental × Asiatic lilies (Lilium): Relevance to intergenomic recombination and backcrossing

Abstract

Cytological modes of the origin of 2n gametes were investigated in six different genotypes of F 1 hybrids between Oriental and Asiatic (OA) lilies (Lilium, 2n = 2x = 24). Chromosome pairing between the parental genomes was very low, the average frequency range from 0.3 to 1.2 bivalents per cell among the genotypes. Within a genotype the frequency of bivalents varied from 0 to 6 in some cases. The normally occurring haploid pollen grains were totally sterile. In contrast, in different genotypes, variable percentages of 2n pollen were found and shown to be fertile as estimated from pollen germination. A cytological analysis of Metaphase I and subsequent stages of meiosis using genomic in situ hybridization (GISH) revealed that there was intergenomic recombination between the alien genomes. Following Metaphase I stage, three different types of abnormal cytological events led to the formation of 2n pollen: (i) Post-Metaphase I division (PMI), (ii) Post-Metaphase II division (PMII) and (iii) Asymmetric Cytokinesis of the pollen mother cell followed by chromosome division. All three cytological events led to first division restitution (FDR) gametes. Based on in vitro pollen germination it was proved for two genotypes that 2n pollen was viable only during the first day of anthesis. It was possible to use 2n pollen successfully for backcrossing. Implications of 2n pollen for intergenomic recombination in BC 1 progenies are discussed.

Technical manual potato reproductive and cytological biology

“…The frequency of unreduced gametes is common in the plant kingdom and its occurrence has been reported in many species of families such as Solanaceae, Brassicaceae, Leguminosae, Rosaceae and Vitaceae (Veilleux, 1985;Camadro, 1986;Barba-González et al, 2005).…”

Manual biología reproductiva y citológica de la papa

“…La incidencia de gametos no reducidos es frecuente en el reino vegetal y su ocurrencia ha sido reportada en muchas especies de familias como Solanaceae, Brassicaceae, Leguminosae, Rosaceae y Vitaceae (Veilleux, 1985;Camadro, 1986;Barba-González et al, 2005).…”

The use of cytogenetic tools for studies in the crop-to-wild gene transfer scenario

“…H. bulbosum (Zhang et al, 1999), Asiatic ! Oriental lilies (Barba- Gonzalez et al, 2005) or Allium cepa ! A. fistulosum (Stevenson et al, 1998) ( Fig.…”