Effect of Arbuscular Mycorrhizal Fungi and Phosphate-Solubilizing Bacteria Consortia Associated with Phospho-Compost on Phosphorus Solubilization and Growth of Tomato Seedlings (Solanum lycopersicum L.)

ABSTRACT

The exploitation of phosphate mines generates an important quantity of phosphate sludge that remains accumulated and not valorized. In this context, composting with organic matter and rhizospheric microorganisms offers an interesting alternative and that is more sustainable for agriculture. This work aims to investigate the synergetic effect of arbuscular mycorrhizal fungi (AMF), phosphate-solubilizing bacteria (PSB) and phospho-compost (PC), produced from phosphate-laundered sludge and organic wastes, and their combination on plant growth, phosphorus solubilization and phosphatase activities (alkaline and acid). Inoculated mycorrhizae and bacteria strains used in this study were selected from plant rhizosphere grown on phosphate-laundered sludge. Significant (p < .05) increases in plant growth was observed when inoculated with both consortia and PC (PC+ PSB+ AMF) similar to those recorded in plants amended with chemical fertilizer. Tripartite inoculated tomato had a significantly (p < .05) higher shoot height; shoot and root dry weight, root colonization and available P content, than the control. Co-inoculation with PC and AMF greatly increased alkaline phosphatase activity and the rate of mycorrhizal intensity. We conclude that PC and endophytic AMF and PSB consortia contribute to a tripartite inoculation in tomato seedlings and are coordinately involved in plant growth and phosphorus solubilization. These results open up promising prospects for using formulate phospho-compost enriched with phosphorus-solubilizing microorganisms (PSM) in crop cultivation as biofertilizers to solve problems of phosphate-laundered sludge accumulation.     

Growth of Date Palm (Phoenix dactylifera L.) in Composts of Olive Oil Mill Waste with Organic Household Refuse

This study highlights the effects of composts of olive mill wastes and organic household refuse with a pH range of 7 to 7.98 and a C/N ratio between 14.9 and 22, to improve the growth and the mineral nutrition of the date palm (Phoenix dactylifera L.). After 7 months of cultivation, plants amended with composts showed higher biomass production than the controls. Compost C1, i.e., the basic compost with no additives phosphate, at 100% and 45% doubled the production of dry matter in comparison with control plants. The rise of root biomass was considerably greater for plants grown with compost C1 without phosphate. In contrast, the shoot biomass was highly significant for composts C2 and C3 enriched with phosphate. The control plants, grown without amendment, showed significantly higher specific root length (SRL) and specific leaf length (SLL). The efficiency of compost application was reflected by the biomass rise, the number of emerged leaves (2.6–4), and the rise in leaf area (3.3 to 6.7 cm²) by improving the mineral nutrition of the date palm. The composts of olive mill waste and organic household refuse supplemented with natural rock phosphate, or not, generated a notable agronomic added value.     

Assessment of Biodegradation of Oleandrin during Co-composting of Nerium oleander L. Wastes

ABSTRACT

Variations in the levels of the highly toxic oleandrin molecules were studied during composting of Nerium oleander L. waste mixed with clippings of the grass Pennisetum clandistenum L. The thermophilic phase is characterized by a rise in temperature, which reached 70°C. After 150 days of co-composting, the C/N ratio was 11, the pH was 8, the NO₃^?/NH₄⁺ ratio was greater than 1 and overall decomposition reached 70%. During the successive stages of co-composting, oleandrin concentrations were monitored by HPLC. The relative abundance of oleadrin was 26.84% at T0 with 10% abatement during the first month and 90% after two months (stabilization phase), reaching 100%, i.e., total removal after 90 days of co-composting (maturation phase). The biodegradation of the toxic substance was largely attributed to the activity of actinomycetes and fungi. The germination index of lettuce and watercress seeds exceeded 50% after 90 days and reached 95% after 150 days, confirming that the final compost was mature, stable, and free from phytotoxicity in spite of the highly poisonous starting material.     

Mycorrhizal autochthonous consortium induced defense-related mechanisms of olive trees against Verticillium dahliae

Journal of Plant Diseases and Protection - The present work aimed to investigate the effect of an autochthonous mycorrhizal consortium in enhancing olive tree tolerance against Verticillium...     

Beneficial Effects of Plant Growth Promoting Rhizobacteria,Arbuscular Mycorrhizal Fungi and Compost on Lettuce (Lactuca sativa) Growth Under Field Conditions

Two independent field experiments (2017 and 2019) were conducted to evaluate the effects of plant growth promoting rhizobacteria (PGPR), arbuscular mycorrhizal fungi (AMF; AMF1: Rhizophagus irregularis strain and AMF2: AMF consortium) and compost (Comp) in comparison to chemical NPK fertilizers on growth and yield of lettuce plants and soil properties. The biofertilizers-biostimulants were applied alone or in combinations and increased significantly the lettuce dry weight (DW), number of leaves, and yield compared to the control. In the first experiment, the highest plant DW was obtained by NPK, PGPR?+?AMF2?+?Comp and PGPR treatments recording an increase of 109, 109, and 95%, respectively, compared to the control plants. In the second experiment the highest plant DW was obtained by the NPK (77%), followed by Comp and PGPR?+?AMF1?+?Comp treatments increasing the plant DW by 52 and 51%, respectively, compared to the control. Concerning to lettuce yield, in the first experiment, the highest yields were obtained by NPK, PGPR?+?AMF2, PGPR?+?AMF1?+?Comp, PGPR, AMF2?+?Comp, AMF1?+?Comp and AMF2 treatments recording an enhancement of 68, 64, 63, 58, 57, 57, and 55%, respectively. In the second experiment, the application of NPK based fertilizers resulted in the highest yield (77%), followed by PGPR?+?AMF1?+?Comp, PGPR?+?AMF2?+?Comp, AMF1?+?Comp, and AMF2?+?Comp treatments, increasing the yield by 61, 61, 54, and 55%, respectively, compared to the control. Concerning the soil organic matter (OM), the applied treatments had significantly increased the amount of the OM compared to the control. The highest amounts of OM were obtained by the PGPR?+?AMF2?+?Comp treatment in the first experiment and the PGPR?+?AMF1?+?Comp treatment in the second experiment. The available phosphorus (P) was significantly increased by the application of all treatments. The highest records were obtained by the application of Comp, PGPR?+?AMF1 and PGPR?+?AMF1?+?Comp treatment after the first experiment. In the second experiment, the highest amount of P was obtained by PGPR?+?AMF2?+?Comp treatment. Application of biofertilizers-biostimulants in combination proved to be beneficial for the improvement of the tested culture yield.

     

Effect of plant growth regulators,calcium and citric acid on copper toxicity in pea seedlings

The present investigation aims to study the potential protective role of exogenous applications of gibberellin, auxin, citric acid and calcium on the growth and cellular redox state of pea (Pisum sativum L.) germinating seeds exposed to copper stress. All tested treatments alleviated the adverse effects of Cu-induced toxicity on the growth, cell viability and mobilization of nutrients from the cotyledons. This alleviation of Cu toxicity occurred by limiting heavy metal biosorption and maintaining cellular redox homeostasis. Redox balance, examined through the study of the redox state of nicotinamide couples NAD⁺/NADH and NADP⁺/NADPH appeared to be protected by the treatments. This correction was correlated to a modulation of NAD(P)H-oxidase and dehydrogenase activities, such as glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malate dehydrogenase. The present research provides evidence that supplementation of plants with gibberellin, auxin, citric acid and calcium was an effective approach for enhancing Cu tolerance in pea seedlings.     

Improving Lettuce Yield and Quality of an Agricultural Soil Using a Combination of Arbuscular Mycorrhizal Fungus and Phosphate-Green Wastes Compost

The use of biofertilizers on agricultural soils could act positively to improve soil fertility and crop productivity. This work was performed to assess the potential beneficial impacts of local produced phospho-compost and/or an exogenous arbuscular mycorrhizal fungus (AMF) (Rhizoglomus irregulare DAOM 197198) on lettuce agro-physiological and soil characteristics under filed conditions. Four treatments were applied: control treatment without any biofertilizer, compost, AMF, and compost?+?AMF treatments. Obtained results showed that shoot nitrogen (N) and phosphorus (P) were significantly improved in lettuce plants treated with compost supplementation and/or AMF inoculation compared to the control with a maximum increment for P in plants treated with compost (106%). As for growth traits, lettuce plants treated with compost?+?AMF recorded the highest values in terms of shoot and root dry weights and yield by 121, 54 and 127%, respectively, compared to the control plants. Considering physiological and biochemical traits, stomatal conductance, and chlorophyll fluorescence as well leaf area index and total soluble sugar and protein concentration were significantly improved in plants treated with compost and/or AMF compared to the control. In addition, soil properties, especially the soil total organic carbon, N, P, and glomalin-related soil protein content were significantly enhanced after two months of field experiment in treated soils with the applied biofertilizers alone or in combination compared to the control. Based on the main obtained results, applied biofertilizers were able to increase lettuce productivity and soil fertility under field conditions, especially the compost?+?AMF treatment, which demonstrated an effectiveness promotion of lettuce productivity and soil fertility.