Biological And Molecular Characterization Of Meloidogyne Enterolobii

Root-knot nematodes (Meloidogyne spp.) are root endoparasites that are capable of causing considerable damage on a variety of crops. To date, approximately 30 species of Meloidogyne have been recorded in China, of which M. enterolobii is currently restricted in distribution to Hainan Province. To assess the potential economic importance of M. enterolobii and to provide means to assist in preventing the spread of the nematode, studies were carried out on the host range, sequence characteristics of mtDNA and rDNA loci and PCR-based detection methods of M. enterolobii populations from Hainan Province.The reproduction potential of four representative M. enterolobii populations were tested on fifteen cultivars of ten economic crops. Biotesting revealed that tomato carrying the resistance gene Mi, kidney bean, cowpea, eggplant, cucumber, watermelon, pepper and tobacco were good hosts of the M. enterolobii populations tested; soybean was a poor host; and cotton was a non-host. The result suggests that M. enterolobii has the potential to cause great economic losses in agriculture.Sequences of three mtDNA and rDNA loci were amplified from and compared between M. enterolobii and the four common species M. incognita, M, javanica, M. arenaria and M. hapla. Amplification products of the mtDNA COII-lrKNA region from the M. enterolobii populations were about 0.85 kb in size, which is distinct from those of the four common root-knot nematodes. Amplification products of the rDNA ITS and IGS2 regions from the M. enterolobii populations were about 760 and 780 bp in size, respectively, which are similar to those from the four common species. However, sequence alignment revealed that M. enterolobii is significantly diverged from the other four species at both the ITS and IGS2 loci. The ITS sequence of M. enterolobii showed 87%, 87%, 87% and 83% homology to those of M. incognita, M. javanica, M. arenaria and M. hapla, respectively, and the IGS2 sequence of M. enterolobii was 84%, 84%, 84% and 70% homologous to those of the four common species, respectively.A single-step PCR diagnostic was developed for M. enterolobii. The diagnostic primers were designed based on an alignment of IGS2 sequences from M. enterolobii,M. incognita, M. javanica, M. arenaria and M. hapla. The reliability of the diagnostic test has been validated by screening different geographic populations of six closely related Meloidogyne species and natural mixed soil nematode populations. The test is fast and sensitive, it can be routinely used for direct diagnosis of a single nematode and for detection of M. enterolobii in mixed soil nematode populations.