Morphological and molecular identification of the potato cyst

Abstract

Summary – The potato cyst nematodes (PCN) Globodera rostochiensis and G. pallida pose one of the greatest threats to potato

crops worldwide and are subject to strict quarantine regulations in many countries. The identification of these Globodera species

based on morphology may be ambiguous due to the variability of the main morphological features and the overlapping of the

standard parameters in these two species; thus, confirmation via molecular methods is recommended. Multiplex PCR with speciesspecificprimers (ITS5/PITSp4 + PITSr3) allows both species to be distinguished. However, despite the development of molecularidentification methods, the morphological approach remains useful as a complementary diagnostic technique. In this work, we report results of morphological and molecular analyses that were carried out in two Globodera species from Portuguese potato fields. The average morphometric values of 40 cysts and 40 second-stage juveniles were generally within the expected ranges for G. pallida and G. rostochiensis with some variations noted. Molecular analysis with multiplex PCR confirmed the morphometric identification. The present results confirmed the occurrence of two potato cyst nematode species, G. rostochiensis and G. pallida. Surprisingly, the analysis of soils from Portuguese potato fields detected a greater number of samples infested with G. pallida, which is contrary to expectation as G. rostochiensis has been considered the most widespread species in Portugal. The distinction between the two species is therefore essential in order to detect their presence in the country with a view to re-evaluating the control measures implemented so far and adopting more effective practices.