Master of Agribusiness / Department of Agricultural Economics / Michael R. Langemeier / The wheat industry has experienced significant changes in recent years due to extreme market volatility in commodity markets. The challenge for farmers, seed dealers, and seed companies, therefore, is to determine value and price amid a rapidly fluxuating market environment. Locally, seed dealers must price seed wheat at a level that is both fair to the farmer with consideration to their local cash market, and yet profitable to the seed company. Ehmke Seed in Lane County, Kansas, is one such seed dealer struggling with determining price in an ever-changing market environment. This study analyzes pricing models based on historical seed prices and the local cash grain market. Twenty-five years of seed wheat prices at Ehmke Seed were compared to local cash wheat and grain sorghum prices at the Garden City Cooperative Elevator in Garden City, Kansas, with a margin analysis conducted on the models with respect to Ehmke Seed’s cost of production. This study also provides a statistical analysis of the competing price models to compare their reliability. A more dependable method of pricing will help Ehmke Seed come to a better understanding of alternative marketing options for wheat, and serve as a basis to help understand how future wheat varieties, such as transgenic wheat, may potentially be priced in the future.

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Common scab, as the name implies, is one of the most common and widespread diseases affecting production of potato in virtually all parts of the world where the crop is grown. In South Africa, the percentage of bags containing scab-infected seed tubers averages 32 %, with a corresponding rejection or decertification of the seed. The disease also reduces the cosmetic value of ware potatoes and, with the growing demand for blemish-free produce, increasingly results in the downgrading of consignments on the ware market. Control is mostly attempted by means of agrochemicals. Streptomyces scabiei is generally considered as the main cause of common scab, also in South Africa. However, various otherStreptomyces species are known to be associated with the disease, either parasitically or saprophytically, but no attempt has yet been made to determine if any of them occur in South Africa. The purpose of this study was to elucidate the etiology of common scab in the country and to evaluate some strategies that could be included in an integrated control programme for managing the disease. The results indicated the following: Isolation and characterisation of streptomycetes from symptomatic seed potato tubers from the five potato-production areas in South Africa worst affected by common scab, showed that the disease is caused by three phenotypically distinct Streptomyces groups, designated 1, 2 and 3, whereas a further three groups were saprophytically associated with scabby tubers. Streptomyces group 1, which corresponded morphologically to the description of S. scabiei, was by far the most common, representing 52 % of all and 82 % of the pathogenic isolates, and occurred in all the regions surveyed. The two other Streptomyces groups containing pathogenic isolates may represent atypical S. scabiei isolates, or could be separate species. Analysis for the production of thaxtomin A, an important pathogenicity factor, confirmed a positive correlation between the pathogenicity of isolates and their ability to produce thaxtomin A. However, 14 % of the pathogenic isolates did not produce thaxtomin A, whereas 6 % of the non-pathogenic isolates tested positively for production of the toxin. Another interesting observation was the ability of 15 % of both all and of the pathogenic isolates to grow at a pH of 4.0, which is atypical of S. scabiei. In the greenhouse, densities of S. scabiei were significantly lower in sand artificially infested with the pathogen and planted to triticale or cabbage than in fallow sand or sand planted to soybean, spinach, maize, pumpkin or sunflower, three months after planting of the crops. Survival in sand planted to rye and pea was also relatively low, albeit not significantly lower than the other crops. Roots of soybean, spinach, rye, sunflower, pea and cabbage were colonised significantly less by S. scabiei than those of pumpkin and maize. Cluster analysis separated the crops into two groups according to their effect on S. scabiei. The first group, comprising pumpkin, maize, soybean, sunflower and spinach, had little impact on survival of the pathogen. The second group, consisting of rye, triticale, pea, and cabbage, showed a distinct suppressive effect and on average supported only 0.23 % of the S. scabiei population sustained by the first group. Incorporation of fresh and dry cabbage residues at rates of 0.25 and 0.1 % (m/v) into soil naturally infested with S. scabiei reduced common scab in the greenhouse by a significant 32 and 41 %, respectively. Amendment of scab-infested soil in the field with dry residues of cabbage, cauliflower, broccoli and Brussels sprouts at 0.33 % (m/v) resulted in reduction in disease of approximately 90 %. / Dissertation (MSc (Agric))--University of Pretoria, 2007. / Microbiology and Plant Pathology / MSc (Agric) / unrestricted

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The mineral nutrient storage reserves in various parts of white spruce (Picea glauca) seeds and somatic embryos were investigated. Somatic embryos are produced in tissue culture from single cells or small groups of cells. These cells are induced to produce a callus, which is then stimulated to produce mature somatic embryos that are desiccated down to moisture content levels comparable to those of a mature dry seed. Morphological comparisons revealed that somatic and zygotic embryos are very similar. Somatic embryos of white spruce; however, were larger, had a flared arrangement of cotyledons, had more prominent suspensor regions, had intercellular spaces in the ground meristem tissue and had ground meristem cells that had divided in several planes of division. Using a wet ashing protocol, anion exchange resins and the molybdenum blue colourimetric reaction, the total levels of P and the amount of P bound to phytic acid were measured. Phytic acid (or phytate) is the major nutrient storage compound in seeds. Although differences were found on a dry weight basis, a single somatic and a single zygotic embryo had similar levels of P. Somatic embryos produced in different batches varied in their levels of phytic acid, but a somatic embryo could have similar levels of phytic acid as a zygotic embryo. The large female gametophyte contained 86% of the total P and 95% of the total phytic acid in a single seed. Electron microscopy and energy dispersive x-ray analysis found phytate-rich globoids in the procambium and ground meristem tissues of both types of embryos. Globoids contained high P, moderate K and Mg, and little if any Ca, Fe and Zn. Globoids were generally larger and more frequent in zygotic embryos. Globoids from the cotyledon procambium of zygotic embryos also contained moderate levels of Fe. Iron-rich particles (possible Fe-phytate deposits) were found in the protoderm, procambium and ground meristem of both types of embryos. These deposits contained high P and Fe, moderate K and Mg, and little if any Ca and Zn. Globoid and Fe-rich particle compositions were similar in both embryo types, but significantly higher Fe:P ratios were found in zygotic embryos. Atomic absorption spectroscopy was used to measure total K, Mg, Ca, Fe and Zn levels. Although differences were found on a dry weight basis, a single white spruce somatic or zygotic embryo contained similar levels of all these elements. The female gametophyte contained high levels of these elements and the seed coat contained considerable Ca. Potassium leakage during imbibition in germination medium revealed that a single somatic and zygotic embryo of white spruce leaked similar levels of K. Pretreatment of somatic embryos in a high relative humidity environment resulted in decreased potassium leakage by 80 and 120 min. of imbibition. The seed coat was found to reduce the amounts of K leaked. Surface cells in dry somatic and zygotic embryos were found to be wrinkled, but cells in zygotic embryos were more shrunken in appearance. During imbibition, cells became more turgid; but after 120 min. of imbibition, surface cells still showed signs of wrinkling. To date, this is the first major report of mineral nutrition in white spruce seeds and is the first comprehensive comparison of mineral nutrients in white spruce seeds and somatic embryos. These results may be useful in producing complete artificial white spruce seeds. / Thesis / Master of Science (MS)

O potencial fisiológico de sementes, determinado pela germinação e vigor, é diretamente responsável pelo desempenho das sementes em campo, podendo até se refletir na produtividade de diversas espécies de hortaliças de importância econômica. Diante disto, o presente trabalho teve como objetivo avaliar a eficiência de diferentes métodos para determinação do potencial fisiológico de sementes de cebola (Allium cepa L.), visando destacar procedimentos adequados para utilização em programas de controle de qualidade; procurou-se, também, verificar a relação dos resultados obtidos em laboratório com a emergência das plântulas e o desempenho das plantas em campo. Para tanto, utilizaram-se seis lotes de sementes dos cultivares Aurora e Petroline, avaliados, em laboratório, quanto ao grau de umidade, germinação e vigor (primeira contagem de germinação, classificação do vigor de plântulas, condutividade elétrica, frio sem terra, envelhecimento acelerado tradicional e com solução salina e deterioração controlada). O desempenho das plantas foi verificado em ensaios de campo, utilizando-se dois sistemas de cultivo: semeadura direta e transplante de mudas; durante o desenvolvimento das plantas avaliaram-se, periodicamente, a altura, o diâmetro na região do colo e a massa de matéria seca das plantas. Após a colheita, determinou-se o rendimento final e efetuou-se a avaliação comercial dos bulbos. Concluiu-se que os testes de envelhecimento acelerado com solução salina (41ºC/72h), de deterioração controlada (ajuste do grau de umidade das sementes para 24% de água/45ºC/24h) e de classificação do vigor de plântulas, são considerados eficientes para avaliação do potencial fisiológico de sementes de cebola. As relações entre o vigor de sementes de cebola e o desempenho das plantas manifestam-se apenas durante a fase inicial do desenvolvimento da cultura, principalmente quando as diferenças entre o potencial fisiológico dos lotes são mais acentuadas, mas não afetam diretamente a produção de bulbos. / Research has emphasized the relationship of laboratory germination and vigor to seedling emergence and stand establishment. In contrast, information relating seed vigor to plant performance is less available. This study was conducted to identify reliable procedures to rank onion ( Allium cepa L.) seed lots according to their physiological potential and to select the most adequate procedures to be used in quality control programs. In addition, it was verified whether the differences in seed vigor influence plant performance in field conditions. Six seed lots of cultivars Aurora and Petroline were evaluated in laboratory for germination and vigor (first count, seedling vigor classification, electrical conductivity, cold test, traditional and saturated salt accelerated aging and controlled deterioration). Field experiments to detect differences in plant development were performed by direct sowing and transplant systems; after the determination of seedling emergence, plant vegetative development was evaluated by plant height, pseudo stem width and dry matter accumulation measurements. After harvest, the bulbs commercial classification and yield evaluation were provided. It was concluded that saturated salt accelerated aging (41ºC/72h), controlled deterioration (24% of water/45ºC/24h) and seedling vigor classification tests were the best procedures to assess the physiological potential of onion seeds. The initial plant development as measured by plant height and dry matter accumulation was affected by seed vigor mainly when the differences of seed physiological potential became wider as a result of the storage period. Influence of seed vigor did not persist during plant vegetative growth and yield was not related to seed vigor level. It was therefore concluded that the use of high vigor seed lots is justified to ensure adequate stand establishment under different environmental conditions.

O potencial fisiológico de sementes, determinado pela germinação e vigor, é diretamente responsável pelo desempenho das sementes em campo, podendo até se refletir na produtividade de diversas espécies de hortaliças de importância econômica. Diante disto, o presente trabalho teve como objetivo avaliar a eficiência de diferentes métodos para determinação do potencial fisiológico de sementes de cebola (Allium cepa L.), visando destacar procedimentos adequados para utilização em programas de controle de qualidade; procurou-se, também, verificar a relação dos resultados obtidos em laboratório com a emergência das plântulas e o desempenho das plantas em campo. Para tanto, utilizaram-se seis lotes de sementes dos cultivares Aurora e Petroline, avaliados, em laboratório, quanto ao grau de umidade, germinação e vigor (primeira contagem de germinação, classificação do vigor de plântulas, condutividade elétrica, frio sem terra, envelhecimento acelerado tradicional e com solução salina e deterioração controlada). O desempenho das plantas foi verificado em ensaios de campo, utilizando-se dois sistemas de cultivo: semeadura direta e transplante de mudas; durante o desenvolvimento das plantas avaliaram-se, periodicamente, a altura, o diâmetro na região do colo e a massa de matéria seca das plantas. Após a colheita, determinou-se o rendimento final e efetuou-se a avaliação comercial dos bulbos. Concluiu-se que os testes de envelhecimento acelerado com solução salina (41ºC/72h), de deterioração controlada (ajuste do grau de umidade das sementes para 24% de água/45ºC/24h) e de classificação do vigor de plântulas, são considerados eficientes para avaliação do potencial fisiológico de sementes de cebola. As relações entre o vigor de sementes de cebola e o desempenho das plantas manifestam-se apenas durante a fase inicial do desenvolvimento da cultura, principalmente quando as diferenças entre o potencial fisiológico dos lotes são mais acentuadas, mas não afetam diretamente a produção de bulbos. / Research has emphasized the relationship of laboratory germination and vigor to seedling emergence and stand establishment. In contrast, information relating seed vigor to plant performance is less available. This study was conducted to identify reliable procedures to rank onion ( Allium cepa L.) seed lots according to their physiological potential and to select the most adequate procedures to be used in quality control programs. In addition, it was verified whether the differences in seed vigor influence plant performance in field conditions. Six seed lots of cultivars Aurora and Petroline were evaluated in laboratory for germination and vigor (first count, seedling vigor classification, electrical conductivity, cold test, traditional and saturated salt accelerated aging and controlled deterioration). Field experiments to detect differences in plant development were performed by direct sowing and transplant systems; after the determination of seedling emergence, plant vegetative development was evaluated by plant height, pseudo stem width and dry matter accumulation measurements. After harvest, the bulbs commercial classification and yield evaluation were provided. It was concluded that saturated salt accelerated aging (41ºC/72h), controlled deterioration (24% of water/45ºC/24h) and seedling vigor classification tests were the best procedures to assess the physiological potential of onion seeds. The initial plant development as measured by plant height and dry matter accumulation was affected by seed vigor mainly when the differences of seed physiological potential became wider as a result of the storage period. Influence of seed vigor did not persist during plant vegetative growth and yield was not related to seed vigor level. It was therefore concluded that the use of high vigor seed lots is justified to ensure adequate stand establishment under different environmental conditions.

Book Summary:Issues: Understanding Controversy and Society brings important issues in today's world to students' attention, highlighting the complete historical background, contemporary status, and global view of each. It provides students authoritative context, diverse expert perspectives, and carefully selected primary and secondary sources for truly understanding the issues that currently affect much of our global society, and for developing informed positions on those engendering controversy.

Book Summary: The business of food and drink is for better and worse the business of our nation and our planet, and to most consumers how it works remains largely a mystery. This encyclopedia takes readers as consumers behind the scenes of the food and drink industries. The contributors come from a wide range of fields, and the scope of this encyclopedia is broad, covering from food companies and brands to the environment, health, science and technology, culture, finance, and more. The more than 150 essay entries also cover those issues that have been and continue to be of perennial importance. Historical context is emphasized and the focus is mainly on business in the United States. Most entries include Further Reading. The frontmatter includes an Alphabetical List of Entries and a Topical List of Entries to allow the reader to quickly find subjects of interest. Numerous cross-references in the entries and blind entries provide other search strategies. The person and subject index is another in-depth search tool.

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