ISOLATION, CHARACTERIZATION, AND APPLICATION OF DNA PROBES SPECIFIC TO MELOIDOGYNE-ARENARIA

Approximately 1,100 clones of a genomic EcoRI plasmid library of Meloidogyne arenaria were differentially screened with P-32-labeled genomic DNA from M. arenaria and M. incognita. One clone (pRIMA17) hybridized preferentially to M. arenaria, and two clones (pRIMA2, pRIMA9) hybridized preferentially to M. arenaria and M. javanica. Restriction mapping and differential screening of pRIMA17 revealed an internal 900-bp ScaI fragment (pSCIMA17) that was specific and produced a strong hybridization signal with DNA from M. arenaria only. Neighboring restriction fragments within pRIMA17 were also species-specific but the hybridization signals were less strong. Fragments of pRIMA17 hybridized to polymorphic interspersed repeats in M. arenaria populations; however, not all fragments produced the same banding patterns. Sequence analysis showed that pSCIMA17 contained a tandem repeat region of 28-bp subunits repeated 19 times extending from the left border. The tandem repeat was followed to the right by a region rich in A and T nucleotides. A dot blot method to identify root-knot nematode species with species-specific DNA probes using egg masses was developed. High sensitivity as a result of internal tandem repeat sequences and hybridization to a high copy number interspersed repeat make pSCIMA17 particularly suitable for diagnostic applications.