Soil organisms are a crucial part of the terrestrial biosphere. Despite their importance for ecosystem functioning, no quantitative, spatially-explicit models of the active belowground community currently exist. In particular, nematodes are the most abundant animals on Earth, filling all trophic levels in the soil food web. Here, we use 6,579 georeferenced samples to generate a mechanistic understanding of the patterns of global soil nematode abundance and functional group composition. The resulting maps show that 4.4 ± 0.64  10 20 nematodes (total biomass ~0.3 Gt) inhabit surface soils across the world, with higher abundances in sub-arctic regions (38% of total), than in temperate (24%), or tropical regions (21%). Regional variations in these global trends also provide insights into local patterns of soil fertility and functioning. These high-resolution models provide the first steps towards representing soil ecological processes into global biogeochemical models, to predict elemental cycling under current and future climate scenarios.

Pseudomonas isolates have frequently been isolated from the rhizosphere of plants, and several of them have been reported as plant growth-promoting rhizobacteria. In the present work, tomato ( Solanum lycopersicum ) seeds were germinated in greenhouse conditions, and the seedling height, length of plants, collar diameter and number of leaves were measured from plants grown in soil inoculated by bacterial isolates. Pseudomonas isolates were isolated from the rhizosphere. We used the Newman-Keuls test to ascertain pairwise differences. Isolates were identified as a new Pseudomonas species by rpo D gene sequencing. The results showed that isolates of Pseudomonas sp. (Q6B) increased seed germination (P = 0.01); Pseudomonas sp. (Q6B, Q14B, Q7B, Q1B and Q13B) also promoted seedling height (P = 0.01). All five isolates promoted plant length and enlarged the collar diameter (P = 0.01). Pseudomonas sp. (Q1B) also increased leaf number (P = 0.01). The investigation found that Pseudomonas isolates were able to solubilize phosphate, produce siderophores, ammonia, and indole-3-acetic acid and colonize the roots of tomato plants. This study shows that these five novel Pseudomonas sp. isolates can be effective new plant growth-promoting rhizobacteria.

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a global database of soil nematode abundance and functional group composition Johan van den Hoogen et al. # as the most abundant animals on earth, nematodes are a dominant component of the soil community. they play critical roles in regulating biogeochemical cycles and vegetation dynamics within and across landscapes and are an indicator of soil biological activity. Here, we present a comprehensive global dataset of soil nematode abundance and functional group composition. This dataset includes 6,825 georeferenced soil samples from all continents and biomes. For geospatial mapping purposes these samples are aggregated into 1,933 unique 1-km pixels, each of which is linked to 73 global environmental covariate data layers. Altogether, this dataset can help to gain insight into the spatial distribution patterns of soil nematode abundance and community composition, and the environmental drivers shaping these patterns.

Plant-parasitic nematodes (PPN) are the most destructive of all plant pathogens. They are an economically important group of soil pathogens, causing significant annual damages of up to 25% of world crop production. Morocco is considered to be a highly productive country for the colorant/medicinal/spice saffron (Crocus sativus L.). Taliouine and Taznakht regions are the most productive areas of this valuable neutraceutical. Due to its metabolic profile, and growth forms, saffron is susceptible to many plant diseases, including plant-parasitic nematodes (PPN). This work aims to assess the diversity of PPN communities in soils of Taliouine and Taznakht regions to facilitate understanding of links between their assemblages with biotic and abiotic parameters. Herein, nematode communities were characterized in 163 soil samples collected from 11 rural communes characterized by altitudinal gradients in Taliouine and Taznakht regions. Fifteen PPN genera belonging to 12 families were identified, among which the four genera Ditylenchus, Aphelenchoides, Pratylenchus and Helicotylenchus, potentiate serious limiting factors in saffron production. Their frequencies are respectively 92, 49, 48 and 36% in the area of Taliouine, while in Taznakht they represent 95, 69, 33, and 28% respectively. Regarding the assessment of diversity at different sites, the genus richness (R) index ranges from 2 to 10 distinct genera, whereas the Shannon diversity (H') index varies from 0.9 to 1.5 and the Evenness (E) index tends to 1. The Co-inertia analyses revealed a substantial relationship between nematode communities and soil types. Soil texture is the major factor influencing the presence and the abundance of a considerable portion of genera. Multivariate analyses (MBPLS) indicated links between humidity, rainfall, minimum temperature and PPN taxa, though maximum temperature did not have an impact. Ditylenchus, Helicotylenchus, Pratylenchus and Paratylenchus were related to the humidity and silt soil that developed in Taliouine. Aphelenchoides, Tylenchus, Tylenchorynchus and Dorylaimus were more prevalent in rainy locations and clay soils of Taznakht. Suitable nematode controlling approaches may be applied and preventative measures should be considered at nursery and field level.