Cytogenetics of Delphinium (Ranunculaceae) Species Native to Oregon

• Main Author: Turner, Jill Yeatman
• Format: Others
• Published: PDXScholar 1992
• Subjects: Delphinium; Biology
• Online Access: https://pdxscholar.library.pdx.edu/open_access_etds/4566; https://pdxscholar.library.pdx.edu/cgi/viewcontent.cgi?article=5637&context=open_access_etds

Evidence of hybridization, known to occur in the genus Delphinium (Ranunculaceae ), has recently been discovered among certain Delphinium species native to Oregon. This issue was investigated by cytogenetic analysis of four native species of Oregon, D. trolliifolium, D. menziesii, D. pavonaceum and D.leucophaeum, and an unidentified purple delphinium, which is possibly a hybrid. Although many species in this genus are karyotypically similar, any variations found among the karyotypes of these Oregon species might be used to identify parental chromosomes in the purple delphinium (proposed hybrid). Meiotic analysis was used to detect structurally heterozygous homologues that are not observable in somatic cells. Reproductive success, an extension of meiosis, was also investigated. In lieu of the endangered status of two of these Oregon species, attempts were made to develop a system for obtaining dividing cells for cytogenetic study that has negligible impact on plant populations. Apical meristems of seed radicles from the Oregon species and the proposed hybrid were stained with orcein. The metaphase chromosomes were photographed and measured, and chromosome arm ratios and relative lengths calculated. Analyses of variance and multiple comparison tests were run to determine if any significant differences in chromosome measurement exist among these Oregon delphiniums. Satellites and other morphological features were noted. Anther contents were also stained with orcein and microsporogenesis examined. Pollen viability and percent seed germination was determined for each of the species and the proposed hybrid. Callus and organized tissue that developed in vitro were stained with orcein and the mitotic cells examined. The unhanded karyotypes of the Oregon species and the proposed hybrid are similar in number, size and shape; major structural differences between species, if present, are not observable at this level of chromosome resolution. No markers for the identification of parental chromosomes in the proposed hybrid are available with this staining technique. However, statistical analysis of mean chromosome arm ratio and length indicates that D. menziesii, D. pavonaceum and D.leucophaeum are more closely related to one another than they are to D. trolliifolium and the proposed hybrid, and vice versa. D. trolliifolium is therefore a candidate parent species of the proposed hybrid whereas the other three species are likely not candidates. Karyotypes of these Oregon species are different from those of some species from outside Oregon. This is evidence of chromosome evolution in this genus. The absence of structural heterozygosity in meiotic metaphase I of the proposed hybrid suggests that (1) if it is a hybrid, the genomes of the parent species are structurally similar or (2), recurrent backcrossing with the same parent species may have gradually eliminated the chromosomes of the other parent from the hybrid line. High numbers of viable pollen and germinated seeds were found in all the species and the proposed hybrid, evidence that reproductive capacity is not adversely affected by its potentially hybrid condition. Mitosis in tissue culture varies, depending, to a large degree, on cell type. Organized tissues such as roots are sources of more stable karyotypes than calluses, which tend to be mixoploid. The development of plant structures in culture indicates a potential for in vitro plant regeneration.