Current Situation,Species Identification And Toxicity Variation Of Root-knot Nematode In Handan Protected Vegetables

Meloidogyne spp.is an important pathogen with many species,wide host range,small individual and wide distribution.In recent years,the planting area of protected vegetables in China has expanded rapidly and the multiple cropping index has increased,which leads to the increasingly serious root-knot nematode disease and seriously affects the yield and quality of crops.However,the occurrence,species and toxicity variation of root-knot nematodes in Handan on protected vegetables are still unknown.Therefore,it is very important to investigate the occurrence of root-knot nematode in this area in time,and to accurately and reliably identify the species and toxicity variation of them in this area.1.Investigation on occurrence,distribution and harm of root-knot nematode in protected vegetables in Handan City.In this study,a total of 235 samples were collected from 22 townships in 6 counties(districts),namely Quzhou County,Yongnian District,Guantao County,Jize County,Feixiang District and Congtai District,which have large protected vegetables planting areas.Results showed that the incidence of root-knot nematode in Quzhou Disituan town was the lowest,33.3%,and that in fertilizer township,Xin-anzhen Town and Maoyanbu township,the highest,60%.To the Disituan town,the disease index is the lowest,13.9;Maoyanbu township has the highest,41.7.The morbidity and disease index in Feixiang district are higher than those in other areas.The occurrence,distribution and damage of root-knot nematode in Handan City were preliminarily determined.2.Identification of plant root-knot nematode in Handan City and determination of dominant population.Twenty-two representative samples were selected for species identification and dominant population determination.Morphological identification of the secondstage juvenile and the female perineal pattern were carried out.The second-stage juvenile had a body length of 389(360～430)μm,a mouth needle length of 11.5(11.0～12.3)μm and a tail length of 51.7(50～53)μm.Female insect perineum pattern back arch is high,like square,side line is clear,line grain is thick to fine,clear.These results have the highest similarity with the morphological characteristics of M.incognita reported.The morphological characteristics were further verified by molecular biology techniques.The r DNA-ITS sequence of the sample was amplified with a common primer,and the fragment size was about 480 bp.The purified PCR products were recovered and sequenced.Blast comparison results showed that the similarity with the submitted M.incognita was up to 98%,which preliminarily determined that M.incognita occurred in vegetables in Handan City was M.incognita.Phylogenetic tree was constructed by ITS sequence,and the results showed that the phylogenetic tree was closely related to M.incognita,M.arenria and M.javanica in Gen Bank on a large branch.In order to accurately identify the species of root-knot nematodes,5 specific primers of root-knot nematodes were used for PCR amplification of the tested root-knot nematode samples.Only the primer MI-F/MI-R had target bands with a size of about 951 bp.The results of morphological and molecular biological identification showed that all the samples were M.incognita.Therefore,the species of plant root-knot nematodes in Handan City was M.incognita,and it was the dominant population of root-knot nematodes in Handan City.3.Purification and toxicity determination of root-knot nematode in vegetables in Handan City.Random samples were collected from 12 M.incognita community,separation and purification were inoculated on the disease of tomato Sufen2003 cultivation,separation and egg mass in sterile water made second-stage juvenile hatch(J2)suspension,respectively inoculated in the disease Lycopersicon esculentum cv.Nemax,each 2000,after 45 d record root-knot nematode disease degree.The results showed that there were different degrees of toxicity differentiation in 12 populations.The disease-resistant tomato showed high resistance to 8 groups,including Beianshang Village,Jize Town,Jize County,and the root-knot index ranged from 0.6 to 1.0,and showed resistance to 4 groups,including Houjia Village,Xin-anzhen Town,Feixiang District,with the root-knot index ranging from 1.2 to 1.6.The results showed that the degree of resistance of resistant tomato to different populations of M.incognita was not consistent,and the pathogenicity of resistant tomato to different populations of M.incognita was not consistent.This study preliminarily clarified the species,distribution and toxicity variation of root-knot nematode in Handan City,providing an important theoretical basis for the comprehensive control and resistant variety layout of root-knot nematode in Handan City.