Amazonian soil fungi are efficient degraders of glyphosate herbicide; novel isolates of Penicillium, Aspergillus, and Trichoderma

Pesticide residues that contaminate the environment circulate within the hydrological cycle can accumulate within the food chain and cause problems to both environmental and human health. Microbes, however, are well known for their metabolic versatility and the ability to degrade chemically stable substances, including recalcitrant xenobiotics. The current study focused on bio-prospecting within Amazonian rainforest soils to find novel strains fungi capable of efficiently degrading the agriculturally and environmentally ubiquitous herbicide, glyphosate. Of 50 fungal strains isolated (using culture media supplemented with glyphosate as the sole carbon-substrate), the majority were Penicillium strains (60%) and the others were Aspergillus and Trichoderma strains (26 and 8%, respectively). All 50 fungal isolates could use glyphosate as a phosphorous source. Eight of these isolates grew better on glyphosate-supplemented media than on regular Czapek Dox medium. LC-MS revealed that glyphosate degradation by Penicillium 4A21 resulted in sarcosine and aminomethylphosphonic acid.

Integration of Stalk Destruction Methods for the Glyphosate Herbicide-Resistant Cotton

The increase in geographical areas used for cultivation of transgenic glyphosate herbicide-resistant cotton has hindered the stalk destruction, compromised the phytosanitary break implementation and consequently increased the population of insect pests and cotton plant pathogens. This study evaluated the efficiency of the combining mechanical and chemical methods in the destruction of transgenic cotton stalk resistant to the glyphosate herbicide. Two experiments were carried out in 2015 and 2016 in Primavera do Leste,-Mato Grosso, Brazil and Luís Eduardo Magalhães, Bahia, Brazil, respectively. The study evaluated different mechanical destruction equipment in combination with the chemical methods. In each environment, a randomized block experiment with four replications was employed. The results of the experiments indicated that the mechanical destruction increased the control efficiency by at least 10% when compared to chemical destruction of the cotton stalk. Chemical destruction with herbicides combined with mechanical destruction methods does not increase the control efficiency of cotton stalks destruction. Furthermore, the application of hormonal herbicides following the mechanical shredding of cotton stalks does not increase the control efficiency of glyphosate-resistant cotton stalk.

Effect of Spraying Glyphosate Herbicide on Solanum elaeagnifolium in Uncultivated Fields and on Physicochemical and Biological Soil Characteristics

Bakkour, F., A. El-Meamar and Z. El-Naser. 2021. Effect of Spraying Glyphosate Herbicide on Solanum elaeagnifolium in Uncultivated Fields and on Physicochemical and Biological Soil Characteristics. Arab Journal of Plant Protection, 39(4): 296-308. https://doi.org/10.22268/AJPP-39.4.296308 Glyphosate herbicide is used in uncultivated fields infested with Solanum elaeagnifolium plants several times a year in all Syrian governorates by the Ministry of Agriculture. This research aimed to study the effect of repeated spraying of glyphosate in uncultivated fields in five different locations in the Syrian governorates, Deir Ezzor (Tebni), Aleppo (Dakwani), Hama (Bostan AL-Omahat), Homs (ALZahoria) and Rural Damascus (Bohter) during the period 2017-2020, on the physiochemical and biological characteristics of the treated soils. Herbicide residues were measured in the leaves of the treated Solanum elaeagnifolium plants and in the soils surrounding the roots of the Solanum elaeagnifolium plants. It was found that the repetition of the pesticide spray 3 and 6 times during the study period did not alter the physical composition, salinity, pH and calcium carbonate content in all study locations. Whereas, spraying glyphosate 3 and 6 times increased the percentage of organic matter and phosphorus available, with a significant difference with the control. The values of available phosphorous after 6 pesticide spray applications reached 176, 203, 196, 227 and 205 mg/kg of soil in Deir Ezzor, Aleppo, Hama, Homs and Rural Damascus, respectively. In addition, repeated spraying with glyphosate of the treated soils led to increase the average general bacteria and fungi populations. These indicators were increased with the increase in the number of pesticide sprays applied. Furthermore, the pesticide residues increased in the soil and Solanum elaeagnifolium leaves with the increase in number of pesticide sprays. Pesticide residue values after 6 sprays were 1.72, 3.53, 4.89, 4.43 and 2.29 mg/kg of soil in Deir Ezzor, Aleppo, Hama, Homs and Rural Damascus locations, respectively. Keywords: Glyphosate, S. elaeagnifolium, residues, microorganisms, soil.

Single Stem Rouging of Banana Xanthomonas Wilt Infected Plants for Orchard Rehabilitation

Banana Xanthomonas Wilt (BXW), caused by Xanthomonas campestris pv. musacearum (Xcm), a devastating disease, causes up to 100% loss and affects all banana varieties. The disease is widespread in East and Central Africa region. Study objective was to evaluate the performance of single stem rouging options for rehabilitation of severely affected banana orchard. Five single stem rouging options were implemented in banana orchard with 80% BXW severity in Western Kenya. The options included rouging of infected banana plants; uprooting, cutting at the base, injecting 20 ml of glyphosate herbicide at the soil base of the pseudostem, uprooting the whole stool and control leaving the infected stools. Initial visual assesment before implementation of the orchard was over 80% infection. Later samples were collected for diagnosis of ten plants per treatment from different plant parts and were subjected to ELISA and PCR procedures for confirmion of the presence of Xcm. Rouging options was implemented for one year. During and after experimentation periodic visual assesment of BXW incidence and severity reduced. Results of ELISA assays and PCR results indicated Xanthomonas was present on banana plants. Rouging the infected banana stems by cutting at the base, uprooting and injection of herbicide reduced BXW incidence within six months. Xanthomonas, an inhibiting bacteria cannot surve without host and by killing the banana plant the Xanthomonas dies. Yields were recovered from the rehabilitated orchard within one year. Banana orchard highly infected with BXW was effectively rehabilitated.

Potential mutagenic effects of the glyphosate herbicide on Gymnotus inaequilabiatus (Valenciennes, 1839)

This study analyzed the occurrence of nuclear damage in the red blood cells of Gymnotus inaequilabiatus (Valenciennes, 1839), exposed in vivo to the herbicide glyphosate. The fish were distributed in four groups, namely: control (without addition of herbicide) and contaminated groups with application of 65 µg/L (concentration allowed by CONAMA Resolution), 1 mg/L (maximum limit recommended by the World Health Organization - WHO and Food and Agriculture Organization - FAO) and 5 mg/L (overdose, five times higher than that by WHO and FAO). For the analysis of cell damage, the method of Nuclear Erythrocytic Abnormalities (NEA) was used, containing 1000 cells for duplicate elimination. An increase in cell damage was observed for 144 hours (6-days) of exposure in all controls. Even under a small concentration, there was a clear effect on segmented, renal, lobed formation and mainly on the formation of micronuclei. The high damage was caused in the first 48 hours and reduced after 144 hours, where the fish can have the herbicidal effect blocked. Studies that analyze the mechanisms of action of glyphosate-based herbicides are essential to determine the risks caused by biota, since there is a great divergence on the maximum tolerable limits in water, which affect quality and integrity of these ecosystems.