Pratylenchus penetrans Parasitizing Potato Crops: Morphometric and Genetic Variability of Portuguese Isolates

The root lesion Pratylenchus penetrans is an economically important pest affecting a wide range of plants. The morphometry of five P. penetrans isolates, parasitizing potato roots in Portugal, was compared and variability within and between isolates was observed. Of the 15 characters assessed, vulva position (V%) in females and the stylet length in both females/males showed the lowest coefficient of intra and inter-isolate variability. Moreover, DNA sequencing of the internal transcribed spacers (ITS) genomic region and cytochrome c oxidase subunit 1 (COI) gene was performed, in order to evaluate the intraspecific genetic variability of this species. ITS revealed higher isolate genetic diversity than the COI gene, with 15 and 7 different haplotypes from the 15 ITS and 14 COI sequences, respectively. Intra- and inter-isolate genetic diversity was found considering both genomic regions. The differentiation of these isolates was not related with their geographical origin. In spite of the high intraspecific variability, phylogenetic analyses revealed that both ITS region and COI gene separate P. penetrans from other related species. Our findings contribute to increasing the understanding of P. penetrans variability.