Identification of genome constitutions in Begonia×chungii and its putative parents, B. longifolia and B. palmata, by genomic in situ hybridization (GISH).

Based mainly on morphological features and geographical distribution, Begonia×chungii (2n=22) was recently reported as a natural hybrid between B. longifolia and B. palmata in Taiwan. This study aims to confirm the hybridity of B.×chungii and to sort out the genome constitutions of its putative parents, using genomic in situ hybridization (GISH). Genomic DNAs of both parental species were used as probes for B.×chungii and the experimental F(1) hybrid, B. palmata×B. longifolia, in GISH analyses. Bicolor-GISH analyses in B.×chungii showed that the 22 chromosomes consisted of six chromosomes hybridized with a probe derived from the B. palmata genome, six with another probe from the B. longifolia genome and the remaining ten with both genomes overlapped. Meanwhile, bicolor-GISH in B. palmata×B. longifolia showed a remarkable similarity to that of B.×chungii. The reciprocal GISH results between B. longifolia and B. palmata were comparable. Our GISH analyses confirmed that B.×chungii is a natural F(1) hybrid between B. longifolia and B. palmata. Genomes of the parental species were shown to be partially homologous, suggesting a derived common ancestral genome in them.