Pathogen Identification And Biological Characteristics Comparison Of Rice Root-Knot Nematode In Different Regions

As one of the world’s major food crops,rice plays an extremely important role in China’s grain production.However,in recent years,root-knot nematode disease of rice occurred frequently in the main rice producing areas in South China,and its occurrence degree and damage area increased year by year,which seriously threatened the food security in China.In this study,rice root-knot nematodes from different geographical locations in china were collected,pathogen isolation and species identification were conducted,the fecundity and pathogenicity of rice root-knot nematodes from different regions were studied,and the differences in temperature adaptability of different geographical populations of rice root-knot nematodes were compared,preliminarily revealing the mechanism of the spread and extension of rice root-knot nematodes and providing a theoretical basis for further prevention and control of rice root-knot nematodes.The following research results were obtained through experiments:1.Identification of pathogenic nematode species of root-knot nematode disease: The diseased plants were collected from rice production areas in five provinces of China in 2020.Through isolation,collection and propagation,eight geographic populations of root-knot nematodes,including Xinxiang in Henan,Anding in Hunan,Wangcheng in Hunan,Yiyang in Guangxi,Rongan in Guangxi,Lingui in Guangdong,Zhanjiang in Guangdong and Lingao in Hainan,were obtained.The morphological analysis and molecular biological identification showed that the pathogenic nematode species isolated from different geographic populations were Meloidogyne graminicola.2.Analysis of the differences of fecundity and pathogenicity among different geographical populations: The test of fecundity and pathogenicity was carried out by nutrient solution floating board method after the tested nematodes were inoculated on rice.The results showed that the reproductive coefficient of the geographical population in Xinxiang,Henan Province was the lowest,at 34.1,and the fecundity was significantly lower than that of the populations in Anding,Wangcheng and Yiyang,Hunan Province(P<0.05).The population with the highest reproductive coefficient in Yiyang was 46.4,and its reproductive capacity was not different from that of Anding population only,but significantly higher than that of other geographical populations except Anding(P<0.05),suggesting that the reproductive capacity of Meloidogyne graminicolain China was different among some populations.The pathogenicity test showed that different geographical populations of C.elegans had different effects on physiological indexes such as fresh weight,plant height and chlorophyll of rice,indicating that there was pathogenicity differentiation among different geographical populations in Meloidogyne graminicola of China.3.Differences in temperature adaptability of different geographical populations: The second-instar larvae and eggs of eight geographical populations were treated with different temperatures for different periods of time to carry out low and high temperature stress tests.The results showed that the longer the treatment time of Meloidogyne graminicola egg under low temperature stress was,the lower the hatchability was.The mortality of second instar larvae of Xinxiang population was the lowest(84.2 %)when treated at 0℃ for 10 days,while that of Zhanjiang and Lingao populations at lower latitude reached 100.0%.The egg hatching rates of Xinxiang,Anding,Wangcheng,Yiyang,Rongan,Lingui and Zhanjiang populations were inhibited to different degrees at 37 ℃,while the egg hatching rate of Lingao population at low latitude increased with the prolonging of treatment time,showing a promoting effect,which indicated that the cold and heat tolerance of different geographical nematode populations were correlated with latitude.In addition,the results of low temperature pretreatment indicated that Meloidogyne graminicola could improve the adaptability to cold stress through low temperature pretreatment,and the populations of Anding,Wangcheng and Yiyang in Hunan Province improved significantly under cold stress after low temperature pretreatment,which were significantly different from the populations of Xinxiang at high latitude and Rongan,Lingui,Zhanjiang and Lingao at low latitude(P<0.05).Studies have shown that Meloidogyne graminicola may improve survival and expand distribution by increasing adaptability.