Morphological And Molecular Characterization Of Root-knot Nematode Parasitizing Citrus In Guilin Of Guangxi Province

Guilin is a main citrus production region in Guangxi Zhuang Autonomous Region.Root-knot nematode(Meloidogyne)is an important pathogen of citrus in Guilin,but the damage caused by the nematode and species has not been reported.The survey was carried out on root-knot nematode disease of cirtus in Guilin region,Guangxi Zhuang Autonomous Region,the root knot nematode parasitizing citrus were identified by morpHological and biological characterizations.Besides,the molecular characterization of the root-knot nematode by pHylogenetic analysis of genes within the rDNA in Meloidogyne spp.were studied.The research showed that root-knot nematode was commonly distributed in citrus producing regions of Guilin,Citrus unshiu with root stock Poncirus trifoliate were main serious damage by the root-knot nematode.The root-knot nematode disease has been one of the most important soil-borne diseases of citrus in Guilin region.The nematode cause obvious varying size galls in citrus fibrous roots,fibrous roots can produce from the the galls,and infected by the nematode,so typical symptoms of root system caused by the nematode was curly fibrous roots system with galls.The species of Meloidogyne parasitizing on citrus in Guiling region was identified as Meloidogyne mingnannica by morpHolgoical characterization.The perineal pattern of females was round to ovoid with a low dorsal arch,with fines striae,and indistinct lateral linest,many broken ciscontinuous striae on the both sides of lateral area or on the anal area region.pHasmids were small,indistinct,which was around marked by circular striae or whorl.There were no parallel continuous striae between anus and vulva.All of the characters were similar to what reported by zhang shaosheng in 1993.Poncirus trifoliate was susceptible host for M.mingnanica based on the inoculation test and result of sodium hypochlorite-acid fuschin staining.Enzyme pHenotypes of M.mingnannica were studied,esterase enzymes(RM = 54.4%)pHenotype was A1 and malate dehydrogenase enzymes(RM = 23.7%)pHenotype was N1.The regions of rDNA-ITS,D2-D3 of 28S rDNA and mtDNA CO ?-IrRNA gene of M.mingnannica were amplified and sequenced.pHylogenetic trees derived from Maximum Likelihood and Bayesian analysis based on the regions of rDNA-ITS,D2-D3 of 28S rDNA and CO ?-lrRNA of mtDNA showed that M.mingnannica can be differentiated from all the root knot nematode species which have corresponding accession deposited on GenBank.The results make up for the lack of molecular characterization about Meloidogyne mingnanica.