Chromosome numbers of hybrid tuberous begonias

Abstract

The somatic chromosome numbers of 67 hybrid tuberous begonia cultivars (Begonia x tuberhybrida Voss) have been determined. The material concerned was collected in Belgium and England and represents several distinct groups, comprising both cultivars originated at the turn of this century and those introduced recently.The old 'Pendula' group is characterized by the diploid chromosome number 28. Among the 'Multiflora' group diploid, triploid and tetraploid cultivars are represented almost equally, while the investigated 'Multiflora maxima' and large-flowered begonias proved to be tetraploid except for one triploid.Mitotic instability, to the extent reported by some authors, was not observed. The variation of the diploid number between 27 and 28, the triploid number between 41 and 42 and of the tetraploid number between 52 and 56 can be explained as a consequence of the fact that in the original hybridization wild tuberous species with 2n = 26 and 2n = 28 were involved.

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

“…Among Begonia species, chromosome numbers range from 2n = 16 for B. rex to 2n = 156 for B. acutifolia. Between these extremes, a wide range of chromosome numbers have been described (Doorenbos et al, 1998;Legro and Doorenbos, 1969;Legro and Doorenbos, 1971;Legro and Doorenbos, 1973). Many species or cultivars exhibit chromosome numbers of 2n = 26 or 28 (x = 13 or 14) or a multiple of this number.…”

“…Many species or cultivars exhibit chromosome numbers of 2n = 26 or 28 (x = 13 or 14) or a multiple of this number. Within the horticultural tuberous begonia group, derived from interspecific crosses between American Begonia, chromosome numbers of 2n=27,28 (diploid), 41,42 (triploid) and between 52 and 56 (tetraploid) are most common (Legro and Haegeman, 1971;Haegeman, 1979), but variation outside this sequence exists. In Asian Begonia, 2n = 22 (x = 11) is the most frequently observed chromosome number.…”

“…Subsequently, chromosome numbers have diverged resulting in some 'new' basic chromosome numbers for some subgroups (eg x = 11 or x = 14), through selective chromosome elimination and polyploidy. Other derived numbers may have resulted from interspecific hybridisation, and Legro & Doorenbos (1969) suggested that 2n = 22 possibly originated out of a cross between 2n = 16 and 2n = 28.…”

Meiotic aberrations during 2n pollen formation in Begonia

“…Begonias are easily grown from seed and cross-hybridize well (Anderson, 2007). A wide variety of chromosome numbers have been reported for Begonia species and cultivars, ranging from 2n ¼ 16 for B. Rex to 156 for B. acutifolia (Legro and Haegeman, 1971;Sarkar, 1989;Doorenbos et al, 1998;Oginuma and Peng, 2002). This suggests frequent polyploidy and aneuploidy in the genus.…”

“…This suggests frequent polyploidy and aneuploidy in the genus. Owing to this diversity, there is no general basic chromosome number for the genus, although x ¼ 11 (several Asiatic begonias; Oginuma and Peng, 2002), 13 and 14 (tuberous begonias; Legro and Haegeman, 1971) are mostly suggested. Several tuberous cultivars are tetraploid, and also tetraploid cultivars of the B. semperflorens cultorum group surpassed the diploid cultivars during their breeding history (Horn, 2004).…”