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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.

Selection of hard red winter wheat lines with diverse resistance to leaf spot diseases

Manley, Aurora Alexandra 19 August 2016 (has links)
<p> Tan spot and Septoria nodorum blotch cause serious yield losses in winter wheat in North Dakota as the majority of commercially grown cultivars are susceptible. This study aimed to identify lines with improved resistance for use as breeding parents. First, advanced NDSU breeding lines and alternative sources of resistance were inoculated with fungal isolates and tested for necrotrophic effector sensitivity. Second, resistant lines were derived from a highly heterogeneous recurrent mass selection F<sub>2</sub> population using single seed descent inbreeding coupled with selection for resistance. Finally, the best performers from both experiments (total of 52 lines) were evaluated to confirm resistance. In addition the 52 lines were analyzed with markers that detect <i>Tsn1</i> and the 1RS rye translocation. Twenty lines were identified with simultaneous resistance to four or three fungal isolates and insensitivity to three, two, or one necrotrophic effectors (of which 11 can be used directly as new parents).</p>

Variation of carbon allocation and competitive ability of different tree species as related to successional position and habitat /

Malavasi, Ubirajara Contro. January 1983 (has links)
Thesis (Ph. D.)--Oregon State University, 1984. / Typescript (photocopy). Includes bibliographical references (leaves 117-125). Also available on the World Wide Web.

Life History of hemlock woolly adelgid, <em>Adelges tsugae</em> Annand, on eastern hemlock, <em>Tsuga canadensis</em> (L.) Carriere, in the southern Appalachians and assessment of egg releases of <em>Sasajiscymnus tsugae</em> (Sasaji and McClure) for its management

Deal, Isaac K. 01 May 2007 (has links)
Studies were conducted in 2005 and 2006 at Baxter Orchard, Great Smoky Mountains National Park, Tennessee to optimize survival of Sasajiscymnus tsugae (St) (Sasaji and McClure) released as eggs on eastern hemlock, Tsuga canadensis (L.) Carriere, for biological control of Adelges tsugae (HWA) Annand. Studies investigated annual abundance and seasonality of HWA lifestages, weekly field and laboratory survival of St, and survival of St egg cohorts of various ages and densities. HWA was determined to be bivoltine on eastern hemlock in Tennessee with an aestivation period between July and October. Lifestages preferred as food by St were present from February through June with peak abundance ca. late March. Weekly survival of St placed in the field and laboratory as eggs was investigated. Less than 10% of St eggs placed in the field between 8 February to 22 March survived because of freezing field temperatures. Survival rose to 30-40% on 30 March and persisted at that level until 7 June, when survival decreased below 10% due to scarcity of food. Studies were conducted to investigate the effect of St egg density on survival of St. Four densities of St eggs (50, 100, 150, and 200 eggs/container) were placed in the field and laboratory. In the laboratory, survival was higher for lower densities of St eggs, implying cannibalism increases with density. Three egg age classes (0-2, 3-5, and 6-8 days old) were used to test the effect of St egg age on survival. St in field cages showed poor survival, likely due to freezing temperatures. However, the oldest (6-8 day) age class showed significantly greater survival in the field than the younger age classes. The two oldest age classes showed significantly greater survival than the youngest (0-2 day) age class in the laboratory. Results of multiple studies over two years support the release of St eggs to enhance biological control efforts against HWA. Studies showed St established as eggs in the field could successfully develop into adults. Survival of St from egg releases is highest when St eggs are released between late March and May, in low densities, and in older age classes.

Cultural Control Methods that Effect the Development and Spread of <em>Corynespora cassiicola</em> (Berk. & Curt.) Wei on African violet (<em>Saintpaulia ionantha</em> Wendl.)

Ross, Hillary Dawn 01 May 2007 (has links)
In recent years, a large commercial grower of African violets (Saintpaulia ionantha Wendl.) in middle Tennessee has experienced epidemics of Corynespora leaf spot caused by Corynespora cassiicola (Berk. & Curt.) Wei (Alan Windham, personal communication). Symptoms of Corynespora leaf spot include rapidly expanding circular lesions on the surface of the leaves and petioles. The disease occurs in propagation material and mature plants of S. ionantha which result in thousands of plants being discarded daily. The objectives of this research were to: 1) determine if irrigation methods affected disease severity, 2) to determine if fungicidal spray intervals could be extended beyond the recommended two week interval, and 3) to determine if leaf age affects the susceptibility of S. ionantha to C. cassiicola. Three irrigation treatments (drip, mist, and ebb & flow) were evaluated for their effect on disease severity of C. cassiicola. Over a seven week period, plants were observed for the presence of lesions on leaves and petioles. This experiment was repeated four times with four to six replications per repetition. Disease severity was not significantly different in the three irrigation treatments in reducing the spread of C. cassiicola. Three fungicides (propiconazole, thiophanate-methyl, chlorothalonil) and a water control were applied to symptomatic S. ionantha. Leaves were collected for eight weeks. Overall, leaves sprayed with the thiophanate-methyl treatment produced the lowest amount of sporulation and isolate growth, but no treatment was effective in inhibiting the growth of C. cassiicola in S. ionantha tissue. The effect of leaf age on disease susceptibility was evaluated using three stages of S. ionantha leaves: juvenile, mature, and senescing. Lesion size was larger on juvenile and senescing leaves than on mature leaves.

Studies in plant ecology and conservation.

Specht, R. L. January 1973 (has links) (PDF)
Thesis (D.Sc.) -- University of Adelaide, Department of Botany, 1975.

Computer applications in plant breeding and genetics.

Gordon, Geoffrey Howard. January 1979 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, Dept. of Agronomy, 1980.

In vitro soil-less (IVS) rooting medium /

Newell, Christopher Jack. January 2006 (has links)
Thesis (Ph. D.)--Murdoch University, 2006. / Thesis submitted to the Division of Science and Engineering. Includes bibliographical references (p. 191-207).

The origin and development of the Compositae

Small, James, January 1919 (has links)
Thesis (doctoral)--University of London. / "Reprinted from the New phytologist, vols. XVI-XVIII, 1917-19." p. [xii]. Includes bibliographical references and index.

The origin and development of the Compositae

Small, James, January 1919 (has links)
Thesis (doctoral)--University of London. / "Reprinted from the New phytologist, vols. XVI-XVIII, 1917-19." p. [xii]. Includes bibliographies and index.

Entwicklungsgeschichte der Prothallien von Equisetum limosum Willd. und Equisetum variegatum Schleich.

Strey, Wilhelm. January 1931 (has links)
Thesis (doctoral)--Universität Marburg, 1931. / "Lebenslauf." Includes bibliographical references (p. 40-44).

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