Basal rot of Narcissus caused by Fusarium oxysporum f.sp. narcissi is the major limiting factor for the increased export of ornamental bulbs from the United Kingdom. There is no known resistance to the disease amongst commercial cultivars. The purpose of this study was to develop techniques for the rapid detection and identification of the pathogen in bulbs, culture and soil, and to develop serological and biochemical tests to investigate differences amongst isolates of this forma specialis from a range of countries. Significant differences in virulence were observed between the isolates tested, two being identified as avirulent. Results suggest that there is wider morphological variation within this forma specialis than previously recorded. Isolates stored at -80°C have remained viable over a three year period. Thirty three species and varieties of Narcissus and seventeen cultivars were screened for resistance to the pathogen. Accessions were either wholly resistant, partially resistant (a variable portion of the bulbs infected) or susceptible. Accessions identified as resistant are now being used as parents in a resistance breeding programme. F. oxysporum Esp. narcissi isolates of low virulence and avirulence showed greater agglutination of microconidia with Narcissus pseudonarcissus lectin. In addition increased lectin levels were found in cultivars showing greater disease resistance; this suggests a possible host pathogen interaction. Polyclonal antisera were elicited against extracts of isolates and a specific and sensitive enzyme-linked immunosorbent assay was developed for the detection of the pathogen in bulbs. Little cross-reactivity was shown by other bulb-rotting fungi. A direct correlation was observed between positive results in the ELISA and recovery of the pathogen on selective media. The ELISA which was developed will be field evaluated with growers during the coming season. In indirect ELISA and Western blotting of fungal extracts, all fungi outside the genus Fusariwn showed consistently low binding. Isolates of F. oxysporum f.sp. narcissi could be discriminated from other Fusarium species and further split into a series of sub-groups. Avirulent isolates or isolates of low virulence showed differential binding to the PAbs. Other sub-groups were not related to virulence. Western blotting allowed greater differentiation of isolates and bands specific to F. oxysporwn f.sp. narcissi were identified. Serological detection of the pathogen in soil proved possible through the inclusion of a soil enrichment stage with a selective medium.

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Thesis (Ph. D.)--Johns Hopkins University. / Biographical note. Reprinted from the "Botanical gazette," vol. 50, 1910. Published also as Contributions from the Botanical laboratory of the Johns Hopkins university no. 14. Literature cited: p. 371.

This item was digitized as part of the Million Books Project led by Carnegie Mellon University and supported by grants from the National Science Foundation (NSF). Cornell University coordinated the participation of land-grant and agricultural libraries in providing historical agricultural information for the digitization project; the University of Arizona Libraries, the College of Agriculture and Life Sciences, and the Office of Arid Lands Studies collaborated in the selection and provision of material for the digitization project.

A commercial bulb growing concern in the Cloverdale section of the Lower Fraser Valley, British Columbia, has been experiencing recently a severe reduction in tonnage of mature bulbs produced. Because of premature ripening of the foliage, the bulbs do not attain an optimum increase in size and weight. The loss is considered to be over fifty percent reduction in crop yield. A bulb forcing experiment was set up in the University of British Columbia greenhouse in order to ascertain the effects of boron and magnesium on the growth and yield of bulbs produced on the Cloverdale farm. Soil, from the farm was used for four sets of flats planted with comparable lots of bulbs; a fifth set of flats was planted, using U.B.C. unfertilized greenhouse soil. The four sets of flats filled with the 'problem' soil were treated as follows: one series of flats was left untreated, a second series was treated with boric acid at the rate of 50 pounds to the acre, a third series was treated with magnesium sulphate at the rate of 200 pounds to the acre and the fourth series, was left until foliar growth was established and at that time was sprayed with a boric acid spray of 100 ppm boron concentration. The bulbs were planted in November and brought into the greenhouse from cold frames in late January for forcing. After the daffodils had bloomed, the flats were placed outside for the ripening off of the foliage. No early die-back occurred and the bulbs were lifted in June. After the bulbs had been dried, they were cleaned and weighed. Increases in yield for each treatment were calculated and analysed statistically. It was found that boron as a foliar spray of 100 ppm had a detrimental effect on bulb weight increase, and. that boron applied as a fertilizer at the rate of 50 pounds, to the acre had no beneficial effect. Magnesium sulphate applied to the soil, at a rate of |00 pounds to the acre, to the 'problem' soil had a significant effect on bulb weight increase of the King Alfred daffodil bulbs forced in the greenhouse. / Land and Food Systems, Faculty of / Graduate

No description available.

Light bulbs play an indispensable role in our lives as they provide unhindered ability to see the world even during the night. Efficiency of light bulbs is becoming increasingly important, and through this experiment, light bulb efficiencies are analyzed from measurements of relative light intensity and power input of various bulbs. Furthermore, this report is aimed to increase awareness of the efficiency advantage in fluorescent bulbs and to encourage their usage in the interest of conserving energy.

Thesis (doctoral)--Universität Zürich, 1909. / Cover title. Includes bibliographical references.

Thesis (doctoral)--Rijksuniversiteit te Utrecht, 1931. / Bibliography: p. [91]-93.

Lachenalia cv. Ronina, a new flower bulb variety developed by the ARC-Roodeplaat Vegetable and Ornamental Plant Institute, has excellent characteristics as a flowering pot plant, but information on cultivation practices is limited. Temperature is the most important environmental factor regulating the growth cycle of this flower bulb, therefore three temperature regimes, representing a cool, moderate and warm winter climate, were chosen to manipulate floral development. During this study the bulb structure, development and growth were determined during the bulb preparation phase (year 1) and subsequently the morphology of the bulb was evaluated during the pot plant phase (year 2). Regarding the bulb structure and development, cultivar Ronina has a typical rhythmic, sympodial, modular growth. Bulb growth and module formation is affected by temperature. The low (L TR) and moderate (MTR) temperature regime, which represent the cool and moderate winter climate in South Africa were found to be the best temperature regimes for bulb production. The high (HTR) temperature regime caused bulbs to develop faster, but flower abortion occurred. At the end of the bulb preparation phase, daughter bulbs were observed in the axils of the leaf bases in bulbs of all three temperature regime treatments. Additional inflorescences from underdeveloped growth modules were detected in the axils of the inner leaf bases of bulbs of the high temperature regime. The bulbs as well as the roots are the main sinks for the carbohydrates, whereas the inflorescence and especially the leaves are the main source for soluble sugars. Due to the more stable temperature that was applied in the growth cabinets, the flowering date of bulbs in all three treatments flowered two months earlier than plants growing in the open. During this production phase, simultaneous flowering occurred more within bulbs that were subjected to the LTR during the bulb preparation phase. These bulbs also produced broader leaves with more spots on and better quality inflorescences with a longer keeping ability than those of the higher temperature regimes. A correlation was found between the leaf number and the number of inflorescences of plants in the pot plant phase, grown from LTR treated bulbs. The bulb fresh mass/size at the end of the bulb preparation phase cannot be used as a reliable criterion to predict the quality of the pot plant. By examining the bulb structure at the end of the bulb preparation phase, the quality of the pot plant can be predicted. / Thesis (PhD Agric (Horticultural Science))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted