RAPD Marker Of Resistance To Metalaxyl Of Phytophthora Infestans

Potato production has been seriously threatened by late blight causing by Phytophthora infestans in the long term. The wide existing and spreading of A2 mating type and resistant isolates of Phytophthora infestans in the world, brought out great threat to the chemical control of potato late blight and management of the development of resistance to metalaxyl. The appearance of molecular-technique provides new method to study fungicide-resistance. But there is much little report about searching metalaxyl-resistance of P. infestans. In this dissertation, the strains of asexual single-zoospores and sexual single-oospores were studied to determine the phenotypic and DNA genotypic trait of the resistant isolates of P. infestans, based on the situation that resistant isolates had occurred widely in China. The results are shown as follows:(1)The optimum crosses combination DK98-1 ×HD01-3 was selected from 16 crosses combination of different isolates of P. infestans. The oospore germination percentage was 10.2%, and the survival percentage was 4.6%. 50 asexual single-zoospore isolates derived from the parent isolate DK98-1 were obtained, named the DZO1 strains. 50 asexual single-zoospore isolates derived from the parent isolate HD01-3 were obtained, named the HZO1 strains. The sexual single-oospore F1 strains were obtained from the crosses DK98-1 ×HD01-3 which include 30 sexual single-oospores.(2)The colony trait, growth rate, capacity of sporangia production were tested of DZO1, HZO1 and Fl strains. The result showed that these biologic characteristics of the asexual progenies were identical with their parent's. But the average growth rate of the sexual progenies was reduced, while the capacity of sporangia production was improved. These meant that sexual reproduction of P. infestans could result in variation of biological traits.(3)The result of testing the mating type and the ability of oospore production indicated that there existed the abruption of mating types in F1 progenies, and the difference of the capacity to produce oospores was great between different strains, and the amounts of oospores ranged from 4 to 3121/ cm~2.(4)The resistance level to metalaxyl were assessed of DZO1, HZO1 and Fl strains. The result showed that the level of the asexual progenies DZO1 and HZO1 was identical to their parent's, however, the level was segregated in sexual progenies. The ration of...