Invasive weeds cause substantial ecological, economical, and social problems, and are currently being controlled by herbicide applications. However, how herbicides affect other ecological interactions of invasive weeds, including their symbiosis with arbuscular mycorrhizal fungi (AMF), remains poorly understood. In this study, we therefore conducted field investigation to understand how the herbicide glyphosate affects the AMF diversity in the rhizosphere of the invasive weed Solidago canadensis. We also performed a greenhouse experiment to study if AMF can contribute to herbicide resistance. The results showed that the AMF colonization rate was significantly higher in S. canadensis when exposed to glyphosate in the field or in greenhouse settings. AMF diversity was also found to be higher in the rhizosphere soil after glyphosate application in the field. AMF colonization in greenhouse experiments also positively correlated with plant growth and reduced amounts of damaged leaves and the plant's content of the stress markers flavonol and anthocyanin. Chlorophyll content was significantly enhanced by AMF colonization, regardless of glyphosate application. These results indicate that herbicide can promote AMF colonization and diversity, and that AMF can enhance the herbicide resistance of S. canadensis. These findings suggest that herbicide application may promote the spread of S. canadensis through enhanced microbial interactions, posing new eco-environmental risks.

Dryland degradation is a global problem, destabilizing ecosystems and disrupting coupled human-natural systems in arid regions. Degradation, caused by livestock grazing, wildfire, vehicles, construction, climate perturbances, and other surface disturbances, open space for invasive plants to establish while damaging soils, biological soil crusts (biocrusts), and vascular plant communities. Due to the scale of invasive plant infestations and the cost of mechanical control, invasive plants are commonly treated with herbicides, but little is known about the consequences of herbicides on biocrust. Biocrusts are communities of biota that aggregate the soil surface and provide ecosystem services, including mitigating soil erosion and fixing nitrogen, making biocrust a promising and emerging tool to counteract degradation. To test biocrust compatibility with standard herbicide treatments, we conducted a organisms (mosses and the lichens Placidium/Clavascidium and Enchylium). We found that response varied based on the herbicide mechanistic family, with the magnitude of response varying for biocrust organisms. Mosses treated with amino acid disrupters (glyphosate and imazapic) had 65-75% less health tissue area than controls after 3 months. Surprisingly, mosses treated with synthetic auxins (2,4-D and aminopyralid) had a similar or slightly greater healthy area. Blue dye and surfactants had no effect on any tested biocrust organism. This greenhouse study suggests that through careful selection of herbicides, biocrust restoration could be simultaneously used with herbicide treatments of invasive plants to improve soil health.

Taking 4-year-old Rosa roxburghii seedlings as the research object, the effects of glyphosate in orchards on the nutritional growth, leaf structure, photosynthetic characteristics, fluorescence characteristics and fruits were studied by soil application of glyphosate. The results show that new leaf morphology was deformed and yellowed, stomatal density and stomatal index were significantly decreased, MDA content was increased, and SOD, CAT and LOX activities were significantly increased after 15 days of glyphosate treatment. PN, GS, Fv/Fm, ABS/RC, TRo/RC, ETo/RC and DIo/RC of new leaves were significantly reduced with increasing glyphosate concentrations. New leaf photosynthetic organ development and photosynthetic pigment accumulation were affected under glyphosate, resulting in inhibition of photosynthesis, leading to a decrease in photosynthetic rate and ultimately affecting fruit development. The protective enzyme activity of new leaves was activated after glyphosate spraying, thereby enhancing its adaptability to adversity, while damage to PSII was reduced by increasing the energy dissipated through heat dissipation and reducing excess excitation energy under low dose glyphosate treatment. The adaptability of new leaf cell membranes could be improved, and thus the damage caused by glyphosate was mitigated in Rosa roxburghii orchards when glyphosate was applied at concentrations of less than 1.84 kg.ha-1.

Fresh market vegetables are an essential component of the human diet. Maximizing yield is critical, and to achieve this goal, fi elds must be weed-free when vegetable crops are planted. Historically, removing emerged weeds just before planting has been accomplished using the herbicide glyphosate. However, recent research has indicated that glyphosate applied to sandy, low-organic-matter soils just before transplanting vegetables can be injurious. Two fi eld experiments investigated 1) the response of transplanted squash to the residual activity of glyphosate, and 2) the effects of implementing tillage, irrigation, or extending the plant-back interval after application and before planting to mitigate injury from glyphosate. Glyphosate applied at 1.3, 2.5, or 3.8 kg ae/ha 1 day before transplanting injured squash 13%, 29%, and 53%, respectively; extending the interval between application and planting to 7 days reduced injury to 1%, 11%, and 28% at the same rates. An interaction between application rate and planting interval was also observed on squash plant widths and biomass, as well as early-season and total marketable fruit numbers and weights. Total marketable fruit number was reduced 29% and 52% by glyphosate at 2.5 or 3.8 kg ae/ha, respectively, and a reduction in fruit production of 36%, 28%, and 23% was observed when glyphosate was applied 1, 4, or 7 days before transplanting, respectively. In a separate study, light tillage (5 cm deep) was the most effective cultural practice evaluated because it eliminated damage by glyphosate. Overhead irrigation of 0.6 cm was not beneficial fi cial in mitigating injury by glyphosate. Recommendations from this research will help vegetable growers avoid injury from the residual activity of glyphosate through a FIFRA 2(ee) recommendation label.

Phosphonates (PHTs), organic compounds with a stable C-P bond, are widely distributed in nature. Glyphosate (GP), a synthetic PHT, is extensively used in agriculture and has been linked to various human health issues and environmental damage. Given the prevalence of GP, developing cost-effective, on-site methods for GP detection is key for assessing pollution and reducing exposure risks. We adopted Agrobacterium tumefaciens CHLDO, a natural GP degrader, as a host and the source of genetic parts for constructing PHT biosensors. In this bacterial species, the phn gene cluster, encoding the C-P lyase pathway, is regulated by the PhnF transcriptional repressor. We selected the phnG promoter, which displays a dose-dependent response to GP, to build a set of whole-cell biosensors. Through stepwise genetic optimization of the transcriptional cascade, we created a whole-cell biosensor capable of detecting GP in the 0.25-50 mu M range in various samples, including soil and water.