Phylogenetic evidence for the invasion of a commercialized European Phasmarhabditis hermaphrodita lineage into North America and New Zealand

Biological control (biocontrol) as a component of pest management strategies reduces reliance on synthetic chemicals, and seemingly offers a natural approach that minimizes environmental impact. However, introducing a new organism to new environments as a classical biocontrol agent can have broad and unanticipated biodiversity effects and conservation consequences. Nematodes are currently used in a variety of commercial biocontrol applications, including the use of Phasmarhabditis hermaphrodita as an agent targeting pest slug and snail species. This species was originally discovered in Germany, and is generally thought to have European origins. P. hermaphrodita is sold under the trade name Nemaslug®, and is available only in European markets. However, this nematode species was discovered in New Zealand and the western United States, though its specific origins remained unclear. In this study, we analyzed 45 nematode strains representing eight different Phasmarhabditis species, collected from nine countries around the world. A segment of nematode mitochondrial DNA (mtDNA) was sequenced and subjected to phylogenetic analyses. Our mtDNA phylogenies were overall consistent with previous analyses based on nuclear ribosomal RNA (rRNA) loci. The recently discovered P. hermaphrodita strains in New Zealand and the United States had mtDNA haplotypes nearly identical to that of Nemaslug®, and these were placed together in an intraspecific monophyletic clade with high support in maximum likelihood and Bayesian analyses. We also examined bacteria that co-cultured with the nematode strains isolated in Oregon, USA, by analyzing 16S rRNA sequences. Eight different bacterial genera were found to associate with these nematodes, though Moraxella osloensis, the bacteria species used in the Nemaslug® formulation, was not detected. This study provided evidence that nematodes deriving from the Nemaslug® biocontrol product have invaded countries where its use is prohibited by regulatory agencies and not commercially available

Description of Penjatinema novaezeelandiae sp. n. (Rhabditida: Cephalobidae) from New Zealand – a second species of a rare genus

A new species ofPenjatinema, P. novaezeelandiae sp. n., is described from coastal sand dune habitats in New Zealand. The new species resembles the type species, P. natalense Heyns & Swart, 1998, described from similar habitats in South Africa. It differs from P. natalense in the following characters: longer body (672-859 vs 590-720 μm), longer tail (69-88 μm vs 40-50 μm; c = 9.7-10.4 vs c = 11.9-17.5; c’ = 4.2-4.8 vs c’ = 2.2-2.8), a more anterior position of excretory pore (20-23 vs 34-40 annuli from anterior end), phasmids located anterior to anus in females, longer (39-44 μm vs 34-36 μm) and more slender spicules in males, arrangement and number of cuticular ridges (eight + four vs ten), presence of four prominent highly refractive rings located in-between the anteriormost annuli, and absence of deirids in both sexes (vs presence in males). The phylogenetic relationships of the new species are inferred from molecular data. Maximum likelihood analyses of the 5 end (including D1/D2/D3 domains) regions of 28S rDNA sequences support a position of Penjatinema nested among Cephalobidae

Prevalence and characterization of plant-parasitic nematodes in lowland and upland rice agro-ecosystems in Luzon, Philippines

The prevalence of plant-parasitic nematodes in lowland and upland rice ecosystems was compared based on soil and root samples from 30 rice fields in five provinces (Bataan, Batangas, Bulacan, Pampanga, and Pangasinan) of Luzon, Philippines. Five nematode genera (Meloidogyne, Hirschmanniella, Pratylenchus, Tylenchorhynchus, and Helicotylenchus) from lowland and nine genera (Rotylenchulus, Aphelenchoides, Criconematidae, Rotylenchus, and those found in lowland) from upland were identified. Meloidogyne graminicola was the most prevalent and abundant plant-parasitic nematode in both ecosystems. Hirschmanniella was the second most prevalent genus in lowland rice, but its density was low in upland rice. Pratylenchus was present in high densities, was not widely distributed in either upland or lowland rice fields. The three most prevalent nematode species, M. graminicola, H. oryzae, and H. mucronata, were morphologically and molecularly characterized. Molecular analyses based on D2D3, ITS1-5.8-ITS2, and 18S rDNA regions generally showed an overall congruence, low intraspecific variation and agreement with classical morphological and morphometrical identifications