Analysis of the specificity of three root-feeders towards grasses in coastal dunes

Abstract

Among the root-feeding nematodes that accumulate in the rhizosphere of grasses in European dunes, the genus Pratylenchus is of special relevance given its diversity and distribution. Although different species of Pratylenchus have been reported in dune grasses, the specificity towards dune plants, a fundamental aspect of the biology of the species, has hitherto not been studied. Two inoculation experiments using different combinations of grasses and nematodes were performed. The multiplication and the effect on plant growth of P. dunensis and P. brzeskii, two species which only occur in dune areas was compared with that of P. penetrans, a broad host-range species. The three Pratylenchus spp. could multiply under all hosts; however, there was a clear host-dependent response. The species-specific response observed might account for the shift of Pratylenchus spp. detected in the field. Although, a negative effect on the growth of A. arenaria was demonstrated for the three nematode species, different densities were needed to observe the same effects in plant biomass which point at nematode-specific tolerance. While the typical dune species needed very high densities to produce damage, P. penetrans needed very few specimens. The results obtained indicate that species with similar feeding adaptations show very different multiplication abilities on co-occurring hosts, an aspect that is usually overlooked for belowground herbivores in natural systems. The obtained results might suggest a coevolutionary relationship between specific nematode species and Ammophila arenaria

Evidence of population differentiation in the dune grass Ammophila arenaria and its associated root-feeding nematodes

“…Experimentally, it has been shown that both species of Pratylenchus are able to cause damage at densities resembling those occurring in the field in dunes (Brinkman et al 2005;de la Peña et al 2008). The level of tolerance of A. arenaria is also different for each of the Pratylenchus species (de la Peña et al 2008). Both facts are in agreement with high reciprocal selection pressures between the plant and root-feeders.…”

“…These migratory endoparasitic nematodes invade, multiply on, feed on and move through the root cortex of the host plant resulting in necrotic lesions that often promote secondary fungal infections (Back et al 2002). Experimentally, it has been shown that both species of Pratylenchus are able to cause damage at densities resembling those occurring in the field in dunes (Brinkman et al 2005;de la Peña et al 2008). The level of tolerance of A. arenaria is also different for each of the Pratylenchus species (de la Peña et al 2008).…”

Interactions between nematodes and their microbial enemies in coastal sand dunes

“…are putatively being controlled is in agreement with the results of previous studies and suggests that these nematodes are regulated by horizontal control (Brinkman et al 2005a, b). The competition between these two genera of nematodes must be occurring through resource limitation, as both genera feed on the same plant (bottom-up control; De la Peña et al 2008). However, it seems that part of this competition effect is trait-mediated by P. penetrans, because it depends on its compatibility with the nematode host Meloidogyne spp.…”

“…Among the PPN found to be involved in marram grass decline, Meloidogyne maritima is considered to be the most aggressive, and is the only PPN found to reduce plant biomass in mesocosm field experiments (Brinkman et al 2005a), although other nematode species could reduce plant biomass in single-species inoculations in pot experiments (de la Peña et al 2008;Piskiewicz et al 2007). Plant-parasitic nematode diversity was found to have an idiosyncratic effect on plant biomass, with responses being dependent on nematode identity (i.e.…”

“…on the particular nematode species involved) rather than the diversity of the nematode community per se. Horizontal control (competition) of PPN was reported after both mesocosm and pot experiments, involving interspecific competition between M. maritima, Heterodera arenaria, Pratylenchus penetrans and Tylenchorhynchus ventralis (Brinkman et al 2005a, b), and intra-specific competition in the P. penetrans populations (de la Peña et al 2008). These interactions appear to be mediated by plant tolerance and attractiveness to the various nematode populations (Brinkman et al 2008;de la Peña et al 2008).…”