The Potential use ofTrichoderma VirideStrain FRP3 in Biodegradation of the Herbicide Glyphosate

Trichoderma as a biological control agent: mechanisms of action, benefits for crops and development of formulations

Currently, the food and economic losses generated by the attack of phytopathogens on the agricultural sector constitute a severe problem. Conventional crop protection techniques based on the application of synthetic pesticides to combat these undesirable microorganisms have also begun to represent an inconvenience since the excessive use of these substances is associated with contamination problems and severe damage to the health of farmers, consumers, and communities surrounding the fields, as well as the generation of resistance by the phytopathogens to be combated. Using biocontrol agents such as Trichoderma to mitigate the attack of phytopathogens represents an alternative to synthetic pesticides, safe for health and the environment. This work explains the mechanisms of action through which Trichoderma exerts biological control, some of the beneficial aspects that it confers to the development of crops through its symbiotic interaction with plants, and the bioremedial effects that it presents in fields contaminated by synthetic pesticides. Also, detail the production of spore-based biopesticides through fermentation processes and formulation development.

Tolerance of microorganisms to residual herbicides found in eucalyptus plantations

Competition with weeds is one of the main factors that limit the development of forest species. Some herbicides used to control these plants have a residual effect on the soil. Bioremediation is an alternative to decontaminate these areas. The aim of this study was to evaluate the tolerance of Aspergillus niger, Penicillium pinophilum and Trichoderma sp. and its degrading potential on residual effect herbicides. The tolerance of Bacillus subtilis, Pseudomonas sp. and Azospirillum brasilense to herbicides was also evaluated. The herbicides used in this study were indaziflam, sulfentrazone, sulfentrazone + diuron, clomazone and glyphosate + s-metolachlor. The analysis of the tolerance and degradation potential of fungi was carried out in Czapek Dox medium and the growth was evaluated by determining the biomass. Bacterial tolerance analysis was performed in Luria Bertani medium and growth monitored by optical density. The data were applied to the Gompertz model to evaluate the behavior of bacteria. Bacterial growth parameters were not influenced by the presence of herbicides. All fungi were tolerant to the herbicides tested and there was an increase in the growth of Trichoderma sp. Thus, the analysis of the degrading potential was performed only for Trichoderma sp. in the presence of herbicides that potentiated its growth. In this analysis, there was no effect of herbicides on fungal growth; the fungus was unable to use the carbon present in the herbicide to enhance its growth; and there was no significant effect of nitrogen in the presence of the herbicide. It is concluded, therefore, that the tested residual herbicides do not interfere with the development of the evaluated microorganisms.

Vineyard Management and Physicochemical Parameters of Soil Affect Native Trichoderma Populations, Sources of Biocontrol Agents against Phaeoacremonium minimum

Native strains of Trichoderma in vineyard soil represent an opportunity for reducing the incidence of grapevine trunk diseases (GTDs) in vineyards. Moreover, its relationship with the environment (physicochemical soil characteristics and farming management practices) remains unclear. In the current study, a survey was carried out on farming management used by viticulturists, and soil samples were studied to analyze their physicochemical properties and to isolate Trichoderma strains. Later, statistical analyses were performed to identify possible correlations between Trichoderma populations, soil management and soil characteristics. In addition, in vitro tests, including antibiosis and mycoparasitism, were performed to select those Trichoderma strains able to antagonize Phaeoacremonium minimum. In this study a positive correlation was found between the iron content and pH in the soil, and a lower pH increases Trichoderma populations in soils. Vineyard management also affects Trichoderma populations in the soil, negatively in the case of fertilization and tillage and positively in the case of herbicide spraying. Two Trichoderma native strains were selected as potential biocontrol agents (Trichoderma gamsii T065 and Trichoderma harzianum T087) using antibiosis and mycoparasitism as mechanisms of action. These results led to the conclusion that native Trichoderma strains hold great potential as biological control agents and as producers of secondary metabolites.

Glyphosate-Eating Fungi: Study on Fungal Saprotrophic Strains' Ability to Tolerate and Utilise Glyphosate as a Nutritional Source and on the Ability of Purpureocillium lilacinum to Degrade It

Glyphosate is the most commonly used herbicide worldwide. Its improper use during recent decades has resulted in glyphosate contamination of soils and waters. Fungal bioremediation is an environmentally friendly, cost effective, and feasible solution to glyphosate contamination in soils. In this study, several saprotrophic fungi isolated from agricultural environments were screened for their ability to tolerate and utilise Roundup in different cultural conditions as a nutritional source. Purpureocillium lilacinum was further screened to evaluate the ability to break down and utilise glyphosate as a P source in a liquid medium. The dose-response effect for Roundup, and the difference in toxicity between pure glyphosate and Roundup were also studied. This study reports the ability of several strains to tolerate 1 mM and 10 mM Roundup and to utilise it as nutritional source. P. lilacinum was reported for the first time for its ability to degrade glyphosate to a considerable extent (80%) and to utilise it as a P source, without showing dose-dependent negative effects on growth. Pure glyphosate was found to be more toxic than Roundup for P. lilacinum. Our results showed that pure glyphosate toxicity can be only partially addressed by the pH decrease determined in the culture medium. In conclusion, our study emphasises the noteworthy potential of P. lilacinum in glyphosate degradation.

Complex gene response of herbicide-resistant Enterobacter strain NRS-1 under different glyphosate stresses

Knowledge of biological evolution and genetic mechanisms is gained by studying the adaptation of bacteria to survive in adverse environmental conditions. In this regard, transcriptomic profiling of a glyphosate-tolerant Enterobacter strain NRS-1 was studied under four different treatments to investigate the gene-regulatory system for glyphosate tolerance. A total of 83, 83, 60 and 74 genes were up-regulated and 108, 87, 178 and 117 genes down-regulated under 60-NPG, 110-NPG, NaCl (355 mM) and HCl (pH 4.46) stress treatments, respectively. Complex gene network was identified to be involved in regulating tolerance to glyphosate. This study revealed that NRS-1 has gained glyphosate tolerance at the cost of osmotic and acidic resistance. The 25 differentially expressed genes are reported to may have partly changed the function for providing resistance to glyphosate directly, among them genes metK, mtbK, fdnG and wzb that might detoxify/degrade the glyphosate. However, under 110-NPG condition, NRS-1 might have utilized economical and efficient ways by depressing its metabolism and activity to pass through this stress. Hence, the present study provides insights into the genes involved in glyphosate tolerance, which can be effectively utilized to engineer herbicide-resistant crop varieties after their proper validation to manage weed growth.

Microbial degradation of herbicides

Herbicides remain the most effective, efficient and economical way to control weeds; and its market continues to grow even with the plethora of generic products. With the development of herbicide-tolerant crops, use of herbicides is increasing around the world that has resulted in severe contamination of the environment. The strategies are now being developed to clean these substances in an economical and eco-friendly manner. In this review, an attempt has been made to pool all the available literature on the biodegradation of key herbicides, clodinafop propargyl, 2,4-dichlorophenoxyacetic acid, atrazine, metolachlor, diuron, glyphosate, imazapyr, pendimethalin and paraquat under the following objectives: (1) to highlight the general characteristic and mode of action, (2) to enlist toxicity in animals, (3) to pool microorganisms capable of degrading herbicides, (4) to discuss the assessment of herbicides degradation by efficient microbes, (5) to highlight biodegradation pathways, (6) to discuss the molecular basis of degradation, (7) to enlist the products of herbicides under degradation process, (8) to highlight the factors effecting biodegradation of herbicides and (9) to discuss the future aspects of herbicides degradation. This review may be useful in developing safer and economic microbiological methods for cleanup of soil and water contaminated with such compounds.