Screening of Casuarina equisetifolia rhizosphere-promoting bacteria and their effects on seed germination and seedling growth.

To promote the growth of Casuarina equisetifolia and address the abnormalities in the structure and function of rhizosphere soil microbial community, we isolated eight strains with multiple functions from the root nodules of C. equisetifolia, including nitrogen fixation (N), production of cell wall-degrading enzymes (protease and cellulase), auxin (IAA) production, siderophore production, ammonia (NH3) production, and phosphate solubilization. Among these strains, LB08, LB18, LB19, LB42, LB46, LB63, and LB69 were identified as Paenibacillus species, while LQ10 was identified as a Brucella sp. Results of seed soaking experiments showed that all the eight strains promoted the growth of C. equisetifolia seedlings. Strain LB69 significantly increased the germination rate and seedling vigor by 19.7% and 28.3%, respectively. Strain LQ10 significantly enhanced root length and root vigor by 48.2% and 334.4%, respectively. Strains LB18 and LB42 had the strongest effects on early shoot length and biomass accumulation, with increases of 22.4% and 32.8%, respectively. After seed soaking, the number of isozymes bands of polyphenol oxidase, superoxide dismutase, and peroxidase increased, with some bands showing enhanced intensity and increased diversity of enzyme isoforms, thereby enhancing stress resistance. In summary, the addition of these eight strains promoted plant growth and antioxidant enzyme activity, indicating their potential role as biofertilizers.

Pseudomonas ZY-1 and Bacillus FY-1 protecting the rice seedlings from the harm of Pseudomonas aeruginosa via indirect seawead lysis.

The local ecosystems, fishery and human health are all threatened by water blooms, so effectively controlling water blooms has become an urgent and challenging issue. Biological control of water blooms is given priority due to its low cost, high efficiency and environmental friendliness. In this study, Pseudomonas ZY-1 and Bacillus FY-1, two highly-effective algicidal bacteria strains which are able to indirectly lyse algae by separating and screening from the vigorous water body in the paddy alga of Northeast China were obtained. The two bacterial strains have stronger ability to lyse alga in the bacterial liquid concentration of 106 CFU/ml, and the alga-lysing rate on 7 d reached 84.03% and 83.11% respectively. The active substance secreted by ZY-1 is not sensitive to the changes of temperature and pH value, while as FY-1 cell-free filtrate is not stable in high temperature above 50 ℃ and pH of 5, it requires the sun light to have the algaecidal effect. The cell-free filtrates of strains ZY-1 and FY-1 had the best lysis effect on Microcystis aeruginosa cells, and the chlorophyll a content of algae decreased to 0.13 ± 0.02 mg/L and 0.14 ± 0.03 mg/L respectively and the Fv/Fm of Microcystis aeruginosa decreased by 97.22% after 7 days. The algaecidal process of ZY-1 and FY-1 may be that the cell-free filtrate inhibits the photosynthesis of Microcystis aeruginosa, and meanwhile it avoids the regeneration and repair of photosynthesis of algal cells by affecting the gene expression and damaging the repair system of algal cells, so the membrane lipid peroxidation is exacerbated and then the membrane of algal cells is broken, the algal cells can't do normal life activities, and finally the algal cell would be killed. The rice seedlings in the algal liquid treatment group are short and show root dysplasia, few roots and brown roots. After treated with cell-free filtrate of ZY-1 and FY-1, the oxidative damage of the rice is obviously reduced, and the harm from Microcystis aeruginosa is reduced, which has the repair effect to the roots of rice seedlings and its aboveground growth. The cell-free filtrate of FY-1 works better than ZY-1. The bacteria strains of ZY-1 and FY-1 have the indirect algaecide trait, which makes them the potential environmentally-friendly algaecidal bacteria and they show broad application in the agricultural production and the control of water blooms.

Deciphering root-associated microbial communities in asymptomatic oil palm seedlings exposed to Ganoderma boninense: new insight into disease tolerance of oil palms.

Understanding the microbial communities in asymptomatic oil palm seedlings is crucial for developing disease-suppressive microbiota against basal stem rot (BSR) in oil palm. In this study, we compared the microbial communities in bulk soil, rhizosphere, and endosphere of control, asymptomatic, and symptomatic seedlings following inoculation with Ganoderma boninense. Our findings revealed significant shifts in microbial structure and interactions, particularly in asymptomatic seedlings. Both Actinobacteriota and Ascomycota were notably enriched in these samples, with Actinobacteriota identified as keystone taxa. Long-read shotgun metagenomics demonstrated that 67.4% of enriched Actinobacteriota taxa were unique to asymptomatic seedlings. Similarly, Ascomycota members showed significant enrichment, suggesting their potential role in BSR suppression. The consistent identification of these phyla across various analyses underscores their importance in disease resistance. This is the first report detailing the shifts in prokaryotic and fungal communities in asymptomatic and symptomatic seedlings, offering insights into potential disease-suppressive taxa across three compartments: bulk soil, rhizosphere, and endosphere of oil palm seedlings.

Antibacterial effect of Cu2O/TiO2 visible-light photocatalytic composite on Xanthomonas campestris.

In this study, a Cu2O/TiO2 (CuTi) visible-light photocatalytic composite was employed for the treatment of Xanthomonas campestris and X. campestris-infected Brassica napus seedlings. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values against X. campestris were determined to be 8 and 32 µg ml-1, respectively. Transmission electron microscopy analysis demonstrated a direct correlation between the extent of bacterial cell damage and the concentration of CuTi. Noteworthily, a bactericidal rate of 100% was achieved at a concentration of 150 µg ml-1 over a treatment duration of 120 min. Moreover, alterations in active oxidants and antioxidants, including reactive oxygen species, glutathione reductase, superoxide dismutase, peroxidase, and catalase within the bacterial cells, were examined to elucidate the underlying mechanism of inhibition by the CuTi. The B. napus infected by X. campestris was treated with CuTi, and the efficacy was validated through determination of plant resistance indexes. The combined data confirmed that the CuTi is characterized by a low dose, fast onset, good effect, and higher safety for killing X. campestris, and it is expected to be developed as an antimicrobial agent for vegetables.

Chitooligosaccharides and Arbuscular Mycorrhizal fungi alleviate the damage by Phytophthora nicotianae to tobacco seedlings by inducing changes in rhizosphere microecology.

Arbuscular mycorrhizal fungi (AMF) and Chitooligosaccharide (COS) can increase the resistance of plants to disease. COS can also promote the symbiosis between AMF and plants. However, the effects of AMF & COS combined application on the rhizosphere soil microbial community of tobacco and the improvement of tobacco's resistance to black shank disease are poorly understood.·We treated tobacco with AMF, COS, and combined application of AMF & COS (AC), respectively. Then studied the incidence, physio-biochemical changes, root exudates, and soil microbial diversity of tobacco seedling that was inoculated with Phytophthora nicotianae. The antioxidant enzyme activity and root vigor of tobacco showed a regular of AC > AMF > COS > CK, while the severity of tobacco disease showed the opposite regular. AMF and COS enhance the resistance to black shank disease by enhancing root vigor, and antioxidant capacity, and inducing changes in the rhizosphere microecology of tobacco. We have identified key root exudates and critical soil microorganisms that can inhibit the growth of P. nicotianae. The presence of caprylic acid in root exudates and Bacillus (WdhR-2) in rhizosphere soil microorganisms is the key factor that inhibits P. nicotianae growth. AC can significantly increase the content of caprylic acid in tobacco root exudates compared to AMF and COS. Both AMF and COS can significantly increase the abundance of Bacillus in tobacco rhizosphere soil, but the abundance of Bacillus in AC is significantly higher than that in AMF and COS. This indicates that the combined application of AMF and COS is more effective than their individual use. These findings suggest that exogenous stimuli can induce changes in plant root exudates, regulate plant rhizosphere microbial community, and then inhibit the growth of pathogens, thereby improving plant resistance to diseases.

Alleviation of cadmium uptake in rice (Oryza sativa L.) by iron plaque on the root surface generated by Providencia manganoxydans via Fe(II) oxidation.

Iron plaque is believed to be effective in reducing the accumulation of heavy metals in rice. In this work, a known soil-derived Mn(II)-oxidizing bacterium, LLDRA6, which represents the type strain of Providencia manganoxydans, was employed to investigate the feasibility of decreasing cadmium (Cd) accumulation in rice by promoting the formation of iron plaque on the root surface. Firstly, the Fe(II) oxidation ability of LLDRA6 was evaluated using various techniques including Fourier Transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, phenanthroline photometry, and FeS gel-stabilized gradient assays. Subsequently, the formation of iron plaque on the root surface by LLDRA6 was investigated under hydroponic and pot conditions. Finally, Cd concentrations were examined in rice with and without iron plaque through pot and paddy-field tests. The results showed that LLDRA6 played an efficient role in the formation of iron plaque on seedling roots under hydroponic conditions, generating 44.87 and 36.72 g kg- 1 of iron plaque on the roots of Huazhan and TP309, respectively. In pot experiments, LLDRA6 produced iron plaque exclusively in the presence of Fe(II). Otherwise, it solely generated biofilm on the root surface. Together with Fe(II), LLDRA6 effectively reduced the concentrations of Cd in Huazhan roots, straws and grains by 25%, 46% and 44%, respectively. This combination also demonstrated a significant decrease in the Cd concentrations of TP309 roots, straws and grains by 20%, 52% and 44%, respectively. The data from the Cd translocation factor indicate that obstruction of Cd translocation by iron plaque predominantly occurred during the root-to-straw stage. In paddy-field tests, the Cd concentrations of grains harvested from the combination treatment of LLDRA6 and Fe(II) exhibited a decline ranging from 40 to 53%, which fell below the maximum acceptable value for Cd in rice grains (0.2 mg kg- 1) as per the China national standard for food security (GB2762-2017). Meanwhile, the relevant phenotypic traits regarding the yield were not adversely affected. These findings have demonstrated that LLDRA6 can impede the uptake of Cd by rice in Cd-contaminated soils through the formation of iron plaque on roots, thus providing a promising safe Cd-barrier for rice production.

Gilvimarinus gilvus sp. nov. and Gilvimarinus algae sp. nov., isolated from kelp seedlings.

Two novel rod-shaped, strictly aerobic, non-motile and Gram-stain-negative bacterial strains, designated SDUM040013T and SDUM040014T, were isolated from kelp seedlings in Weihai, PR China. Cells of strain SDUM040013T were 0.3-0.4 µm wide and 0.8-1.8 µm long, catalase-positive and oxidase-positive. Growth of SDUM040013T was observed at 0-37 °C (optimum, 28-30 °C) and pH 5.5-9 (optimum, pH 8.0) and in the presence of 1-8 % (w/v) NaCl (optimum, 2 %). The DNA G+C content of strain SDUM040013T was 50.5 %. Strain SDUM040013T showed the highest 16S rRNA gene sequence similarity (97.1 %) to Gilvimarinus chinensis. Cells of strain SDUM040014T were 0.4-0.5 µm wide and 1.0-1.4 µm long, catalase-positive and oxidase-positive. Growth of SDUM040014T was observed at 4-40 °C (optimum, 28-30 °C) and pH 5.5-9 (optimum, pH 8.5) and in the presence of 0-8 % (w/v) NaCl (optimum, 2 %). The DNA G+C content of strain SDUM040014T was 56.5 %. Strain SDUM040014T showed the highest 16S rRNA gene sequence similarity (96.2%) to Gilvimarinus polysaccharolyticus. The isoprenoid quinone of both strains was Q-8 and the predominant fatty acids were summed feature 3 (C16 : 1 ω7c and/or C16 : 1 ω6c), summed feature 8 (C18 : 1 ω7c) and C16 : 0. Diphosphatidylglycerol, phosphatidylglycerol and phosphatidylethanolamine were the major polar lipids. Given these phenotypic and chemotaxonomic properties, as well as phylogenetic data, strains SDUM040013T and SDUM040014T were considered to represent two novel species of the genus Gilvimarinus, for which the names Gilvimarinus gilvus sp. nov. and Gilvimarinus algae sp. nov. are proposed. The type strains are SDUM040013T (=KCTC 8123T=MCCC 1H01413T) and SDUM040014T (=KCTC 8124T=MCCC 1H01414T), respectively.

Effects of Different Light Conditions on Anatomical and Histological Features of Galls in Bacterial Gall Disease of Cerasus × yedoensis.

Cerasus × yedoensis (cherry 'Somei-yoshino' Fujino) is affected by bacterial gall disease caused by Pseudomonas syringae pv. cerasicola (PSC). C. × yedoensis is often infected with PSC under weak light intensity, which indicates that susceptibility of C. × yedoensis to PSC is affected by light. To evaluate the effects of white light intensity and different light qualities, white or blue, on bacterial gall disease development, we quantitatively assessed the anatomical and histological features of bacterial-inoculated sites on branches of 2-year-old potted C. × yedoensis seedlings grown under different light intensities and qualities. The stronger the white light intensity, the less severe the gall symptoms. Gall formation was suppressed more by blue than white light of the same intensity. The validity of a simple gall index for assessing gall development with the naked eye, via quantitative evaluation of gall shape by measuring gall height, width, and volume, showed that the gall index could be used as a practical method for on-site assessments of gall development. The ratio of degeneration area in the gall remained constant, suggesting the presence of some regulatory mechanism preventing PSC from affecting the entire gall within the plant. Microscopy showed that the gall tissue is composed primarily of callus cells and has voids containing gummy material that is exuded from cracks in the gall, and the periderm develops at the gall foot but not at the gall apex, so the cells at the gall apex were necrotic or collapsed.

The potential of Burkholderia gladioli KRS027 in plant growth promotion and biocontrol against Verticillium dahliae revealed by dual transcriptome of pathogen and host.

Verticillium dahliae is a destructive, soil-borne pathogen that causes significant losses on numerous important dicots. Recently, beneficial microbes inhabiting the rhizosphere have been exploited and used to control plant diseases. In the present study, Burkholderia gladioli KRS027 demonstrated excellent inhibitory effects against Verticillium wilt in cotton seedlings. Plant growth and development was promoted by affecting the biosynthesis and signaling pathways of brassinosteroids (BRs), gibberellins (GAs), and auxins, consequently promoting stem elongation, shoot apical meristem, and root apical tissue division in cotton. Furthermore, based on the host transcriptional response to V. dahliae infection, it was found that KRS027 modulates the plants to maintain cell homeostasis and respond to other pathogen stress. Moreover, KRS027 induced disruption of V. dahliae cellular structures, as evidenced by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses. Based on the comparative transcriptomic analysis between KRS027 treated and control group of V. dahliae, KRS027 induced substantial alterations in the transcriptome, particularly affecting genes encoding secreted proteins, small cysteine-rich proteins (SCRPs), and protein kinases. In addition, KRS027 suppressed the growth of different clonal lineages of V. dahliae strains through metabolites, and volatile organic compounds (VOCs) released by KRS027 inhibited melanin biosynthesis and microsclerotia development. These findings provide valuable insights into an alternative biocontrol strategy for Verticillium wilt, demonstrating that the antagonistic bacterium KRS027 holds promise as a biocontrol agent for promoting plant growth and managing disease occurrence.

Nanosecond-pulsed plasma protects against bacterial fruit blotch and promotes melon seedling growth.

BACKGROUND: Bacterial fruit blotch (BFB), known as the 'cancer' of cucurbits, is a seed-borne disease of melons caused by Acidovorax citrulli. Traditional chemical treatments for BFB are ineffective and adversely affect the environment. Using dielectric barrier discharge (DBD) nanosecond-pulsed plasma technology, melon seeds were treated to promote germination and growth and to control BFB. RESULTS: Based on the evaluation parameters of seed germination, seedling growth, leaf yellowing and bacterial infection after seed plasma treatments, 9 min at 20 kV was selected as the optimal plasma discharge parameter. In this study, seedling growth was significantly improved after treating melon seeds carrying A. citrulli using this discharge parameter. The number of first true leaves measured on the eighth day was 2.3 times higher and the disease index was reduced by 60.5% compared to the control group. Attenuated total reflectance-Fourier transform infrared measurements show that plasma treatments penetrate the seed coat and denature polysaccharides and proteins in the seed kernel, affecting their growth and sterilization properties. CONCLUSION: Pre-sowing treatment of melon seeds carrying A. citrulli using nanosecond-pulsed plasma technology can effectively control seedling BFB disease and promote melon seedling growth by optimizing DBD parameters. © 2024 Society of Chemical Industry.

CmPIF8-CmERF27-CmACS10-mediated ethylene biosynthesis modulates red light-induced powdery mildew resistance in oriental melon.

Powdery mildew is a serious fungal disease in protected melon cultivation that affects the growth, development and production of melon plants. Previous studies have shown that red light can improve oriental melon seedlings resistance to powdery mildew. Here, after inoculation with Podosphaera xanthii, an obligate fungal pathogen eliciting powdery mildew, we found that red light pretreatment increased ethylene production and this improved the resistance of melon seedlings to powdery mildew, and the ethylene biosynthesis gene CmACS10 played an important role in this process. By analysing the CmACS10 promoter, screening yeast one-hybrid library, it was found that CmERF27 positively regulated the expression of CmACS10, increased powdery mildew resistance and interacted with PHYTOCHROME INTERACTING FACTOR8 (CmPIF8) at the protein level to participate in the regulation of ethylene biosynthesis to respond to the red light-induced resistance to P. xanthii, Furthermore, CmPIF8 also directly targeted the promoter of CmACS10, negatively participated in this process. In summary, this study revealed the specific mechanism by which the CmPIF8-CmERF27-CmACS10 module regulates red light-induced ethylene biosynthesis to resist P. xanthii infection, elucidate the interaction between light and plant hormones under biological stress, provide a reference and genetic resources for breeding of disease-resistant melon plants.

Distinct effects of phyllosphere and rhizosphere microbes on invader Ageratina adenophora during its early life stages.

Microbes strongly affect invasive plant growth. However, how phyllosphere and rhizosphere soil microbes distinctively affect seedling mortality and growth of invaders across ontogeny under varying soil nutrient levels remains unclear. In this study, we used the invader Ageratina adenophora to evaluate these effects. We found that higher proportions of potential pathogens were detected in core microbial taxa in leaf litter than rhizosphere soil and thus leaf inoculation had more adverse effects on seed germination and seedling survival than soil inoculation. Microbial inoculation at different growth stages altered the microbial community and functions of seedlings, and earlier inoculation had a more adverse effect on seedling survival and growth. The soil nutrient level did not affect microbe-mediated seedling growth and the relative abundance of the microbial community and functions involved in seedling growth. The effects of some microbial genera on seedling survival are distinct from those on growth. Moreover, the A. adenophora seedling-killing effects of fungal strains isolated from dead seedlings by non-sterile leaf inoculation exhibited significant phylogenetic signals, by which strains of Allophoma and Alternaria generally caused high seedling mortality. Our study stresses the essential role of A. adenophora litter microbes in population establishment by regulating seedling density and growth.

Combined effects of cadmium and simulated acid rain on soil microbial communities in the early cultivation of Populus beijingensis seedlings.

The combined cadmium (Cd) and acid rain pollution poses a significant threat to the global ecological environment. Previous studies on the combined adverse effects have predominantly focused on the aboveground plant physiological responses, with limited reports on the microbial response in the rhizosphere soil. This study employed Populus beijingensis seedlings and potting experiments to simulate the impacts of combined mild acid rain (pH=4.5, MA) or highly strong acid rain (pH=3.0, HA), and soil Cd pollution on the composition and diversity of microbial communities, as well as the physiochemical properties in the rhizosphere soil. The results showed that Cd decreased the content of inorganic nitrogen, resulting in an overall decrease of 49.10 % and 46.67 % in ammonium nitrogen and nitrate nitrogen, respectively. Conversely, acid rain was found to elevate the content of total potassium and soil organic carbon by 4.68 %-6.18 % and 8.64-19.16 %, respectively. Additionally, simulated acid rain was observed to decrease the pH level by 0.29-0.35, while Cd increased the pH level by 0.11. Moreover, Cd alone reduced the rhizosphere bacterial diversity, however, when combined with acid rain, regardless of its intensity, Cd was observed to increase the diversity. Fungal diversity was not influenced by the acid rain, but Cd increased fungal diversity to some extend under HA as observed in bacterial diversity. In addition, composition of the rhizosphere bacterial community was primarily influenced by the inorganic nitrogen components, while the fungal community was driven mainly by soil pH. Furthermore, "Metabolism" was emerged as the most significant bacterial function, which was markedly affected by the combined pollution, while Cd pollution led to a shift from symbiotroph to other trophic types for fungi. These findings suggest that simulated acid rain has a mitigating effect on the diversity of rhizosphere bacteria affected by Cd pollution, and also alters the trophic type of these microorganisms. This can be attributed to the acid rain-induced direct acidic environment, as well as the indirect changes in the availability or sources of carbon, nitrogen, or potassium.

Deciphering the mechanistic role of Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52) in bio-sorption and phyto-assimilation of Cadmium via Linum usitatissimum L. Seedlings.

Three Cd2+ resistant bacterium's minimal inhibition concentrations were assessed and their percentages of Cd2+ accumulation were determined by measurements using an atomic absorption spectrophotometer (AAS). The results revealed that two isolates Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52), identified by 16S rDNA gene sequencing, showed a higher percentage of Cd2+ accumulation i.e., 83.78% and 81.79%, respectively. Moreover, both novel strains can tolerate Cd2+ levels up to 2000 mg/L isolated from district Chakwal. Amplification of the czcD, nifH, and acdS genes was also performed. Batch bio-sorption studies revealed that at pH 7.0, 1 g/L of biomass, and an initial 150 mg/L Cd2+ concentration were the ideal bio-sorption conditions for Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52). The experimental data were fit to Langmuir isotherm measurements and Freundlich isotherm model R2 values of 0.999 for each of these strains. Bio sorption processes showed pseudo-second-order kinetics. The intra-diffusion model showed Xi values for Bacillus paramycoides (PM51) and Bacillus tequilensis (PM52) of 2.26 and 2.23, respectively. Different surface ligands, was investigated through Fourier-transformation infrared spectroscopy (FTIR). The scanning electron microscope SEM images revealed that after Cd2+ adsorption, the cells of both strains became thick, adherent, and deformed. Additionally, both enhanced Linum usitatissimum plant seed germination under varied concentrations of Cd2+ (0 mg/L, 250 mg/L,350 mg/L, and 500 mg/L). Current findings suggest that the selected strains can be used as a sustainable part of bioremediation techniques.

Investigating the in vivo biocontrol and growth-promoting efficacy of Bacillus sp. and Pseudomonas fluorescens against olive knot disease.

Olive knot disease, caused by Pseudomonas savastanoi, poses a significant threat to olive cultivation, necessitating sustainable alternatives to conventional chemical control. This study investigates the biocontrol effectiveness of Bacillus sp. (Og2) and Pseudomonas fluorescens (Oq5), alone and combined, against olive knot disease. Olive plants were sprayed with 5 ml of the bacteria until uniformly wet, with additional application to the soil surface. Pathogen injection occurred 24 h later. The results revealed that treating plants with a combination of both bacteria provided the highest reduction in disease severity (89.58 %), followed by P. fluorescens alone (69.38 %). Significant improvements were observed in shoot height, particularly with the combination of Bacillus sp. and P. fluorescens. The root length of olive seedlings treated with P. fluorescens and Bacillus sp., either alone or in combination, was significantly longer compared to the control and pathogen-treated seedlings. In terms of root dry weight, the most effective treatments were treated with P. fluorescens was the highest (82.94 g) among all treatments followed by the combination of both isolates with seedlings inoculated with P. savastanoi. These findings underscore the potential of Bacillus sp. and Pseudomonas fluorescens as effective biocontrol agents against olive knot disease and promoting olive seedlings growth, providing a sustainable and environmentally friendly approach to disease management.

Plant-soil microbe feedbacks depend on distance and ploidy in a mixed cytotype population of Larrea tridentata.

PREMISE: Theory predicts that mixed ploidy populations should be short-lived due to strong fitness disadvantages for the rare ploidy. However, mixed ploidy populations are common, suggesting that the fitness costs for rare ploidies are counterbalanced by ecological benefits that emerge when rare. We investigated whether differences in ecological interactions with soil microbes help to maintain a tetraploid-hexaploid population of Larrea tridentata (creosote bush) in the Sonoran Desert, California, United States, where prior work documented ploidy-specific root-associated microbes. METHODS: We used a plant-soil feedback (PSF) experiment to test whether host-specific soil microbes can alter the outcomes of intraploidy vs. interploidy competition. Host-specific soil microbes can build up over time; thus, distance from a host plant can affect the fitness of nearby plants. RESULTS: Seedlings grown in soils from near plants of a different ploidy produced greater biomass relative to seedlings grown in soils from near plants of the same ploidy. Moreover, seedlings grown in soils from near plants of a different ploidy produced more biomass than those grown in soils that were farther from plants of a different ploidy. These results suggest that the ecological consequences of PSF may facilitate the persistence of mixed ploidy populations. CONCLUSIONS: This is the first evidence, to our knowledge, that is consistent with plant-soil microbe feedback as a viable mechanism to maintain the coexistence of multiple ploidy levels in a single population.

Rice foliar-adapted Pantoea species: Promising microbial biostimulants enhancing rice resilience against foliar pathogens, Magnaporthe oryzae and Xanthomonas oryzae pv. oryzae.

Foliar fungal blast and bacterial leaf blight have significant impacts on rice production, and their management through host resistance and agrochemicals has proven inadequate. To achieve their sustainable management, innovative approaches like leveraging the foliar microbiome, which collaborates with plants and competes against pathogens, are essential. In our study, we isolated three Pantoea strains (P. agglomerans Os-Ep-PPA-1b, P. vagans Os-Ep-PPA-3b, and P. deleyi Os-Ep-VPA-9a) from the rice phylloplane. These isolates exhibited antimicrobial action through their metabolome and volatilome, while also promoting rice growth. Our analysis, using Gas Chromatography-Mass Spectrometry (GC-MS), revealed the presence of various antimicrobial compounds such as esters and fatty acids produced by these Pantoea isolates. Inoculating rice seedlings with P. agglomerans and P. vagans led to increased root and shoot growth. Additionally, bacterized seedlings displayed enhanced immunocompetence, as evidenced by upregulated expressions of defense genes (OsEDS1, OsFLS2, OsPDF2.2, OsACO4, OsICS OsPR1a, OsNPR1.3, OsPAD4, OsCERK1.1), along with heightened activities of defense enzymes like Polyphenol Oxidase and Peroxidase. These plants also exhibited elevated levels of total phenols. In field trials, the Pantoea isolates contributed to improved plant growth, exemplified by increased flag-leaf length, panicle number, and grains per panicle, while simultaneously reducing the incidence of chaffy grains. Hypersensitivity assays performed on a model plant, tobacco, confirmed the non-pathogenic nature of these Pantoea isolates. In summary, our study underscores the potential of Pantoea bacteria in combatting rice foliar diseases. Coupled with their remarkable growth-promoting and biostimulant capabilities, these findings position Pantoea as promising agents for enhancing rice cultivation.

Comparison of Ganoderma boninense Isolate's Aggressiveness Using Infected Oil Palm Seedlings.

Basal stem rot incidence caused by a white-rot fungus, Ganoderma boninense, is the major disease of oil palm in Southeast Asia. The rate of disease transmission and host damage are affected by variations in pathogen aggressiveness. Several other studies have used the disease severity index (DSI) to determine G. boninense aggressiveness levels while verifying disease using a culture-based method, which might not provide accurate results or be feasible in all cases. To differentiate G. boninense aggressiveness, we employed the DSI and vegetative growth measurement of infected oil palm seedlings. Disease confirmation was performed through scanning electron microscopy and molecular identification of fungal DNA from both infected tissue and fungi isolated from Ganoderma selective medium. Two-month-old oil palm seedlings were artificially inoculated with G. boninense isolates (2, 4A, 5A, 5B, and 7A) sampled from Miri (Lambir) and Mukah (Sungai Meris and Sungai Liuk), Sarawak. The isolates were categorized into three groups: highly aggressive (4A and 5B), moderately aggressive (5A and 7A), and less aggressive (2). Isolate 5B was identified as the most aggressive, and it was the only one to result in seedling mortality. Out of the five vegetative growth parameters measured, only the bole size between treatments was not affected. The integration of both conventional and molecular approaches in disease confirmation allows for precise detection.

The Leucine-Rich Repeat Receptor-Like Kinase Protein TaSERK1 Positively Regulates High-Temperature Seedling Plant Resistance to Puccinia striiformis f. sp. tritici by Interacting with TaDJA7.

Somatic embryogenesis receptor kinases (SERKs) belong to the leucine-rich repeat receptor-like kinase (LRR-RLK) subfamily, and many LRR-RLKs have been proven to play a key role in plant immune signal transmission. However, the functions of SERKs in resistance to stripe rust caused by Puccinia striiformis f. sp. tritici remains unknown. Here, we identified a gene, TaSERK1, from Xiaoyan 6, a wheat cultivar possessing high-temperature seedling-plant (HTSP) resistance to the fungal pathogen P. striiformis f. sp. tritici and expresses its resistance at the seedling stage. The expression level of TaSERK1 was upregulated upon P. striiformis f. sp. tritici inoculation under relatively high temperatures. The transcriptional level of TaSERK1 was significantly increased under exogenous salicylic acid and brassinosteroids treatments. The barley stripe mosaic virus-induced gene silencing assay indicated that TaSERK1 positively regulated the HTSP resistance to stripe rust. The transient expression of TaSERK1 in tobacco leaves confirmed its subcellular localization on the plasma membrane. Furthermore, TaSERK1 interacted with and phosphorylated the chaperone protein TaDJA7, which belongs to the heat shock protein 40 subfamily. Silencing TaDJA7 compromised the HTSP resistance to stripe rust. The results indicated that when the membrane immune receptor TaSERK1 perceives the P. striiformis f. sp. tritici infection under relatively high temperatures, it transmits the signal to TaDJA7 to activate HTSP resistance to the pathogen.

Assessment of copper (Cu) nanoparticle for their biocontrol activity against Xanthomonas oryzae pv. oryzae, growth promotion, and physiology of rice (Oryza sativa L.) plants.

Among the various biotic factors that disrupt crop yield, Xanthomonas oryzae pv oryzae (Xoo) is the most ruinous microbe of rice and causes bacterial leaf blight (BLB) disease. The present study focused on the utilization of copper nanoparticles (Cu-NPs) to control BLB. The copper nanosuspension (259.7 nm) prepared using Na-CMC, CuSO4·7H2O, and NaOH showed effectively inhibited Xoo (65.0 µg/ml). The performance of Cu-NPs in vivo showed enhanced plant attributes (127.9% root length and 53.9% shoot length) compared to the control and CuSO4 treated seedling. Furthermore, Cu-NPs treated seedlings showed 23.01% disease incidence (DI) compared to CuSO4 (85.71%) treated and control plants (91.83%). In addition to enhancing the growth parameters and reducing DI, seed priming with Cu-NPs improved the total chlorophyll content to 36.0% compared to the control. The assessment of antioxidant enzymes such as superoxide dismutase (1.9 U), polyphenol oxidase, peroxidase, and phenylalanine ammonia-lyase (two- to three-fold) in roots and shoots of rice plants revealed significant enhancement in Cu-NPs treated seedlings (P < 0.05). The present study suggests that Cu-NPs can be used to control Xoo and enhance rice growth.