Karyotype analysis by FISH and GISH techniques on artificial backcrossed interspecific hybrids involving Passiflora sublanceolata (Killip) MacDougal (Passifloraceae)

Karyotype analysis of first generation (F1) and backcrossed (BC1) interspecific hybrids were preformatted, suggesting important cytological events in the origin of artificial hybrids. Characterization was performed in 16 backcrossed plants and their genitors by conventional staining, fluorescence in situ hybridization (FISH) with probes for 5S and 45S rDNA and telomeric probes. Genomic identification of hybrids was performed by Genomic In Situ Hybridization (GISH). The chromosome number (2n = 22) was F1 verified in both genitor species P. sublanceolata and P. foetida of the F1 hybrids. However, greater variations in chromosome numbers (2n = 20, 21 and 22) were verified in F1 and BC1 hybrids. A triploid BC1 hybrid was also found suggesting non-reduced female gamete in P. sublanceolata. Variation for number and position of 45S and 5S rDNA sites was also verified in the population, suggesting recombination in homeologous and in non-homeologous chromosomes. Telomeric sites were restricted to terminal regions, discarding the hypotheses of translocation involving telomere sites. GISH clearly distinguished genomes from the genitor species, genome-S (P. sublanceolata) and genome-F (P. foetida), in F1 and BC1 plants, thereby revealing differences in the origin of recombinant chromosomes. Differences in the number and nature of recombinant chromosomes in BC1 hybrids suggests there is high homology between the progenitor genomes, but differences in meiotic recombination in F1 plants. Numerical chromosome modifications, such as chromosome elimination and polyploidization and also chromosome recombination and/or translocations, are hypothesized as common events for the establishment of artificial Passiflora hybrids involving taxa from the Section Dysosmia.