Visser, B.Van Der Westhuizen, A. J.Bezuidenhout, Mariëtte2015-11-032015-11-032006-12-012004-09-042006-12-01http://hdl.handle.net/11660/1500English: Sunflower (Helianthus annuus) is a commercially important crop plant. Susceptible plants infected with leaf rust (Puccinia helianthi) leads to great yield losses. The aim of this study was to identify putative protein kinase genes from a resistant sunflower cultivar that are involved in the early resistance response when the plant is infected with leaf rust. Several differentially expressed cDNA fragments were isolated from infected resistant sunflower. One of these identified clones (D15) showed an 8.5 fold induction of gene expression 3 h.p.i. in infected resistant sunflower, while the expression in the susceptible infected cultivar was repressed. A second 31 fold activation was found 15 h.p.i. This second induction most probably forms part of induced SAR in the uninfected plant tissue. This cDNA clone showed homology to several protein kinase genes. In addition, the gene is present as a single copy within the genomes of susceptible and resistant sunflowers. A polymorphism in size was however evident between the genes present in the two cultivars. Three other cDNA clones were also selected on the basis of their expression profiles. These cDNAs showed homology to Apyrases, a Rac-protein and Xyloglucan endotransglycosylases respectively. The involvement of all four cDNAs in the activation of plant defense however still needs to be confirmed.Afrikaans: Sonneblom (Helianthus annuus) is ‘n kommersieël belangrike gewas. Vatbare kultivars wat met blaarroes (Puccinia helianthi) geïnfekteer is, lei tot grootskaalse verliese. Die doel van hierdie studie was om ‘n proteïenkinasegeen te identifiseer wat in die weerstandbiedende kultivar ‘n belangrike rol speel tydens die verdedigingsreaksie wanneer die plant met blaarroes geïnfekteer word. Verskeie differensieël uitgedrukte cDNA fragmente is uit geïnfekteerde weerstandbiedende sonneblomme geïsoleer. Een van die klone (D15) het ‘n 8.5 voudige induksie van uiting slegs 3 ure na infeksie in die geïnfekteerde weerstandbiedende plante getoon. Die uitdrukking van hierdie geen was egter aktief in die geïnfekteerde vatbare kultivar onderdruk. ‘n Tweede induksie van die geen was ook 15 ure na infeksie in die weerstandbiedende plante gevind. Hierdie tweede induksie vorm moontlik deel van die indusering van sistemiese verworwe weerstand in die ongeïnfekteerde weefsel. Hierdie kloon toon homologie met verskeie proteïenkinasegene uit verskillende plante. Die D15-geen kom as ‘n enkelkopie voor in beide die weerstandbiedende en vatbare kultivars. ‘n Moontlike polimorfisme is gevind deurdat die gehibridiseerde fragmente in grootte verskil in die twee kultivars. Drie ander cDNA klone is ook geselekteer na aanleid ing van hul induksieprofiele. Hierdie klone toon homologie met Apirases, ‘n Rac-proteïen en ‘n Xyloglukanendotransglikosilase onderskeidelik. Die betrokkenheid van al vier hierdie cDNAs tydens die aktivering van plant verdediging moet egter verder nog bevestig word.enDissertation (M.Sc. (Plant Sciences))--University of the Free State, 2004Sunflowers -- Disease and pest resistance -- Genetic aspectsSunflowers -- Diseases and pestsRust diseases -- South AfricaPuccinia helianthiDDRT-PCRProtein kinase genePlant defenseHelianthus annuusDissertationUniversity of the Free State