Effects of sublethal herbicides on offspring germination and seedling growth: Redroot pigweed (Amaranthus retroflexus) vs. velvetleaf (Abutilon theophrasti)

A synergistic bacterial pool decomposes tebuthiuron in soil

This study aimed to propose an eco-compatible strategy to mitigate the possible environmental contamination caused by tebuthiuron. Therefore, we screened potential tebuthiuron-degrading microorganisms from conventional (CS) and no-till (NTS) systems producing sugarcane. Then, they were bioprospected for their ability of decomposing the target-molecule at 2.48 mmol g-1 and 4.96 mmol g-1 into CO2 via respirometry. Integrating microbiota from CS and NTS into an advantageously synergistic bacterial pool produced the highest specific-growth rate of CO2 of 89.60 mg day-1, so outstripped the other inoculum. The bacterial CN-NTS framework notably stabilized the sigmoidal Gompertz curve on microbial degradation earliest and enabled the seeds of Lactuca sativa to germinate healthiest throughout ecotoxicological bioassay for cross-validation. Our study is preliminary, but timely to provide knowledge of particular relevance to progress in the field's prominence in remediating terrestrial ecosystems where residual tebuthiuron can persist and contaminate. The analytical insights will act as an opening of solutions to develop high-throughput biotechnological strategies for environmental decontamination.

Assessment of the efficacy of slow-release formulations of the tribenuron-methyl herbicide in field-grown spring wheat

The efficacy of slow-release formulations of tribenuron-methyl (TBM) embedded in the matrix of degradable poly(3-hydroxybutyrate) blended with birch wood flour [polymer/wood flour/herbicide 50/30/20 wt.%] was compared with the efficacy of TBM as the active ingredient of the Mortira commercial formulation, which was applied as post-emergence spray to treat spring wheat cv. Novosibirskaya 15. The study was conducted in Central Siberia (in the environs of the city of Krasnoyarsk, Russia) from May to August 2020. The biological efficacy of the embedded TBM was 92.3%, which was considerably higher than the biological efficacy of the Mortira formulation used as the post-emergence spray (15.4%). The embedding of TBM into degradable blended matrix enabled long-duration functioning of this unstable herbicide in soil. The sensitivity of weed plants to TBM differed depending on the species. TBM was more effective against A. retroflexus and A. blitoides, which were killed at an earlier stage, than against C. album and G. aparine, whose percentage increased in the earlier stage and which were controlled by the herbicide less effectively and at later stages. On the plot treated with the embedded herbicide, the parameters of the wheat yield structure were the best, and the total yield was the highest: 3360 ± 40 kg/ha versus 3250 ± 50 kg/ha in the group of plants sprayed with the Mortira formulation. The grain produced in all groups was of high quality and was classified as Grade 1 food grain. The highest quality parameters (grain hectoliter mass, gluten, and protein contents) were obtained in the group of plants treated with the embedded herbicide. The study of the embedded TBM confirmed the high efficacy of the experimental formulation.

Identification and Comprehensive Evaluation of Resistant Weeds Using Unmanned Aerial Vehicle-Based Multispectral Imagery

Atrazine is one of the most widely used herbicides in weed management. However, the widespread use of atrazine has concurrently accelerated the evolution of weed resistance mechanisms. Resistant weeds were identified early to contribute to crop protection in precision agriculture before visible symptoms of atrazine application to weeds in actual field environments. New developments in unmanned aerial vehicle (UAV) platforms and sensor technologies promote cost-effective data collection by collecting multi-modal data at very high spatial and spectral resolution. In this study, we obtained multispectral and RGB images using UAVs, increased available information with the help of image fusion technology, and developed a weed spectral resistance index, WSRI = (RE-R)/(RE-B), based on the difference between susceptible and resistant weed biotypes. A deep convolutional neural network (DCNN) was applied to evaluate the potential for identifying resistant weeds in the field. Comparing the WSRI introduced in this study with previously published vegetation indices (VIs) shows that the WSRI is better at classifying susceptible and resistant weed biotypes. Fusing multispectral and RGB images improved the resistance identification accuracy, and the DCNN achieved high field accuracies of 81.1% for barnyardgrass and 92.4% for velvetleaf. Time series and weed density influenced the study of weed resistance, with 4 days after application (4DAA) identified as a watershed timeframe in the study of weed resistance, while different weed densities resulted in changes in classification accuracy. Multispectral and deep learning proved to be effective phenotypic techniques that can thoroughly analyze weed resistance dynamic response and provide valuable methods for high-throughput phenotyping and accurate field management of resistant weeds.

Transcriptome analysis reveals gene responses to herbicide, tribenuron methyl, in Brassica napus L. during seed germination

Background

Tribenuron methyl (TBM) is an herbicide that inhibits sulfonylurea acetolactate synthase (ALS) and is one of the most widely used broad-leaved herbicides for crop production. However, soil residues or drifting of the herbicide spray might affect the germination and growth of rapeseed, Brassica napus, so it is imperative to understand the response mechanism of rape to TBM during germination. The aim of this study was to use transcriptome analysis to reveal the gene responses in herbicide-tolerant rapeseed to TBM stress during seed germination.

Results

2414, 2286, and 1068 differentially expressed genes (DEGs) were identified in TBM-treated resistant vs sensitive lines, treated vs. control sensitive lines, treated vs. control resistant lines, respectively. GO analysis showed that most DEGs were annotated to the oxidation-reduction pathways and catalytic activity. KEGG enrichment was mainly involved in plant-pathogen interactions, α-linolenic acid metabolism, glucosinolate biosynthesis, and phenylpropanoid biosynthesis. Based on GO and KEGG enrichment, a total of 137 target genes were identified, including genes involved in biotransferase activity, response to antioxidant stress and lipid metabolism. Biotransferase genes, CYP450, ABC and GST, detoxify herbicide molecules through physical or biochemical processes. Antioxidant genes, RBOH, WRKY, CDPK, MAPK, CAT, and POD regulate plant tolerance by transmitting ROS signals and triggering antioxidant enzyme expression. Lipid-related genes and hormone-related genes were also found, such as LOX3, ADH1, JAZ6, BIN2 and ERF, and they also played an important role in herbicide resistance.

Conclusions

This study provides insights for selecting TBM-tolerant rapeseed germplasm and exploring the molecular mechanism of TBM tolerance during germination.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07614-1.

Efficacy of Slow-Release Formulations of Metribuzin and Tribenuron Methyl Herbicides for Controlling Weeds of Various Species in Wheat and Barley Stands

The herbicidal activity of long-acting formulations of metribuzin and tribenuron methyl herbicides embedded in granules prepared from a mixture of degradable poly(3-hydroxybutyrate) and birch wood flour was studied in laboratory-grown weeds of various species and in wheat Triticum aestivum and barley Hordeum vulgare stands infested by weeds. The constructed formulations effectively suppressed all species of weeds studied. The biological effectiveness of herbicide formulations toward intact plants in wheat and barley stands infested with weeds was close to 100%, which was significantly higher than the effect of their free forms. The more effective suppression of weeds by embedded herbicides was beneficial for the growth of crops whose aboveground biomass was 8-13 to 20% greater than that of the crops in the treatments with free herbicides. Embedded metribuzin and tribenuron methyl exhibit sustained and pronounced herbicidal activity and are effective for pre-emergence soil application for crops infested with weeds of various species.

Biological effects of the free and embedded metribuzin and tribenuron-methyl herbicides on various cultivated weed species

The present study addresses the herbicidal activity and biological effects of the metribuzin (MET) and tribenuron-methyl (TBM) herbicides used to control various weed species (Amaranthus retroflexus, Sinapis arvensis, and Leucanthemum maximum). The effects of the free herbicides and the herbicides embedded in granules of degradable polymer poly-3-hydroxybutyrate [P(3HB)] blended with birch wood flour were compared. Metribuzin, regardless of the form, caused 100% mortality of the three weeds by day 21. The herbicidal activity of tribenuron-methyl was lower than that of metribuzin, but the embedded TBM was superior to the free herbicide in the length and strength of its action on the weeds. Both metribuzin forms dramatically decreased the main parameters of fluorescence: maximum quantum yield of photosystem-II [Y(II)_max], maximum quantum yield of non-photochemical quenching [Y(NPQ)_max], and maximum rate of non-cyclic electron transport [ETR_max] and concentrations of chlorophyll a and b. The effect of the embedded TBM on the photosynthetic activity of the weeds was lower in the first two weeks of the growth of herbicide-treated plants but lasted longer than the effect of the free TBM and increased over time. Embedding of metribuzin in the matrix of degradable blend did not decrease its herbicidal activity.

Effects of herbicides on non-target plant species diversity and the community composition of fallow fields in northern China

Despite the important ecological and agricultural production value of fallow field vegetation in agricultural landscapes, it is often affected by herbicide drift and runoff from neighboring sprayed fields. However, little is known about the impact of herbicides on the non-target plant community of fallow fields. In this study, the plant community of fallow fields was investigated following annual sublethal exposure to atrazine or tribenuron-methyl by a 3-year (2014–2016) randomized block field study. The two herbicides both changed the species composition, reduced the number of plant species and the relative frequencies of some plants, and significantly reduced the Margalef species richness index and Shannon’s diversity index of the plant community in the fallow field. The effects of the two herbicides on species number and community composition were not consistent. The effects of herbicide doses less than the recommended field application concentration (RFAC) on the plant community composition and community diversity of the fallow field were not lower than the effects of the RFAC of the herbicides. Indeed, doses less than the RFAC had an even greater impact on the community diversity than the RFAC of the herbicides. As the number of years of herbicide application increased, the effects of the herbicides on the plant community diversity did not increase compared to the effects of the blank control, and the herbicides did not change the functional composition of the plant communities in the fallow field. Our results suggest that the ecological risks of herbicides, even at low concentrations, on non-target wild plant communities in agricultural landscapes should not be neglected in the development of practical plant diversity conservation strategies.