Meloidogyne luci, a new root-knot nematode parasitizing potato in Portugal

In 2013, during a field survey conducted in Portugal on potato, Solanum tuberosum L., an unusual esterase (EST) phenotype was detected in a root-knot nematode (RKN) from potato roots collected in Coimbra. This Portuguese isolate was purified and maintained on tomato, S. lycopersicum L., and studied by morphological, biochemical and molecular characteristics. Perineal pattern morphology was highly variable, similar to M. ethiopica and not useful for the identification. The EST phenotype, from young egg-laying females, displayed three bands similar to the Brazilian M. luci (L3) and distinct from M. ethiopica (E3). Phylogenetic analyses of mitochondrial cytochrome oxidase subunit I and mitochondrial DNA region between COII and 16S rRNA genes revealed that the Portuguese isolate grouped with M. luci isolates close to M. ethiopica isolates. However, considering the ITS1-5.8S-ITS2 region the Portuguese isolate grouped with isolates of M. luci, M. ethiopica and M. hispanica, which limits the confidence of this region for M. luci diagnosis, and its differentiation from other species with morphological similarities. The M. luci pathogenicity to potato were also assessed in 16 commercial cultivars and compared with M. chitwoodi, considered a quarantine RKN species by EPPO. All potato cultivars were susceptible to both Meloidogyne species with gall indices of 5 and higher reproduction factor values ranging from 12.5 to 122.3, which suggest that M. luci may constitute a potential threat to potato production. In the present study, M. luci is reported for the first time attacking potato in Portugal. This article is protected by copyright. All rights reserved.