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Vernonia galamensis is a potential new crop for production of epoxidized oil with many industrial applications. This plant is native to equatorial Africa, and not adapted for culture in temperate zones since it requires a short daylength to initiate flowering and subsequent seed development. One collection of V. galamensis ssp. galamensis var. petitiana, flowered freely and produced seeds during long-day conditions throughout the United States. This variety lacks important plant characters for successful commercialization. The favorable genetic recombination of day-neutral response with more desirable plant growth characteristics, desirable seed oil and fatty acid content from other accessions of V. galamensis has been accomplished in hybrids and segregating populations, and selections are being widely evaluated throughout the U.S..
Almost all Amaryllis (Hippeastrum) forced in the U.S. and Canada by either homeowners or commercial forcers are grown overseas. In order to comply with USDA/APHIS plant quarantine regulations, all bulbs must be free of soil. Thus, they are washed once or twice prior to packing and shipping. As a result of this treatment, the bulbs arrive with only basal roots and no secondary roots. Therefore, over the past year, 2 hand made mixes and 7 commercially prepared mixes were evaluated using 2 cultivars each of Swaziland- and Dutch-grown bulbs. The effects of these media on forcing characteristics, e.g. total plant height, leaf length, flower number, etc. were examined. Also, the influence of the various media on basal root growth and formation of new secondary roots was measured. The results of these 2 studies will be presented.
Patterns of diversity among thirty diploid clones of banana (Musa acuminata Colla.), collected in Papua New Guinea and the surrounding islands between 1987 and 1989, were examined genetically using the polymerase chain reaction (PCR) and random primers, to detect random amplified polymorphic DNA (RAPDs). PCR products were visualized on ethidium bromide stained agarose gels. Twenty of 60 random primers examined detected RAPDS in CTAB-extracted genomic DNA. Banding patterns ranged from very simple (1 or 2 bands/gel) to very complex (more than 20 bands/gel). All 30 Musa clones were distinguishable from each other based on their unique RAPD banding pattern. Principal component analysis (PCA) revealed several clusters of closely related clones within the materials examined. However, these clusterings were not correlated with either the geographic origin or the morphological characteristics of the clones. A role of the use of RAPDs in germplasm characterization is discussed.
This work was conducted to determine if characteristics of the hardwood cutting (such as size of the cutting and the number of buds) could be correlated to rooting and subsequent development. Dormant wood of 13 cultivars of Actinidia arguta were cut into lengths which varied from 3.5-18 cm containing from 1-9 buds. After being treated with 0.3% indolebutyric acid, cuttings were then stuck into Oasis Rootcubes and placed under intermittent mist. Cultivars of Actinidia arguta included 74-46, 74-55, 124-40, 125-40, 127-40, 119-40-B. “Meader Male”, “Meader Female #1”, “Geneva #1”, “Ananasnaja”, “Michigan State”, arguta cordifolia 1563-51 and a New Zealand cordifolia selection. There was a significant effect of cultivar on number of roots, root grade, length of roots, and callus. All rooting parameters were highly correlated with length of the cutting and number of buds in active growth. Caliper was negatively correlated with only root grade.
Four each of landscape-sized Fraxinus Pennsylvania Marsh. (green ash), Quercus coccinea Muenchh. (scarlet oak), Corylus colurna L. (Turkish hazelnut) and Syringa reticulata Hara `Ivory Silk' (tree lilac) were established on a rhizotron in Ithaca, New York, and root and shoot growth characteristics were observed throughout 1992. Root growth did not begin on any species before bud break. Green ash, scarlet oak and Turkish hazelnut exhibited recurrent shoot growth. Most root growth occurred during periods of bud rest, although no marked antagonism between shoot and root growth was evident. Green ash root growth was synchronous with shoot growth. The root harvest zone of green ash and tree lilac contained higher root length densities, and roots contained within appeared less suberized than that of Turkish hazelnut or scarlet oak. Root spread: crown spread ratio was greatest for Turkish hazelnut. Little root growth occurred on any species after fall leaf drop or when soil temperatures were below 5C. Implications for transplanting are discussed.
Citrus rootstock improvement has relied historically on clonal selections chosen on the basis of field performance. A few rootstocks have come inadvertently from cold-hardy citrus scion improvement programs, and these have become the most commonly used rootstocks in Florida citriculture. In addition to biological impediments to genetic progress, the lack of understanding of the genetics underlying important characteristics and the subsequent inability to select superior individuals in an efficient, cost-effective manner have limited the impact of applied plant breeding on citrus rootstock improvement. Genetic research on the cellular and molecular levels, using recently developed techniques, has provided new opportunities for progress. The potential of plant transformation, somatic hybridization, and genome mapping to ameliorate the breeder's efforts at citrus rootstock improvement will be discussed.
Though California is currently not facing the intense disease pressure that led to the development of the Troyer and Carrizo citrange rootstocks (sweet orange × trifoliate orange hybrids) that replaced the sweet orange (Citrus sinensis [L.] Osbeck) rootstocks, the California industry is still actively involved in breeding and evaluating rootstocks.
All potential rootstocks are still screened for the common fungal and viral diseases of citrus as well as for nematode susceptibility and nursery characteristics. The candidates that prove resistant are then evaluated as budded trees for scion compatibility, climatic and edaphic adaptability, and horticultural traits. Currently, rootstocks are not evaluated for salinity.
Currently C-32 and C-35, citrange hybrids of `Ruby' orange and trifoliate orange (Citrus sinensis [L.] Osbeck and Poncirus trifoliata [L.] Raf.) are being evaluated with a number of navel and Valencia scions. There is also increasing interest in finding compatible productive rootstocks for new mandarin and grapefruit introductions.
A teaching module was developed for computer-aided instruction of mutation theory. The Hypercard-driven, Macintosh compatible module illustrates the concepts of: 1) Changes in allele frequency with mutation pressure; 2) Number of alleles maintained in populations, and; 3) The Neutrality Hypothesis. The concepts are integrated in an application by using a game format.
Mutation is the ultimate source of genetic variation. Mutation pressure results in changes in allele frequency. Concept 1 illustrates the theoretical changes in allele frequency under pressure of reversible mutation. Mutation equilibrium is depicted as P=V/u+v; where v=mutation rates of allele A and u of allele a. The Infinite-Alleles Model of mutation is illustrated in Concept 2 and specifies characteristics of new mutations by F=1/4Nu+1, where F=fixation index and N=number in population. Concept 3 demonstrates the hypothesis that polymorphisms result from selectively neutral alleles maintained in a balance between mutation and random genetic drift.
`Mark' rootstock is a relatively new dwarfing rootstock that induces precocity in apple trees. While `Mark' has desirable horticultural characteristics, it has been difficult to propagate in some areas of the United States. To determine the optimum budding date at two climatically diverse locations, `Jonagold' buds were chip-budded onto `Mark' rootstock on 20 July, 10 Aug., 31 Aug. and 21 Sept. 1989 at Atlas, Illinois and Wenatchee, Washington. Prior to budbreak, unions were sampled from each budding date and the callus, bud plate and rootstock were measured and photographed. Trees budded and grown in Illinois had more callus growth than those budded in Washington. In Illinois, the callus of trees budded on 20 July averaged 3.2 mm., whereas those budded on 21 Sept. averaged 1.0 mm. Trees grown in Washington had 0.4 mm of callus at both budding dates. Callus growth will be correlated with union compatibility and strength in Nov. 1990.
demand for local and organically grown fresh-market tomatoes, Midwest growers require cultivars that are well adapted to local climatic conditions, are competitive under organic production conditions, and have fruit quality characteristics desired by