Browsing by Author "Teparkum, Sirasak"
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- Embryogenic response of potato anther culture to colchicineTeparkum, Sirasak (Virginia Tech, 1996)Colchicine, an antimicrotubule agent, has enhanced the androgenic response of cruciferous and graminaceous species. Our objectives were to determine if colchicine treatments enhanced androgenic embryo production in diploid potato, and if colchicine treatments during anther culture affected the ploidy of anther-derived plants. An additional study, analysis of genetic identity among regenerated anther-derived plants based on RAPD markers, was also conducted. Anther culture of a hybrid between Solanum chacoense and S. phureja (clone CP2) was conducted with five colchicine treatments (0, 25, 50, 100, and 200 mg/L) for 24 h. Anthers containing late uninucleate pollen were cultured on modified liquid LS medium. A mean of 0.25 embryos per anther was obtained; however, there was no significant difference among the colchicine treatments, which ranged from a mean of 0.17 to 0.28 embryos per anther for 200 mg/L colchicine and control, respectively. In total 56 plants were regenerated of which 11% were monoploid. The second experiment using the same colchicine treatments was conducted with 54 hybrids derived by crossing six anther-derived doubled monoploids with three heterozygous pollinators. A mean of 1.78 embryos per anther was obtained; again, there was no significant difference among the colchicine treatments, which ranged from 1.27 to 2.75 for 50 mg/L colchicine and control, respectively. In total 679 plants were regenerated. The 312 plantlets for which ploidy was determined, 75% were monoploid. The third experiment was conducted to study various durations (0, 90 sec vacuum infiltration, 24, 48, and 72 h) of high colchicine treatment (200 mg/L) applied to S. phureja family DM 13-14 202 x ID 5. There was nearly significant difference among treatments (α = 0.05). Mean embryos per anther ranged from 0.96 to 1.90 for 48 h and 90 sec vacuum infiltration, respectively. In an additional study, 26 regenerated anther-derived monoploid plants, from the DM 13-14 202 x ID 5 family, from the second experiment, were genetically characterized based on RAPD markers. Forty-three loci were scored from 13 primers for groups of monoploids derived from the same flasks of anther culture. From one flask, two pairs of monoploids were found to be genetically identical. From a second flask 6 of 7 were genetically identical, and from a third 3 of 7 were genetically identical. The presence of genetically identical individuals within three monoploid populations indicates the prevalence of secondary embryogenesis during anther culture such that a single embryogenic microspore can generate many anther-derived plants.
- Interaction Between Insects and Apple (Malus X Domestica Borkh.): Insect Behavior, Genotypic Preference, and Plant Phenolics With Emphasis on Japanese Beetle (Popillia Japonica Newman)Teparkum, Sirasak (Virginia Tech, 2000-05-02)Leaves and fruit of nine apple (Malus x domestica Borkh.) genotypes were evaluated for insect injury in 1998 and 1999. Foliar and fruit injury from 12 insect species was inconsistently affected by genotype. Spraying trees with oil affected neither fruit insect injury nor fruit phytotoxicity. In choice feeding assays, incidence of Japanese beetle (JB) feeding and leaf area consumed was greater for 'Liberty' than for 'York.' Genotypes did not differ in no-choice feeding assays. Choice and no-choice feeding assays between apple and oak indicated that JB could distinguish host plants in an artificial environment. Trichome density appeared different among three genotypes. 'York', the non-preferred genotype, had highest specific leaf weight and concentration of phloridzin, a feeding repellent. 'Liberty' the preferred genotype, had the lowest specific leaf weight, and had the highest concentration of quercitrin, a feeding stimulant. Olfactory stimuli of JB was evaluated with a Y-tube olfactometer. Beetles preferred the side of the Y-tube containing leaf tissue of apple or Virginia creeper over the side with no leaf. Beetles did not choose one plant species over the other. Bias test of beetle orientation in the Y-tube olfactometer indicated that in the morning, but not the afternoon, beetles preferentially moved into the left side of the Y-tube. Humidity did not affect beetle orientation. In darkness JB preferred a leaf disc over a paper disc and beetles tended to remain on the leaf.