A Study On The Classification And Geographical Distribution Of Nematodes Of Hetericoideae In China

Cyst nematode(Heteroderinae)is a typical plant parasitic nematodes which has strong adaptability,wide distribution,varied host range and obvious host specialization.It caused huge economic losses to the worldwide crop production every year.Those pathogenic nematodes are very tiny and difficult to be find.It is difficult to control when the damage is serious.The systematic study on cyst nematode is helpful to identify population distribution and its evolutionary relationship,which has great significance to the prevention of this disease in agriculture.This stduy collected various plant roots soil samples and investigated in major soybean producing areas in each province/city all over the country.The cysts were separated by panningsieving method in soil samples and morphology combined with molecular biology were used to identify the isolated cysts and to calculate the population density.The following results were obtained:1.Identification and geographical distribution of Heteroderinae: From 2017 to 2019,a total of 349 rhizospheric soil samples were collected in 7 provinces and cyst were isolated and identified from those soil sample.By morphology and molecular identification,We identified a new specie of Cactodera,which was named Cactodera chenopodiae n.sp.And we also identified a new disease in China,Heterodera elachista,which harmed corn.C.estonica was first found in the Inner Mongolia autonomous region.We summarized the geographical distribution of the population of Cyst nematodes which caused serious damage in agricultural production.2.Soybean cyst nematode(SCN)population density survey and virulence type: From 2017 to 2019,soybean rhizospheric soil samples were collected from 337 farmlands in 18 provinces of China,and SCNs were isolated fromthose soil samples.The survey found that SCN distributed all of the 18 provinces.Combined with the previous research,the dynamic change of population density of SCNs were analysed by heat map from 2015 to 2019.The virulence phenotype of SCN were tested from samples fo Liaoning province,HG types of SCNs were the first identified in Dalian,Huludao,Benxi,Jinzhou and Tieling area,and the HG Types 7 was the first reported in Faku county,Shenyang.3.The phylogenetic relationships analysis of Heteroderinae: We have generated a number of signature sequences for the mitochondrial COI gene abtained our samples,the preliminary phylogenetic studies of Heteroderinae have been shown in combination with Gen Bank database.Population of SCN(H.glycines)had genetic diversity in different regions.SCNs can be defined two clades which were shown in Bayesian inference(BI)and maximum likelihood(ML)tree of representatives of the Heteroderinae in China.And the method of extracting the total DNA of a single nematode was optimized to obtain the total DNA of nematode more conveniently and quality.