Advance in meiosis studies in intergeneric hybrids between Petunia and Calibrachoa

Abstract

large number of the ornamental species cultivated in the world come from improved South American germplasm. The enormous ornamental potential of the flora of our country has not yet been fully exploited. The Solanaceae family, although cosmopolitan, presents the highest concentration of genera and species in South America. Contributions on Solanaceae from Argentina dealing with meiotic chromosomes are fragmentary. Previous studies allowed obtaining an intergeneric hybrid between Petunia inflata and Calibrachoa hybrida var. kabloom yellow called HPC. It presented 95% sterile pollen and 5% fertile pollen, the latter being sufficient to allow its use as a bridge plant in crosses with different species of the Petunia and Calibrachoa genera. The objectives of this work were to observe the chromosomes of the HPC hybrid by means of classical cytogenetics to determine the degree of chromosomal homology between its parental species and the meiotic constitution of the hybrid to be used as a bridge plant in future crosses with different species of Petunia and Calibrachoa. The presence of sterile pollen is due to its irregular meiosis with univalent, bivalent, and tetravalent, fragment-less bridge, and multipolar spindles, while fertile pollen grains could be the product of mechanisms of elimination of two chromosomes and reduction of the gametic chromosome number with the in order to form balanced gametes that allow the production of new hybrid plants in bridge crosses with the genus Petunia. Future studies using in situ hybridization techniques, such as fluorescence in situ hybridization (FISH) and genomic in situ hybridization (GISH), will make it possible to present an authentic model for analyzing individual chromosomes, chromosome segments, or plant genomes. hybrids and thus confirm whether the missing chromosomes really belong to the genus Calibrachoa.