Genetic Diversity Of Geographical Populations Of Rotylenchulus Reniformis In China

Rotylenchulus reniformis is a plant semi-parasitic nematode, which is widely distributed in tropical and subtropical area of the world, can parasite variety of vegetable crops and tropical fruits like cotton, sweet potato, pineapple and banana, and can cause great harm to host plants. In recent years, R. reniformis has become a major disease in the upland cotton in America, which severely affects the cotton production. It is reported that the R. reniformis has become one of the dominant species in some areas of China, and may cause serious damage to our crops.DNA sequence analysis technology was used in this study. rDNA sequence variation between individuals and within populations of3reniform nematode populations from Zhejiang, Fujian and Chongqing were analyzed; qPCR technology was used to analyze the relationship between the content of different types of rDNA in the genome; and use of mitochondrial DNA marker to analyze genetic diversity and genetic differentiation of3geographical populations of reniform nematode were made. The main results are as follows:1. Two kinds of rDNA gene sequence variants were detected from each nematode of three populations of R. reniformis, which named as variant1(RN_VAR1) and variant2(RN_VAR2), respectively. The variation was found in18S gene,28S gene and ITS regeion. And ITS region is more variable than other part of rDNA gene. The length and GC content of ITS region characterized by RN_VAR1:705-712,45.1%-46.7%; and RN_VAR2:854-860,48.4%-50.0%, respectively. The percent identity between RNVAR1and RNVAR2is relatively low which only ranged between62.1%and65.6%. The percent identity between all clones in RN_VAR1is89.9%-100%, and in RNVAR2is91.4%-99.8%. Neighbor-joining tree shows that both RN variants can be distinguished from other nematode by ITS sequence alignment, while it is hard for differentiation intrapopulation of/?, reniformis.2. The qPCR experiments show that RNVAR1does make up the56%of rDNA units with relatively well-conserves in18S RNA gene, whereas RNVAR2is40%. It indicate that these two rDNA variants are the main form of rDNA gene in reniform nematode.3. Genetic diversity analysis of reniform nematode base on COII-LrRNA gene showed that mtDNA of COII-LrRNA gene region has557-563bp sequence. AT content is85.5%, much more than GC content. The total variation sites, number of haplotypes, haplotype diversity, nucleotide diversity of3population were176,40, 0.946and0.1574respectively. The AMOVA shows that the coefficient of genetic differentiation is0.05815, places these isolates into a moderate range of genetic differentiation and a weak genetic structure. And the variation within populations is94.18%and only5.82%of the variation occurred among populations. In general, the variation among COII-LrRNA gene sequence of reniform nematodes in China is obvious, indicating that reniform nematodes in China has abundant genetic diversity, and a strong ability to adapt to environmental change, with large living space in the southern area of China.