Morphological and molecular characterization of reniform nematodes in the olive orchard of central Italy.

Reniform nematodes belonging to the genus Rotylenchulus are semi-endoparasites that affect the roots of various herbaceous and woody plants. The genus Rotylenchulus Linford & Oliveira, 1940 comprises 10 valid species, showing high intraspecific variability of some diagnostic features, making identification, based only on morphology, a difficult task. Nematode surveys of plant-parasitic nematodes in Italy, undertaken during the last few years on several crops, including sugarcane, sorghum, maize, grapevine, olive, and wild olive have revealed feederroot infections and heavy soil infestations of Rotylenchulus spp. The main objective of this study was to investigate the biodiversity of reniform nematodes in olive orchards of central Italy, conducted with a traditional management strategy. Reniform nematodes recovered from two olive groves were characterized using a polyphasic approach, combining morphological and molecular characterization. Morphological and morphometric analyses identified at species level reniform nematodes in both sampling sites as Rotylenchulus macrodoratus. Molecular analyses, based on D2-D3 segments of 28S rRNA gene and mitochondrial COI confirmed the high intraspecific and interspecific variability within Italian Rotylenchulus populations. Blast search based on the D2-D3 sequences revealed that one population showed a 97-98% similarity with the corresponding Italian populations of R. macrodoratus from GenBank, while the second population showed 95% similarity suggesting the occurrence of a species complex for R. macrodoratus or a high intraspecific variability. Further molecular analyses are ongoing to correctly identify these nematodes that are frequently ignored or misdiagnosed as pests, and this may potentially pose a threat to food securi