Genetic characterization and pollen viability of a natural putative hybrid of Begonia boliviensis x B. micranthera (Begoniaceae) from Argentina

An orange-flowered natural putative hybrid of Begonia boliviensis x B. micranthera was recently discovered from Calilegua National Park in Jujuy Province, Argentina. Propionic hematoxilyn method was applied to study its chromosomal behavior during meiosis, Muntzing's stain solution was used to determine pollen grain fertility and ITS2 and rbcL sequences were amplified to help confirm the parentage of the putative hybrid. This plant has a gametophytic chromosome number of n = 13, very regular meiotic behavior and an intermediate percentage of viable pollen compared to other studied natural putative hybrids. The ITS2 sequence data support the parentage of the putative hybrid begonia but sequence comparison shows its ITS2 sequence is more similar to B. micranthera than to B. boliviensis. The molecular marker rbcLa revealed that there are no differences between the sequences for B. boliviensis, B. micranthera and the putative hybrid. Begonia boliviensis x B. micranthera is a diploid plant that, due to its moderately high pollen fertility (43.3%) compared to other natural Begonia hybrids (which are often sterile) and regular meiosis, would likely be able to self-cross or cross with other begonia taxa.