Meloidogyne incognita is considered the most damaging and common root-knot nematode to numerous host plants worldwide. During a survey of nematodes in Vietnam, 1,106 samples from 22 different plant species were collected. M. incognita was recorded on 13 of the 22 host plants. Four populations of M. incognita from four host plants were chosen for comparison and confirmation of their morphologic, morphometric, and molecular characteristics. Genetically based phylogenetic trees were constructed to show relationships among root-knot nematodes. Molecular barcodes of four gene regions, ITS, D2-D3 of 28S rRNA, COI, and Nad5 mtDNA, integrated with morphologic and morphometric data were used as reliable references for molecular identification of M. incognita. Our analyses indicated that tropical root-knot nematodes are very similar in characterization of ITS, D2-D3 of 28S rRNA, and COI regions. However, these gene regions can be used to separate the tropical root-knot nematode group from other groups. On the other hand, the analysis of Nad5 mtDNA and multiplex-PCR with specific primers can be used to distinguish tropical species.
Keywords: barcode; black pepper; coffee; cucumber; medicinal plant; molecular; root-knot nematode; taxonomy; tomato; variation.