High resolution microscopy to evaluate the efficiency of surface sterilization of Zea Mays seeds

Synergistic effects of Trichoderma and biochar on the biocontrol of two soil-borne phytopathogens in chickpeas

Introduction

This study aims to identify and characterize four Trichoderma isolates using molecular techniques, Fourier transform infrared spectroscopy (FTIR), and volatile organic compounds (VOC) profiling.

Methods

The antagonistic activity of these isolates was assessed against Fusarium oxysporum f. sp. ciceri (FOC) and Sclerotium rolfsii (SR) using a dual culture technique. The synergistic effect of Trichoderma harzianum (accession no. PP256488) combined with biochar (BC) was evaluated for plant growth enhancement and disease suppression. Four Trichoderma isolates (T. harzianum, T. asperellum, T. virens, and T. lixii) were identified through ITS region analysis, VOC profiling, and FTIR spectroscopy.

Results

Molecular analysis confirmed their distinct identities, and GC-MS analysis revealed 37 VOCs out of 162 with antipathogenic properties. Unique FTIR peaks were recorded at 3271.96 cm-1 for T. virens, 2800-2900 cm-1 for T. asperellum, and 2850-2950 cm-1 for both T. lixii and T. harzianum. Scanning electron microscopy (SEM) analysis of T. harzianum revealed mycoparasitic structures, including hyphal coils, penetration holes, and appressoria, indicating effective pathogen interaction. The combined application of Trichoderma and biochar (T9) significantly enhanced root length (9.23 cm), plant height (26.03 cm), and root mass (43.33 g) in chickpea plants. Moreover, treatments (T9) and (T10) reduced the disease incidence in chickpeas, decreasing fusarium wilt by 27% and collar rot by 33%, respectively.

Conclusion

This sustainable approach exhibits the potential of combined application of Trichoderma and biochar which can enhance plant growth and reduce disease incidence, and improve food security.

Growth-promoting effects of arbuscular mycorrhizal fungus Funneliformis mosseae in rice, sesame, sorghum, Egyptian pea and Mexican hat plant

Excessive use and overreliance on chemical fertilizers threatens soil health and environmental sustainability, necessitating eco-friendly alternatives like arbuscular mycorrhizal fungi (AMF). The benefits of AMF are well-documented in staple crops, their effects on diverse species-particularly legumes and non-crop models under uniform conditions-remain underexplored, limiting their scalable adoption. This study evaluated Funneliformis mosseae's role in enhancing growth, nutrient uptake, and stress resilience across five species: rice (Oryza sativa), sesame (Sesamum indicum), sorghum (Sorghum bicolor), Egyptian pea (Sesbania sesban), and the non-crop Kalanchoe daigremontiana. The pot-experiment was conducted in natural open-field conditions (e.g., ambient light, temperature, and humidity) and inoculated plants were analyzed for biomass yield, nutrient concentrations, and physiological parameters to evaluate F. mosseae's efficacy as a sustainable growth promoter. Inoculation with F. mosseae significantly enhanced plant performance across all species. Rice exhibited a 43% increase in dry biomass, alongside 53% higher phosphorus uptake and 24.5% greater magnesium accumulation. Root development improved markedly, with sesame, sorghum, Egyptian pea, and Mexican hat plants showing root length increases of 66.7, 42.9, 35, and 33.3%, respectively. Biomass gains were consistent: Egyptian pea (29% fresh biomass, 33% dry), sesame (30% fresh, 39% dry), sorghum (36.6% total), and Mexican hat plant (31% fresh, 34% dry). Nutrient uptake surged systemically, including potassium (sesame: 42%, Egyptian pea: 17.8%), calcium (sesame: 54.5%, sorghum: 29.4%), and magnesium (Mexican hat plant: 32.4%, Egyptian pea: 22.5%). Physiologically, photosynthetic rates rose by 21.4-45% (highest in Egyptian pea), stomatal conductance improved by 23.3-71.4% (peak in sesame), and chlorophyll a and b levels increased by 30-39.1% and 44.4-150.8%, respectively, across species. These results suggested that F. mosseae could provide a sustainable, environment friendly substitute for chemical fertilizers, preparing for the future of agriculture, where ecological services such as crop productivity and soil fertility depend on mycorrhizas alongside conventional cultivation practices. Integrating AMF into agricultural systems offers a potential strategy for eco-friendly farming practices that are viable and secure for long-term food security and eco-sustainability.

Contribution of arbuscular mycorrhiza and exoenzymes to nitrogen acquisition of sorghum under drought

Introduction

For low-fertile and degraded soils of sub-Saharan Africa, nitrogen (N) is often the most growth-limiting factor restricting crop yields. The often-suggested exploitation of advantageous rhizosphere traits such as enzyme secretion and/or the symbiosis with arbuscular mycorrhizal fungi (AMF) remains to be validated as a potential strategy to overcome N limitation, especially when N deficiency co-occurs with further abiotic stresses such as water scarcity.

Methods

Three sorghum genotypes were cultivated in soil mesocosms with a root-exclusion compartment, where only AMF could scavenge for nutrients under drought and optimal conditions. Plant carbon (C) investment into the rhizosphere and N uptake were tracked by 15N application coupled with 13CO2 labeling.

Results

Under drought, uptake of mineral 15N by AMF from the root-exclusion compartment increased 4-12 times compared to well-watered conditions. In addition, water stress enhanced below-ground allocation of recently assimilated C into microbial biomass. Drought reduced the enzymatic potential (Vmax) of chitinase while increasing leucine aminopeptidase (LAP) activity. This suggests that N acquisition via protein mineralization in soil was relatively enhanced compared to that of chitin following moisture limitation. LAP substrate affinity (Km) was reduced by drought compared to that of chitinase with genotype-specific shifts in the rhizosphere enzyme systems observed.

Conclusion

Our findings suggest that below-ground C allocation activated AMF symbiosis and its associated microbiome. This not only led to a shift in enzyme-driven exploitation of distinct organic N sources but also induced a strong increase in AMF-based mineral N acquisition from the mycosphere. This trait plasticity in response to drought may be harnessed to stabilize food production from low-fertile soil under the increasingly negative impacts of droughts due to climate change.

Efficacy of fungal antagonists against aflatoxins, ochratoxin A, and fumonisins at different pathogen:antagonist inoculum ratios on grain corn agar and grain corn kernel

AIM

The present work investigated the efficacy of native biocontrol candidates (antagonists) against aflatoxins, ochratoxin A (OTA), and fumonisins produced by native mycotoxigenic fungi isolated from Malaysia at different pathogen: antagonist inoculum ratios on grain corn agar and grain corn kernels.

METHODS AND RESULTS

Five pathogen: antagonist inoculum ratios (100:0, 75:25, 50:50, 25:75, and 0:100) were employed. Non-aflatoxigenic Aspergillus flavus Af1KD and Af5TD, and Penicillium janthinellum were used against aflatoxin B1 (AFB1) and aflatoxin B2 (AFB2) by A. flavus. Against OTA by A. niger, and fumonisin B1 (FB1) and fumonisin B2 (FB2) by Fusarium verticillioides and F. proliferatum, respectively, the antagonists Trichoderma asperelloides, T. asperellum, and T. harzianum were used. Non-aflatoxigenic A. flavus Af1KD was the most effective against AFB1 and AFB2 at all tested ratios and substrates. All Trichoderma spp. were effective against OTA by A. niger on grain corn agar at all tested ratios. Trichoderma asperelloides and T. asperellum were effective against FB1 and FB2 produced by F. verticillioides at all tested ratios and substrates. Trichoderma asperelloides was effective against FB1 and FB2 by F. proliferatum at all tested ratios and substrates.

CONCLUSION

The native biocontrol candidates were effective against mycotoxigenic fungi and mycotoxin production on grain corn agar and grain corn kernels, and could be developed into biocontrol agents.

Influence of Seed Disinfection Treatments on the Germination Rate and Histamine-Degrading Activity of Legume Sprouts

Edible legume sprouts have been proposed as a promising plant-based source of the enzyme diamine oxidase (DAO), which plays a key role in degrading histamine at an intestinal level and preventing the development of histamine intolerance symptoms. However, the temperature and humidity conditions required for seed germination can also favor the rapid growth of yeast and mold, potentially compromising sprout yield and quality. The aim of this study was to evaluate the influence of different seed disinfection treatments on both the germination rate and DAO enzymatic activity in sprouts of four Leguminosae species. Seed disinfection with 70% ethanol for either 5 or 15 min slightly increased the germination rates of chickpea and soybean sprouts without affecting DAO activity, regardless of treatment duration. However, in lentil and green pea sprouts, ethanol disinfection caused a statistically significant reduction in histamine-degrading capacity. In contrast, treating seeds with sodium hypochlorite for 15 min increased germination rates by up to 14% and preserved DAO activity in all legume sprouts tested. These results indicate that incorporating a seed disinfection step during legume sprouting may affect both the DAO enzymatic activity and germination rate.

Demonstration of the synergistic effect of biochar and Trichoderma harzianum on the development of Ralstonia solanacearum in eggplant

Soil degradation has been accelerated by the use of chemical pesticides and poor agricultural practices, which has had an impact on crop productivity. Recently, there has been a lot of interest in the use of eco-friendly biochar applications to enhance soil quality and sequester carbon in sustainable agriculture. This study aimed to determine the individual and combined effects of Leaf Waste Biochar (LWB) and the bio-control agent Trichoderma harzianum (BCA) on the development of bacterial wilt in eggplants (Solanum melongena) caused by Ralstonia solanacearum (RS). The effects of LWB and BCA on eggplant physiology and defense-related biochemistry were comprehensively examined. Inoculated (+RS) and un-inoculated (-RS) eggplants were grown in potting mixtures containing 3% and 6% (v/v) LWB, both with and without BCA. The percentage disease index was considerably reduced (90%) in plants grown in the 6% LWB+ BCA amended treatments. Moreover, the plants grown in LWB and inoculated with BCA had higher phenolics, flavonoids and peroxidase contents compared to the non-amended control. The level of NPK was significantly increased (92.74% N, 76.47% P, 53.73% K) in the eggplants cultivated in the 6% LWB + BCA composition. This study has shown that the association of T. harzianum with biochar improved plant growth and reduced R. solanacearum induced wilt. Furthermore, the combined impact of biochar and T. harzianum was greater in terms of wilt suppression and increase in plant physiological measurements when the biochar concentration was 6%. Biochar and bio-control agents triggered biochemical alterations, thus enhancing the management of disease-infested soils.

The association between Dioscorea sansibarensis and Orrella dioscoreae as a model for hereditary leaf symbiosis

Hereditary, or vertically-transmitted, symbioses affect a large number of animal species and some plants. The precise mechanisms underlying transmission of functions of these associations are often difficult to describe, due to the difficulty in separating the symbiotic partners. This is especially the case for plant-bacteria hereditary symbioses, which lack experimentally tractable model systems. Here, we demonstrate the potential of the leaf symbiosis between the wild yam Dioscorea sansibarensis and the bacterium Orrella dioscoreae (O. dioscoreae) as a model system for hereditary symbiosis. O. dioscoreae is easy to grow and genetically manipulate, which is unusual for hereditary symbionts. These properties allowed us to design an effective antimicrobial treatment to rid plants of bacteria and generate whole aposymbiotic plants, which can later be re-inoculated with bacterial cultures. Aposymbiotic plants did not differ morphologically from symbiotic plants and the leaf forerunner tip containing the symbiotic glands formed normally even in the absence of bacteria, but microscopic differences between symbiotic and aposymbiotic glands highlight the influence of bacteria on the development of trichomes and secretion of mucilage. This is to our knowledge the first leaf symbiosis where both host and symbiont can be grown separately and where the symbiont can be genetically altered and reintroduced to the host.

Correction: High resolution microscopy to evaluate the efficiency of surface sterilization of Zea Mays seeds

[This corrects the article DOI: 10.1371/journal.pone.0242247.].

Physiological and biochemical characterization of biochar-induced resistance against bacterial wilt of eggplants

The abrupt variation in climatic patterns has become a global concern in terms of food security. Biochar, known to ameliorate climatic adversities by sequestering carbon and activating systemic resistance pathways in plants, has become increasingly relevant. Therefore, the study was aimed to characterize leaf waste biochar (LWB) by Fourier-transform infrared spectroscopy, scanning electron microscopy with energy dispersive X-ray (SEM-EDX) and X-ray diffraction analytical techniques as well as determination of its impact on the development of bacterial wilt (BW) in eggplant (Solanum melongena) caused by Ralstonia solanacearum (RS). The effect of LWB on the physiology and defence-associated biochemistry of eggplants was investigated thoroughly. Eggplants either inoculated (+RS) or uninoculated (-RS) were cultivated in potting mixture containing 3 and 6% (v/v) LWB separately. In comparison with substrate (soil only), percentage disease index was significantly reduced (71%) in plants grown in 6% LWB-amended treatments. Biochar-induced increase in level of total chlorophyll content as well as in biochemicals such as phenolics, flavonoids and peroxidases were evident on plants in terms of resistance response against BW. Moreover, biochar also significantly affected the level of NPK in the eggplants. In conclusion, biochar-triggered biochemical alterations played a pivotal role in the management of BW along with the curing of the disease-infested soils.

Tracking deuterium uptake in hydroponically grown maize roots using correlative helium ion microscopy and Raman micro-spectroscopy

BACKGROUND

Investigations into the growth and self-organization of plant roots is subject to fundamental and applied research in various areas such as botany, agriculture, and soil science. The growth activity of the plant tissue can be investigated by isotope labeling experiments with heavy water and subsequent detection of the deuterium in non-exchangeable positions incorporated into the plant biomass. Commonly used analytical methods to detect deuterium in plants are based on mass-spectrometry or neutron-scattering and they either suffer from elaborated sample preparation, destruction of the sample during analysis, or low spatial resolution. Confocal Raman micro-spectroscopy (CRM) can be considered a promising method to overcome the aforementioned challenges. The substitution of hydrogen with deuterium results in the measurable shift of the CH-related Raman bands. By employing correlative approaches with a high-resolution technique, such as helium ion microscopy (HIM), additional structural information can be added to CRM isotope maps and spatial resolution can be further increased. For that, it is necessary to develop a comprehensive workflow from sample preparation to data processing.

RESULTS

A workflow to prepare and analyze roots of hydroponically grown and deuterium labeled Zea mays by correlative HIM-CRM micro-analysis was developed. The accuracy and linearity of deuterium detection by CRM were tested and confirmed with samples of deuterated glucose. A set of root samples taken from deuterated Zea mays in a time-series experiment was used to test the entire workflow. The deuterium content in the roots measured by CRM was close to the values obtained by isotope-ratio mass spectrometry. As expected, root tips being the most actively growing root zone had incorporated the highest amount of deuterium which increased with increasing time of labeling. Furthermore, correlative HIM-CRM analysis allowed for obtaining the spatial distribution pattern of deuterium and lignin in root cross-sections. Here, more active root zones with higher deuterium incorporation showed less lignification.

CONCLUSIONS

We demonstrated that CRM in combination with deuterium labeling can be an alternative and reliable tool for the analysis of plant growth. This approach together with the developed workflow has the potential to be extended to complex systems such as plant roots grown in soil.

Alnus nitida and urea-doped Alnus nitida-based silver nanoparticles synthesis, characterization, their effects on the biomass and elicitation of secondary metabolites in wheat seeds under in vitro conditions

Nano-fertilizers are superior to conventional fertilizers, but their effectiveness has not yet been adequately explored in the field of agriculture. In this study, silver nanoparticles using leaves extract of an Alnus nitida plant were synthesized and further doped with urea to enhance the plant biomass and metabolic contents. The synthesized Alnus nitida silver nanoparticles (A.N-AgNPs) and urea-doped silver nanoparticles (U-AgNPs) were characterized using Scanning Electron Microscopy, Transmission Electron Microscopy, Powder X-ray Diffraction, and Energy Dispersive X-ray. The wheat seeds were grown in media under controlled conditions in the plant growth chamber. The effectiveness of nanoparticles was studied using different A.N-AgNPs and U-AgNPs concentrations (0.75 μg/ml, 1.5 μg/ml, 3 μg/ml, 6 μg/ml, and 15 μg/ml). They were compared with a control group that received no dose of nanoparticles. The plant biomass, yield parameters, and wheat quality were analyzed. The effect of silver nanoparticles and U-AgNPs were examined in developing wheat seeds and their potency in combating biotic stresses such as nematodes, herbivores, fungi, insects, weeds and bacteria; abiotic stresses such as salinity, ultraviolet radiation, heavy metals, temperature, drought, floods etc. In the seedlings, six possible phytochemicals at a spray dose of 6 μg/ml of U-AgNPs were identified such as dihydroxybenzoic acids, vanillic acid, apigenin glucosidase, p-coumaric acid, sinapic acid, and ferulic acid whereas in other treatments the number of phenolic compounds was lesser in number as well as in concentrations. Moreover, various parameters of the wheat plants, including their dry weight and fresh weight, were assessed and compared with control group. The findings of the study indicated that A.N-AgNPs and U-AgNPs act as metabolite elicitors that induced secondary metabolite production (total phenolic, flavonoid, and chlorophyll contents). In addition, U-AgNPs provided a nitrogen source and were considered a smart nitrogen fertilizer that enhanced the plant biomass, yields, and metabolite production.

Monilinia fructigena Suppressing and Plant Growth Promoting Endophytic Pseudomonas spp. Bacteria Isolated from Plum

Brown rot caused by Monilinia spp. fungi causes substantial losses in stone and pome fruit production. Reports suggest that up to 90% of the harvest could be lost. This constitutes an important worldwide issue in the food chain that cannot be solved by the use of chemical fungicides alone. Biocontrol agents (BCAs) based on microorganisms are considered a potential alternative to chemical fungicides. We hypothesized that endophytic bacteria from Prunus domestica could exhibit antagonistic properties towards Monilinia fructigena, one of the main causative agents of brown rot. Among the bacteria isolated from vegetative buds, eight isolates showed antagonistic activity against M. fructigena, including three Pseudomonas spp. isolates that demonstrated 34% to 90% inhibition of the pathogen's growth when cultivated on two different media in vitro. As the stimulation of plant growth could contribute to the disease-suppressing activity of the potential BCAs, plant growth promoting traits (PGPTs) were assessed for bacterial isolates with M. fructigena-suppressing activity. While all isolates were capable of producing siderophores and indole-3-acetic acid (IAA), fixating nitrogen, mineralizing organic phosphate, and solubilizing inorganic phosphate and potassium, only the Pseudomonas spp. isolates showed 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity. Overall, our study paves the way for the development of an eco-friendly strategy for managing M. fructigena pathogens by using BCAs including Pseudomonas spp. bacteria, which could also serve as growth stimulators.

Incorporation of engineered nanoparticles of biochar and fly ash against bacterial leaf spot of pepper

In agriculture, the search for higher net profit is the main challenge in the economy of the producers and nano biochar attracts increasing interest in recent years due to its unique environmental behavior and increasing the productivity of plants by inducing resistance against phytopathogens. The effect of rice straw biochar and fly ash nanoparticles (RSBNPs and FNPs, respectively) in combination with compost soil on bacterial leaf spot of pepper caused by Xanthomonascampestris pv. vesicatoria was investigated both in vitro and in vivo. The application of nanoparticles as soil amendment significantly improved the chili pepper plant growth. However, RSBNPs were more effective in enhancing the above and belowground plant biomass production. Moreover, both RSBNPs and FNPs, significantly reduced (30.5 and 22.5%, respectively), while RSBNPs had shown in vitro growth inhibition of X.campestris pv. vesicatoria by more than 50%. The X-ray diffractometry of RSBNPs and FNPs highlighted the unique composition of nano forms which possibly contributed in enhancing the plant defence against invading X.campestris pv. vesicatoria. Based on our findings, it is suggested that biochar and fly ash nanoparticles can be used for reclaiming the problem soil and enhance crop productivity depending upon the nature of the soil and the pathosystem under investigation.

Surface sterilization for isolation of endophytes: Ensuring what (not) to grow

Endophytic microbiota opens a magnificent arena of metabolites that served as a potential source of medicines for treating a variety of ailments and having prospective uses in agriculture, food, cosmetics, and many more. There are umpteen reports of endophytes improving the growth and tolerance of plants. In addition, endophytes from lifesaving drug-producing plants such as Taxus, Nothapodytes, Catharanthus, and so forth have the ability to produce host mimicking compounds. To harness these benefits, it is imperative to isolate the true endophytes, not the surface microflora. The foremost step in endophyte isolation is the removal of epiphytic microbes from plant tissues, called as surface sterilization. The success of surface sterilization decides "what to grow" (the endophytes) and "what not to grow" (the epiphytes). It is very crucial to use an appropriate sterilant solution, concentration, and exposure time to ensure thorough surface disinfection with minimal damage to the endophytic diversity. Commonly used surface sterilants include sodium hypochlorite (2%-10%), ethanol (70%-90%), mercuric chloride (0.1%), formaldehyde (40%), and so forth. In addition, the efficiency could further be improved by pretreatment with surfactants such as Triton X-100, Tween 80, and Tween 20. This review comprehensively deals with the various sterilants and sterilization methods for the isolation of endophytic microbes. In addition, the mechanisms and rationale behind using specific surface sterilants have also been elaborated at length.