CYTOGENETICAL ANALYSIS OF HYBRIDS BETWEEN SUNFLOWER AND 4 WILD RELATIVES

Patterns of chromosome pairing were examined in pollen meiocytes of plants derived from crosses between cultivated sunflower, Helianthus annuus L., and four relative species, H. niveus ssp, niveus (Benth) Branbegee, H. maximiliani Schrad., H. ciliaris DC and H, tuberosus L. Except in plants derived from crosses with H. niveus, meioses showed both asyndesis (univalent) and multivalent configurations. Mathematical models of genome analysis were used to interpret these data for phylogenetic purposes. We confirm that sunflower and H. tuberosus share the sunflower B genome and establish that the other two genomes of H, tuberosus are homologous. Our results support the genomic formula (AAAABB) and allopolyploid origin previously ascribed to H. tuberosus. We also provide the first evidence that H. ciliaris has the sunflower B genome, and propose an allopolyploid origin through natural hybridization between an annual diploid species (B genome) and a perennial diploid species (A genome) for this species. Finally, our results suggest some homology between the sunflower B genome and the perennial diploid A genome and provide indirect evidence of the ancient polyploid origin of sunflower B genome.