Rice Blast Research Articles

Synthesis and Fungicidal Activity Evaluation of Novel Triazole Thione/Thioether Derivatives Containing a Pyridylpyrazole Moiety.

Compounds containing N-pyridylpyrazole motif have aroused interest and brought about research hotspots due to their highly-efficient insecticidal activity. The fungicidal potential of N-pyridylpyrazole derivatives has gradually been disclosedin recent years. To discover new agrochemicals with poly-heterocyclic features, a series of novel triazole thione/thioether derivatives containing pyridylpyrazole motif (8-11) wassynthesized.The new compounds were identified by melting point, 1H NMR, 13C NMR, 19F NMR, HRMS,and elemental analysis. The bioassaysshowed that most of the pyridylpyrazole-containing triazole thione Mannich bases possessed favorable in vitrofungicidal activitytoward pathogenic fungi, such as Magnaporthe oryzae, Sclerotinia sclerotiorum, Botrytis cinerea andFusarium verticillioides, and were comparable with those of the contrast compounds Aand triadimefon. Some of them exhibited moderate to good in vivofungicidal activityagainst S. sclerotiorumat 0.2 mg/mL(e.g. 8fcontrol efficacy: 60.9±3.2%).The SEM observation displayed that 8f might cause disruptionof cell membrane and wall of S. sclerotiorum.Compounds 8a, 8c, 8f-8h, 8pand 9bcan serve as promising new fungicidal agents to make further structural optimization.The findings in this article provide useful clue and guidance for the design and development of new poly-heterocyclic agrochemicals.

Identification of rice samples with rice blast resistance genes Pi-2 and Pi-b

Since rice blast is a disease that causes significant damage to rice all over the world, the intensive development of disease-resistant genotypes is of great urgency. The use of molecular biology technologies, new biotechnological approaches and molecular genetic methods allows creating disease-resistant varieties while reducing the time of their development, which plays an important role in growing competitive products. The current paper has highlighted the results of estimating rice samples developed at the FSBSI “ARC “Donskoy” for blast resistance. The objects of the study were new samples developed in the laboratory of rice breeding and seed production. In 2022–2023, there were screened one hundred eighty-seven rice samples. They were identified on a presence of the blast resistance gene Pi-2. One hundred fifteen samples were estimated for the blast resistance gene Pi-b. Genomic DNA was isolated from young rice leaves. After estimating the quantity and quality of the isolated DNA there was conducted a polymerase chain reaction for the target genes Pi-2 and Pi-b. In order to identify the alleles of the desired genes there were used specific intragenic molecular SSR markers of dominant (for Pi-2) and codominant (for Pi-b) types. Electrophoresis of the obtained amplicons was performed on 2 % agarose gels during an hour. The results of the analysis were recorded in ultraviolet light and processed in ImageLab 5.1 software. As a result of the conducted study, there were identified new rice breeding samples that carry blast resistance genes Pi-2 and Pi-b. These samples are recommended for use in the further breeding process for blast resistance.

In vitro inhibition mechanisms of Trichoderma yunnanense TM10 against Pyricularia oryzae and Rhizoctonia solani causing blast and sheath blight diseases in rice (Oryza sativa L.)

Blast and sheath blight diseases, caused by Pyricularia oryzae and Rhizoctonia solani, respectively, are major threats to rice production worldwide. Efforts should be made to limit the spread of these phytopathogens, preferably through sustainable methods. In this study, we investigated the antagonistic potential of the local isolate Trichoderma yunnanense TM10 against the pathogenic fungi P. oryzae and R. solani. The results demonstrated that T. yunnanense TM10 inhibited the growth of P. oryzae and R. solani through mechanisms such as competition, mycoparasitism, and antibiosis. Dual culture, filtrate culture, and double plate assays showed that T. yunnanense TM10 could inhibit the growth of both P. oryzae and R. solani. Slide culture and scanning electron microscope (SEM) tests confirmed that T. yunnanense TM10 exhibited mycoparasitic activity, including attachment, coiling, penetration, lysis, and destruction of pathogen hyphae. Additionally, T. yunnanense TM10 was capable of producing cell wall-degrading enzymes (CWDEs) such as chitinase and cellulase, as well as volatile organic compounds (VOCs) such as hydrogen cyanide (HCN). The multifaceted abilities of T. yunnanense TM10 for limiting the growth of P. oryzae and R. solani underscore its potential as an effective biocontrol agent for enhancing productivity and sustainability in rice cultivation.

The Mediator complex subunit MoMed15 plays an important role in conferring sensitivity to isoprothiolane by modulating xenobiotic metabolism in M. oryzae.

Rice blast caused by Magnaporthe oryzae is one of the most economically important rice diseases. Fungicides such as isoprothiolane (IPT) have been used extensively for rice blast control, but resistance to IPT in M. oryzae is an emerging threat. In this study, molecular mechanisms of resistance in IPT-resistant mutants were identified. Through whole-genome sequencing and genetic transformation, we identified the gene MoMed15, encoding a transcriptional glutamine-rich co-activator Mediator complex subunit, in which mutations or deletion resulted in moderate IPT resistance. Further research found that MoMed15 physically interacted with the IPT resistance regulatory factor MoIRR to simultaneously regulate both MoIRR expression and the expression of multiple xenobiotic-metabolizing enzymes in response to IPT stress. We hypothesize that some xenobiotic-metabolizing enzymes enhance IPT toxicity by modifying the IPT structure. Variation of MoMed15 affected the recruitment of the transcriptional Mediator complex and decreased the expression of these xenobiotic-metabolizing enzymes, resulting in moderate IPT resistance. We also found that MoPGR1, encoding a protein that activates cytochrome P450 enzymes, was essential to confer IPT sensitivity, and its expression was directly regulated by MoIRR.IMPORTANCEIsoprothiolane (IPT) has been used extensively for the management of rice blast disease and IPT-resistant subpopulations have emerged in Chinese rice fields. The emergence of resistant pathogen populations has led to a steep increase in fungicide use, increasing pesticide risk for the applicator and the environment. The molecular mechanisms of IPT resistance in M. oryzae remain elusive. In this study, we demonstrated that transcriptional co-activator MoMed15 interacts with IPT resistance regulator MoIRR to recruit the Mediator complex, which promotes the expression of xenobiotic-metabolizing enzymes, leading to exacerbated IPT toxicity. The MoMed15 could be used for IPT resistance detection in rice fields.

Nuclear localization sequence of MoHTR1, a Magnaporthe oryzae effector, for transcriptional reprogramming of immunity genes in rice.

Plant pathogens secrete nuclear effectors into the host nuclei to modulate the host immune system. Although several nuclear effectors of fungal pathogens have been recently reported, the molecular mechanism of NLS-associated transport vehicles of nuclear effectors and the roles of NLS in transcriptional reprogramming of host immunity genes remain enigmatic. We previously reported the MoHTR1, a nuclear effector of the rice blast fungus, Magnaporthe oryzae. MoHTR1 is translocated to rice nuclei but not in fungal nuclei. Here, we identify the core NLS (RxKK) responsible for MoHTR1's nuclear localization. MoHTR1 is translocated in the host nucleus through interaction with rice importin α. MoHTR1 NLS empowers it to translocate the cytoplasmic effectors of M. oryzae into rice nuclei. Furthermore, other nuclear effector candidates of the blast pathogen and rice proteins which have RxKK also exhibit nuclear localization, highlighting the crucial role of RxKK in this process. We also unveil the importance of SUMOylation in the stability of MoHTR1 and translocation of MoHTR1 to host nuclei. Moreover, MoHTR1 NLS is essential for the pathogenicity of M. oryzae by reprogramming immunity-associated genes in the host. Our findings provide insights into the significance of plant-specific NLS on fungal nuclear effectors and its role in plant-pathogen interactions.

Novel SNPs Linked to Blast Resistance Genes Identified in Pearl Millet Through Genome-Wide Association Models

Foliar blast, caused by Pyricularia grisea, poses a major challenge to pearl millet (Pennisetum glaucum (L.) R. Br) production, leading to severe yield losses, particularly in rainfed ecologies. This study aimed to elucidate the genetic basis of blast resistance through a genome-wide association study (GWAS) involving 281 diverse pearl millet inbreds. GWAS panel was phenotyped for blast resistance against three distinct isolates of P. grisea collected from Delhi, Gujarat, and Rajasthan locations, revealing a significant variability with 16.7% of the inbreds showing high resistance. Bayesian information and linkage disequilibrium iteratively nested keyway (BLINK) and Multi-Locus Mixed Model (MLMM) models using transformed means identified 68 significant SNPs linked to resistance, with hotspots for resistance-related genes on chromosomes 1, 2, and 6. These regions harbor genes involved in defense mechanisms, including immune response, stress tolerance, signal transduction, transcription regulation, and pathogen defense. Genes, namely 14-3-3-like proteins RGA2, RGA4, hypersensitive-induced response proteins, NHL3, NBS-LRR, LRR-RLK, LRRNT_2, and various transcription factors such as AP2/ERF and WRKY, played a crucial role in the stress-responsive pathways. Analyses of transporter proteins, redox processes, and structural proteins revealed additional mechanisms contributing to blast resistance. This study offers valuable insights into the complex genetic architecture of blast resistance in pearl millet, offering a solid foundation for marker-assisted breeding programs and gene-editing experiments.

District Level Crop Weather Calendars and Advisories for Kharif Rice in Odisha, India

The crop weather calendar is a visual depiction of key facts about crop growth phases, typical crop water requirements, and alerts that should be sent out in response to weather that is conducive to the spread of pests and diseases. Farmers and other stakeholders may successfully plan crops, schedule irrigation, and take plant protection measures by using these calendars, which are practical and helpful tools for farmers. The crop weather calendars are prepared in different languages for better understanding to farmers and explain the usage importance and plan farm operation and activities by taking decisions as per the prevalent crop weather conditions in fields. It plays a vital role for important crops and various varieties through research & development-based process at village/ panchayat level. It also helpful for improving the quality of medium range weather forecast based on Agro-Advisory Services (AAS). The AAS provides strategies based on weather for crop and livestock management to increase production and food security. The AAS has been useful to advise farmers regarding farm operations to manage the inclement weather for effective crop production in the changing environment. The Research was carried out on the studies of crop weather calendar on Rice crop in different districts of Odisha by All India co-ordinated research project on Agrometeorology, Bhubaneswar centre with the support of Agro Meteorological Field Unit (AMFU). It has been prepared with an objective to study climate normal of past 30 years from (1993-2023). Climatic data of Rice crop in Kharif season has been taken 25th SMW to 42nd SMW for medium duration (125 days) and 26th to 49th SMW for long duration (150 days) Rice crop in both English and Odia (local) languages for the coastal districts i.e (Khordha, Puri, Kendrapada and Jagatsinghpur) of Odisha. From the crop weather calendar the medium duration of rice crop, it was found that for sowing to seeding the mean temperature is 290C, before the transplanting and the water requirement of 670-690 mm is found congenial for better yield of the crop. The growth of the crops severely affected where the temperature falls below 200C, for high yielding of Rice crop during the kharif season the favourable weather conditions are Tmax: 300C, Tmin: 260C, Rainfall: 78 mm to 110 mm during the 29th to 30th week with RH 87%. For the pest likes stem borer and leaf folder the congenial weather conditions are Temperature :20 to 300C, RH:87%, Wind speed (Km/h) <5 and Rainfall: 00-30 mm. Similarly for Blast and BLB diseases, the favourable conditions during the 28th-31st week to 48th week, when the temperature range 20-300C, RH=> 90 %, Wind speed < 5 (Km/h) RH:30-50%. It has been found that the severity of pest and diseases increases with decreases in temperature and High RH and very low rainfall.

Whole Genome Sequencing and Comparative Genomic Analysis of Pseudomonas aeruginosa SF416, a Potential Broad-Spectrum Biocontrol Agent Against Xanthomonas oryzae pv. oryzae

Rice is one of the most important staple crops worldwide. However, the bacterial blight of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) poses a major threat to the production of rice. In this study, we isolated and identified the strain Pseudomonas aeruginosa SF416, which exhibited significant antagonistic activity against Xoo, from a soil sample collected in a winter wheat field in Shannanzhalang County, Tibet, China. The bacterial solution (BS) and cell-free supernatant (CFS) of SF416 had significant prevention effects for the bacterial blight of rice, with an efficacy of 45.1% and 34.18%, respectively, while they exhibited a slightly lower therapeutic efficiency of 31.64% and 25.09%. The genomic analysis showed that P. aeruginosa SF416 contains genes involved in cell motility, colonization, cold and hot shock proteins, antibiotic resistance, and plant growth promotion. SF416 also harbors two sets of phenazine-1-carboxylic acid (PCA) synthesis gene clusters, phz1 (phzA1-G1) and phz2 (phzA2-G2), and other phenozine product-synthesis--related genes phzS, phzM, and phzH, as well as genes in the SF416 genome that share high similarity with the ones in the genomes of P. aeruginosa M18, suggesting that the two sets of PCA synthesis gene clusters are responsible for the antagonistic effect of SF416 against Xoo. A comparative antiSMASH analysis revealed that P. aeruginosa SF416 contains 17 gene clusters related to secondary metabolite synthesis, 7 of which, encoding for pyochelin, azetidomonamide A/B, L-2-amino-4-methoxy-trans-3-butenoic acid, hydrogen cyanide, pyocyanine, pseudopaline, and bicyclomycin, are conserved in strains of P. aeruginosa. Moreover, SF416 can produce protease and siderophores and display a broad-spectrum antagonistic activity against various major plant pathogenic bacteria and fungi. The results suggest that P. aeruginosa SF416 could be a potential candidate agent for the bacterial blight of rice.

The endosomal-vacuolar transport system acts as a docking platform for the Pmk1 MAP kinase signaling pathway in Magnaporthe oryzae.

In Magnaporthe oryzae, the Pmk1 MAP kinase signaling pathway regulates appressorium formation, plant penetration, effector secretion, and invasive growth. While the Mst11-Mst7-Pmk1 cascade was characterized two decades ago, knowledge of its signaling in the intracellular network remains limited. In this study, we demonstrate that the endosomal surface scaffolds Pmk1 MAPK signaling and Msb2 activates Ras2 on endosomes in M. oryzae. Protein colocalization demonstrated that Msb2, Ras2, Cap1, Mst50, Mst11, Mst7, and Pmk1 attach to late endosomal membranes. Damage to the endosome-vacuole transport system influences Pmk1 phosphorylation. When Msb2 senses a plant signal, it internalizes and activates Ras2 on endosome membrane surfaces, transmitting the signal to Pmk1 via Mst11 and Mst7. Signal-sensing and delivery proteins are ubiquitinated and sorted for degradation in late endosomes and vacuoles, terminating signaling. Plant penetration and lowered intracellular turgor are required for the transition from late endosomes to vacuoles in appressoria. Our findings uncover an effective mechanism that scaffolds and controls Pmk1 MAPK signaling through endosomal-vacuolar transport, offering new knowledge for the cytological and molecular mechanisms by which the Pmk1 MAPK pathway modulates development and pathogenicity in M. oryzae.

OsPIPK-FAB, A Negative Regulator in Rice Immunity Unveiled by OsMBL1 Inhibition

Phosphatidylinositol signaling system plays a crucial role in plant physiology and development, phosphatidylinositol phosphate kinases (PIPKs) are one of the essential enzymes responsible for catalyzing the synthesis of phosphatidylinositol bisphosphate (PIP2) within this signaling pathway. However, its mechanism of signal transduction remains poorly exploited in plants. OsMBL1, a jacalin-related mannose-binding lectin in rice, plays a crucial role in plant defense mechanisms, acting as a key component of the pattern-triggered immunity (PTI) pathway. Here, a rice phosphatidylinositol-phosphate kinase FAB (OsPIPK-FAB), a member of the rice PIPKs family, as an interacting protein of OsMBL1 through yeast-two-hybrid (Y2H) screening assay. And this interaction was confirmed by using co-immunoprecipitation (Co-IP) and pull-down assay techniques. Furthermore, we demonstrated that the deletion of OsPIPK-FAB gene in plant enhanced resistance against rice blast while overexpression of OsPIPK-FAB increases sensitivity to the fungal infection. Additionally, through determination and measurement of the plant inositol 1,4,5-trisphosphate (IP3) contents and the plant phosphatidylinositol 4-phosphate 5-kinase (PIP5K) activity, we revealed that OsMBL1 inhibits the PIP5K kinase activity of OsPIPK-FAB as well as the plant IP3 contents in rice. Conclusively, these findings indicated that OsPIPK-FAB serves as a novel and critical component that is negatively involved in PTI activation and was inhibited by OsMBL1.

Optimization of Ferimzone and Tricyclazole Analysis in Rice Straw Using QuEChERS Method and Its Application in UAV-Sprayed Residue Study.

Rice straw is used as livestock feed and compost. Ferimzone and tricyclazole, common fungicides for rice blast control, can be found in high concentrations in rice straw after unmanned aerial vehicle (UAV) spraying, potentially affecting livestock and human health through pesticide residues. In this study, an optimized method for the analysis of the two fungicides in rice straw was developed using the improved QuEChERS method. After the optimization of water and solvent volume, extraction conditions including ethyl acetate (EtOAc), acetonitrile (MeCN), a mixed solvent, and MeCN containing 1% acetic acid were compared. Different salts, including unbuffered sodium chloride, citrate, and acetate buffer salts, were compared for partitioning. Among the preparation methods, the MeCN/EtOAc mixture with unbuffered salts showed the highest recovery rates (88.1-97.9%, RSD ≤ 5.1%). To address the severe matrix effect (%ME) of rice straw, which is characterized by low moisture content and cellulose-based complex matrices, samples were purified using 25 mg each of primary-secondary amine (PSA) and octadecylsilane (C18), without pesticide loss. The developed method was validated with a limit of quantification (LOQ) of 0.005 mg/kg for target pesticides, and recovery rates at levels of 0.01, 0.1, and 2 mg/kg met the permissible range (82.3-98.9%, RSD ≤ 8.3%). The %ME ranged from -17.6% to -0.3%, indicating a negligible effect. This optimized method was subsequently applied to residue studies following multi-rotor spraying. Fungicides from all fields and treatment groups during harvest season did not exceed the maximum residue limits (MRLs) for livestock feed. This confirms that UAV spraying can be safely managed without causing excessive residues.

Antifungal activity and mechanism of mefentrifluconazole against Magnaporthe grisea causing rice blast

Rice blast, caused by Magnaporthe grisea, is one of the most destructive diseases of rice worldwide. Mefentrifluconazole, a novel isopropanol triazole fungicide, exhibits excellent bioactivity to a wide range of fungi. However, its antifungal activity against M. grisea is not well studied. In this study, the sensitivity of 103 M. oryzae strains to mefentrifluconazole was determined by mycelial growth rate method, and the effect of mefentrifluconazole on the biochemical and physiological characteristers was examined. The results indicated that mefentrifluconazole exhibited excellent inhibitory activity against M. oryzae with EC50 values of 103 M. oryzae strains tested ranging from 0.363 to 1.576 μg/mL, and the average EC50 value of 0.958 ± 0.298 μg/mL. After mefentrifluconazole treatment, the apical branches of M. oryzae mycelia increased and the mycelia became distorted, twisted and ruptured. In addition, mefentrifluconazole increased relative conductivity, disrupted cell wall and membrane integrity, and significantly reduced ergosterol content. The expression levels of demethylation inhibitor resistance-associated genes Cyp51A, ABC6 and MFS1 were all significantly upregulated, suggesting an adaption response to mefentrifluconazole of M. oryzae. Furthermore, the results of pot experiment showed that mefentrifluconazole provided >70% control efficacy against rice blast at 300 μg/mL, surpassing the performance of carbendazim, prochloraz and azoxystrobin at the same concentration. Overall, this study demonstrated the strong inhibitory activity of mefentrifluconazole against M. oryzae and the excellent efficacy in controlling rice blast, thus providing new sights into rice blast control as well as the practical application of mefentrifluconazole.

Using Marker-Assisted Selection to Develop a Drought-Tolerant Rice Line with Enhanced Resistance to Blast and Brown Planthopper

Rice is a major global staple crop, but rising temperatures and freshwater shortages have made drought one of the most severe abiotic stresses affecting agriculture. Additionally, rice blast disease and brown planthopper infestations significantly impact yields. Therefore, developing water-saving, drought-resistant, high-yielding, and disease-resistant rice varieties is critical for sustainable rice production. The new water-saving and drought-resistant (WDR) rice ‘Huhan 1516’, bred using marker-assisted selection (MAS) and marker-assisted backcrossing (MABC) techniques, addresses these challenges. This variety is highly adaptable to drought-prone and water-scarce regions such as the Yangtze and Huai River basins. With its high yield, drought tolerance, and broad-spectrum resistance to rice blast (conferred by the Pi2 gene) and brown planthopper (BPH), ‘Huhan 1516’ is suitable for various farming systems and environments. Field trials show that this variety outperforms control varieties by 2.2% in yield and exhibits moderate resistance to both rice blast and brown planthopper. ‘Huhan 1516’ has been recognized as a new water-saving and drought-resistant rice variety by the state, and as a released cultivar, it has great potential for market promotion and application.

Near complete assembly of Pyricularia penniseti infecting Cenchrus grass identified its eight core chromosomes

Fungi from the Pyricularia genus cause blast disease in many economically important crops and grasses, such as wheat, rice, and Cenchrus grass JUJUNCAO. Structure variation associated with the gain and loss of effectors contributes largely to the adaptive evolution of this fungus towards diverse host plants. A telomere-to-telomere genome assembly would facilitate the identification of genome-wide structural variations through comparative genomics. Here, we report a telomere-to-telomere, near-complete genome assembly of a Pyricularia penniseti isolate JC-1 infecting JUJUNCAO. The assembly consists of eight core chromosomes and two supernumerary chromosomes, named mini1 and mini2, spanning 42.1 Mb. We annotated 12,156 protein-coding genes and identified 4.54% of the genome as repetitive sequences. The two supernumerary chromosomes contained fewer genes and more repetitive sequences than the core chromosomes. Our genome and results provide valuable resources for the future study in genome evolution, structure variation and host adaptation of the Pyricularia fungus.

Investigating the Role of OsHDT701 and Other Blast-Associated Negative Regulatory Genes in Indica Rice Cultivar Ranjit Using Combined Wet Lab and Computational Approaches.

Rice blast, caused by Magnaporthe oryzae, severely impacts global rice production. Understanding the role of the host's blast negative regulatory genes is crucial for combating this disease. We studied the expression of seven rice blast negative regulatory genes (previously characterized in ssp. japonica) in susceptible (Ranjit and Mahsuri) and tolerant/resistant (Shahsarang 1 and IR64) indica rice cultivars during M. oryzae infection. The selected genes showed differential expression patterns, with OsHDT701 (histone H4 deacetylase) downregulated in tolerant/resistant and upregulated in susceptible cultivars. Promoter analysis of OsHDT701 in cv. Ranjit revealed biotic stress-responsive and M. oryzae effector binding motifs (MoHTR2 and MoSPAB1). Protein-DNA docking showed an interaction for both the effectors and promoter sequences. Furthermore, a strong interaction between the OsERF922 transcription factor (a negative regulator of rice blast) and GCC box at the promoter suggests OsERF922-mediated regulation of OsHDT701. Next, a comparative analysis of ssp. japonica (Nipponbare) OsHDT701 CDS to 11 indica rice cultivars, including Ranjit, detected an SNP (T-A) at position 591. Moreover, the structure modeling and protein-protein interaction reveal that OsHDT701 may form a complex with other histone deacetylases to regulate defense-related gene expression. Taken together, our study unveils new possibilities for OsHDT701 regulation mechanisms during M. oryzae infection.

Mechanized Transplanting Improves Yield and Reduces Pyricularia oryzae Incidence of Paddies in Calasparra Rice of Origin in Spain

The rice variety Bomba is grown in Calasparra—a rice of origin in southeast Spain—resulting in a product with excellent cooking quality, although its profitability has declined in recent years due to low grain yields and susceptibility to rice blast disease (Pyricularia oryzae Cavara). An innovation project to test the efficacy of mechanized transplanting against traditional direct seed sowing was conducted in 2022 and 2023 at four locations for the first time. A lower plant density (67–82 plants m−2) and shorter plants with higher leaf nitrogen content were observed in transplanted plots compared with seed sowing (130–137 plants m−2) in the first year. The optimal climatic conditions for P. oryzae symptom appearance were determined as temperatures of 25–29 °C and a 50–77% relative humidity. The most-affected sowing plots presented 3–20% leaf area damage and a reduction in yield to values of 1.5 t ha−1 in the first year and 2.12 t ha−1 in the second year. In transplanted plots, there was generally less humidity at the plant level and therefore, disease incidence was low in both seasons. Grain yields did not significantly differ among the treatments studied; however, there were differences in the yield components of panicle density and the number of grains for panicles. Principal component analysis revealed two principal components that explained 81% of the variability. Variables related to yield contributed positively to the first component, while plant biomass variables contributed to the second component. Plant density, tiller density, and panicle density were found to be positively correlated (r > 0.81 ***). Overall, transplanting (frame of 30 × 15–18 cm2) resulted in uniform crop growth with less rice blast disease, as well as higher grain yields (2.92–3.89 t ha−1), in comparison with the average for the whole D.O. Calasparra (2.3–2.5 t ha−1) in both seasons and a good percentage of whole grains at milling. This is novel knowledge which can be considered useful for farmers operating in the region.

Discovery of Acaricidal, Insecticidal, and Fungicidal Candidates Inspired by Natural Ethyl Cinnamate Compounds Isolated from Polygonum orientale L.

As a continuation of our research on the pesticide development of Polygonum orientale L., the chemical constituents of the seeds of P. orientale were systematically investigated. Eleven natural compounds (PO-1 to PO-11) were isolated from the EtOAc extract of P. orientale. Notably, compound PO-9 and its dimeric compound PO-10 were first isolated from P. orientale and possessed excellent acaricidal activity against Tetranychus cinnabarinus. With PO-9 and PO-10 as the lead compounds, two series of cinnamate derivatives were further synthesized, and their acaricidal, insecticidal, and fungicidal activities were evaluated systematically. The insecticidal activity results showed that dimeric derivative NKY-70 displayed the highest acaricidal activity against T. cinnabarinus and insecticidal activities against Brevicoryne brassicae and Myzus persicae. Furthermore, most of these compounds showed excellent in vitro antifungal activity against plant fungi. Compound NKY-66 displayed the highest and broad spectrum of antifungal activity against 23 fungi, and the respective EC50 values were 0.09, 0.08, 0.12, 0.18, 0.12, and 0.09 mg/mL against Valsa mali, Fusarium oxysporum f. sp. cucumerinum, Fusarium graminearum, Magnaporthe oryzae, Colletotrichum capsici, and Phytophthora infestans, which were more potent than those of chlorothalonil and procymidone. Moreover, the in vivo fungicidal evaluation also demonstrated that compound NKY-66 could effectively control plant fungal diseases in the greenhouse and in the field, such as damping off, powdery mildew, and cucumber downy mildew. Therefore, these findings implied that the cinnamate derivative NKY-66 displayed superior in vitro and in vivo fungicidal activities and could be a potential candidate against plant fungal diseases.

Bacterial endophyte Pseudomonas mosselii PR5 improves growth, nutrient accumulation, and yield of rice (Oryza sativa L.) through various application methods

BackgroundPseudomonas spp. have drawn considerable attention due to their rhizospheric abundance and exceptional plant growth-promoting attributes. However, more research is needed on the optimal application methods of Pseudomonas mosselii for rice growth, nutrient accumulation, and yield improvement. This research explored the application of the endophytic bacterium P. mosselii PR5 on rice cultivar BRRI dhan29 with four treatments: control, seedling priming, root drenching, and bacterial cell-free culture (CFC) foliar application.ResultsPR5 led to better rice growth, improved nutrient acquisition, and higher yields compared to the control, regardless of the application method used. The highest results in fresh weight of root (146.93 g/pot), shoot (758.98 g/pot), and flag leaf (7.88 g/pot), dry weight of root (42.16 g/pot), shoot (97.32 g/pot), and flag leaf (2.69 g/pot), and grains/panicle (224.67), were obtained from seedling priming treatment, whereas root drenching resulted in maximum plant height (105.67 cm), root length (49.0 cm), tillers/pot (23.7), and panicles/pot (17.67). In all three application methods, rice grain yield per pot was higher in PR5 inoculated treatments, compared to the control. The amount of P, Mg and Zn in the shoot and N, P, Ca, Mg and Si content in the flag leaf was significantly increased along with effective suppression of naturally occurring blast disease in bacterial CFC foliar application, validated by multivariate analysis.ConclusionOur results indicated that rice seedlings priming with PR5 improved rice growth, yield and nutrient uptake, whereas CFC foliar application significantly increased the concentration of most nutrients in the rice plant and suppressed the naturally occurring rice blast disease. This research highlights the significant potential of P. mosselii PR5 in enhancing rice growth, yield, and nutrient uptake, particularly through seedling priming and CFC foliar application methods.

Labor-saving application of thifluzamide and tricyclazole to seedling trays for integrated control of rice blast and sheath blight

Rice blast (Magnaporthe grisea) and sheath blight (Rhizoctonia solani) are limiting factors for rice production. Co-infection of these pathogens results in a disease complex which is difficult to control. In China, growers are accustomed to applying individual fungicides to manage blast and sheath blight, which require large amounts of labor. Application to seedling trays is a new promising solution for saving labor. In this study, application of combined fungicides with different modes of action to seedling trays to integrate control rice blast and sheath blight was evaluated in vitro assays and field trials. The results showed that the combination of thifluzamide and tricyclazole in the 1:2 ratio had significant synergistic inhibitory effects on the mycelial growth of M. grisea and R. solani, with a synergistic ratio (SR) of 2.17 and 1.49. Results from field trials revealed that thifluzamide + tricyclazole at 1107 and 958.5 g/ha applied to seedling trays was the most effective treatment to reduce the disease index of rice blast with control effects of 83.74–84.96% and 81.34–83.26% in 2022 and 2023, respectively, and no significant differences were observed from tricyclazole at 300 g/ha as foliar sprays twice. Compared to the untreated control, disease index of rice sheath blight was notably reduced by all treatments containing thifluzamide. The highest control was recorded in the treatment of thifluzamide + tricyclazole applied at 1107 g/ha to seedling trays. Moreover, compared to the untreated control, all treatments significantly enhanced rice grain yield by 7.67–17.86% and 3.38–18.91% in 2022 and 2023, respectively. The greatest yield (7429.73 and 7404.73 kg/ha in 2022 and 2023, respectively) was observed from the treatment of thifluzamide + tricyclazole at 1107 g/ha applied to seedling trays, with no significant differences among all the treatments containing tricyclazole. Taken together, these results indicated that seedling tray application of thifluzamide + tricyclazole could be a labor-saving approach to the integrated control of rice blast and sheath blight disease complex, while increasing rice grain yield.

Proteomic identification of apoplastic proteins from rice, wheat, and barley after Magnaporthe oryzae infection

The fungal pathogen Magnaporthe oryzae causes devastating blast disease in various cereals, including rice (Oryza sativa), wheat (Triticum aestivum), maize (Zea mays), and barley (Hordeum vulgare). Despite previous reports on fungal host specificity, the mechanisms underlying differential host infection strategies remain unclear. This study aimed to identify differentially abundant proteins (DAPs) in the apoplast of rice, barley, and wheat following infection with two M. oryzae pathovars using liquid chromatography-tandem mass spectrometry (LC–MS/MS). LC–MS/MS analysis revealed an enrichment of both M. oryzae and host proteins in the apoplast during the compatible reaction compared to the incompatible reaction. DAPs from M. oryzae involved in the host interaction included secreted extracellular enzymes (e.g., hydrolases), which were significantly increased in the M. oryzae Oryzae (MoO)-infected rice apoplast. Among host proteins, the proportion of protein-modifying enzymes increased in the M. oryzae Triticum (MoT)-infected rice and MoO-infected wheat apoplastic fluids, particularly rice glycosidases, peroxidases, and serine proteases, as well as wheat serine proteases. Furthermore, DAPs from MoL-infected rice were enriched in carbohydrate metabolism, suggesting that carbohydrate metabolism-related proteins may play a vital role in rice resistance to MoL. Additionally, protein-modifying and cytoskeletal proteins, as well as stress-responsive proteins, were enriched in the MoO-infected wheat apoplastic fluid. Finally, DAPs from both MoO- and MoL-infected barley were enriched in hydrogen peroxide catabolism, suggesting that peroxidases may be vital for barley resistance to M. oryzae. The identification of DAPs from both M. oryzae strains and the three host plants offers valuable insights into the host specificity mechanisms of M. oryzae in cereal crops.