Root-lesion and root-knot nematodes parasitizing potato

Root-lesion nematodes (RLN), Pratylenchus spp., are economically important plant-parasitic nematodes (PPN) of several crops, including potato. In Portugal, potato cyst nematodes (PCN), Globodera spp., are a frequent problem and root-knot nematodes (RKN), Meloidogyne spp., have been found coexisting with PCN. Although the diversity and pathogenicity of PCN on potato are well documented, little work has been done to evaluate the importance of other PPN. This study aimed at assessing the diversity of RLN and RKN in potato. Sampling encompassed fields located in four regions of Portugal: North, Centre, Lisboa and Algarve. Nematodes were extracted from 40 soil/root samples, using standard extraction techniques, identified at genus level and population densities quantified. RLN species were identified on basis of morphological characters, species specific primers, and D2D3 28S rDNA sequencing. RKN and PCN species were identified by esterase phenotype and PCR-RFLP, respectively. RLN were detected in all sampled regions in 83 % of soil and 78 % of root samples. Pratylenchus penetrans was the most abundant species and P. neglectus, P. crenatus and P. thornei were detected for the first time associated with potato in Portugal. Meloidogyne arenaria, M. hapla, M. incognita and M. javanica were found in 10 % of soil and 20 % of roots. Globodera pallida and G. rostochiensis were detected in 15 and 8 % of soil and roots. RKN and PCN were found in samples infected with RLN. The information obtained on the ubiquity and diversity of RLN and RKN reinforces the need for a careful monitoring of these nematodes in potato crops.