Transformation Of R-genes To Late Blight And Development Of Differential Sets In Potato

Potato (Solanum tuberosum) is the fourth crop in the world, which plays an important role in people 'sdiet nowadays. Late blight (Phytophthora infestans de Bary) is a very serious disease on potato, andmolecular breeding could be an useful approach for breeding potato cultivars, with durable resistance.This study has been divided into three parts.Firstly, triple-gene vector pBINPLUS: Rpi-sto1+Rpi-vnt1.1+Rpi-blb3 was constructed based onselection after testing 28 isolates from four regions in China, with the method of detached leaf assay(DLA). The triple-gene vector was used to transform R-genes cassette into susceptible cv Desiree.Regenerated shoots obtained from marker aided (NptII as a selection marker gene in thetransformation) and marker free transformation were screened with PCR for testing the existence ofthe R-genes. 2 tested NptII containing regenerated shoots and 2 out of 280 marker free regeneratedshoots were turned out to be Rpi-sto1 positive. The instant transformation efficiency is 0.71% (56 daysafter transformation).Secondly, three potato differential sets have been set up so far, which were all hetergeneous.Comparison was made between the one of these three heterogeneous sets and another homogeneousdifferential set, using DLA with 17 isolates, possessing different virulence spectrums. This is aimed atfiguring out whether differential sets, with different genetic background could effect the screening oflate blight isolates or not. Heterogeneous and homogeneous differential sets did not show the samevirulence spectrum to the same isolate. Further conclusion can be made after testing more isolates.Thirdly, pBINPLUS: Rpi-pta1 was transformed into susceptible cv Desiree and regenerated shootswere screened by PCR, southern blotting and DLA. Results turned out that all tested regeneratedshoots were transformants, 26 out of 77 tested transformants contained one copy number of Rpi-pta1,and 72 out of 74 tested transformants showed resistance to the isolate, which contained thecorresponding Avr gene. In addition, the resistance spectrums from three homologous R-genes Rpi blb1, Rpi-sto1 and Rpi-pta1 in cv Desiree background and three accessions from these R-genes clonedspecies were compared using 6 potentially broken isolates, originated from nature in Mexico and fieldin the Netherlands. Two Mexican isolates Pic99189 and Pic99192 were found to have broken theresistance of these homologous R-genes.Another observation was that the heterogeneous accessionscontaining Rpi-blb1 and Rpi-sto1 were still resistant. Only the accession pta767-1 from S. papitaappeared to be susceptible to isolate Pic99192. Combining the result from the first part, thesehomologous R-genes still had their potential use in China.