Nematodes as suitable indicators for soil health

During the Greenresilient project, nematode communities will be characterized at the beginning, in the middle and at the end of the field trials to identify shifts in their community. These shifts will be analysed to determine whether the chosen ‘innovative’ methods tested in the project are beneficial for soil health, causing an increased resilience to pests and diseases and a more balanced nutrient supply, for more sustainable and high-quality crop production. This leaflet explains why nematodes can be excellent indicators for soil health

Leaflet on nematodes as suitable indicators for soil health

The new Greenresilient leaflet explains why nematodes can be excellent indicators for soil health

A new entomopathogenic nematode species for Turkey, Heterorhabditis megidis Poinar, Jackson & Klein 1987 (Rhabditida: Heterorhabditidae)

During a survey on the occurrence of entomopathogenic nematodes (EPNs) in the Eastern Black Sea region of Turkey, a heterorhabditid species was isolated using the Galleria-baiting technique. Based on morphology and morphometrics, the isolate was identified as Heterorhabditis megidis. Sequences of the ITS region of its rDNA confirmed this identification. The species is recorded for the first time from Turkey. A more intensive survey to determine the distribution of this species, covering all parts of the Black Sea region of Turkey, is currently underway

Heat tolerance among different strains of the entomopathogenic nematode Heterorhabditis bacteriophora

Quality of biological control products based on entomopathogenic nematodes can be severely damaged due to exposure to high temperature surpassing 40A degrees C. The study screened 36 natural populations and 18 hybrid or inbred strains of Heterorhabditis bacteriophora for their response to high temperature. Nematodes were tested with or without prior adaptation to heat at 35A degrees C for 3 h. Five strains of H. indica and one of H. megidis were also included. Molecular identification using nuclear ribosomal DNA sequences confirmed the designation to the three Heterorhabditis spp. The mean tolerated temperature ranged from 33.3A degrees C to 40.1A degrees C for non-adapted and from 34.8A degrees C to 39.2A degrees C for adapted strain populations. H. indica was the most tolerant, followed by H. bacteriophora and H. megidis. No correlation was recorded between tolerance assessed with and without adaptation to heat, implying that different genes are involved. Correlation between heat tolerance and mean annual temperature at place of origin of the strains was weak. A high variability in tolerance among strains and the relatively high heritability (hA(2)A = 0.68) for the adapted heat tolerance recorded for H. bacteriophora provide an excellent foundation for future selective breeding with the objective to enhance heat tolerance of H. bacteriophora

Effects of synthetic fertilizer and farm compost on soil nematode community in long-term crop rotation plots : a morphological and metabarcoding approach

Soil biodiversity plays a key regulation role in the ecosystem services that underpin regenerative sustainable agriculture. It can be impacted by agricultural management techniques, both positively (through measures such as compost application) and negatively (through, for example, application of synthetic nitrogen). As one of the most numerous members of the soil biota, nematodes are well established as indicators for the soil food web. However, compost application also includes the addition of nematodes present in compost and their subsequent survival in soil is unknown. Nematode communities within the compost applied to soil, and nematode communities in the soil of a multi-year rotational cropping field trial in Melle (Belgium) were studied using morphological and metabarcoding techniques. Compost (C) and nitrogen fertilizer (NF) treated plots were compared. Three replicate plots were investigated for each of the following treatments: C application only; C and NF application; NF only; no C and no NF (control). Plots were sampled six times between 2015-2017, before and after C or NF were added each spring and after crop harvest (except for 2017). NF treatment resulted in a significant decrease of fungal feeding and predatory nematodes, while herbivorous nematodes were positively affected. Remarkably, we did not find compost addition to exert any noticeable effects on the soil nematode community. The morphological and metabarcoding data resulted in different results of the nematode community composition. However, trends and patterns in the two data sets were congruent when observed with NMDS plots and using the nematode maturity index. Metabarcoding of individual compost nematode taxa demonstrated that nematodes originating from compost did not persist in soil

Characterisation of a population of Pratylenchus hippeastri from bromeliads and description of two related new species, P. floridensis n. sp. and P. parafloridensis n. sp. from grasses in Florida

Morphological and molecular analyses confirmed the presence of P. hippeastri in regulatory samples collected in commercial bromeliad operations from genera Guzmania, Neoregelia and Vriesea in central and south Florida, USA. These P. hippeastri from bromeliads contained males which were not detected in the type population from amaryllis. The rDNA sequences of these males matched those of P. hippeastri female type material. Pratylenchus hippeastri and related root-lesion nematodes from several hosts in Florida were characterized at the morphological and molecular level, whereas other samples from Russia and South Africa at the molecular level only. Phylogenetic and sequence analysis using the ITS rRNA gene of these root-lesion nematodes revealed the presence of eight putative new species (spH1-H8) closely related to P. hippeastri. However, detailed morphological and molecular analyses are still required to confirm their unique species status. Here we describe two Florida representatives of the amphimictic root-lesion nematodes from Bahia grass (N1) and maidencane (N2), previously characterized by Inserra et al. (1996) and Duncan et al. (1999), as two new species phylogentically related to P. hippeastri and named Pratylenchus floridensis n. sp. and P. parafloridensis n. sp., respectively. The small round or oval, rarely rectangular and occasionally oblong and enlarged spermatheca and the bluntly pointed or subacute tail with smooth and occasionally indented terminus separate P. floridensis n. sp. from P. parafloridensis n. sp., which has a quadrangular spermatheca and a sub hemispherical or bluntly pointed tail with generally smooth and rarely indented terminus. However, these characters may overlap in some specimens making the morphological separation problematic without the use of molecular analysis. The close phylogenetic relationships shared by the species characterized in this study indicate that they are representatives of a P. hippeastri species complex

How to monitor soil health with DNA-metabarcoding of nematode communities – see this new video from the Greenresilient project

In the Greenresilient project, we investigate soil health by characterising nematode communities. However, the traditional way of identifying nematodes using a microscope is very time-consuming. Specialists need 1 day to analyse 2 soil samples, and still only a part of all the nematodes are identified. That is why we started using the advanced DNA-sequencing method, called DNA-metabarcoding. In this video, we will explain how that works

How to monitor soil health with DNA-metabarcoding of Nematode communities

In the Greenresilient project, we investigate soil health by characterising nematode communities. However, the traditional way of identifying nematodes using a microscope is very time-consuming. Specialists need 1 day to analyse 2 soil samples, and still only a part of all the nematodes are identified. That is why we started using the advanced DNA-sequencing method, called DNA-metabarcoding. In this video, we will explain how that works