Early Detection of the Root-Knot Nematode Meloidogyne hapla Through Developing a Robust Quantitative PCR Approach...

Root-knot nematodes (RKNs) are major threats to crops through attacking the roots, which induces an abnormal development of the plant. Meloidogyne hapla is of particular concern, as it is currently expanding its distribution area and displays a wide host range. Effective plant protection against this RKN requires early detection, as even a single individual can cause severe economic losses on susceptible crops. Molecular tools are of particular value for this purpose, and among them, quantitative PCR (qPCR) presents many advantages (i.e., sensitivity, specificity, and rapidity of diagnosis at a reduced cost). Although a few studies have already been proposed for detecting M. hapla through this technique, they lack experimental details and performance testing, suffer from low taxonomic resolution, and/or require expensive hydrolysis probes. Here, we propose a qPCR detection method that uses SYBR Green with developed primers amplifying a fragment of the cytochrome oxidase I mitochondrial region. The method was developed and evaluated following the minimum information for publication of quantitative real-time PCR experiments (MIQE) guidelines to ensure its quality (i.e., sensitivity, specificity, repeatability, reproducibility, and robustness). The results demonstrate that the newly developed method fulfills its goals, as it proved specific to M. hapla and allowed for a reproductible detection level as low as 1.25 equivalent of a juvenile individual. All criteria associated with the MIQE guidelines were also met, so the method is of general use for the reliable early detection of M. hapla.