Meiotic aberrations during 2n pollen formation in Begonia

Use of 2n Gametes in Plant Breeding

“…In a normal meiosis, one mother cell (2n) divides in 4 (n) daughter cells (tetrad formation). Aberrations during chromosome pairing, spindle formation (parallel spindle, tripolar spindle, fused spindle, sequential spindle or lack of spindle) or cytokinesis might result in the formation of triads, dyads or monads (Bretagnolle & Thompson, 1995;Dewitte et al, 2010c;Taschetto & Pagliarini, 2003). This finally results in pollen grains with the same DNA content (2n in the case of dyads or triads) or a doubled DNA content (4n in the case of monads) compared to the somatic 2n plant cell.…”

The Origin of Diversity in Begonia: Genome Dynamism, Population Processes and Phylogenetic Patterns

“…In horticultural crosses, the interspecific hybrid B. 'Tamo' (2n = 23) showed irregular chromosome pairing with multivalents of up to 7 chromosomes (Dewitte et al, 2010c). These associations were often observed between chromosomes with large differences in size, which indicated associations between non-homologous chromosomes and possible recombination between these non-homologous DNA segments (illegitimate recombination).…”

“…Illegitimate recombination is the driving force behind genome size decrease in Arabidopsis (Bennetzen et al, 2005;Devos et al, 2002), but can also be an important mechanism for exon shuffling, a major process for generating new genes (Long, 2001;Long et al, 2003). In some hybrids, tight associations between chromosomes resulted in chromosome bridges and fragments during anaphase I (Dewitte et al, 2010c). This might be indirect evidence for the presence of paracentric inversions during crossing-over (Newman, 1966).…”

Syncyte and ‘2<i>n</i>’ Pollen Grain Formation in <i>Heracleum pinnatum</i>: A Possible Mechanism for the Origin of Intraspecific Polyploids

“…Production of such 2n pollen grains through sexual polyploidization (through syncytic meiocytes) certainly has the advantage over synthetic PPDS (polyploids produced through the use of spindle inhibitors). Moreover, syncytic PPDS have fixed heterozygosity, while in sexual PPDS, heterozygosity is not fixed because of the recombination between parental chromosomes which might play a role in evolution (Soltis and Soltis 2000, Dewitte et al 2010). The possible causes of syncyte formation in plants may be diverse and are presumed to be due to chemicals, X-rays, temperature and moisture, stress or genetic factors (Merwine and Bennett 1966, Pantulu and Manga 1971, Rao and Koduru 1978, Rao et al 1991, Nirmala and Rao 1996, Kumar and Srivastava 2009.…”