| With the implementation of Chinese potato staple food strategy, potato industry has been confronted with great opportunities and challenges. The Northeast and the North China are the major potato regions in the north. The Northeast and the North China was also the main manufacturing base of potato seed and the potato mechanized planting concentration area. Potato late blight which occurred frequently was particularly defended in this area. This epidemic disease was caused by Phytophthora infestans, whose population structure and genetic diversity closely related to the incidence and epidemic of this disease. This study intended to collect and separate isolates from the Northeast and the North China, and by measuring the mt DNA haplotype and SSR fingerprinting to determine the population structure and genetic diversity level. On the other hand, we also analyzed the thermal adaptability and pathogenicity of different mt DNA haplotype isolates. This study would offer scientific basis for developing controlling strategies. The main results were as follows:1. The collection and separation of P. infestans: A total of 463 isolates were separated from Hebei, Inner Mongolia, Heilongjiang, Jilin and Liaoning in 2013 and 2014.2. The determination and analysis of P. infestans mt DNA haplotypes in the Northeast and the North China: A total of 311 P. infestans isolates collected from the Northeast and the North China in 2013 and 2014 were determined by PCR. We detected 5 haplotypes, which were IR3, IIR3, IIR2, IR1, and IR2 haplotype. Haplotype IR3 and IIR3 were the two major haplotypes totaling 293 isolates, accounted for 40.83% and 50.16% respectively. Haplotype IR1, IIR2 and IR2 were accounted for 9.01%. P. infestans group of Heilongjiang and Liaoning were of 5 and 4 haplotypes, which was also with the most haplotypes. Except Hebei and Liaoning groups, the percentage and haplotypes changed a lot in the other P. infestans groups.3. The determination and analysis of P. infestans groups’ SSR genotype in the Northeast and the North China: 305 P. infestans isolates were analyzed by 12 pairs of SSR primers, and 98 genotypes were identified. 83 isolates were with the genotype G-07, which was the predominant genotype, and accounted for 27.31%. The secondary genotypes were G-16, G-34, G-59, G-66, G-68 and G-69, which including 93 isolates and accounted for 30.26%. The results showed that the genotype of P. infestans groups gave priority to G-07, which was in dominant position. We detected 62 and 42 genotypes in 2013 and 2014, respectively, only 6 genotypes both were constant. The result showed that great changes occurred in P. infestans populations between years. There were also certain differences among the 5 P. infestans groups. The genetic diversity in descending order were Liaoning, Heilongjiang, Jilin, Hebei and Inner Mongolia and the Shannon index were 0.8319, 0.7350, 0.5866, 0.5286 and 0.4594, which showed the genetic diversity of the Northeast of P. infestans population was higher than that of the North China P. infestas. The gene flow among 5 P. infestans groups was 4.1167, which showed strong isolates communication. The genetic variation among and within the 5 P. infestans groups were 6.67% and 93.33%, which showed the variation within population were the major source of population genetic variation.4. The determination of thermal adaptability and pathogencity for isolates with different mt DNA haplotypes: The colonial morphology and growth of different mt DNA haplotype P. infestans were detected and we found that there were sharp distinctions between IR3/IIR3 and IR1/ IIR2 haplotype in the colonial morphology. Isolates of IR3 and IIR3 haplotype were with lower growth rate than that of IR1 and IIR2, and there were significant differences between them especially in 15℃, 20℃, 25℃ and 27℃. On the contrary, isolates of IR3 and IIR3 haplotype were with higher spores production and pathogenicity than that of IR1 and IIR2, which meant the dominant mt DNA haplotype were very competitive in the populations. |
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