A survey of entomopathogenic nematode species in continental Portugal

Abstract

Entomopathogenic nematodes (EPN) are lethal parasites of insects, used as biocontrol agents. The objectives of this work were to survey the presence of EPN in continental Portugal and to characterize the different species. Of the 791 soil samples collected throughout continental Portugal, 53 were positive for EPN. Steinernema feltiae and Heterorhabditis bacteriophora were the two most abundant species. Analysis of EPN geographical distribution revealed an association between nematode species and vegetation type. Heterorhabditis bacteriophora was mostly found in the Alentejo region while S. feltiae was present in land occupied by agriculture with natural vegetation, broadleaved forest, mixed forest and transitional woodland-shrub, agro-forestry areas, complex cultivated patterns and non-irrigated arable land. Although no clear association was found between species and soil type, S. feltiae was typically recovered from cambisols and H. bacteriophora was more abundant in lithosols. Sequencing of the internal transcribed spacer (ITS) region indicated that S. feltiae was the most abundant species, followed by H. bacteriophora. Steinernema intermedium and S. kraussei were each isolated from one site and Steinernema sp. from two sites. Phylogenetic analyses of ITS, D2D3 expansion region of the 28S rRNA gene, as well as mitochondrial cytochrome c oxidase subunit I (COXI) and cytochrome b (cytb) genes, was performed to evaluate the genetic diversity of S. feltiae and H. bacteriophora. No significant genetic diversity was found among H. bacteriophora isolates. However, COXI seems to be the best marker to study genetic diversity of S. feltiae. This survey contributes to the understanding of EPN distribution in Europe.

Morphological and molecular characterization of entomopathogenic nematode, Heterorhabditis baujardi (Rhabditida, Heterorhabditidae) from Mizoram, northeastern India

“…Accurate identification of the EPNs is very important prior to use as biological control agent since different species exhibited different adaptations and behaviour (Valadas et al 2014). Simulteneously, identification of Heterorhabditis species, in particular, based on morphology is not an easy task because of limited morphological variation (Dolinski et al 2008).…”

A survey of entomopathogenic nematodes and their symbiotic bacteria in agricultural areas of northern Thailand

“…Therefore, S. siamkayai may be frequently found in the agricultural areas. In Portugal, Steinernema feltiae was mostly recovered in agricultural land (Valadas et al ., 2014). Also noted in Italy were S. feltiae and H. bacteriophora , which were found to be related with vegetation habitat (Tarasco et al ., 2015).…”

Characterization of a new isolate of entomopathogenic nematode, Steinernema sangi (Rhabditida, Steinernematidae), and its symbiotic bacteria Xenorhabdus vietnamensis (γ-Proteobacteria) from Mizoram, northeastern India

“…The relationship between habitat and abundance of entomopathogenic nematodes had been reported by a number of workers. The high rate of occurrence is reported in disturbed habitat with high human impacts like agricultural fields (Campos-Herrera et al 2007;de Brida et al 2017), whereas, it is higher in natural habitats (Stock et al 2008;Valadas et al 2014). It is thus obvious that the occurrence of EPNs relative to the habitat type varied among the species, and also depending on the geographical areas.…”