Search Results (30)

Background: Weed herbicide resistance is a serious problem in crop protection globally. Giant foxtail (Setaria faberi R.A.N. Herrm.) populations cannot be controlled by acetolactate synthase (ALS)-inhibiting herbicides in a few corn (Zea mays L.) monoculture fields. Methods: Five putative resistant giant foxtail populations, originating from corn monoculture fields in northeastern Greece, were evaluated for possible evolution of ALS-inhibitor resistance (nicosulfuron, rimsulfuron). The resistance ratio, the underlying resistance mechanism, and its impact on competitive ability against corn were studied. Results: The whole-plant rate-response assays showed that these populations were resistant (R) to the sulfonylureas nicosulfuron and rimsulfuron, but susceptible (S) to imidazolinone imazamox, triketone 4-hydroxyphenylpyruvate dioxygenase inhibitor tembotrione, and acetyl-CoA carboxylase inhibitor cycloxydim. The sequencing of the ALS gene did not reveal the presence of resistance-associated point mutations, indicating that the resistance was probably not target-site mediated. This was confirmed by the application of piperonyl butoxide two hours before nicosulfuron application, which reversed the resistance in all R giant foxtail populations, supporting the evidence of enhanced metabolism-mediated resistance. The competition study between corn and R or S giant foxtail populations indicated no stable trend reduction in corn traits, suggesting that the resistance mechanism was not associated with the competitive ability of the R populations. The novel ALS genotype in S. faberi, characterized for the first time and submitted to the GenBank database with accession number PV016837, indicated a closer genetic relationship with the S. viridis ALS gene than with S. italica. Conclusions: Five giant foxtail populations have evolved metabolism-based resistance to the ALS-inhibiting herbicides nicosulfuron and rimsulfuron. Full article

Rhizobial bacteria perform a number of extremely important functions in the soil environment. In addition to fixing molecular nitrogen and transforming it into a form available to plants, they participate in the circulation of elements and the decomposition of complex compounds present in the soil, sometimes toxic to other organisms. This review article describes the molecular mechanisms occurring in the most diverse group of rhizobia, the genus Bradyrhizobium, allowing these bacteria to adapt to selected substances found in the soil. Firstly, the adaptation of bradyrhizobia to low and high concentrations of elements such as iron, phosphorus, sulfur, calcium and manganese was shown. Secondly, the processes activated in their cells in the presence of heavy metals such as lead, mercury and arsenic, as well as radionuclides, were described. Additionally, due to the potential use of Bradyrhziobium as biofertilizers, their response to pesticides commonly used in agriculture, such as glyphosate, sulfentrazone, chlorophenoxy herbicides, flumioxazine, imidazolinone, atrazine, and insecticides and fungicides, was also discussed. The paper shows the great genetic diversity of bradyrhizobia in terms of adapting to variable environmental conditions present in the soil. Full article

The Clearfield^® technology is an useful tool for controlling weedy rice due to the effectiveness of imazamox and the cultivation of rice varieties resistant to imidazolines. However, residual imazamox in the soil probably causes phytotoxicity to subsequent non-resistant rice crops. We previously found that pyrroloquinoline quinone (PQQ), a bioactive elicitor, can enhance rice tolerance to imazamox. In this study, we explored the molecular mechanism of PQQ-mediated rice tolerance to imazamox by RNA-seq analysis, real-time quantitative PCR (RT-qPCR) assay, and enzyme activity assay. The results indicated that compared to imazamox at 66.7 mg a.i./L (IMA) alone, rice plants treated with imazamox at 66.7 mg a.i./L and PQQ at 0.66 mg a.i./L (IMA + PQQ) exhibited significantly reduced sensitivity to imazamox. Seven days post-treatment, IMA + PQQ-treated rice plants showed partial chlorosis and leaf curling, but IMA-treated rice plants had severe wilting and died. The fresh weight inhibition rate was 29.3% in the IMA + PQQ group, significantly lower than that of 56.6% in the IMA group alone. RNA-seq analysis showed differentially expressed genes were mainly involved in phenylpropanoid biosynthesis, diterpenoid biosynthesis, and MAPK signaling pathways in response to IMA + PQQ treatment. Both RNA-seq analysis and RT-qPCR assay showed that the expression of OsCATB gene in the catalase (CAT) gene family was upregulated at 12 h, the expression of OsGSTU1 gene was upregulated at 12, 24, and 48 h, while the expressions of OsABCB2, OsABCB11, and OsABCG11 genes were upregulated at 24 and 48 h. Enzyme activity assays revealed that the activity of superoxide dismutase in the IMA + PQQ group was increased by 47.45~120.31% during 12~72 h, compared to that in the IMA group. CAT activity in the IMA + PQQ group was increased by 123.72 and 59.04% at 12 and 48 h, respectively. Moreover, malondialdehyde levels indicative of oxidative damage were consistently lower in IMA + PQQ-treated plants, with a reduction of 46.29, 11.37, and 14.50% at 12, 36, and 72 h, respectively. Overall, these findings discover that PQQ has potential in reducing imazamox phytotoxicity in rice by enhancing antioxidant enzyme activities and regulating oxidative stress responses. They will provide valuable strategies for improving imazamox tolerance in crops. Full article

Resistance of agricultural crops to herbicides is an important topic that concerns many researchers. One of the most popular groups of herbicides is the imidazolinone group. Resistant forms of crops such as wheat (Triticum aestivum L.), sunflower (Helianthus annuus L.), corn (Zea mays L.), rice (Oryza sativa L.) and oilseed rape (Brassica napus L.) have been developed to this group of herbicides. All crops resistant to this group of herbicides have the commercial name Clearfield^®. In this review, the information concerning oilseed rape resistance to the imidazolinone group of herbicides is collected and summarized; it will be useful for breeders and researchers engaged in this direction. This review touches upon the topic of mechanisms of oilseed rape resistance to imidazolinones. Mutation variants known to date, which provide resistance to this group of herbicides, are described, and known molecular markers of them are presented. Approaches to the selection of oilseed rape for resistance to the imidazolinone group of herbicides are mentioned. Various methods of utilizing imidazolinone resistance to improve the purity of hybrid seeds are also considered. Full article

Weedy rice is the most challenging weed species to remove in rice production. We found a novel phenotype of seedling leaves which rapidly generates necrotic spots in response to imidazolinone herbicides in weedy rice, but its influencing factors and formation basis are still unknown. In this study, we used the leaf necrotic spot-producing type of weedy rice as the material. First, leaf necrotic spots were defined as physiological and vacuole-mediated cell necrosis by microscopic examination. The imazethapyr concentration was positively correlated with the degree of necrotic spots occurring, while the action site was in accordance with necrosis using herbicide stability tests combined with fluorescence parameters. Furthermore, transcriptome analysis revealed significant differences in the gene expression of endoplasmic reticulum stress and the lipid metabolism membrane structure damage pathway during necrosis, as confirmed by transmission electron microscopy. The light–temperature test also showed that high temperature and intense light could promote the appearance of necrotic spots. These experimental results are helpful in clarifying the process and basis of imazethapyr in inducing the rapid generation of necrotic spots in rice leaves and providing new insight into understanding the mechanism of response to imidazolinone herbicides and the control of weedy rice. Full article

Rice is a staple food for more than half of the global population due to its food security and sustainable development. Weeds compete with crops for sunlight and indispensable nutrients, affecting the yield and quality of crops. Breeding herbicide-tolerant rice varieties paired with herbicide application is expected to help with weed control. In this study, 194 Japonica/Geng rice varieties or lines collected from the Huanghuaihai region of China were screened by Kompetitive Allele-Specific PCR (KASP) markers based on four mutation sites within OsALS1 (LOC_Os02g30630), which is the target of imidazolinone (IMI) herbicides. Only the OsALS1^627N haplotype was identified in 18 varieties, including the previously reported Jingeng818 (JG818), and its herbicide resistance was validated by treatment with three IMIs. To investigate the origin of the OsALS1^627N haplotype in the identified varieties, six codominant PCR-based markers tightly linked with OsALS1 were developed. PCR analysis revealed that the other 17 IMI-tolerant varieties were derived from JG818. We randomly selected three IMI-tolerant varieties for comparative whole-genome resequencing with known receptor parent varieties. Sequence alignment revealed that more loci from JG818 have been introduced into IMI-tolerant varieties. However, all three IMI-tolerant varieties carried clustered third type single nucleotide polymorphism (SNP) sites from unknown parents, indicating that these varieties were not directly derived from JG818, whereas those from different intermediate improved lines were crossed with JG818. Overall, we found that only OsALS1^627N from JG818 has been broadly introduced into the Huanghuaihai region of China. Additionally, the 17 identified IMI-tolerant varieties provide alternative opportunities for improving such varieties along with other good traits. Full article

Nowadays, large areas of agricultural land are contaminated with chemical plant-protection products. Agricultural soils are also susceptible to oil pollution as a result of accidents on oil pipelines. Bioremediation of such soils from oil with the help of hydrocarbon-oxidizing bacteria is hindered by the presence of additional pollutants such as herbicides. In this work, seven strains of Pseudomonas were isolated and identified, which showed differences in ability of oil biodegradation (32.7–77.3%). All strains showed resistance to herbicides based on 2,4-D and substances from the class of imidazolinones, possessed phosphate-solubilizing and nitrogen-fixing activity, and produced indolyl-3-acetic acid (305–1627 ng/mL culture liquid). They stimulated the growth of barley and clover in soil with oil, as well as the growth of clover in soil with herbicide. In a vegetative experiment (duration 30 days, initial oil content in soil 2% wt., herbicide based on imazethapyr 0.002% wt.) of barley plants and P. alcaligenes UOM 10 or P. frederiksbergensis UOM 11, oil degradation was 48.1–52.7%, the same strains and clover plants, 37.9–38.6%. The studied bacteria have the potential to be used in the bioremediation of oil-contaminated agricultural soils, including in combination with phytomeliorant plants. Full article

A simultaneous analytical method, which used LC/MSMS for imidazolinone herbicides from livestock products (egg, milk, beef, pork, and chicken) for monitoring, was developed with a QuEChERS preparation. A weighed sample (5 g) in a 50 mL conical tube was added to 0.1 M potassium phosphate dibasic solution (5 mL) and shaken for 10 min. After shaking, 0.5 mL of 6 N HCl and 5 mL of acetonitrile were added, and this solution was shaken for 10 min. Additionally, QuEChERS extraction salts (original method, 4 g MgSO₄, 1 g NaCl) were added to the sample in a 50 mL conical tube. The mixture was strongly shaken for 1 min and centrifuged at 3000× g for 10 min. The acetonitrile layer was purified with dSPE (150 mg MgSO₄, 25 mg C₁₈) and was centrifuged at 13,000× g for 5 min. The supernatant was filtered with a membrane filter (pore size: 0.2 μm) before analysis. The ME (%, matrix effect) range for almost all analytes was −6.56 to 7.11%. MLOD (method limit of detection) and MLOQ (method limit of quantitative) values were calculated by the S/N ratio. MLOQs were 0.01 mg/kg. The linear correlation coefficients (R²) were >0.99 with the range of 0.5~25 μg/kg for all of the imidazolinone herbicides. The recoveries (of imidazolinone herbicides) were in the range of 76.1~110.6% (0.01 mg/kg level), 89.2~97.1% (0.1 mg/kg level), and 94.4~104.4% (0.5 mg/kg level). These are within the validation criteria (to recover 70–120% with RSD <20%). The method demonstrated the simple, rapid, high throughput screening and quantitative analysis of imidazolinone herbicide residues for monitoring in livestock products. Full article

In the synthesis of imidazolinone herbicides, 2-Amino-2,3-dimethylbutyramide (ADBA) is an important intermedium. In this study, the recombinant production of nitrile hydratase (NHase) in Escherichia coli for ADBA synthesis was explored. A local library containing recombinant NHases from various sources was screened using a colorimetric method. NHase from Pseudonocardia thermophila JCM3095 was selected, fused with a His-tag and one-step purified. The enzymatic properties of recombinant NHase were studied and indicated robust thermal stability and inhibition of cyanide ions due to substrate degradation. After systematic optimization of fermentation conditions, the OD₆₀₀ (optical density at 600 nm), enzyme activity and specific activity of recombinant strain E. coli BL21(DE3)/pET-28a+NHase reached 19.4, 3.72 U/mL and 1.04 U/mg protein at 42 h, representing 5.86-, 26.6- and 4-fold increases, respectively. These results offered an efficient recombinant whole-cell biocatalyst for ADBA synthesis. Full article

Cases of weed resistant to herbicides have changed the dynamics of agricultural areas in Brazil, and in recent years, Erigeron species have caused major problems to farmers in the country, mainly in relation to the ineffectiveness of herbicide treatments used. The objective of this study was to confirm the cross-resistance to ALS inhibitors in populations of Erigeron sumatrensis as well as to investigate the existence of mutations in the site of action of ALS-inhibiting herbicides. To do this, 30 populations collected in the 2016/2017 crop season were grown in a greenhouse. Dose–response (chlorimuron-ethyl and cloransulam-methyl), inhibition of cytochrome P-450 with malathion, and ALS gene sequencing experiments were carried out in the F1 generations of two fleabane populations. The results proved the cross-resistance to chlorimuron-ethyl and cloransulam-methyl herbicides applied in the post-emergence of the resistant population of E. sumatrensis. The higher activity of P450 enzymes is unlikely responsible for the resistance of the population studied. The resistance mechanism found in R was the target site mutation Pro197Ser at the ALS gene. This is the first study in Brazil to identify a target-site change as a survival mechanism in E. sumatrensis for the resistance to ALS-inhibiting herbicides. Full article

Detections of the regulated noxious parasitic weed branched broomrape (Phelipanche ramosa) in California tomato fields have led to interest in eradication, sanitation, and management practices. Researchers in Israel developed a decision-support system and herbicide treatment regime for management of Egyptian broomrape (P. aegyptiaca) in tomato. Research was conducted in 2019 and 2020 to evaluate whether similar treatments could be used to manage branched broomrape in California processing tomatoes and to provide registration support data for the herbicide use pattern. Treatment programs based on preplant incorporated (PPI) sulfosulfuron and chemigated imazapic were evaluated in 2019 and 2020 to determine safety on the processing tomato crop and on common rotational crops. Three single-season tomato safety experiments were conducted and a single rotational crop study was conducted in which a tomato crop received herbicide treatments in 2019 and several common rotational crops were planted and evaluated in 2020 in a site without branched broomrape. In 2020, an efficacy study was conducted in a commercial tomato field known to be infested with branched broomrape to evaluate the efficacy of PPI sulfosulfuron and chemigated imazapic, imazapyr, imazethapyr, and imazamox. After two field seasons, sulfosulfuron and imazapic appeared to have reasonable crop safety on tomato in California; however, rotational crop restrictions will need to be considered if sulfosulfuron is used to manage branched broomrape. In the efficacy study, there was a trend in which the sulfosulfuron and imidazolinone treatments had fewer broomrape shoots per plot than the grower standard treatments, however, none were fully effective and there were no significant differences among the various sulfosulfuron and imidazolinone treatment combinations. Additional research is needed to optimize the treatment timing for management of branched broomrape in this cropping system. Because of registration barriers with imazapic in the California market, future research will focus on treatment combinations of PPI sulfosulfuron and chemigated imazamox rather than imazapic. Full article

Chickpea (Cicer arietinum L.) is an important crop in crop-rotation management in Israel. Imidazolinone herbicides have a wide spectrum of weed control, but chickpea plants are sensitive to acetohydroxyacid synthase (AHAS; also known as acetolactate synthase [ALS]) inhibitors. Using the chemical mutagen ethyl methanesulfonate (EMS), we developed a chickpea line (M2033) that is resistant to imidazolinone herbicides. A point mutation was detected in one of the two genes encoding the AHAS catalytic subunit of M2033. The transition of threonine to isoleucine at position 192 (203 according to Arabidopsis) conferred resistance of M2033 to imidazolinones, but not to other groups of AHAS inhibitors. The role of this substitution in the resistance of line M2033 was proven by genetic transformation of tobacco plants. This resistance showed a single-gene semidominant inheritance pattern. Conclusion: A novel mutation, T192I (T203I according to Arabidopsis), providing resistance to IMI herbicides but not to other groups of AHAS inhibitors, is described in the AHAS1 protein of EMS-mutagenized chickpea line M2033. Full article

Oilseed rape production is under pressure due to a limited availability of herbicides. Therefore, the performance in terms of management intensity (MI) and herbicide strategy (HS) and the involved yield formation was evaluated in a two-year Clearfield^® oilseed rape field experiment. Furthermore, weed density and weed composition were also investigated. The variants of MI were standard sowing density (StS; seed rate: 50 seeds m⁻², primary tillage: plow, row width: 12 cm), reduced sowing density (RD; seed rate: 25 seeds m⁻², primary tillage: plow, row width: 50 cm), and strip-till (ST; seed rate: 25 seeds m⁻², primary tillage: strip tillage, row width: 50 cm). The variants of HS were preemergence strategy (PES; application of dimethachlor, napropamide, clomazone in preemergence and application of prapaquizafop in postemergence) and Clearfield^® strategy (CLS; application of imazamox, quinmerac in preemergence, no postemergence herbicide application). In the first year of the trial, there were no interactions between the factors in terms of grain yield. Grain yield in StS was 3.85 t and 5.2% significantly lower than in ST, and the value of RD was not significantly different from StS and ST. Grain yield in CLS was 3.7 t and 2.7% lower than in PES. In the second year of the trial, the grain yield in ST CLS was significantly lower, and there were no significant differences between the other variants. Higher weed emergence was observed in CLS RD (2.7 to 4 times higher weed density compared to PES RD) and CLS ST (2.8 to 4.5 times higher weed density compared to PES ST). No significant differences existed between StS PES and StS CLS in both trial years. The Clearfield^® system offers significant advantages in the control of cruciferous weeds. Although these did not occur on the trial fields, the Clearfield^® system in this study showed to be an alternative to the more common pre-emergence system, especially with regard to the parameter grain yield. Full article

Wild sunflower (Helianthus annuus L.) is an invasive species widely distributed in several regions of the world, where it shares a large area with domesticated sunflower. The imidazolinone-tolerant sunflower enables the control of problematic weeds (such as Xanthium spp., Brassica spp., wild sunflower) with imidazolinone herbicides (Clearfield^® production system) in cultivated sunflower crops, but could facilitate the gene transfer of herbicide resistance, from cultivated sunflower to wild sunflower, generating hard-to-control weed biotypes or herbicide-resistant populations. The development of new practices that involve the selective inhibition of reproduction structures, such as pollen granules, could be an innovative strategy to minimize outcrossing and the origin of weed–crop hybrids in Clearfield^® production systems. In this study, the effects of mugwort (Artemisia vulgaris L.) aqueous extract on cytosolic Ca²⁺ and the germination of pollen grains collected from conventional, wild and IMI-tolerant sunflower were tested. The results showed that mugwort deregulated Ca²⁺ homeostasis and markedly reduced the germination of conventional and wild sunflower pollen, but not IMI-tolerant pollen. The HPLC analysis revealed the presence of phenolic acids belonging to the hydroxycinnamic and benzoic classes in the mugwort extract. Hydroxycinnamic acids (caffeic and ferulic) deregulated the cytosolic Ca²⁺ of conventional and wild sunflower pollen, but not those which were IMI-tolerant, similar to mugwort extract. Selective inhibition of wild sunflower pollen in the Clearfield^® sunflower crop contributes to a possible new weed management strategy, reducing the wild sunflower reproduction by seed, minimizing the potential risks of outcrossing with the formation of weed–crop hybrids. The Ca²⁺ selective chelating activity of caffeic or ferulic acids provides elements to be investigated for their possible use as an alternative to mugwort extract. Full article

The consumption of water and food contaminated by pathogens is a major cause of numerous diseases and deaths globally. To control pathogen contamination and reduce the risk of illness, a system is required that can quickly detect and monitor target pathogens. We developed a simple and reproducible strategy, termed three-way junction (3WJ)-induced transcription amplification, to detect target nucleic acids by rationally combining 3WJ-induced isothermal amplification with a light-up RNA aptamer. In principle, the presence of the target nucleic acid generates a large number of light-up RNA aptamers (Spinach aptamers) through strand displacement and transcription amplification for 2 h at 37 °C. The resulting Spinach RNA aptamers specifically bind to fluorogens such as 3,5-difluoro-4-hydroxybenzylidene imidazolinone and emit a highly enhanced fluorescence signal, which is clearly distinguished from the signal emitted in the absence of the target nucleic acid. With the proposed strategy, concentrations of target nucleic acids selected from the genome of Salmonellaenterica serovar Typhi (S. Typhi) were quantitatively determined with high selectivity. In addition, the practical applicability of the method was demonstrated by performing spike-and-recovery experiments with S. Typhi in human serum. Full article