Genetic Diversity Of Phytophthora Infestans And The Analysis Of F1 Progeny Isolates Using SSR Marker

Potato late blight is one of the most serious diseases in the potato growing areas all over the world. The population structure and variation of Phytophthora infestans are associated with the occurrence and epidemics of this disease. When the potato late blight re-emerged in 1980s, the research on the late blight was focused on the population structure of the pathogen. The genetic diversity of P. infestans population was assessed by SSR marker so that its diversity was further clarified in some investigated areas of China. In addition, the gene recombination of single-oospore isolates was analyzed using co-dominant SSR marker. The main results in the study are as follows:1. One hundred and sixty isolates collected from five provinces of China were tested with the eight pairs of SSR primers. The results showed that 22 alleles were found in all and the number of alleles per locus ranged from 2 to 4, and was 2.8 on average. The range of distribution of Shannon index was from 0.4008 to 0.9858, and its average value was 0.6864.2. Cluster analysis by UPGMA showed that 160 isolates could be divided into four groups where the genetic distance was 0.80.The 13 isolates collected from Fujian province were classified into groupâ… ; The groupâ…¡contains the 7 isolates which come from Yunnan province; Only one isolate (H12-1) from Yunnan province is classified into groupâ…¢; The groupâ…¤contains the most isolates collected from Inner Mongolia, Hebei and Heilongjiang province. The SSR genotopy of 160 isolates were correlated to groups defined by geographical origin.3. Parameters of genetic diversity calculated by POPGENE software about P. infestans population in China indicate that the genetic distance between Heilongiang province and Hebei province is 0.0007, which has the lowest discrepancy, while the genetic disparity between Inner Mongolia are deep and the genetic distance is 1.0852.The genetic disparity between colonies are large, meanwhile, the isolates from North part of China have small difference in hereditary character, however, the isolates from south part of Chinese have big difference in genetics. 4. Using two codominance molecular SSR to test the recombination of 55 oospore offsprings. The result indicate that 53 offsprings have the same band with their parents strains , only two offsprings be tested have genetic recombibination.