Identification of Root-knot Nematodes (Meloidogyne spp.) of Arkansas using Molecular Diagnostics

Root-knot nematodes (Meloidogyne spp.) are highly-adaptable, obligate plant parasites distributed worldwide. In addition, root-knot nematodes are an economically important genus of plant-parasitic nematodes. Meloidogyne incognita, M. arenaria, M. javanica, M. hapla and M. graminis have been reported from Arkansas during 1964 to 1994. Previous identifications were based primarily on morphological characters and host differentials. In this study, identification using molecular diagnostics methods was performed to identify Meloidogyne species present in Arkansas. A total of 106 soil and root samples from 36 of the 75 counties were collected and processed to obtain root-knot nematodes. Polymerase chain reaction (PCR) was performed to amplify a region between cytochrome oxidase II and 16s ribosomal mitochondrial DNA (mtDNA) genes of root-knot nematodes. Of the species identified in the present survey, M. incognita was the most abundant followed by a few isolated samples of M. marylandi, M. haplanaria, M. hapla, M. arenaria and M. partityla. As a result of the sequencing analysis, a new set of PCR primers that amplifies the same region of mtDNA was designed to identify M. incognita. Furthermore, a species specific PCR protocol was developed using mitochondrial marker for routine nematode identifications of the most common species, M. incognita. Additionally, cultures of different species identified were established and maintained in the greenhouse on a suitable host to facilitate future research. Since correct identification of species in the field is imperative for effective control of any pathogen, findings from this research will be useful in developing suitable crop management strategies in Arkansas