Characterization Of Meloidogyne Populations From China Using Isoenzyme Phenotypes And MtDNA-PCR-RFLP

Root-knot nematodes (Meloidogyne spp.) are polyphagous obligate endoparasites of plant roots. These nematodes currently constitute one of the most economically important groups of pathogens of agricultural crops in China. In order to assess the occurrence and rapid and reliable identification methods of Meloidogyne species in China , studies were carried out on isozyme phenotypes and mitochondrial DNA (mtDNA) polymophisms of 40 populations of Meloidogyne collected from economic plants from 13 provinces in China. Polyacrylaimide gel electrophoresis was used to reveal malate dehydrogenase (Mdh) and esterase (Est) activities. The 33 single-eggmass-derived and seven field populations tested exhibited two Mdh (Nl and HI) and five Est (II, J3, Al, A2 and HI) phenotypes. On the basis of Mdh-Est phenotypes, four species were identified from the populations. Of the 33 single-eggmass-derived populations, 24 were M. incognita with a Mdh-Est phenotype of N1-I1; three M. javanica with N1-J3; five M. arenaria with N1-A2 or N1-A1; and one M. hapla with HI-HI. Of the seven field populations, three were pure M. incognita, one pure M. hapla, two a mixture of M incognita and M. javanica, and one a mixture of M incognita and M. arenaria.Primers C2F3 and MRH106 were chosen to amplify the intergenic region between COII and IrRNA genes of mtDNA to assess mtDNA polymorphisms among Meloidogyne populations from China. Primary amplified fragments were =1.8 kb for populations of M. incognita, M. javanica and M. arenaria with the Mdh-Est phenotypes of N1-I1, N1-J3 and N1-A1, respectively, =1.3 kb for populations of M arenaria with N1-A2, and =0.6 kb for populations of M hapla. When the amplified products were digested with the restriction enzyme HinfI, characteristic restriction patterns were detected that distinguished each Mdh-Est type of populations from each other. The majority of M. incognita populations with N1-I1 displayed three restriction fragments of =1.3 kb, 0.4 kb and 0.1 kb; M. javanica populations with N1-J3 one unrestricted fragment of =1.8 kb; a M. arenaria population with N1-A1 two restriction fragment of ^1.7 kb and 0.1 kb; M. arenaria populations with N1-A2 tworestriction fragments of =1.2 kb and 0.1 kb; and M. hapla populations with HI-HI two restriction fragments of ^0.5 kb and 0.1 kb.The present studies revealed that M. incognita, M. javanica, M. arenaria and M hapla are common Meloidogyne species in China, and M. incognita occurs predominantly in southern China; that natural field Meloidogyne populations frequently consist of more than one species; and that Mdh-Est phenotypes of Chinese Meloidogyne populations correlate strictly with their specific restriction patterns of amplied mtDNA regions, and hence both isozyme and mtDNA -PCR-RFLP analyses are rapid and reliable approaches for the identification of common Meloidogyne species in China.