Search Results (55)

Barnyard grass, a widespread and persistent weed in rice paddies, belongs to the same family as rice and may act as a bridge host for the rice blast fungus. This study utilized comparative genomics to analyze six Pyricularia oryzae strains isolated from barnyard grass (Baicao series) and rice (GDYJ7 and ZJX18), integrating pathogenicity assays, whole-genome sequencing, and functional annotation. Pathogenicity tests demonstrated host specificity, as Baicao series strains caused typical lesion symptoms on barnyard grass but not on rice leaves, while GDYJ7 and ZJX18 caused lesions mainly on rice. Genomic analyses indicated that Baicao series strains possessed larger genomes (41.04 Mb to 41.16 Mb) with a higher content of repetitive sequences (6.68% to 7.09%) compared to rice strains GDYJ7 and ZJX18 (38.69 Mb and 39.05 Mb; 3.66% and 3.71% repeats). Phylogenetic analysis confirmed that Baicao series strains represent a grass-infecting pathotype of P. oryzae species, as they were grouped with the established grass-isolated P. oryzae strains, while GDYJ7 and ZJX18 were grouped with rice-isolated P. oryzae strains. However, Baicao series, GDYJ7 and ZJX18 are all relatively distant from P. grisea species. PCR amplification revealed that Baicao series strains harbored significantly fewer avirulence genes (Avr-Pib, Avr-Pizt, PWL3) than GDYJ7 and ZJX18 (Avr-Pib, Avr-Pizt, Avr-Pi9, Avr-Pik, PWL2), with Baicao9 retaining only Avr-Pib. In summary, our results suggested that the genomic sequences of the barnyard grass-isolated strains serve as a valuable resource for the study of P. oryzae strains with differential host preference and provide novel insights into the evolution of pathogen genomes during host adaptation. Full article

The long-term application of traditional chemical herbicides has caused a significant escalation in herbicide resistance of barnyard grass (Echinochloa crus-galli). As an eco-friendly alternative, biological herbicides demonstrate substantial application potential. Acknowledging the growing herbicide resistance of E. crus-galli, this study aimed to screen target bacteria with inhibitory effects on the growth for bio-herbicide development. By using ungerminated E. crus-galli seeds as the screening substrate, a bacterial strain (BFYBC-8) with potent inhibitory activity was isolated and identified as Brucella pseudorignonensis. Pot experiments revealed that inoculation with B. pseudorignonensis BFYBC-8 significantly suppressed E. crus-galli growth, reducing plant height by 16.7% and root length by 85.1%, while markedly inhibiting biomass accumulation. Fluorescent labeling with green fluorescent protein (GFP) showed that BFYBC-8 successfully colonized the root intercellular spaces of E. crus-galli and extended continuously along the tissue matrix. Additionally, the strain’s supernatant metabolic products exhibited exceptional thermostability: inhibitory activity against E. crus-galli was maintained after thermal treatment at 28 °C, 60 °C, 80 °C, and 100 °C. Crucially, the bacterium displayed no toxicity to agronomically important crops such as rice, wheat, and corn. This study highlights B. pseudorignonensis BFYBC-8 as a promising candidate for bioherbicide development and provides an important reference for applying seed-associated pathogenic bacteria in developing bioherbicides for sustainable weed management. Full article

Despite our preliminary research about the inductive effect of exogenous abscisic acid (ABA) on the weed-suppressive activity of rice in a hydroponic system, there is a lack of knowledge regarding the induction mechanism for ABA application to enhance the ability for weed control underground. Here, two pot experiments using rice–barnyard grass mixed culture were conducted to investigate the effects of exogenous ABA treatment on weed inhibition strategies in both allelopathic rice PI312777 (PI) and non-allelopathic rice Lemont (Le). The largest observed weed inhibition changes in the two rice accessions both occurred with the 9 μmol/L ABA treatment. ABA induction on PI significantly increases the inhibitory effect on the plant height of barnyard grass with root contact and root segregation by 25.7% and 19.1%, respectively, with 23.5% increases observed in Le rice with root contact and no significant increases in plants with root segregation with nylon mesh. ABA induction also significantly increased the root distribution in the soil of Le. Compared with the uninduced group, ABA treatment significantly elevated the total amounts of reversibly adsorbed phenolic acids in the two soil layers of PI and the irreversibly adsorbed phenolic acids in Le soil layers. Furthermore, exogenous ABA could change the bacterial composition in rhizosphere soil of the two rice accessions, with the change in the species composition in the rhizosphere soil of the allelopathic rice PI being greater. Importantly, the bacterial compositions (Anaerolineales, Bacteroidales, and Myxococcale) in the PI rhizosphere soil of rice induced by ABA were more related to the contents of reversibly adsorbed phenolic acids in the soil. However, the core bacterial compositions that promote plant growth (Sphingomonadales, Cyanobacteriales, and Rhizobiales) in the Le rhizosphere soil were more related to the contents of irreversibly adsorbed phenolic acids in the soil. These findings suggested that the ABA induction mainly changed root distribution and core bacterial compositions in Le to enhance resource competition, whereas it stimulated the release of reversibly adsorbed phenolic acids to modulate the specific bacterial compositions in rhizosphere soil of PI and to strengthen allelopathic effects. Full article

Barnyard grass is a major noxious weed in paddy fields. Accurate and efficient identification of barnyard grass is crucial for precision field management. However, existing deep learning models generally suffer from high parameter counts and computational complexity, limiting their practical application in field scenarios. Moreover, the morphological similarity, overlapping, and occlusion between barnyard grass and rice pose challenges for reliable detection in complex environments. To address these issues, this study constructed a barnyard grass detection dataset using high-resolution images captured by a drone equipped with a high-definition camera in rice experimental fields in Haicheng City, Liaoning Province. A lightweight field barnyard grass detection model, YOLOv8n-SSDW, was proposed to enhance detection precision and speed. Based on the baseline YOLOv8n model, a novel Separable Residual Coord Conv (SRCConv) was designed to replace the original convolution module, significantly reducing parameters while maintaining detection accuracy. The Spatio-Channel Enhanced Attention Module (SEAM) was introduced and optimized to improve sensitivity to barnyard grass edge features. Additionally, the lightweight and efficient Dysample upsampling module was incorporated to enhance feature map resolution. A new WIoU loss function was developed to improve bounding box classification and regression accuracy. Comprehensive performance analysis demonstrated that YOLOv8n-SSDW outperformed state-of-the-art models. Ablation studies confirmed the effectiveness of each improvement module. The final fused model achieved lightweight performance while improving detection accuracy, with a 2.2% increase in mAP_50, 3.8% higher precision, 0.6% higher recall, 10.6% fewer parameters, 9.8% lower FLOPs, and an 11.1% reduction in model size compared to the baseline. Field tests using drones combined with ground-based computers further validated the model’s robustness in real-world complex paddy environments. The results indicate that YOLOv8n-SSDW exhibits excellent accuracy and efficiency. This study provides valuable insights for barnyard grass detection in rice fields. Full article

Barnyard grass is the most problematic weed in paddy fields in Ningxia. Its substantial morphological variation complicates both identification and control, yet the genetic diversity of barnyard grass infesting paddy fields in Ningxia has not been thoroughly studied. In this research, we analyzed the genetic diversity of 46 barnyard grass populations from Ningxia’s paddy fields based on the assessment of morphological traits, DNA barcoding, and SCoT-targeted gene markers. Nine morphological traits were quantitatively analyzed, among which three phenological traits, i.e., leaf length, stem diameter, and plant height, exhibited notable variations. Correlational analysis revealed a positive relationship between morphological traits and multi-herbicide resistance profiles. To assess genetic diversity, four DNA barcodes (ITS, psbA, matK, and trnL-F) were used, among which ITS demonstrated the strongest potential in single-gene barcoding for barnyard grass species identification. Cluster analysis based on ITS barcode sequences was performed to group the populations into five main categories. Additionally, SCoT marker analysis using six primers was performed to classify the 46 barnyard grass samples into five groups. The results showed that the predominant barnyard grass species in Ningxia were E. colona, E. crus-galli var. Formosensis, E. crusgalli, E. oryzoides, and E. crusgalli var. Zelayensis, with E. colona being the most prevalent. The differences observed between the morphological and molecular marker-based classifications were method-dependent. However, both SCoT molecular marker technology and DNA barcoding contributed to identifying the genetic diversity of barnyard grass. Taken together, our study revealed significant morphological and genetic variations among barnyard grass populations, which correlated with herbicide sensitivity in Ningxia’s paddy fields, underscoring the necessity for an integrated weed management approach to combat this troublesome weed species. Full article

Flusulfinam is a 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicide applied post-emergence (POST) to control Echinochloa crus-galli (L.) P.Beauv., Leptochloa chinensis (L.) Nees, Digitaria sanguinalis (Linn.) Scop. and other annual weeds in directly seeded and transplanted paddy fields in China, registered in September 2024. Notably, compared with other HPPD inhibitors in rice, flusulfinam exhibits consistently high safety in both japonica and indica rice varieties. Meanwhile, flusulfinam has no target-site cross-resistance with traditional acetolactate synthase (ALS)-inhibiting, acetyl-CoA carboxylase (ACCase)-inhibiting, and auxin herbicides. Moreover, as the only heterocyclic-amide-structured herbicide in the HPPD inhibitors, it poses a low risk of metabolic cross-resistance with the other HPPD inhibitors, making it a promising candidate for managing herbicide-resistant weeds in rice fields. In this study, the baseline sensitivity to flusulfinam of E. crus-galli and L. chinensis in paddy fields in China was established using dose–response assays between June and October 2023. Thirty-nine populations of E. crus-galli and forty-three populations of L. chinensis, collected from rice fields across various major rice-producing regions in China, exhibited susceptibility to flusulfinam. The GR₅₀ values ranged from 0.15 to 19.39 g active ingredient (a.i.) ha⁻¹ for E. crus-galli and from 7.82 to 49.92 g a.i. ha⁻¹ for L. chinensis, respectively, far below the field recommended rate of flusulfinam. Meanwhile, the GR₅₀ values of E. crus-galli and L. chinensis to flusulfinam were both distributed as a unimodal curve, with baseline sensitivity (GR₅₀b) of 6.48 g a.i. ha⁻¹ and 22.38 g a.i. ha⁻¹, respectively. The SI₅₀ value showed 129.27-fold and 6.38-fold variability in flusulfinam sensitivity among the 39 E. crus-galli field populations and 43 L. chinensis filed populations, while the variability declined to 2.99-fold and 2.23-fold when the SI₅₀b value was used. This study substantiated the efficacy of flusulfinam against E. crus-galli and L. chinensis in Chinese paddy fields and furnished a benchmark for monitoring temporal variations in the susceptibility of field populations of E. crus-galli and L. chinensis to flusulfinam. Full article

It is possible to reduce herbicide doses while maintaining their high efficacy, provided they are applied with appropriately selected adjuvants and zinc sulphate in a split-dose system. The effect of multicomponent adjuvants and zinc sulphate on the efficacy of bromoxynil + terbuthylazine + nicosulfuron, applied once at full (144 + 400 + 40 mL ha⁻¹) and in a split-dose system (herbicides applied twice, each time after new weed germination) at reduced doses (54 + 150 + 14 mL ha⁻¹, on herbicide efficacy and grain yield was evaluated. At full dose, bromoxynil, terbuthylazine, and nicosulfuron greatly controlled lambsquarters (92–100%). Barnyard grass was controlled by 94–100%, at reduced 67–93%, with adjuvants in a split-dose system, as efficacy increased to 94–100%, and with zinc it increased to 88–91%. The efficacy of herbicides containing zinc sulphate and surfactant was 80–96%, with that of other adjuvants 97–99%. Regardless of the dose and application system, herbicide application increased grain yield by 11.4–13.9 t ha⁻¹ compared to 4.8–5.0 from untreated check. The grain yield from split-dose treatments was comparable to that from plots with the recommended dose. The enhanced herbicide efficacy with adjuvants applied twice, despite higher treatment expenses, led to the development of maize plants and enhanced yields. This may ultimately translate into improved production profitability. Full article

Barnyard grass is one of the most serious rice weeds, often growing near paddy fields and therefore potentially serving as a bridging host for the rice blast fungus. In this study, we isolated three fungal strains from diseased barnyard grass leaves in a rice field. Using a pathogenicity assay, we confirmed that they were capable of causing blast symptoms on barnyard grass and rice leaves to various extents. Based on morphology characterization and genome sequence analyses, we confirmed that these three strains were Epicoccum sorghinum (SCAU-1), Pyricularia grisea (SCAU-2), and Exserohilum rostratum (SCAU-6). The established Avirulence (Avr) genes Avr-Pia, Avr-Pita2, and ACE1 were detected by PCR amplification in SCAU-2, but not in SCAU-1 or SCAU-6. Furthermore, the whole-genome sequence analysis helped to reveal the genetic variations and potential virulence factors relating to the host specificity of these three fungal pathogens. Based on the evolutionary analysis of single-copy orthologous proteins, we found that the genes encoding glycoside hydrolases, carbohydrate esterases, oxidoreductase, and multidrug transporters in SCAU-1 and SCAU-6 were expanded, while expansion in SCAU-2 was mainly related to carbohydrate esterases. In summary, our study provides clues to understand the pathogenic mechanisms of fungal isolates from barnyard grass with the potential to cause rice blast. Full article

Successful seed germination and plant seedling growth often require association with endophytic bacteria. Barnyard grass (Echinochloa crus-galli (L.) P. Beauv.) is a main weed during rice cultivation and has frequently been found in drought-prone fields such as cornfields in recent years. To determine whether endophytic bacteria enhance the survival chances of barnyard grass in dryland conditions, endophytic bacteria were collected from barnyard grass seeds. An endophytic bacterial strain, BC-14, was selected and confirmed as Cronobacter dublinensis based on its morphology, physiology, biochemistry, and genomic information. Moreover, C. dublinensis BC-14 secreted IAA in the Luria–Bertani broth up to 28.44 mg/L after 5 days; it could colonize the roots of barnyard grass. After the inoculation with seeds or the well-mixed planting soil, the bacterium can significantly increase the root length and plant height of barnyard grass under drought conditions. When comparing with the control group on the 28th day, it can be seen that the bacterium can significantly increase the contents of chlorophyll b (up to 7.58 times) and proline (37.21%); improve the activities of superoxide dismutase, catalase, and peroxidase (36.90%, 51.51%, and 12.09%, respectively); and reduce the content of malondialdehyde around 25.92%, which are correlated to the drought tolerance. The bacterial genomic annotation revealed that it contains growth-promoting and drought-resistant functional genes. In a word, C. dublinensis BC-14 can help barnyard grass suppress drought stress, promote plant growth, and enhance biomass accumulation, which is helpful to interpret the mechanism of weed adaptability in dry environments. Full article

Rice allelopathy is a natural method of weed control that is regarded as an eco-friendly practice in agroecology. The root growth of allelopathic rice at the seedling stage plays an important role in its weed control. Our study characterizes a plant hormone that promotes root growth, abscisic acid (ABA), to explore its role in the induction of rice allelopathy. Increasing the root morphology traits (root length, root tip number, and root biomass) in rice using different concentrations of exogenous ABA resulted in increased inhibitory ratios against barnyard grass (Echinochloa crus-galli), both in a hydroponic experiment and pot test. In particular, the relative proportion of induced allelopathy to total allelopathy in non-allelopathic rice Lemont (Le) was higher than that in allelopathic rice PI31277 (PI). The total content of phenolic acid, which is an important allelochemical in rice, as previously reported, was significantly elevated in the root exudates of both PI and LE. The gene expression levels of OsPAL, OsC4H, and OsCOL related to phenolic acid synthesis were also up-regulated, with a higher regulatory fold in PI. ABA also increased the expression of OsKSL4 and CYP75B4 involved in the biosynthesis of momilactone B and tricin. Moreover, low concentrations of exogenous ABA mainly positively regulate the expression of OsIAA11, an AUX/IAA transcription factor gene, in the root of PI and Le. These findings suggest that the application of ABA could significantly enhance the weed-suppressive activity of both rice cultivars through regulating root growth and the synthesis of allelochemicals secreted by rice roots, providing an option for the improvement of rice allelopathy through chemical induction. Full article

Dichloroquinolinic acid is a hormone-type herbicide widely used to control barnyard grass during crop cultivation. However, it can seriously inhibit the growth of susceptible crops, including tobacco, because it degrades slowly under field conditions. Additionally, the mechanism by which it damages crops is unclear. More specifically, the transcriptional changes in plants induced by dichloroquinolinic acid remain unknown. In this study, differentially expressed genes (DEGs) in tobacco treated with dichloroquinolinic acid (varying concentrations and durations) were analyzed and validated to explore the global transcriptome changes. The number of DEGs, which were determined according to the FPKM, varied from 758 to 21,340. The KEGG analysis revealed that many DEGs were involved in starch and sucrose metabolism, phenylpropanoid biosynthesis, photosynthesis, porphyrin and chlorophyll metabolism, and glutathione metabolism. Transcriptomic analyses indicated that dichloroquinolinic acid can inhibit tobacco growth by inhibiting photosynthesis and storage of energy. We discovered that the toxicity mechanism of the hormone herbicide dichloroquinolinic acid differs from that of high concentrations of IAA (Indoleacetic acid), despite studies confirming that the effects of hormone herbicides are consistent with the physiological disturbances and growth inhibition exhibited by plants in IAA overdose. Particularly, dichloroquinolinic acid suppresses photosynthesis while high concentration IAA stimulates nucleotide synthesis and photosynthesis. More importantly, we found by editing the IAA-responsive gene IAA16, tobacco could develop resistance to dichloroquinolinic acid. The results will help clarify plant responses to hormone-type herbicides at the transcriptional level, thereby providing insights into the diversity in the gene’s response to herbicides, the molecular targets of hormone-type herbicides, and the mechanism underlying the susceptibility of tobacco to dichloroquinolinic acid. Accordingly, this study may be helpful for future research to enhance crop resistance to herbicides residues. Full article

The challenge of managing invasive weed species continues to affect the agricultural industry, presenting ecological, economic, and agronomic hurdles that lead to over 100 billion USD in annual crop losses globally. One such concern is the management of Agrostis stolonifera L., commonly known as creeping bentgrass, particularly due to its ability to form hybrids. This scenario underscores the urgent need for innovative, effective, and environmentally sustainable herbicides, steering the focus toward natural substances as potential candidates. We report here a promising natural lactone, commonly known as menthalactone, which is derived from Mentha piperita L. Its phytotoxic activity was assessed against the monocot, bentgrass, and a dicot, lettuce (Lactuca sativa L.). Menthalactone displayed outstanding activity against bentgrass and was further evaluated for phytotoxic characteristics. The germination of A. stolonifera seeds was significantly inhibited with an IC₅₀ value of 4.9 ± 1.2 µM. In contrast to bentgrass seeds, Lemna pausicostata L. plants were less responsive to menthalactone treatment, shown by an IC₅₀ of 293.4 ± 70.6 µM. Both species are monocots, and the results suggest that menthalactone might have effects on seed germination but not on the metabolism of green tissues. The susceptibility of three common, obnoxious weed species, i.e., ryegrass (Lilium perenne), barnyard grass (Echinochloa crus-galli (L.) P. Beauv.), and crabgrass (Digitaria sanguinalis (L.) Scop.), to menthalactone was assessed. Menthalactone at 1000 µM completely inhibited the germination of all three species of grasses, while 330 µM inhibited germination by less than 50%. The post-emergence application of menthalactone at 1% did not produce a significant inhibitory effect against ryegrass, barnyard grass, or crabgrass. Full article

Calamus tenuis is a shrub species distributed across South Asia. It grows well in diversified habitats and tends to dominate plants in the surrounding environment. The phytotoxicity of C. tenuis and the action of its phytochemicals against other plant species could explain its dominant behavior. Compounds with phytotoxic activity are in high demand as prospective sources of ecofriendly bioherbicides. Therefore, we investigated the phytotoxicity of C. tenuis. Aqueous methanol extracts of this plant species significantly limited the growth of four test plant species, two monocots (barnyard grass and timothy), and two dicots (alfalfa and cress), in a dose- and species-dependent manner. Bio-directed chromatographic isolation of the C. tenuis extracts yielded two major active substances: a novel compound, calamulactone {(S)-methyl 8-(5-oxo-2,5-dihydrofuran-2-yl) octanoate}, and 3-oxo-α-ionone. Both of the identified compounds exerted strong growth inhibitory effects on cress and timothy seedlings. The concentrations of 3-oxo-α-ionone and calamulactone required to limit the growth of the cress seedlings by 50% (I₅₀) were 281.6–199.5 and 141.1–105.5 µM, respectively, indicating that the effect of calamulactone was stronger with lower I₅₀ values. Similarly, the seedlings of timothy also showed a considerably higher sensitivity to calamulactone (I₅₀: 40.5–84.4 µM) than to 3-oxo-α-ionone (I₅₀: 107.8–144.7 µM). The findings indicated that the leaves of C. tenuis have marked growth-inhibitory potential, and could affect surrounding plants to exert dominance over the surrounding plant community. Moreover, the two identified phytotoxic substances might play a key role in the phytotoxicity of C. tenuis, and could be a template for bioherbicide development. This paper was the first to report calamulactone and its phytotoxicity. Full article

Investigation of allelopathic substances from herbal plants may lead to the development of allelochemical-based natural herbicides. Croton oblongifolius (Roxb.) is a well-known herbal plant with a long history of being used for traditional medicines and for being the source of a diverse range of bioactive compounds. This plant has been reported to have allelopathic potential; however, its allelopathic-related substances have not yet been described. Therefore, we conducted this investigation to explore the allelopathic substances from the leaves of C. oblongifolius. Aqueous methanol extracts of C. oblongifolius leaves exhibited significant growth inhibitory potential against four test plants (monocot barnyard grass and timothy, and dicot cress and lettuce). The leaf extracts were purified in various chromatographic steps and yielded four active compounds identified as (3R,6R,7E)-3-hydroxy-4-7-megastigmadien-9-one (I), 2-hydroxy alpinolide (a novel compound) (II), alpinolide (III), and epialpinolide (IV) via an analysis of the spectral data. These identified compounds significantly restricted the seedling growth of cress. The concentration necessary for 50% growth reduction of the cress seedlings varied from 0.15 to 0.24 mM for (3R,6R,7E)-3-hydroxy-4-7-megastigmadien-9-one, 0.04 to 0.11 mM for 2-hydroxy alpinolide, 0.07 to 0.12 mM for alpinolide, and 0.09 to 0.16 mM for epialpinolide. Therefore, the leaf extracts of C. oblongifolius and the characterized compounds have the potential to be used as weed-suppressive resources for natural weed control. Full article

Trewia nudiflora Linn. is a valuable forest resource due to its economic, ethnomedicinal, and ecological properties; however, its allelopathic potential is undocumented. Therefore, this research was designed to investigate the allelopathic impacts of T. nudiflora leaf extracts on alfalfa (Medicago sativa L.) and barnyard grass (Echinochloa crus-galli (L.) P. Beauv.) growth, as well as to isolate and to identify the active allelopathic substances responsible for these effects. A bioassay experiment with eight different treatments (0.1, 0.3, 1, 3, 10, 30, 100, and 300 mg dry weight (DW) equivalents of T. nudiflora extracts in mL⁻¹) was carried out. The results showed that the growth of both plants decreased with increasing contents of T. nudiflora extracts, with the effect depending on the plant species and reaching its peak at a concentration of a 300 mg DW equivalent of T. nudiflora extract in mL⁻¹. Active substances were isolated and identified using an HPLC system, which revealed the presences of methyl gallate and pinoresinol in aqueous methanol extracts of T. nudiflora. The shoot and root lengths of the alfalfa and the barnyard grass decreased significantly when they were treated with the methyl gallate and the pinoresinol. The allelopathic inhibition increased with increasing compound concentrations, with the root growth being more sensitive to the pinoresinol than to the methyl gallate, and it was significantly higher at the concentration of 10 mM. These results indicated that the T. nudiflora leaf extracts limited the growth of the treated plants, and the methyl gallate and pinoresinol in the extracts may have caused the inhibition of the T. nudiflora extracts. Thus, the leaf extracts of T. nudiflora and the substances methyl gallate and pinoresinol could be incorporated into sustainable agricultural practices or used to develop bioherbicides that would promote sustainable weed management practices. Full article