In Vivo and Real-Time Metabolic Profiling of Plant-Microbe Interactions in Leaves, Stems, and Roots of Bacterially Inoculated Chardonnay Plantlets using SpiderMass.

There is growing interest in limiting the use of fungicides and implementing innovative, environmentally friendly strategies, such as the use of beneficial bacteria-triggered immunity, to protect grapevines from natural pathogens. Therefore, we need rapid and innovative ways to translate the knowledge of the molecular mechanisms underlying the activation of grapevine defenses against pathogens to induced resistance. Here, we have implemented an in vivo minimally invasive approach to study the interaction between plants and beneficial bacteria based on metabolic signatures. Paraburkholderia phytofirmans strain PsJN and PsJN-grapevine were used as bacterial and plant-bacterium interaction models, respectively. Using an innovative tool, SpiderMass, based on water-assisted laser desorption ionization with an IR microsampling probe, we simultaneously detect metabolic and lipidomic species. A metabolomic spectrum was thus generated, which was used to build a library and identify the most variable and discriminative peaks between the two conditions. We then showed that caftaric acid (m/z 311.04), caftaric acid dimer (m/z 623.09), derived caftaric acid (m/z 653.15), and quercetin-O-glucuronide tended to accumulate in grapevine leaves after root bacterization with PsJN. In addition, together with these phenolic messengers, we identified lipid biomarkers such as palmitic acid, linoleic acid, and α-linoleic acid as important messengers of enhanced defense mechanisms in Chardonnay plantlets. Taken together, SpiderMass is the next-generation methodology for studying plant-microorganism metabolic interactions with the prospect of in vivo real-time analysis in viticulture.

Exploring the Antifungal Activity of Moroccan Bacterial and Fungal Isolates and a Strobilurin Fungicide in the Control of Cladosporium fulvum, the Causal Agent of Tomato Leaf Mold Disease.

The causal agent of tomato leaf mold, Cladosporium fulvum, is prevalent in greenhouses worldwide, especially under high humidity conditions. Despite its economic impact, studies on antifungal agents targeting C. fulvum remain limited. This study evaluates biocontrol agents (BCAs) as alternatives to chemical controls for managing this disease, alongside the strobilurin fungicide azoxystrobin. From a Moroccan collection of potential BCAs, five bacterial isolates (Alcaligenes faecalis ACBC1, Pantoea agglomerans ACBC2, ACBP1, ACBP2, and Bacillus amyloliquefaciens SF14) and three fungal isolates (Trichoderma spp. OT1, AT2, and BT3) were selected and tested. The in vitro results demonstrated that P. agglomerans isolates reduced mycelial growth by over 60% at 12 days post-inoculation (dpi), while Trichoderma isolates achieved 100% inhibition in just 5 dpi. All bacterial isolates produced volatile organic compounds (VOCs) with mycelial inhibition rates ranging from 38.8% to 57.4%. Likewise, bacterial cell-free filtrates significantly inhibited the pathogen's mycelial growth. Greenhouse tests validated these findings, showing that all the tested isolates were effective in reducing disease incidence and severity. Azoxystrobin effectively impeded C. fulvum growth, particularly in protective treatments. Fourier transform infrared spectroscopy (FTIR) analysis revealed significant biochemical changes in the treated plants, indicating fungal activity. This study provides valuable insights into the efficacy of these BCAs and azoxystrobin, contributing to integrated management strategies for tomato leaf mold disease.

Deep Learning-Based Barley Disease Quantification for Sustainable Crop Production.

Net blotch disease caused by Drechslera teres is a major fungal disease that affects barley (Hordeum vulgare) plants and can result in significant crop losses. In this study, we developed a deep learning model to quantify net blotch disease symptoms on different days postinfection on seedling leaves using Cascade R-CNN (region-based convolutional neural network) and U-Net (a convolutional neural network) architectures. We used a dataset of barley leaf images with annotations of net blotch disease to train and evaluate the model. The model achieved an accuracy of 95% for Cascade R-CNN in net blotch disease detection and a Jaccard index score of 0.99, indicating high accuracy in disease quantification and location. The combination of Cascade R-CNN and U-Net architectures improved the detection of small and irregularly shaped lesions in the images at 4 days postinfection, leading to better disease quantification. To validate the model developed, we compared the results obtained by automated measurement with a classical method (necrosis diameter measurement) and a pathogen detection by real-time PCR. The proposed deep learning model could be used in automated systems for disease quantification and to screen the efficacy of potential biocontrol agents to protect against disease.

Phosphate solubilizing Pseudomonas and Bacillus combined with rock phosphates promoting tomato growth and reducing bacterial canker disease.

Nowadays, sustainable agriculture approaches are based on the use of biofertilizers and biopesticides. Tomato (Solanum lycopersicum L.) rhizosphere could provide rhizobacteria with biofertilizing and biopesticide properties. In this study, bacteria from the rhizosphere of tomato were evaluated in vitro for plant growth promotion (PGP) properties. Five Pseudomonas isolates (PsT-04c, PsT-94s, PsT-116, PsT-124, and PsT-130) and one Bacillus isolate (BaT-68s), with the highest ability to solubilize tricalcium phosphate (TCP) were selected for further molecular identification and characterization. Isolates showed phosphate solubilization up to 195.42 µg mL-1. All isolates showed phosphate solubilization by organic acid production. The six isolates improved seed germination and showed effective root colonization when tomato seeds were coated with isolates at 106 cfu g-1 in axenic soil conditions. Furthermore, the selected isolates were tested for beneficial effects on tomato growth and nutrient status in greenhouse experiments with natural rock phosphate (RP). The results showed that inoculated tomato plants in the presence of RP have a higher shoot and root lengths and weights compared with the control. After 60 days, significant increases in plant Ca, Na, P, protein, and sugar contents were also observed in inoculated seedlings. In addition, inoculated tomato seedlings showed an increase in foliar chlorophyll a and b and total chlorophyll, while no significant changes were observed in chlorophyll fluorescence. In greenhouse, two Pseudomonas isolates, PsT-04c and PsT-130, showed ability to trigger induced systemic resistance in inoculated tomato seedlings when subsequently challenged by Clavibacter michiganensis subsp. michiganensis, the causal agent of tomato bacterial canker. High protection rate (75%) was concomitant to an increase in the resistance indicators: total soluble phenolic compounds, phenylalanine-ammonia lyase, and H2O2. The results strongly demonstrated the effectiveness of phosphate-solubilizing bacteria adapted to rhizosphere as biofertilizers for tomato crops and biopesticides by inducing systemic resistance to the causal agent of tomato bacterial canker disease.

Unlocking Nature's Secrets: Molecular Insights into Postharvest Pathogens Impacting Moroccan Apples and Innovations in the Assessment of Storage Conditions.

Apple production holds a prominent position in Morocco's Rosaceae family. However, annual production can fluctuate due to substantial losses caused by fungal diseases affecting stored apples. Our findings emphasize that the pre-storage treatment of apples, disinfection of storage facilities, box type, and fruit sorting are pivotal factors affecting apple losses during storage. Additionally, the adopted preservation technique was significantly correlated with the percentage of damage caused by fungal infections. Blue mold accounts for nearly three-quarters of the diseases detected, followed by gray rot with a relatively significant incidence. This study has revealed several fungal diseases affecting stored apples caused by pathogens such as Penicillium expansum, Botrytis cinerea, Alternaria alternata, Trichothecium roseum, Fusarium avenaceum, Cadophora malorum, and Neofabraea vagabunda. Notably, these last two fungal species have been reported for the first time in Morocco as pathogens of stored apples. These data affirm that the high losses of apples in Morocco, attributed primarily to P. expansum and B. cinerea, pose a significant threat in terms of reduced production and diminished fruit quality. Hence, adopting controlled atmosphere storage chambers and implementing good practices before apple storage is crucial.

Unveiling the Role of Hydrolytic Enzymes from Soil Biocontrol Bacteria in Sustainable Phytopathogen Management.

BACKGROUND: Phytopathogens, encompassing fungi, bacteria, viruses, and nematodes, pose a significant threat to the agricultural industry by causing substantial economic losses through severe plant diseases. The excessive use of synthetic fungicides to combat phytopathogens has raised environmental and human health concerns. RESULTS: Consequently, there is an increasing demand for safe and environmentally friendly biopesticides to align with consumer preferences for uncontaminated food. One particularly promising alternative to synthetic fungicides involves harnessing biocontrol bacteria that produce extracellular hydrolytic enzymes. These enzymes serve to effectively manage phytopathogens while concurrently fostering sustainable plant protection. Among the pivotal hydrolytic enzymes generated by biocontrol bacteria are chitinase, cellulase, protease, lipase, glucanase, and amylase. These enzymes exert their influence by breaking down the cell wall, proteins, and DNA of phytopathogens, thereby establishing a dependable method of biocontrol. CONCLUSIONS: Recognizing the critical role of these hydrolytic enzymes in sustainable biocontrol, this review seeks to delve into their primary functions, contribution to sustainable plant protection, and mechanisms of action. Through an exploration of the potential presented by biocontrol bacteria and their enzymatic mechanisms, we can discern effective and environmentally conscious strategies for managing phytopathogens in agriculture.

The Hidden World within Plants 2.0.

Interactions between plants and microorganisms are complex, with some microorganisms causing damage by employing strategies that hinder plant growth and reproduction, while others positively influence plant growth through various physiological activities [...].

Plant and Trees Pathogens: Isolation, Characterization and Control Strategies (1.0).

Agricultural production is under constant threat from biotic and abiotic stresses [...].

Modes of Action of Biocontrol Agents and Elicitors for sustainable Protection against Bacterial Canker of Tomato.

Tomato is one of the world's most commonly grown and consumed vegetables. However, it can be attacked by the Gram-positive bacterium Clavibacter michiganensis subsp. michiganensis (Cmm), which causes bacterial canker on tomato plants, resulting in significant financial losses in field production and greenhouses worldwide. The current management strategies rely principally on the application of various chemical pesticides and antibiotics, which represent a real danger to the environment and human safety. Plant growth-promoting rhizobacteria (PGPR) have emerged as an attractive alternative to agrochemical crop protection methods. PGPR act through several mechanisms to support plant growth and performance, while also preventing pathogen infection. This review highlights the importance of bacterial canker disease and the pathogenicity of Cmm. We emphasize the application of PGPR as an ecological and cost-effective approach to the biocontrol of Cmm, specifying the complex modes of biocontrol agents (BCAs), and presenting their direct/indirect mechanisms of action that enable them to effectively protect tomato crops. Pseudomonas and Bacillus are considered to be the most interesting PGPR species for the biological control of Cmm worldwide. Improving plants' innate defense mechanisms is one of the main biocontrol mechanisms of PGPR to manage bacterial canker and to limit its occurrence and gravity. Herein, we further discuss elicitors as a new management strategy to control Cmm, which are found to be highly effective in stimulating the plant immune system, decreasing disease severity, and minimizing pesticide use.

Production of high molecular-ordered stilbene oligomers for the study of their biological activity: total synthesis, bio-catalyzed synthesis and production by plant systems.

Though the iconic stilbene resveratrol and its related dimers constitute a top storyline in the field of natural product research, resveratrol oligomers (condensation >2) have been left aside despite their higher biological activity compared to that of the monomers. This situation largely results from the difficulty of getting them in sufficient quantities to enable evaluation of their biological properties in vivo. We present here a synthetic and critical analysis of the methods used for the production of high molecular-ordered stilbene oligomers of potential biomedical interest, gathering the most salient data regarding the approaches employed to prepare them by total synthesis, use of biomimetic approaches or through plant systems.

Comparison of Serological and Molecular Methods for Detection of Spiroplasma citri in Moroccan Citrus-Growing Areas.

Spiroplasma citri, a helical motile, wall-less, and cultivable microorganism of the class Mollicutes, is the agent of the citrus stubborn disease. There is currently a lack of data about the presence of this pathogen in Moroccan citrus orchards. This study aims to validate serological and molecular methods for routine S. citri diagnosis in Moroccan citrus groves. To provide an update on the present status of the outbreak of the pathogen in Moroccan citrus orchards, a survey of S. citri was conducted in the main citrus-growing regions of Morocco. A total of 575 leaf samples were collected from citrus trees with symptoms attributable to S. citri infection. Samples were collected during 2020 and 2021 from 23 citrus orchards. The presence of S. citri was tested in all samples using the double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). Using this method, 57 samples were found to be infected with S. citri, 41 samples had doubtful results, and the remaining samples were negative. To corroborate the results of the DAS-ELISA test, 148 samples were chosen for additional molecular testing using conventional polymerase chain reaction (PCR) and real-time PCR (qPCR) based on specific primer pairs targeting three different genes (putative adhesion-like gene P58, putative adhesion gene P89, and spiralin gene). Using primers that target the putative adhesion-like gene P58, S. citri was detected by conventional and real-time PCR amplification from plant tissue with differing degrees of specificity. The results allowed us to determine the incidence of S. citri in all Moroccan citrus orchards, with a wide range of positive samples varying from 6.5% to 78%, and to show that molecular tests, particularly real-time PCR assays that target the putative adhesion-like gene P58, are the most sensitive for making an accurate diagnosis of S. citri. Indeed, the real-time PCR with P58-targeting primers yielded positive results from all positive and doubtful ELISA samples as well as some negative samples, with an OD value close to 1.5× times healthy samples, thus demonstrating a high sensibility of this technique.

The Hidden World within Plants.

Plants offer an ecosystem for microorganisms from diverse phylogenetic domains and phyla as well as viruses and viroids [...].

The Amount of the Rare Sugar Tagatose on Tomato Leaves Decreases after Spray Application under Greenhouse Conditions.

Tagatose is a rare sugar that suppresses plant diseases, such as late blight of tomato, caused by Phytophthora infestans. Tagatose can be metabolized by some microorganisms and no information is available on its persistence on tomato leaves. The aim of this study was to assess the persistence of tagatose on tomato leaves under commercial greenhouse conditions. The amount of tagatose on tomato leaves and the inhibitory activity against P. infestans decreased seven days after spray application in the absence of rain wash-off. Potential tagatose-degrading bacteria were isolated from tomato leaves, and they belonged to Acinetobacter sp., Bacillus sp., Comamonas sp., Enterobacter sp., Methylobacterium sp., Microbacterium sp., Pantoea sp., Plantibacter sp., Pseudomonas sp., Ralstonia sp., Rhodococcus sp., Sphingobium sp., and Sphingomonas sp. Thus, indigenous phyllosphere microorganisms could partially metabolize tagatose laid on plant leaves after spray application, reducing the persistence of this fungal inhibitor on tomato leaves.

Chitosan as a potential natural compound to manage plant diseases.

The necessity for non-chemical approaches has grown as awareness of the dangers posed by pesticides has spread. Chitosan, due to its biocompatibility, biodegradability, and bioactivity is one the effective choice in phytopathology. Chitosan is a biopolymer that reduces plant diseases through two main mechanisms: (1) Direct antimicrobial function against pathogens, including plasma membrane damage mechanisms, interactions with DNA and RNA (electrostatic interactions), metal chelating capacity, and deposition onto the microbial surface, (2) Induction of plant defense responses resulting from downstream signalling, transcription factor activation, gene transcription and finally cellular activation after recognition and binding of chitin and chitosan by cell surface receptors. This biopolymer have potential with capability to combating fungi, bacteria, and viruses phythopathogens. Chitosan is synthesized by deacetylating chitin. The degree of deacetylation and molecular weight of chitosan are variable and have been mentioned as important structural parameters in chitosan's biological properties. Chitosan with a higher degree of deacetylation (>70 %) has better biological properties. Many crops able to withstand pre- and post-harvest illnesses better after receiving chitosan as a seed treatment, soil amendment, or foliar spray. This review discussed the properties and use of chitosan and focuses on its application as a plant resistance inducer against pathogens.

Potential for Biological Control of Pythium schmitthenneri Root Rot Disease of Olive Trees (Olea europaea L.) by Antagonistic Bacteria.

Several diseases affect the productivity of olive trees, including root rot disease caused by Pythium genera. Chemical fungicides, which are often used to manage this disease, have harmful side effects on humans as well as environmental components. Biological management is a promising control approach that has shown its great potential as an efficient eco-friendly alternative to treating root rot diseases. In the present study, the antagonistic activity of ten bacterial isolates was tested both in vitro and in planta against Pythium schmitthenneri, the causal agent of olive root rot disease. These bacterial isolates belonging to the genera Alcaligenes, Pantoea, Bacillus, Sphingobacterium, and Stenotrophomonas were chosen for their potential antimicrobial effects against many pathogens. Results of the in vitro confrontation bioassay revealed a high reduction of mycelial growth exceeding 80%. The antifungal effect of the volatile organic compounds (VOCs) was observed for all the isolates, with mycelial inhibition rates ranging from 28.37 to 70.32%. Likewise, the bacterial cell-free filtrates showed important inhibition of the mycelial growth of the pathogen. Overall, their efficacy was substantially affected by the nature of the bacterial strains and their modes of action. A greenhouse test was then carried out to validate the in vitro results. Interestingly, two bacterial isolates, Alcaligenes faecalis ACBC1 and Bacillus amyloliquefaciens SF14, were the most successful in managing the disease. Our findings suggested that these two antagonistic bacterial isolates have promising potential as biocontrol agents of olive root rot disease.

Botryosphaeria Dieback (Lasiodiplodia viticola): An Imminent Emerging Threat to the Moroccan Vineyards.

A decline of various grapevines (Vitis vinifera L.) in the province of Doukkala in Morocco was observed in 2021. The causal pathogen was identified as Lasiodiplodia viticola based on morphological characteristics and phylogenetic analysis of the internal transcribed region (ITS), the ß-tubulin gene (TUB) and calmodulin (cmdA). Koch's postulates were confirmed by successful re-isolation of L. viticola from plants inoculated with the pathogen under controlled conditions. The disease was shown to be prevalent in Bni Hilal (71.43%), Laamria (60%), and Boulaouane (40%) districts, but was quasi-absent in Lmechrek. To understand the dominance of L. viticola as one of the grapevine trunk pathogens, effects of temperature (10-40 °C) and pH (pH 3-pH 12) on growth and sporulation were investigated. The species were able to grow in a range of temperatures ranging from 15 to 40°C and showed a higher growth rate at 35 °C. The fungus were also characterized by a broad optimum pH ranging between 3-12. This study is the first report dealing with L. viticola associated with grapevine trunk diseases in Morocco. Additional studies are therefore required to understand the high occurrence of this disease in vineyards, which is likely due to climate changes. A good understanding of this complex disease might help to develop a reliable and sustainable preventive control strategy.

A Panoramic View on Grapevine Trunk Diseases Threats: Case of Eutypa Dieback, Botryosphaeria Dieback, and Esca Disease.

Grapevine trunk diseases (GTD) are currently one of the most devastating and challenging diseases in viticulture, leading to considerable yield losses and a remarkable decline in grapevine quality. The identification of the causal agents is the cornerstone of an efficient approach to fighting against fungal diseases in a sustainable, non-chemical manner. This review attempts to describe and expose the symptoms of each pathology related to GTD, the modes of transmission, and the harmfulness of recently reported agents. Special attention was given to new diagnostic tests and technologies, grapevine defense mechanisms, molecular mechanisms of endophytes fungal colonization, and management strategies used to control these threats. The present extended review is, therefore, an updated state-of-the-art report on the progress in the management of vineyards.

Plant Beneficial Bacteria as Bioprotectants against Wheat and Barley Diseases.

Wheat and barley are the main cereal crops cultivated worldwide and serve as staple food for a third of the world's population. However, due to enormous biotic stresses, the annual production has significantly reduced by 30-70%. Recently, the accelerated use of beneficial bacteria in the control of wheat and barley pathogens has gained prominence. In this review, we synthesized information about beneficial bacteria with demonstrated protection capacity against major barley and wheat pathogens including Fusarium graminearum, Zymoseptoria tritici and Pyrenophora teres. By summarizing the general insights into molecular factors involved in plant-pathogen interactions, we show to an extent, the means by which beneficial bacteria are implicated in plant defense against wheat and barley diseases. On wheat, many Bacillus strains predominantly reduced the disease incidence of F. graminearum and Z. tritici. In contrast, on barley, the efficacy of a few Pseudomonas, Bacillus and Paraburkholderia spp. has been established against P. teres. Although several modes of action were described for these strains, we have highlighted the role of Bacillus and Pseudomonas secondary metabolites in mediating direct antagonism and induced resistance against these pathogens. Furthermore, we advance a need to ascertain the mode of action of beneficial bacteria/molecules to enhance a solution-based crop protection strategy. Moreover, an apparent disjoint exists between numerous experiments that have demonstrated disease-suppressive effects and the translation of these successes to commercial products and applications. Clearly, the field of cereal disease protection leaves a lot to be explored and uncovered.

Combination of Sodium Bicarbonate (SBC) with Bacterial Antagonists for the Control of Brown Rot Disease of Fruit.

Simultaneous treatment with antagonistic bacteria Bacillus amylolquefaciens (SF14), Alcaligenes faecalis (ACBC1), and the food additive sodium bicarbonate (SBC) to control post-harvest brown rot disease caused by Monilinia fructigena, and their effect on the post-harvest quality of nectarines were evaluated. Four concentrations of SBC (0.5, 2, 3.5, and 5%) were tested. Results showed that bacterial antagonists displayed remarkable compatibility with different concentrations of SBC and that their viability was not affected. The results obtained in vitro and in vivo bioassays showed a strong inhibitory effect of all treatments. The combination of each bacterial antagonist with SBC revealed a significant improvement in their biocontrol efficacies. The inhibition rates of mycelial growth ranged from 60.97 to 100%. These results also indicated that bacterial antagonists (SF14 or ACBC1) used at 1 × 108 CFU/ mL in combination with 2, 3.5, or 5% SBC significantly improved the control of M. fructigina by inhibiting the germination of spores. Interestingly, disease incidence and lesion diameter in fruits treated with SF14, ACBC1 alone, or in combination with SBC were significantly lower than those in the untreated fruits. In vivo results showed a significant reduction in disease severity ranging from 9.27 to 64.83% compared to the untreated control, while maintaining the appearance, firmness, total soluble solids (TSS), and titratable acidity (TA) of fruits. These results suggested that the improved disease control by the two antagonistic bacteria was more likely due to the additional inhibitory effects of SBC on the mycelial growth and spore germination of the pathogenic fungus. Overall, the combination of both bacteria with SBC provided better control of brown rot disease. Therefore, a mixture of different management strategies can effectively control brown rot decay on fruits.