Cytological Study of <i>Begonia</i> Sect. <i>Platycentrum</i> (Begoniaceae) with Chromosome Number 2<i>n</i>=22

Abstract

Previous chromosome information for Asian Begonia sect. Platycentrum with 2n=22 is restricted to 28 taxa. Here we add another 23 species to the list and reconfirm this chromosome number for nine species of sect. Platycentrum. The number of species of sect. Platycentrum with 2n=22 reported is increased to 51 taxa, covering ca. 70.8% of the 72 taxa with reported chromosome numbers in the section. Additionally, we provide the first report of karyotypes of 32 species with 2n=22 of the section. Based on the present results and previous chromosome reports for a total of 51 taxa with 2n=22, the chromosome evolution for 2n=22 in sect. Platycentrum is discussed.

Cytological study of <i>Begonia</i> sect. <i>Platycentrum</i> (Begoniaceae) with chromosome numbers 2<i>n</i>=24, 26, and 52

“…1G, H). Chromosomes at mitotic metaphase are 2n=26, disagreeing with a previous report of 2n=22 (Kono et al 2022c). Variation in chromosome size is gradual; the longest chromosome is ca.…”

“…Platycentrum have 10 m-chromosomes and two smchromosomes in common. Consequently, our studies of Asian Begonia cytology show that all chromosome variants (ranging from 2n=12 to 44) within 10 sections [i.e., Baryandra (Kono et al 2021a), Coelocentrum (Kono et al 2020), Diploclinium (Kono et al 2021b), Flocciferae (Kono et al 2023a), Haagea (Kono et al 2022a), Jackia (Kono et al 2023b), Parvibegonia (Kono et al 2023a), Petermannia (Kono et al 2022a), Platycentrum (Kono et al 2022b, c), and Reichenheimia (Kono et al 2023b)], consistently have two or four sm-chromosomes within their respective chromosome complements in common.…”

“…Chromosome fusions play an important role in chromosome evolution in Asian Begonia. As an example, 2n=22= 12m+ 10sm(st) 2sm could have resulted from 2n=30= 8m+ 22sm(st) 2sm by chromosome fusion: among 12 m-chromosomes of 2n=22, 4 m-chromosomes fused with 4 sm(st)-chromosomes in 2n=30= 8m+ 22sm(st) 2sm , and the remaining 4 m-chromosomes resulted from 8 sm(st)-chromosomes fused each other in 2n=30= 8m+ 22sm(st) 2sm (Kono et al 2022c). We also speculate that 2n=24 and 2n=26 are similarly derived from 2n=30.…”

“…(Legro and Doorenbos 1969, 1971, Doorenbos et al 1998] that covers ca. 23.5% of the 34 African species with chromosome counts (Kono et al 2023b). It should be noted, though, that African Begonia is classified under 18 sections (Begonia Resource Centre, Moonlight et al 2018).…”

Cytological Study of <i>Begonia</i> Sections <i>Flocciferae</i>, <i>Parvibegonia</i> and <i>Platycentrum</i> (Begoniaceae) with Chromosome Numbers 2<i>n</i>=28 and 56

“…The chromosome number 2n=56 in B. baliensis is the first such count in sect. Platycentrum (Kono et al 2022b(Kono et al , 2022c. Its karyotype 2n=56= 20m+ 36sm(st) 4sm consists of four sets of 14 chromosomes of n=5m+ 9sm(st) 1sm , suggesting that the species is tetraploid of 2n=28= 10m+ 18sm(st) 2sm .…”