Köln, University, Diss., 2002.

No description available.

Diseases caused by micro-organisms are still a major threat to the agro-industry worldwide. Diseases not only have negative effects on crop yields, but also they can affect the quality of crops post-harvest. Genetic engineering is one of several strategies that have been developed to control plant diseases and to enhance plant disease resistance to pathogens. Although some genetic strategies have provided plants with enhanced disease resistance, some pathogens can easily overcome this resistance by rapid evolution resulting in a lack of durability in the field. The oomycete Phytophthora infestans, the causal pathogen of late blight disease of potato, is an example of a crop pathogen that causes a major problem in one of the most important crops worldwide. Many efforts have been made trying to control this pathogen including chemical controls and genetic engineering, but unfortunately it remains a severe problem and the control measures are rarely very successful. Due to the complexity of this pathogen, and to limit the need for chemical control, breeding programmes to incorporate durable forms of genetic resistance are crucially needed. Although, this type of resistance is believed to be effective against all known races of P. infestans and provide in additional some level of general resistance, until now the genetic bases of this type of resistance is still unknown and the molecular mechanisms poorly understood. This project set out to isolate and identify gene sequences that are induced during the compatible interaction between cultured potato plants and P. infestans, specifically those leading to the establishment of durable resistance. It was demonstrated that the potato variety Stirling is capable of developing this type of resistance as judged by the development of resistant shoots during the interaction with Phytophthora. These shoots showed very strong resistance not only to Phytophthora but also to other potato pathogens (R. solani and F. sulphureum) even after two generations of culturing the plants in the absence of the pathogen. The fast production of ROS and the tight deposition of callose surrounding the hypersensitive cells, which deprive the pathogen of nutrients and limit pathogen growth to a small region of the plant, may be important factors in the success of the durable plants in defending themselves against the pathogen attack.

In order to identify potential avirulence factors of <i>Phytophthora infestans</i>, secreted protein profiles of six strains (IPO-0, CBS431.90, IPO-655-2A, IPO-428-2, 88069 and 90128) with different avirulence phenotypes were analysed by proteomics.  The proteins from culture filtrates were visualised on 2D gels with a total number between 350 and 1000.  PiAVR X was found only in avirulent strains and considered therefore as a possible avirulence determinant.  Its expression increased in all strains tested when grown in Modified Henniger medium.  Single nucleotide polymorphisms (SNPs) were detected within a 735 nt fragment of <i>PiAvrX</i> but none was linked to avirulence characteristics.  The consensus EST database facilitated identification of approximately 50% of 45 most abundant proteins excised from strain 88069.  Beta-glucosidase, Pi-NIP2 (<i>Phytophthora infestans</i> necrosis inducing protein-like protein), enoyl CoA hydratase, glutathione S transferase, peptidylprolyl isomerase, acidic chitinase and Pi-PR1 (<i>Phytophthora infestans </i>homologue of plant PR-1 protein) were among the identified proteins with a recognisable signal sequence.  Enolase, quinine-oxido reductase, nucleoside di-phosphate kinase, actin depolymerisation factor, thioredoxin, ubiquitin and 14-3-3 protein were also identified but without a signal peptide.  The occurrence and expression of <i>Pi-nip2, Pi-chi1 </i>and <i>Pi-pr1</i> were confirmed in the strains tested.  Transformants were obtained from <i>P. infestans</i> strain T30-4 via a biolistic particle delivery approach using a single plasmid vector containing <i>Pi-pr1</i>.  Detailed analysis of these transformants did not demonstrate induction of homology-dependent gene silencing.  It was found that transformation rates were different among the tested <i>P. infestans</i> strains.

Typescript. / Thesis (Ph. D.)--University of Hawaii at Manoa, 1990. / Includes bibliographical references (leaves 110-115) / Microfiche. / xiv, 115 leaves, bound ill. (some col.) 29 cm

Hohenheim, Univ., Diss., 2007.

Thesis (Lic. Ing. Agronómica)--Universidad Católica Boliviana San Pablo, Unidad Académica de Carmen Pampa Carrera de Ingeniería Agronómica, 2003. / Reproduced from copy at BYU's Benson Institute. Includes bibliographical references (leaves 59-63).

Thesis (Ph. D.)--Ohio State University, 2003. / Title from first page of PDF file. Document formatted into pages; contains xiv, 156 p.; also includes graphics (some col.) Includes bibliographical references (p. 141-156). Available online via OhioLINK's ETD Center

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Universiẗat, Diss., 2001--Bonn.