Optimization of liquid-state fermentation conditions for the glyphosate degradation enzyme production of strain Aspergillus oryzae by ultraviolet mutagenesis

This study aimed to obtain strains with high glyphosate-degrading ability and improve the ability of glyphosate degradation enzyme by the optimization of fermentation conditions. Spore from Aspergillus oryzae A-F02 was subjected to ultraviolet mutagenesis. Single-factor experiment and response surface methodology were used to optimize glyphosate degradation enzyme production from mutant strain by liquid-state fermentation. Four mutant strains were obtained and named as FUJX 001, FUJX 002, FUJX 003, and FUJX 004, in which FUJX 001 gave the highest total enzyme activity. Starch concentration at 0.56%, GP concentration at 1,370?mg/l, initial pH at 6.8, and temperature at 30°C were the optimum conditions for the improved glyphosate degradation endoenzyme production of A. oryzae FUJX 001. Under these conditions, the experimental endoenzyme activity was 784.15?U/100?ml fermentation liquor. The result (784.15?U/100?ml fermentation liquor) was approximately 14-fold higher than that of the original strain. The result highlights the potential of glyphosate degradation enzyme to degrade glyphosate.     

Induction of glutathione S-transferase activity and glutathione level in plants exposed to glyphosate

Treatment with the herbicide glyphosate led to significantly increased activities of the enzyme gluiathione S-transferase (GST, EC 2.5.1.18) in wheat ( Triticum aestivum L. cv. Kadett and cv. Satu), pea ( Pisum sativum L. ev. Debreceni Világoszöld) and in maize ( Zea mays. L. Pioneer 3839 hybrid) tissues. GST activities in wheat seedlings (cv. Kadett) exposed to 960 μM glyphosate for 4 days were ca 6-fold and 3-fold higher in shoots and roots, respectively, than in the controls. Glyphosate increased the GST activity to a lesser extent in pea and maize than in wheat. In wheat seedlings (cv. Satu) exposed let 120 μM glyphosate gradual increases in the content of non-protein thiols were observed. After 7 days exposure to glyphosate the thiol levels rose to about 360% and 220% of the controls in wheal shoots and roots, respectively. The elevation of thiol content in glyphosate-treated plants was shown to be primarily due increases of glutathione level. These results suggest that the enhanced glutathione metabolism may have a role in the mode of action or degradation of this herbicide.     

Low concentrations of glyphosate‐based herbicide cause complete loss of sperm motility of yellowtail tetra fish Astyanax lacustris

Environmental relevant concentrations of glyphosate‐based herbicide as 50 µg l^?1, 300 µg l^?1 and 1800 µg l^?1 can affect sperm quality of yellowtail tetra fish Astyanax lacustris . Viability of sperm cells was impaired at 300 µg l^?1, a concentration that is within legal limits in U.S.A. waterbodies, while motility was impaired at 50 µg l^?1, which is the more stringent limit set in Brazilian law. Therefore, environment protection agencies must review regulations of glyphosate‐based herbicides on water bodies.     

Commercially formulated glyphosate can kill non‐target pollinator bees under laboratory conditions

The use of glyphosate‐based herbicides in agroecosystems has increased over the past few years because of the advent of genetically modified glyphosate‐resistant crops and resistant weeds. This is alarming because of potential damaging effects on non‐target organisms. In sub‐Saharan Africa, for example Ghana, many rural farmers have not received training in the use of glyphosate‐based herbicides, thus tend to apply higher than recommended concentrations on farms. Therefore, this study investigated the effect of glyphosate‐based herbicides on beneficial insects under laboratory conditions, using Apis mellifera L. (Hymenoptera: Apidae, Apini) and Hypotrigona ruspolii (Magretti) (Hymenoptera: Apidae, Meliponini) as models. The bees were put in contact for 24 h with the recommended concentration of Sunphosate 360 SL, a glyphosate‐based herbicide, 2× the recommended concentration, or distilled water as control. The effect of the herbicide on the bees was compared to the effect of a lambda‐cyhalothrin insecticide. Generally, more bees died after contact with plants freshly sprayed with the herbicide than on herbicide‐treated filter paper. In both cases, more bees died after contact with the higher concentration of the herbicide. These findings suggest that beneficial insects, specifically A. mellifera and H. ruspolii, may get killed if they are sprayed upon or come into contact with plants that have been freshly sprayed with (more than) the recommended concentration of glyphosate‐based herbicides. Therefore, it is important to restrict access and use of such herbicides to trained personnel who will comply with spraying guidelines, that is, recommended concentrations and timing of spray. Spraying at a time when insects are flying about may be detrimental to beneficial insects such as pollinator bees, parasitoids, and predators.     

除草剂对黄河三角洲入侵植物互花米草的影响

互花米草(Spartina alterniflora)作为我国危害最严重的外来入侵植物之一,严重威胁滨海湿地生态系统安全。筛选可高效灭除互花米草的除草剂,为互花米草防治提供技术支持。2017年7月在黄河三角洲潮间带对互花米草茎叶喷施不同除草剂,在施药当年和次年对互花米草生长状况和大型底栖动物密度进行跟踪调查。研究结果表明:1)高效氟吡甲禾灵对互花米草的灭除效果最好,既能杀死互花米草地上部分从而完全抑制有性繁殖,又可完全抑制次年的无性繁殖;2)氰氟草酯对互花米草的灭除效果也比较好,可以完全抑制互花米草的生长和结穗,但抑制根状茎无性繁殖能力的效果稍差,草甘膦可以完全抑制互花米草的有性繁殖,但无法抑制次年互花米草的无性繁殖;3)施用除草剂在短期内会毒害某些底栖动物,但在1年后底栖动物种群数量与对照处理无显著差异。除草剂对环境的影响程度与除草剂用量和施用时间息息相关,未来研究中,应在保证灭草效果的前提下,探索最佳用药时间和最低用量以最大限度地降低环境影响。     

An individual‐based model of seed‐ and rhizome‐propagated perennial plant species and sustainable management of Sorghum halepense in soybean production systems in Argentina

Perennial plants which propagate through both seeds and rhizomes are common in agricultural and nonagricultural systems. Due to their multifaceted life cycle, few population models are available for studying such species. We constructed a novel individual‐based model to examine the effects of ecological, evolutionary, and anthropogenic factors on the population dynamics of perennial species. To exemplify the application of the model, we presented a case study of an important weed, Sorghum halepense (L.) Pers. (Johnsongrass), in soybean productions in Argentina. The model encompasses a full perennial weed life cycle with both sexual (seeds) and asexual (rhizomes) propagations. The evolution of herbicide resistance was modeled based on either single genes or quantitative effects. Field experiments were conducted in the species' native environment in Argentina to parameterize the model. Simulation results showed that resistance conferred by single‐gene mutations was predominantly affected by the initial frequency of resistance alleles and the associated fitness cost. Population dynamics were influenced by evolved resistance, soil tillage, and rhizome fecundity. Despite the pivotal role of rhizomes in driving the population dynamics of Johnsongrass, most herbicides target the aboveground biomass, and chemical solutions to control rhizomes are still very limited. To maintain effective (short‐term) and sustainable (long‐term) weed management, it is recommended to combine soil tillage with herbicide applications for suppressing the rhizomes and delaying the evolution of resistance. This novel model of seed‐ and rhizome‐propagated plants will also be a useful tool for studying the evolutionary processes of other perennial weeds, cash crops, and invasive species.     

Residual herbicide treatments reduce Andropogon gayanus (Gamba Grass) recruitment for mine site restoration in northern Australia

Weed invasion is a major threat to Australian tropical savannas, and controlling weeds is essential for successful re‐establishment of native species on disturbed sites. Gamba Grass (Andropogon gayanus) is an African grass which has invaded large areas of tropical savanna across northern Australia. Current management strategies in northern Australia focus on fire and glyphosate to effectively control mature plants; however, re‐establishment of infestations from the soil seed bank remains a major challenge to eradication efforts. This study focused on the effects of soil seed bank treatments on Gamba Grass recruitment on a mine site in northern Australia. Adult Gamba Grass plants within test plots were killed with glyphosate to exclude resource competition. Chemical, physical and biological treatments were then applied, and the treatment effects on subsequent Gamba Grass seedling emergence and survival quantified. Seedling emergence was significantly reduced by three of the four residual herbicide treatments tested. The most effective herbicide treatments, dalapon and sulfometuron, reduced emergence by 90% compared to the standard glyphosate treatment alone. This equated to a reduction in Gamba Grass seedling emergence from 1 seedling/m² to 1 seedling 10 m^?2, a major improvement for Gamba Grass management. These residual herbicide treatments significantly reduced the population density of Gamba Grass for at least 5 months after emergence. The physical and biological treatments did not have a significant effect on seedling emergence. This significant reduction in Gamba Grass seedling emergence and survival can substantially improve Gamba Grass management. Reducing re‐colonisation from the soil seed bank using residual herbicides provides a valuable management tool for land managers, integrating readily with established strategies for controlling the mature plants.     

草甘膦对茶树叶片主要生化成分的影响

以金观音茶树为试材,将草甘膦定量施于栽培基质,通过观察叶片的表观药害,并采用超高效液相串联质谱方法测定草甘膦施用前(0天)和施用后(7天和33天)叶片中的农药残留(草甘膦及氨甲基膦酸)及生化成分(游离氨基酸、儿茶素和生物碱)的含量变化,从而科学地评估草甘膦的使用对茶叶质量安全的影响.结果表明:草甘膦施用33天,茶树叶片...