Chromosome numbers in Begonia.

The somatic chromosome numbers of 100 Begonia species were counted, of which 72 have been determined for the first time. Eighteen different numbers have been established, ranging between 22 and 156, fifteen of which could be fitted into a tentative scheme of five polyploid series. The most common numbers were 22 (14 species), 28 (35 species) and 56 (17 species). The species have been grouped into sections according to Irmscher. In some cases these sections appeared to have a characteristic chromosome number whereas in others, e.g. Pritzelia and Begoniastrum, a great diversity in chromosome number was encountered. [For earlier work see H.A., 39: 5182.]-Univ. Wageningen. (Abstract retrieved from CAB Abstracts by CABI’s permission

Chromosome numbers in Begonia.3.

The somatic chromosome numbers are presented of 34 spp. of African, Asiatic and American origin. Many spp. had not previously been investigated cytologically. [For part 2 see HcA 42, 1737.]. (Abstract retrieved from CAB Abstracts by CABI’s permission

The cytological background of Cyclamen breeding = De cytologische achtergrond van de cyclamen-veredeling

Cytological studies and crossing experiments were carried out in both cultivars and species of Cyclamen in connection with breeding. Within 278 groups of Cyclamen cvs. grown at different nurseries in Western Europe, there were 48 diploids with 2n = 48, 168 tetraploids with 2n = 96, 58 and 4 aneuploids with 2n = 92 and 94, 95, respectively. It was known that the first tetraploid and aneuploid originated in 1863 and 1898, respectively.The results of reciprocal crosses between diploids and tetraploids were studied. On genetic evidence the origin of the unexpectedly high number of tetraploid descendants was explained by dispermy (fertilization of the female gamete by two male gametes) in the cross 4n x 2n and analogously by endogamy (fusion of 2 haploid embryo sac nuclei) in the 2n x 4n cross.The chromosome range of 14 Cyclamen spp. was determined as 20, 22, 30, 34, 48, 84-86, 96 and 136, to be grouped into 3 polyploid series with the basic numbers n = 10, 17 and 24. Attempts to produce interspecific hybrids failed, except once. Reconstruction of some numbers and creation of missing links by crossing the present-day species was therefore impossible.<p/