The Northern Root-Knot Nematode Meloidogyne hapla: New Host Records in Portugal

SIMPLE SUMMARY: Damage caused by plant-parasitic nematodes (PPNs) is usually underestimated as many farmers are oblivious of their presence. Root-knot nematodes (RKNs) are an economically important group of PPNs and one of the most devastating. The species Meloidogyne arenaria, M. hapla, M. incognita and M. javanica are considered the most important, due to their worldwide distribution and polyphagia, being the northern RKN, Meloidogyne hapla the most important species occurring in cold regions. During 2019–2022, surveys were carried out in different districts of Portugal in horticultural and ornamental crops. From the samples collected, nine were identified morphologically and molecularly as M. hapla, indicating that its prevalence is increasing, and demonstrating its importance and impact in agricultural systems. ABSTRACT: Root-knot nematodes (RKNs), Meloidogyne spp., are a group of plant-parasitic nematodes (PPNs) of great economic significance worldwide. The northern root-knot nematode, Meloidogyne hapla, is one of the most important species of RKNs occurring in cold regions. In Portugal so far, M. hapla has been found parasitizing potato and fig trees. During surveys carried out in 2019–2022 in fields for horticultural and ornamental production, soil and root samples were collected. Roots were observed under a stereomicroscope to determine the presence of galls. Nematodes were extracted from the soil. Morphological features showed a high similarity and consistency with previous descriptions of the genus. For molecular analysis, total genomic DNA was isolated from single nematodes and used to amplify in multiplex reaction using the species-specific primers JMV1, JMV2 and JMVhapla, and for sequencing of the ITS region with the primers TW81/AB28. Multiplex PCR amplification produced a specific fragment of 440 bp and PCR amplification of the ITS region yielded a single fragment of 550 bp, as expected. The obtained sequences showed a similarity ranging from 99.8% to 100% with the sequences of M. hapla available in the database. The phylogenetic tree revealed that the isolates grouped with M. hapla isolates. From the 690 samples collected, M. hapla was detected in three different hosts (grapevine, eucalyptus and potato) in four districts of mainland Portugal and on Madeira Island. To our knowledge, this is the first report of M. hapla infecting the grapevine and eucalyptus in Portugal.