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- Author or Editor: Richard Craig x
Pelargoniums represent a major floricultural crop in international markets. Intellectual property protection in the form of U.S. plant patents (200 since 1980) and European breeders' rights have been used for asexually propagated Pelargoniun. In addition, the hundreds of F', hybrid seed-reproduced cultivars are protected as trade secrets. International protection through the International Union for the Protection of New Varieties of Plants (UPOV) and the use of utility patents will accelerate breeding efforts; however, issues such as “essentially derived” and the farmer and research exemptions still must be resolved.
This is an age of transition for horticultural plant breeding. The recent developments in physiological and biochemical genetics and their application to plant breeding signify only the beginning of this new era. To define the term New Genetics is extremely difficult especially when it is applied to horticultural plant breeding. For the purpose of this paper New Genetics will mean all of. those methods, machines, ideas and information that can assist in the future breeding of better horticultural plants.
Nine cultivars of Pelargonium × domesticum representing three germplasm sources were evaluated for the effect of daily light integral on floral initiation. Plants were grown at four daily light integrals: 5, 10, 15, or 20 mols/day for a 16-h photoperiod in environmental growth chambers at constant 15.5 °C. Meristems were examined at 50-mol intervals (0 to 350 mols) for morphological changes associated with floral initiation. Two phenotypes were identified, cultivars with an association between floral initiation and irradiance and those with association between floral initiation and chronological time. Genotypic variation was observed among the cultivars of each phenotype.
Floral initiation signals the commencement of sexual reproduction in angiosperms. In many plant species this developmental phase is controlled by photoperiod. However, it may be regulated by other factors, such as plant age or specific temperature or irradiance requirements. Floral initiation occurs in Pelargonium ×domesticum (regal Pelargoniums) in response to exposure to cool (7–12°C) temperatures for about 4–6 weeks, or to cumulative irradiance at 18–23°C. Broad genetic variability exists so that floral initiation in some cultivars is almost completely controlled by temperature, while in others it is almost completely controlled by cumulative irradiance. Among the latter group of genotypes, genetic variability exists for the amount of irradiance required. The purpose of this study was to determine the precise irradiance requirements for nine commercially important cultivars. The cultivars varied significantly in their response to irradiance with respect to floral initiation. Low irradiance requiring genotypes developed visible (5 mm) buds with as little as 250 mol of total cumulative irradiance; floral initiation in these cultivars occurred with only 50 mol of irradiance. High irradiance requiring genotypes still had vegetative meristems after 300 mol of total cumulative irradiance. Further studies were conducted on `Majestic', chosen for its high irradiance requirement. The objective of this study was to determine whether cool temperatures (7–12°C) or heat stress (23–28°C) could replace the irradiance effect. The results indicated that neither of these environmental conditions could replace the effects of moderate temperature (18–23°C) and high cumulative irradiance in this cultivar.
Research in Penn State's Exacum breeding program has revealed genotypic variation for the development of zinc deficiency, which may indicate the presence of zinc efficiency factors. Through preliminary experiments, we have identified both genetic families and individual genotypes that can be classified as either zinc-efficient or zinc-inefficient. Chi-square contingency analyses indicate significant differences (P < 0.001) in segregation patterns for zinc deficiency among hybrid families. Segregation patterns within families ranged from 100% of the progeny developing zinc deficiency to 100% of the progeny remaining healthy. Two genotypes contrasting in zinc efficiency have been identified and used in experiments designed to investigate physiological factors related to zinc efficiency. The zinc-efficient genotype has a significantly higher ability to decrease solution pH (P < 0.01), significantly higher root cation exchange capacity (P < 0.007), significantly lower root/shoot ratio (P < 0.001), significantly lower water loss/cm2 leaf (P < 0.03), and significantly higher fresh weight/dry weight ratio (P < 0.001). Research on zinc uptake rates is currently being conducted utilizing the efficient and inefficient genotypes. Based on all of our research, we conclude that 1) a strong genetic effect is involved in the zinc nutritional status of interspecific Exacum hybrids and 2) a number of physiological traits differ between zinc-efficient and zinc-inefficient genotypes.
The morphology of interspecific Exacum hybrids was investigated in order to determine transmission patterns of several horticultural traits and to confirm interspecific hybrid status of plants. The evaluations utilized 557 accessions from interspecific hybridization of the following species: Exacum. macranthum, E. pallidum, E. pedunculatum, E. trinervium ssp. ritigalensis, and E. trinervium ssp. trinervium. Transmission patterns are proposed for stem shape (three phenotypes- clylindrical, winged-cylindrical and qudrangular; no dominance), petal shape (two phenotypes-rounded and acuminate; rounded dominant to acuminate) and flower form (two phenotypes- imbricate and separate; imbricate dominant to separate) Examination of the progenies confirm interspecific hybridization by the appearance of combinations of traits from the parental species and/or the observation of unique forms not previously observed.
The Plant Systematics course at Penn State University was reformatted in 1995 based on a three-dimensional model. It now includes several collaborative learning activities: a learning fair hosted by the enrolled students for elementary school students; applied laboratory exercises; and applied laboratory examinations. Each activity has a specific objective and was constructed to strengthen teaching effectiveness and to aid students in developing useful skills for future employment. A survey was administered to students enrolled in the course from 2003 through 2005 in part to assess the collaborative learning activities. Most students “strongly agreed” or “agreed” that they liked working in collaborative groups and learned from other group members. Students preferred working in groups for laboratory examinations more than for the Asteraceae Fair and learned more from their peers while completing the laboratory exercises than in laboratory examinations. Student participation in the lecture portion of the course increased as collaborative learning activities were completed. Camaraderie with peers through group work may have created an atmosphere conducive to participation and/or involvement during lectures. Organization and planning were vital to the success of these activities, as were using small groups and providing adequate incentives for completing activities. These activities engaged students to become active participants in the teaching and learning process.
Floral ontogeny of two cultivars of Pelargonium ×domesticum L.H. Bailey, (regal pelargonium) `Duchess' and `Jennifer', was examined. Plants of both cultivars were grown together in a growth chamber at 15.5 °C with a photosynthetic photon flux of 10 mol·m-2·d-1. Meristems were examined at 5-day intervals over an experimental period of 170 days. The initial vegetative meristem was convex with leaf primordia initiated on either side in an alternate pattern. Early floral initiation was characterized by formation of two clefts on either side of the meristem. Between the clefts new meristems developed. Proliferation of meristems continued until numerous meristems were organized in a cluster arrangement at the apex of the shoot. New meristems lacked leaf primordia and would develop into flowers. Floral organ primordia on a floral meristem were initiated in a succession of four whorls: sepals, petals, androecia, and gynoecium.
A variety of cooperative activities are part of the plant systematics course at The Pennsylvania State University: a learning fair hosted by the students enrolled in the course for elementary school students, applied laboratory examinations, and applied laboratory exercises. Each activity was constructed to engage students in the learning process as well as to aid in developing useful skills for future employment. A survey administered to students enrolled in the course from 2003 to 2005 revealed that most students “strongly agreed” or “agreed” that they liked working in cooperative groups and learned from other group members. Student participation in the lecture portion of the course increased as cooperative activities were completed. Organization and planning were vital to using these activities, as were small groups and adequate incentives for completing activities.