In vitro screening of soil bacteria for inhibiting phytopathogenic fungi

At present, the greatest interest resides with the development and application of specific biocontrol agent for the control of diseases on plant and this form the focus of this work. Several soil bacteria were evaluated in vitro for their effectiveness on the basis of their ability to suppress fungi in plate inhibition assays. 51 strains of 12 bacterial species were performed against 12 strains of 10 phytopathogenic mould species. Almost all soil bacteria species; but about 50% of the bacteria strains, showed an antagonistic activity against at least one phytopathogenic fungus. Sphingomonans spp was the only specie that did not show any antagonistic effect to all fungi. Bradyrhizobium japonicum could highly inhibit the mycelial growth of five moulds (Botrytis cinerea, Phoma medicaginis, Fusarium verticilloides, Rhizoctonia solani and Phytophtora infestans) with a growth inhibition varying between 12.38 and 37.61%. 12 Bacillus strains and five Pseudomonas strains were antagonistic to the major phytopathogenic moulds used in this trial. Bacillus subtilis exhibited strong antagonism against fungi both from cultural medium and from sterile filtrate. Results show that bacterial suspension and bacterial supernatant did not operate in the same way. Supernatant from bacterial strains seemed to be efficient against phytopathogenic moulds. The mycelial growth of R. solani, P. medicaginis and F. verticilloides was inhibited by 12-fold dilution of the supernatant from B. japonicum. The latter draws a conclusion that bacteria isolated from soil are promising natural biocontrol agents and should be further studied and tested for the control of numerous plant diseases. Additional studies are required to definitively determine their mode of antifungal action, safety and biocompatibility.Keywords: Bacteria, phytopathogenic fungi, antagonis

Genetic diversity and salt tolerance of bacterial communities from two Tunisian soils

Microbial ecology studies on arid soils are particularly important for the analysis of biological functions during desertification. Although much is known about the arid saline flora, few researches have directly compared the bacterial communities of saline arid soils with cultivated soils in Northern Africa. Bacterial communities present in two soils from Soliman (north of Tunisia), one salty and neglected, and the other cultivated, were investigated by using both cultivation dependent and independent approaches. The first approach was used to assess the presence of salt tolerant bacteria and the relationships among salt (NaCl) resistance phenotype, soil characteristics and phylogenetic assignment of strains. Total community analysis, performed by T-RFLP on total DNA, was carried out to investigate the relationships between total community fingerprinting with cultivated isolates diversity. The cultivated isolates from salty soil were more genetically diverse, harbouring strains that can grow at high salt concentration. Moreover, the salt resistance of isolates was found not to be related to any particular phylogenetic group, being widespread among isolates belonging to different bacterial subdivisions. Ribotype richness, evaluated as number of different T-RFLP bands (TRFs), was shown to be higher in the agricultural soil than in the salty soil and several agricultural soil-specific TRFs were detected

LEGU-MED: Developing Biodiversity-Based Agriculture with Legume Cropping Systems in the Mediterranean Basin

Environmental degradation and the decrease of ecosystem service provision are currently of major concern, with current agricultural systems being a major driver. To meet our future environmental and sustainability targets a transformation of the agro-food systems and current agricultural value chain are crucial. One approach to redesign farming systems is the concept of biodiversity-based agriculture (BBA) which relies on sustainable diversification of biological components and their natural interactions in farming systems to maximize fertility, productivity, and resilience to external perturbations. Despite minimizing anthropogenic inputs, BBA is not yet able to meet all beneficial environmental objectives. BBA applied in the Mediterranean basin requires urgent innovation in approaches, methodologies, and models for small-holder traditional farming systems to ensure a stable provision of ecosystem services and better resilience to environmental stresses linked to climate change. Legumes are the backbone of the Mediterranean agro-ecosystems from ancient times, but their unique and wide biodiversity was not sufficiently valorized, especially by North-African countries. Here, we present LEGU-MED, a three-year international project funded by PRIMA initiative 2019. An international consortium was established involving five universities, 5 research institutes, and one private company from 8 countries: Italy, Germany, Spain, Algeria, Tunisia, Turkey, Lebanon, and Croatia. The main objective of this project is to put forward an international and well-integrated plan to valorize the legume agrobiodiversity of the Mediterranean in biodiversity-based farming systems and consequently enhance agro-ecosystem functions and services in the Mediterranean basin. The successful completion of LEGU-MED will have the following impacts on Mediterranean legume-based farming systems: (1) improve water use efficiency, (2) reduce the use of anthropogenic inputs through the maintenance of soil fertility, (3) enhance pollination and improve ecological connectivity with flora and fauna, (4) protect close-by wildland ecosystems, (5) enhance other ecosystem services (e.g., pest, disease, and weed suppression), and (6) provide healthier and safer protein-rich food. © 2022 by the authors. Licensee MDPI, Basel, Switzerland

Microbial Inoculants and Their Impact on Soil Microbial Communities: A Review

The knowledge of the survival of inoculated fungal and bacterial strains in field and the effects of their release on the indigenous microbial communities has been of great interest since the practical use of selected natural or genetically modified microorganisms has been developed. Soil inoculation or seed bacterization may lead to changes in the structure of the indigenous microbial communities, which is important with regard to the safety of introduction of microbes into the environment. Many reports indicate that application of microbial inoculants can influence, at least temporarily, the resident microbial communities. However, the major concern remains regarding how the impact on taxonomic groups can be related to effects on functional capabilities of the soil microbial communities. These changes could be the result of direct effects resulting from trophic competitions and antagonistic/synergic interactions with the resident microbial populations, or indirect effects mediated by enhanced root growth and exudation. Combination of inoculants will not necessarily produce an additive or synergic effect, but rather a competitive process. The extent of the inoculation impact on the subsequent crops in relation to the buffering capacity of the plant-soil-biota is still not well documented and should be the focus of future research

Microbial inoculants and their impact on soil microbial communities: a review. Biomed Res Int 2013; 2013: 863240

The knowledge of the survival of inoculated fungal and bacterial strains in field and the effects of their release on the indigenous microbial communities has been of great interest since the practical use of selected natural or genetically modified microorganisms has been developed. Soil inoculation or seed bacterization may lead to changes in the structure of the indigenous microbial communities, which is important with regard to the safety of introduction of microbes into the environment. Many reports indicate that application of microbial inoculants can influence, at least temporarily, the resident microbial communities. However, the major concern remains regarding how the impact on taxonomic groups can be related to effects on functional capabilities of the soil microbial communities. These changes could be the result of direct effects resulting from trophic competitions and antagonistic/synergic interactions with the resident microbial populations, or indirect effects mediated by enhanced root growth and exudation. Combination of inoculants will not necessarily produce an additive or synergic effect, but rather a competitive process. The extent of the inoculation impact on the subsequent crops in relation to the buffering capacity of the plant-soil-biota is still not well documented and should be the focus of future research

Inoculation of Lupinus albus with the nodule-endophyte Paenibacillus glycanilyticus LJ121 improves grain nutritional quality

Metabolic changes occurring in white lupine grain were investigated in response to Plant Growth Promoting Rhizobacteria (PGPR) root inoculation under feld condition. We precisely targeted lipids and phenolics changes occurring in white lupine grain in response to Pseudomonas brenneri LJ215 and/or Paenibacillus glycanilyticus LJ121 inoculation. Lipids and phenolic composition were analyzed using an Ultra High‐Performance Liquid chromatography/Tandem Mass Spectrometry Methods. As compared to grain of un-inoculated control plant, Paenibacillus glycaniliticus inoculation highly increased the total lipids content (from 232.55 in seeds of un-inoculated control plant to 944.95 mg/kg) and the relative percentage of several fatty acid such as oleic acid (+20.95%) and linoleic acid (+14.28%) and decreased the relative percentage of glycerophospholipids (−13.11%), sterol (−0.2% and −0.34% for stigmasterol and campesterol, respectively) and prenol (−17.45%) class. Paenibacillus glycaniliticus inoculation did not afect total phenolic content, while it modulated content of individual phenolic compounds and induced the accumulation of “new” phenolics compounds such as kaempferol. Paenibacillus glycanilyticus LJ121 can be a useful bio-fertilizer to enhance nutritional quality of white lupine grain

Proximate composition, lipid and phenolic profiles, and antioxidant activity of different ecotypes of Lupinus albus, Lupinus luteus and lupinus angustifolius

Lupine seed represents an interesting, non-genetically modified, and low cost alternative to soybean as an important source of protein and oil. In this study, we compare seed protein, mineral, fiber and starch content, lipid and phenolic profile, and antioxidant properties of three lupine wild species (Lupinus albus, Lupinus luteus, and lupinus angustifolius). For each lupine species, nutritional composition of different Tunisian ecotypes was compared to determine the influence of geographical origin on these compounds. Standard protocols and ultra-high‐performance liquid chromatography/tandem mass spectrometry methods were used. Results revealed that several compounds showed a significant difference between species as well as between local ecotypes and commercialized variety. L. albus seeds were shown characterized by the highest protein and oleic acid content and the lowest starch content. Results revealed that lipids and phenolics were highly influenced by the ecotype factor. Large differences were found between L. luteus ecotypes for oleic acid and linoleic acid content, ranging from 164.97 to 302.73 mg kg−1 DM and from 306.03 to 616.97 mg kg−1 DM, respectively. Little amount of miristoleic acid, lignoceric acid, and margaric acid were found in lupine seeds for the first time. For phenolic profile, interestingly to highlight for the first time the presence of morin dihydrate among lupines species, especially in L. tbk2 which showed the highest antioxidant activity

First isolation and molecular characterization of Toxoplasma gondii strains from human congenital toxoplasmosis cases in Monastir, tunisia

International audienceToxoplasma gondii is a protozoon parasite that can cause severe clinical problems such as congenital toxoplasmosis. The distribution of T. gondii genotypes varies from one geographic area to another. So far, little is known about the parasite genotypes in Tunisia, North Africa. The present study aimed isolating and genotyping T. gondii from the amniotic fluid (AF) and placenta of pregnant women in Monastir, Tunisia. Amniotic fluid and/or placenta from 80 women who acquired toxoplasma infection during pregnancy were tested by PCR and/or mouse bioassay. Genotyping of T. gondii isolates from these samples was performed with 15 microsatellite markers. Four viable T. gondii strains were isolated from either the AF or placenta of four women. Specifically, strains TUN001-MON1 and TUN002-MON2 were isolated from both the AF and placenta, TUN003-AHA from only the placenta, and TUN004-NEL from only the AF. The four viable strains were not virulent for mice. Genotyping revealed that the four strains were type II strains. This is the first report on isolation and genotyping of T. gondii from AF human samples in Tunisia. Further studies focused on T. gondii genotyping on a larger number of human cases and on animals in Tunisia are needed to improve the knowledge and epidemiology of toxoplasmosis