The dagger nematodes Xiphinema pachtaicum and X. index are one of the most widespread and frequently occurring Xiphinema species co-infesting vineyards and other crops and natural habitats worldwide. The prevalence of X. pachtaicum and the importance of X. index as a virus-vector, together with the possibility of the latter being a n introduced species and occupying a more restricte d habitat than X. pachtaicum make them interesting nematodes for the study of p opulation genetics. The primary objective of this study was to determine th e genetic structure of X. pachtaicum and X. index populations using nine and seven populations, respe ctively, from different “wine of denomination of origin (D.O.) zones” in Spain and Sardinia (Italy), by the study of the mitochondrial (cytochrome oxidase c subunit 1 or COI ) and nuclear (D2-D3 expansion segments of 28S rDNA ) markers. Both Xiphinema species showed low intra-specific divergence among COI sequences, ranging from 0.2% (1 base substitution) to 2.3% (10 substitutions) in X. pachtaicum , and from 0.2% (1 base substitution) to 0.4% (2 substitutions) in X. index . Population genetic structure with a significant v ariation among populations within D.O. zones and within population s were found for both species. Nevertheless, molecular differences among grapevine-growing areas were not significant. It is hypothesized that this genetic structure may have been originated by exten sive and continuous grapevine cultivation in the sampled geographic areas, as well as inadequate san itation practices during long periods. Results also demonstrated that the two DNA regions studied are s uitable diagnostic markers for X. index and X. pachtaicum .

This research, part of the PhD project of the first author, was supported by grants P06-AGR-01360 from ‘Consejería de Economía, Innovación y Ciencia’ of Junta de Andalucía, and AGL2009-06955 from ‘Ministerio de Ciencia e Innovación’ of Spain and the European Social Fund.

Peer reviewed