Changes in soil aggregation and glomalin-related soil protein content as affected by the arbuscular mycorrhizal fungal species Glomus mosseae and Glomus intraradices.

Arbuscular mycorrhizal (AM) fungi are key organisms of the soil/plant system, influencing soil fertility and plant nutrition, and contributing to soil aggregation and soil structure stability by the combined action of extraradical hyphae and of an insoluble, hydrophobic proteinaceous substance named glomalin-related soil protein (GRSP). Since the GRSP extraction procedures have recently revealed problems related to co-extracting substances, the relationship between GRSP and AM fungi still remains to be verified. In this work the hypothesis that GRSP concentration is positively correlated with the occurrence of AM fungi was tested by using Medicago sativa plants inoculated with different isolates of Glomus mosseae and Glomus intraradices in a microcosm experiment. Our results show that (i) mycorrhizal establishment produced an increase in GRSP concentration – compared to initial values – in contrast with non-mycorrhizal plants, which did not produce any change; (ii) aggregate stability, evaluated as mean weight diameter (MWD) of macroaggregates of 1–2 mm diameter, was significantly higher in mycorrhizal soils compared to non-mycorrhizal soil; (iii) GRSP concentration and soil aggregate stability were positively correlated with mycorrhizal root volume and weakly correlated with total root volume; (iv) MWD values of soil aggregates were positively correlated with values of total hyphal length and hyphal density of the AM fungi utilized. The different ability of AM fungal isolates to affect GRSP concentration and to form extensive and dense mycelial networks, which may directly affect soil aggregates stability by hyphal enmeshment of soil particles, suggests the possibility of selecting the most efficient isolates to be utilized for soil quality improvement and land restoration programs

Heavy metals accumulation in willows growing on Spolic Technosols from the abandoned Imperina Valley mine in Italy

Human activities such as metals mining and milling operations provide one of the most important sources of contamination in the environment. Abandoned mines can be an important source of toxic elements. The threat of heavy metal pollution posed by mine soils generally concerns more than one metal. The aim of this study was to assess total concentration of six potentially toxic metals (Cd, Cr, Cu, Pb, Zn and Fe) in the soil and plant samples of three dominant willow species (Salix purpurea L., Salix caprea L. and Salix eleagnos Scop.) collected from abandoned mixed sulphide mine dumps (Imperina Valley, North-east Italy).Results demonstrate that metal concentrations in soils are in general above the Italian average limits and they are also significantly (except Cr), as compared with controls (p≤0.05), with averages of 2.12mgCdkg-1, 2267mgCukg-1, 9552mgPbkg-1, 1243mgZnkg-1 and 299,973mgFekg-1. The phytoremediation ability of selected Salix species for heavy metals was estimated. The results have revealed significant differences among willow species (p. ≤. 0.05) regardless of the species selected. The transfer factor and bioaccumulation coefficient of selected metals varied among plant species and from different sites. Some of the investigated species have potential for soil stabilization and extraction of heavy metals. The results indicate that there is an increasing need for further research projects mainly focused on the mechanisms whereby such willows are able to survive in contaminated soil

Assessment of phenolic herbicide toxicity and mode of action by different assays

A phytotoxicity assay based on seed germination/root elongation has been optimized and used to evaluate the toxic effects of some phenolic herbicides. The method has been improved by investigating the influence of experimental conditions. Lepidium sativum was chosen as the most suitable species, showing high germinability, good repeatability of root length measurements, and low sensitivity to seed pretreatment. DMSO was the most appropriate solvent carrier for less water-soluble compounds. Three dinitrophenols and three hydroxybenzonitriles were tested: dinoterb, DNOC, 2,4-dinitrophenol, chloroxynil, bromoxynil, and ioxynil. Toxicity was also determined using the Vibrio fischeri MicrotoxA (R) test, and a highly significant correlation was found between EC50 values obtained by the two assays. Dinoterb was the most toxic compound. The toxicity of hydroxybenzonitriles followed the order: ioxynil > bromoxynil > chloroxynil; L. sativum exhibited a slightly higher sensitivity than V. fischeri to these compounds. A QSAR analysis highlighted the importance of hydrophobic, electronic, and hydrogen-bonding interactions, in accordance with a mechanism of toxic action based on protonophoric uncoupling of oxidative phosphorylation. The results suggest that the seed germination/root elongation assay with L. sativum is a valid tool for the assessment of xenobiotic toxicity and can be recommended as part of a test battery

Heavy metals accumulation in willows growing on Spolic Technosols from the abandoned Imperina Valley mine in Italy

Human activities such as metals mining and milling operations provide one of the most important sources of contamination in the environment. Abandoned mines can be an important source of toxic elements. The threat of heavy metal pollution posed by mine soils generally concerns more than one metal. The aim of this study was to assess total concentration of six potentially toxic metals (Cd, Cr, Cu, Pb, Zn and Fe) in the soil and plant samples of three dominant willow species (Salix purpurea L., Salix caprea L. and Salix eleagnos Scop.) collected from abandoned mixed sulphide mine dumps (Imperina Valley, North-east Italy).Results demonstrate that metal concentrations in soils are in general above the Italian average limits and they are also significantly (except Cr), as compared with controls (p≤0.05), with averages of 2.12mgCdkg-1, 2267mgCukg-1, 9552mgPbkg-1, 1243mgZnkg-1 and 299,973mgFekg-1. The phytoremediation ability of selected Salix species for heavy metals was estimated. The results have revealed significant differences among willow species (p. ≤. 0.05) regardless of the species selected. The transfer factor and bioaccumulation coefficient of selected metals varied among plant species and from different sites. Some of the investigated species have potential for soil stabilization and extraction of heavy metals. The results indicate that there is an increasing need for further research projects mainly focused on the mechanisms whereby such willows are able to survive in contaminated soil

A history of invasion: COI phylogeny of Manila clam Ruditapes philippinarum in Europe

The Manila clam Ruditapes philippinarum – synonym Venerupis philippinarum (Adams and Reeve, 1850) is now one of the top 5 most commercially valuable bivalve species worldwide. Originally from the Indo-Pacific region, it has been introduced in many countries for fisheries and aquaculture, including estuarine environments along Atlantic and Mediterranean European coasts. Yet despite its commercial value and widespread distribution, the precise origins of stocks remain speculative and the genetic diversity of introduced populations is poorly known. Thus, the aim of this work was to collect mtDNA COI (Cytochrome oxidase I) gene sequences from 5 European countries with Manila clam stocks and compare them with native Asian populations to evaluate their genetic diversity and identify possible routes of invasion. The COI gene sequencing supported a strong founder effect in the European populations with 3 main haplotypes occurring at high frequencies, derived from Japan. However, high haplotype diversity was also observed due to the occurrence of 10 rare haplotypes. This supports hypotheses (i) there have been additional, previous unrecorded, introductions as previously hypothesized by analysis of 16S rDNA, and (ii) there has been a limited loss of genetic diversity in introduced populations, as previously suggested by microsatellite data. This is the first genetic comparison of Manila clam populations introduced in to Europe with native clams. Genetic data herein presented are fundamentally important for the traceability of clam products and stock management programmes and will also inform discussion on the potential resilience of exploited Manila clam populations

Effects of long-term land use on arbuscular mycorrhizal fungi and glomalin-related soil protein

The maintenance of soil health and productivity is a central aim of sustainable agriculture. Arbuscular mycorrhizal fungi (AMF) are soil biota fundamental for soil fertility and plant nutrition, which may be used in the evaluation of the impact of agronomic practices on soil quality. In the present study we evaluated the influence of three different land uses on AMF populations and correlated glomalin-related soil protein (GRSP) content with AMF biomass parameters, such as spore density and biovolume. Among the differently managed sites - maize monoculture, grassland and poplar grove - maize soil showed the lowest AMF spore number and GRSP content. The same morphological taxa were found in the three sites, except for one additional morphotype in poplar grove. A good correlation between GRSP and spore biovolume was found, suggesting that GRSP may represent a useful biochemical parameter for the assessment of biological soil fertility in sustainable agriculture

Miglioramento del suolo e biostabilizzazione di metalli pesanti mediati da glomalina

La glomalina è una glicoproteina di recente scoperta, prodotta in grande quantità dai funghi micorrizici arbuscolari (AM). Nei suoli, la quantità di glomalina è risultata essere correlata con i principali parametri di fertilità. In questo lavoro viene valutato il cambiamento nei contenuti di glomalina e di aggregati stabili all'acqua (WSA1-2mm), in un terreno agrario dopo 4 mesi di coltura di Medicago sativa micorrizata e non micorrizata. In considerazione della affinità della glomalina verso il ferro, è stato inoltre analizzato il contenuto in metalli del suolo e la percentuale di questi legata alla proteina. I risultati indicano un significativo aumento di glomalina e WSA nel terreno coltivato con le piante micorrizate rispetto alle non micorrizate. Differenze sono state anche riscontrate nella produzione di glomalina tra isolati diversi di due specie di AM: Glomus mosseae e Glomus intraradices. Tali evidenze confermano le potenzialità dei funghi AM nel miglioramento di suoli compromessi o sottoposti ad intenso regime agronomico ed indicano che la glomalina è in grado di chelare fortemente non solo il ferro, ma anche metalli pesanti potenzialmente tossici. La possibilità di selezione e successivo impiego di isolati di funghi AM ad alta efficienza, in termini di produzione di glomalina, può rappresentare un utile strumento per il miglioramento e il recupero di suoli compromessi e per la biostabilizzazione di metalli pesanti in suoli contaminat