Weed control by metabolites produced from Diaporthe schini.

Weed control is a critical factor to ensure productivity and quality for food production. Chemical control is the main method used worldwide, but the demand for healthier food and the farmers' health and environment concerns have led to an increase in the search for alternative control methods. In this way, the use of biomolecules produced by microorganisms that present phytotoxic activity against weeds, such as exopolysaccharides, is attracting attention. For this purpose, this work compared two techniques (solid-state and submerged fermentation) for bioherbicide production by Diaporthe schini. Physicochemical characterization of both fermented broth and evaluation of bioherbicidal effect in post-emergence of Amaranthus viridis, Bidens pilosa, Echinocloa crusgalli, and Lollium multiflorum were performed. Fungal broth obtained by submerged fermentation presented better physicochemical characteristics in terms of viscosity, density, and surface tension. Overall, it was more effective than the broth obtained by solid-state fermentation for weed control because it presented an average inhibition of 40% of weed growth and 45% lower surface tension if compared to the control test. Also, reductions of 1.4-4.2 times of root dry mass, 2.9-5.8 times of shoot dry mass and 1.2-3.9 times of weeds heights, if compared to the control test, were achieved.

Powder containing biomolecules from Diaporthe schini for weed control.

This study describes the use of spray drying technology to obtain a powder containing biomolecules with herbicidal activity produced by submerged fermentation using Diaporthe schini. The efficiency of the bioherbicide was tested for the post-emergence control of Bidens pilosa L., Amaranthus viridis L., Echinochloa crusgalli (L.) Beauv., and Lolium multiflorum Lam. In the first step, different additives were used and lactose was the most suitable one because it resulted in high herbicidal activity and weed suppression. In the second step, process variables were investigated, including inlet air temperature, drying air flow rate, and feed flow rate. The highest herbicidal activity was obtained with an inlet air temperature of 100°C, and air and feed flow rates of 1.4 m3/min and 0.22 L/h, respectively. Maximum herbicidal activities were 38, 45, 21 and 18%, while weed heights reduction were 69.0, 74.3, 20.4 and 24.8% for B. pilosa, A. viridis, E. crusgalli and L. multiflorum, respectively. The bioherbicide was effective to suppress weed growth and spray drying is a promising technology for the production of solid formulations of bioherbicides.

Concentration of metabolites from Phoma sp. using microfiltration membrane for increasing bioherbicidal activity.

This study is focused on the concentration of fermented broth from Phoma sp. to increase its herbicidal activity. For this purpose, biomolecules produced by submerged fermentation using Phoma sp. were concentrated by hollow fiber microfiltration membranes. The membrane feed was separated into two streams (retentate and permeate) and the crude broth was concentrated to 10, 30, 50, 70 and 90% (relative to the initial volume). The retentate samples were submitted to bioassays (triplicate) for evaluating their phytotoxic effects on five young leaves of species of Cucumis sativus and also on pre-emergence of weeds as Bidens pilosa and Amaranthus retroflexus. The highest herbicidal activity was 80.7% obtained for a concentration of 30% in the retentate fraction. At this condition, the bioherbicide presented severe damage symptoms on the detached leaves of Cucumis sativus if compared to the crude fermented broth. In the pre-emergence of B. pilosa and A. retroflexus, 100% control was obtained for assays performed in a germination chamber. For greenhouse assays using the substrate, the control rate of A. retroflexus was dependent of concentration of bioherbicide. The promising results achieved in the research with membrane separation process allow us to propose and develop further studies for evaluating this technology in the concentration of other metabolites produced by fermentation which also have bioherbicidal activity.

Extracts from Lupinus albescens: antioxidant power and antifungal activity in vitro against phytopathogenic fungi.

Fungi are considered the most damaging microorganisms in agriculture. The indiscriminate use of chemical treatments in agricultural products causes the development of pest resistance and affects human health. An alternative to synthetic fungicides is the use of natural products such as plant extracts for the management of fungal diseases in plants. Extracts from different parts of Lupinus albescens (roots, stalks, leaves, and flowers) were obtained by extraction using supercritical carbon dioxide (CO2) or compressed liquefied petroleum gas (LPG). Thereafter, the antioxidant activity of each extract was measured, and the antifungal activity in vitro of extracts was evaluated against Fusarium oxysporum and Fusarium verticillioides. For a concentration of 5000 mg/L, the half maximal inhibitory concentration (IC50) ranged from 29.25 µg/mL to 192.96 µg/mL. Antifungal tests showed that all matrices presented inhibitory effect against both fungi tested. The extracts obtained from roots by CO2 and LPG presented 70.1% and 65.1% inhibition against F. oxysporum, and 67.8% and 61.2% inhibition against F. verticillioides, respectively. These results suggest that the extracts obtained from L. albescens by extractions using supercritical CO2 and compressed LPG might be a potential source of antioxidants and natural fungicides.

Production of bioherbicide by Phoma sp. in a stirred-tank bioreactor.

The objective of this work was to produce an herbicide by submerged fermentation in a stirred-tank bioreactor and to assess the potential herbicidal in pre-emergence, post-emergence, and in a detached leaves of Cucumis sativus var species. wisconsin (cucumber) and Sorghum bicolor (sorghum) species. Fermentations were carried out in a stirred-tank bioreactor with useful volume of 3L. Stirring rate (40, 50, and 60 rpm) and aeration (1, 2 and 3 vvm) were the variables studied for bioherbicide production. Fermented broth was fractioned with different solvents to identify the molecules produced by the fungus in a multi-dimensional gas chromatograph system. Bioherbicide showed 100% inhibition of germination of both species in the pre-emergence tests. From detached leaves tests were verified yellowish lesions in Cucumis sativus and necrotic lesions on leaves of Sorghum bicolor. Post-emergence test presented variation of the phytotoxicity from 25 to 66% for the species C. sativus and from 32 to 58% by S. bicolor. The metabolites produced by submerged fermentation of Phoma sp. presented activity in pre-emergence, post-emergence, and detached leaves of C. sativus and S. bicolor and it could be an alternative in the future for weed control.