Pathogen Inoculation Research Articles

Immune Priming Promotes Thermotolerance, Whereas Thermopriming Suppresses Systemic Acquired Resistance in Arabidopsis.

Heat stress and pathogens are two serious yield-limiting factors of crop plants. Plants that previously experienced high but sub-lethal temperatures become subsequently tolerant to higher temperatures through the development of acquired thermotolerance (ATT). ATT activation is associated with the elevated expression of heat shock (HS)-related genes such as HSFA2, HSFA3, and HSP101. Similarly, through the development of systemic acquired resistance (SAR), previously experienced plants achieve a higher resistance than naïve plants. SAR activation requires mobile signals and primarily depends on salicylic acid (SA) signaling. Studies to understand the interaction between ATT and SAR are limiting. To investigate the possible interconnection, we studied cross-protection between SAR and ATT on 4-week-old soil-grown Arabidopsis plants. We observed localized pathogen inoculation provides thermotolerance. Pathogens activate the expressions of HSFA2, HSFA3, HSA32, and HSP101 in pathogen-free systemic tissues. Interestingly, pathogen-induced SAR activation is impaired in hsfa2, hsfa3, and hsp101 mutants, suggesting these HS memory genes are essential for SAR induction. In contrast, thermopriming by exposing plants to sublethal temperatures, blocks SAR activation by pathogens. Thermopriming suppresses SAR mobile signal generation, accumulation of SA, and PR1 gene expression in systemic leaves. Altogether, our results demonstrate a complex interaction between SAR and ATT induction pathways in plants.

Rhamnolipid Modified Silica Nanoparticles Control Rice Blast Disease by Enhancing Antifungal Activity In Vivo and Antioxidant Defense System of Rice (Oryza sativa L.).

Blast disease caused by Magnaporthe oryzae is a devastating disease that limits rice grain production. Here, we synthesized rhamnolipid (RL) modified silica nanoparticles (SiO2NPs) based on the excellent antimicrobial activity of RL against various phytopathogens and the role of SiO2NPs in alleviating plant diseases and investigated the roles and mechanisms of RL@SiO2NPs application in controlling rice blast disease. Two-week-old rice seedlings were sprayed with 100 mL/L of different materials before pathogen inoculation, and blast incidence was investigated 5 days after inoculation. The results showed that RL0.1@SiO2NPs were the most suitable mixture ratio in suppressing blast and enhanced plant resistance. Compared with the control, application of RL0.1@SiO2NPs significantly reduced rice blast disease incidence by 10.80% and the relative growth of fungus by 97.05% and increased the shoot dry biomass by 13.33%, which alleviated the infection pressure of rice blast fungus. Additionally, after RL0.1@SiO2NPs treatment, peroxidase, ascorbate peroxidase, and polyphenol oxidase activities in rice leaves were significantly increased by 47.02%, 34.26%, and 44.36%, respectively, the total phenolics content was significantly increased by 24.14%, and the malondialdehyde and hydrogen peroxide content was decreased by 5.28% and 14.58%, respectively. RL0.1@SiO2NPs also improved plant nutrient status and enhanced disease resistance of infected plants by restoring nutrient balance or ion homeostasis, including increased potassium concentration (23.84%) in leaves and Si concentration (60.34%) in roots and decreased magnesium (11.89%) and iron concentrations (30.55%) in rice leaves. In summary, our results suggest that RL0.1@SiO2NPs enhance rice plant resistance against blast by enhancing the antifungal activity in vivo, activating the antioxidant defense system, and affecting nutrient acquisition in rice seedlings. RL@SiO2NPs have shown potential application as green and efficient agricultural chemical substitutes in plant disease management.

Interaction of Meloidogyne incognita and Pseudomonas syringae pv. aptata in different types of soil on plant growth, photosynthetic pigments and proline contents of beetroot (Beta vulgaris L.).

Effect of Meloidogyne incognita and Pseudomonas syringae pv. aptata (Psa) was observed singly, together and pre and post inoculations in 4 soil types on plant growth, parameters, chlorophyll, carotenoid and proline contents of beetroot (Beta vulgaris L). Plant growth, chlorophyll and carotenoid contents were greater in loam soil followed by 20% fly ash soil, 10% fly ash plus 10% sand amended soil and least in 20 % sand mix soil. However, proline contents were high in 20% sand mix soil and least in loam soil. Plant growth (root dry weight), chlorophyll and carotenoid contents were reduced in plants inoculated with any test pathogen while proline contents were increased in plants inoculated with pathogens under study. Inoculation of both pathogens together caused a greater reduction of plant growth, chlorophyll and carotenoid contents than their individual inoculation. Inoculation of M. incognita 20 days prior to Psa resulted in greatest reduction in plant growth, chlorophyll and carotenoid and maximum proline contents. Inoculation of Psa with M. incognita reduced galling and nematode multiplication while prior inoculation of Psa caused maximum reduction in galling and nematode multiplication. Galling and nematode multiplication was high in 20% sand mix soil followed by loam soil and least in 20% fly ash amended soil. Bacterial leaf spot indices by Psa was 3 when alone. Disease indices were 5 when Psa was inoculated with M. incognita. Prior inoculation of M. incognita predisposed beetroots to Psa and aggravates the disease. Influence of M. incognita, Psa and their interactions in different soil types on various studied parameters in diseased plants was demonstrated by Principal component analysis.

Hemp Microbiome Composition and Function Under Developing Pest Management Solutions

Conventional pesticides used in cropping systems prevent damage caused by pathogens and pests but may also have unintended consequences for non-target organisms associated with plants. For example, fungicide application may affect microbes such as fungal endophytes that potentially confer protective benefits to the host, such as pathogen or pest resistance. Here we investigated how fungicide application and pathogen inoculation altered the communities of pathogenic and non-target endophytic leaf microbes in hemp (Cannabis sativa L.). We found that fungicide application and inoculation with fungal pathogens affected hemp-associated microbial communities. Fungicide application altered fungal endophyte community composition, increased heterogeneity of fungal communities, reduced pathogen abundance, and decreased diversity of the endophytic fungal community. Inoculation with pathogenic fungi decreased the abundance of bacterial endophytes relative to control and fungicide-treated plants. We then investigated the potential of a common fungal endophyte isolated from this study, Ophiocordyceps sp., as a biological control agent for Helicoverpa zea, a common insect pest in hemp. Contrary to our expectations, larvae preferred food inoculated with Ophiocordyceps sp., though it did not alter growth or mortality of larvae. Together, our results indicate that hemp-associated endophyte communities are sensitive to abiotic and biotic manipulations, and that fungicide application impacts non-target microorganisms that could confer important functions for crop health. We encourage future studies to analyze the impact of biological control agents on host ecology in an integrated pest management plan and to examine ways to better utilize existing microbial associations to create biological controls.

Characterization of Fusarium falciforme Inciting Wilt in Peace Lily (Spathiphyllum wallisii)

Severe wilt incidence with characteristic yellowing of older leaves was observed in Spathiphyllum plants of different commercial nurseries of Andhra Pradesh, India during 2021-23. Upon isolation on potato dextrose agar medium, the fungus displayed aerial greyish white mycelium on upper surface and with yellow pink pigmentation on the lower surface. Microscopic observation of the three types of conidia namely microconidia, macroconidia and chlamydospores confirmed the morphological identity of the pathogen as genus Fusarium. Multi-gene sequencing analysis, utilizing ITS, Tef-1α, RPB1, and RPB2 gene sequences, further confirmed the pathogen's identity at the species level as Fusarium falciforme. Pathogenicity assays in 30 days old Spathiphyllum plants demonstrated that yellowing of leaves was observed seven days after pathogen inoculation using a non-invasive method, followed by complete wilting of the plants within 15 days. In addition, host range analysis revealed that the isolated pathogen isolate from wilted Spathiphyllum plants could cause complete wilting within 12-15 days post-inoculation in other economically important solanaceous crops such as tomato, brinjal, chili and tobacco, further highlighting its economic significance. Studies evaluating different fungicides revealed that root zone application of carbendazim 50%WP at 1g/l and tebuconazole 25.9% EC at 1ml/l were effective in controlling wilt incidence, achieving 77.78% reduction as a prophylactic treatment and 66.67% reduction as a curative treatment. To the best of our knowledge, this is the first comprehensive study on Spathiphyllum wilt incidence and its management worldwide.

Excess mortality of infected ectotherms induced by warming depends on pathogen kingdom and evolutionary history.

Climate change is causing extreme heating events and can lead to more infectious disease outbreaks, putting species persistence at risk. The extent to which warming temperatures and infection may together impair host health is unclear. Using a meta-analysis of >190 effect sizes representing 101 ectothermic animal host-pathogen systems, we demonstrate that warming significantly increased the mortality of hosts infected by bacterial pathogens. Pathogens that have been evolutionarily established within the host species showed higher virulence under warmer temperatures. Conversely, the effect of warming on novel infections-from pathogens without a shared evolutionary history with the host species-were more pronounced with larger differences between compared temperatures. We found that compared to established infections, novel infections were more deadly at lower/baseline temperatures. Moreover, we revealed that the virulence of fungal pathogens increased only when temperatures were shifted upwards towards the pathogen thermal optimum. The magnitude of all these significant effects was not impacted by host life-stage, immune complexity, pathogen inoculation methods, or exposure time. Overall, our findings reveal distinct patterns in changes of pathogen virulence during warming. We highlight the importance of pathogen taxa, thermal optima, and evolutionary history in determining the impact of global change on infection outcomes.

Impact of spot blotch pathogen Bipolaris sorokiniana on important seed quality parameters in wheat and its management with biocontrol agents and newer fungicide molecules.

Spot blotch disease is prominent amongst several biotic stresses challenging wheat yield and quality. The impact of seed inoculation with Bipolaris sorokiniana, on important wheat seed quality of popular cultivar (cv.) DBW 187, was estimated in comparison to susceptible check WH 147. DBW 187 responded very effectively against pathogen keeping all parameters well ahead of susceptible check. The variety could resist declination in per cent germination with 8.07% in comparison to WH 147 which resulted in 14.72% reduction in germination after pathogen inoculation. Similarly, after pathogen's inoculation, speed of germination (80.06) and vigour index I (2677) and II (24379) were significantly higher in cv. DBW 187 as against cv. WH 147, which resulted in lower speed of germination and vigour index I and II, i.e. 74.37, 2249, and 16715, respectively. Amongst the biocontrol agents, Trichoderma harzianum was found to be the most effective in managing this pathogen, which caused 86.30% inhibition in mycelial growth of B. sorokiniana. Amongst the seven fungicides used to manage Bipolaris sorokiniana in vitro, tebuconazole 50% + trifloxystrobin 25% WG, propiconazole 25% EC both at 75 and 100ppm, and kresoxim methyl 44.3% SC at 100ppm were most effective against Bipolaris sorokiniana, causing complete inhibition in its radial growth. Conclusively, wheat cv. DBW 187 has capacity to resist seed health deterioration caused by the pathogen. Out of seven evaluated fungicides, the best three newer fungicide molecules, viz., tebuconazole 50% + trifloxystrobin 25% WG, propiconazole 25% EC, and kresoxim methyl 44.3% SC, can judiciously be utilized in combination with biocontrol agents, Trichoderma harzianum, T. asperellum, and Chaetomium globosum, keeping the fungicide load minimum for the effective management of B. sorokiniana.

OsbHLH5 Synergically Regulates Phenolamide and Diterpenoid Phytoalexins Involved in the Defense of Rice Against Pathogens.

Rice (Oryza sativa) produces phenolamides and diterpenoids as major phytoalexins. Although the biosynthetic pathways of phenolamides and diterpenoids in plants have been revealed, knowledge of their accumulation regulatory mechanisms remains limited, and, in particular, no co-regulatory factor has been identified to date. Here, using a combined co-expression and evolutionary analysis, we identified the basic helix-loop-helix (bHLH) transcription factor OsbHLH5 as a positive bifunctional regulator of phenolamide and diterpenoid biosynthesis in rice. Metabolomic analysis revealed that OsbHLH5 significantly increased the content of phenolamides (such as feruloyl tryptamine (Fer-Trm) and p-coumaroyl tyramine (Cou-Tyr)) and diterpenoid phytoalexins (such as momilactones A, momilactones B) in the overexpression lines, while their content was reduced in the OsbHLH5 knockout lines. Gene expression and dual-luciferase assays revealed that OsbHLH5 activates phenolamide biosynthetic genes (including putrescine hydroxycinnamoyltransferase 3 (OsPHT3), tyramine hydroxycinnamoyltransferases 1/2 (OsTHT1/2), and tryptamine benzoyltransferase 2 (OsTBT2)) as well as diterpenoid biosynthetic genes (including copalyl diphosphate synthase 4 (OsCPS4) and kaurene synthase-like 4/7/10/11 (OsKSL4/7/10/11)). Furthermore, we have demonstrated that OsbHLH5 is induced by jasmonic acid (JA), while pathogen inoculation assays indicated that the overexpression of OsbHLH5 in transgenic rice plants leads to enhanced resistance to Xanthomonas oryzae pv. oryzae (Xoo). Overall, we have identified a positive regulator of phenolamide and diterpenoid biosynthesis and have demonstrated that biotic stress induces phytoalexin accumulation partly in an OsbHLH5-dependent manner, providing new insights into the metabolic interactions involved in pathogen response and offering valuable gene resources for the development, through genetic improvement, of new rice varieties that are resistant to diseases.

Efficacy of L-arabinose in managing cucumber Fusarium wilt and the underlying mechanism of action.

Cucumber Fusarium wilt (CFW), triggered by Fusarium oxysporum f. sp. cucumerinum, leads to substantial yield reductions in global cucumber (Cucumis sativus L.) production. Common management strategies for CFW include soil fumigation, grafting, and crop rotation. However, these methods have limitations regarding safety and efficacy stability, necessitating the development of new, cost-effective, and eco-friendly control strategies. Our prior research demonstrated that L-arabinose, an inexpensive and safe sugar commonly used in food and beverages, effectively suppressed bacterial wilt in tomatoes. This study explores the potential of L-arabinose in managing CFW and investigates its mechanism of action. Soil applications of L-arabinose, ranging from 0.00001 to 0.01%, effectively suppressed CFW. The most significant suppressive effect was observed at 0.01%, reducing the disease severity index by 67.5% compared to the control treatment. Microscopic examination of transverse root sections showed that pathogen hyphae colonized the epidermis but seldom penetrated the cortical layer of roots in L-arabinose-treated seedlings. In contrast, the entire root tissue of control seedlings was colonized by the pathogen. Quantitative real-time PCR revealed a significant increase in the expression of defense-related genes dependent on salicylic acid, jasmonic acid, and ethylene in L-arabinose-treated plants compared to control plants, 6 and 10 days post pathogen inoculation. This study demonstrated that soil application of L-arabinose can effectively suppress CFW by priming root tissues for multiple defense signaling pathways. Therefore, L-arabinose holds potential as a new fungicide for managing CFW. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Effect of Black Soldier Fly Larvae Frass as Organic Fertilizer on Postharvest Quality and Shelf Life of Open-field-grown Tomato (Solanum lycopersicon L.)

Open-field-grown tomatoes in Saudi Arabia are stressed by poor soil fertility because of the low organic matter content, low nutrient availability, and high pH. Thus, high chemical fertilizer inputs are crucial for commercial production; however, they cause economic loss as well as negatively affect environmental sustainability. The use of efficient organic fertilizers would be useful for developing more cost-effective, environmentally friendly, and sustainable agriculture. The current study evaluated the impact of Black soldier fly (Hermetia illucens L.) frass (BSFF) fertilizer applications as organic fertilizer on postharvest fruit quality and shelf life of open-field-grown F1 hybrid ‘Sinag Tala’ tomatoes compared with those grown under control treatment (received recommended doses of chemical fertilizers for tomato production under open field conditions). The experiment was conducted using a randomized complete block design with four replicates. The results showed that the application of BSFF fertilizer, especially at the higher rate (5 ton/ha; BSFF3), improved the overall quality of tomato fruit. The BSFF fertilizer treatments reduced weight loss, maintained higher firmness, antioxidants [vitamin C, total phenol content (TPC) and total flavinoid (TFC)], total soluble solids (TSS), and titratable acidity (TA) contents, and lowered the TSS/TA ratio of fruits during shelf life compared with those of the control. The decay incidence was only detected after 9 days of shelf life and was significantly lower in all the BSFF fertilizer treatments (range, 8.40%-12.05%) than in the control (15.9%). In addition, BSFF fertilizer treatments reduced both disease incidence and severity of gray mold following pathogen inoculation during shelf life compared with those of the control. These results might be attributable to the higher antioxidants content (vitamin C, TPC, and TFC) and higher polyphenol oxidase activity in BSFF-fertilized tomatoes. In conclusion, BSFF fertilizer could be used as a potential eco-friendly alternative to chemical fertilizers to improve tomato fruit quality during shelf life.

Pathological Characterization and Management of Lasiodiplodia theobromae, a Hemibiotroph with an Interkingdom Host Range.

Heart rot disease, caused by Lasiodiplodia theobromae, is destructive for date palms and other woody plants. The disease was reported in several oases in Egypt, and the pathogen was found in association with infected trees suffering dieback and rachis blight. Seven phylogenetically distinct fungal isolates were selected, and their pathogenicity was confirmed on date palms. The isolates exhibited variable degrees of virulence on inoculated leaves, which confirms the variation. We examined the antifungal effect of microbial bioagents and plant extracts on heart rot disease. The isolates of Trichoderma spp. gave moderate reduction of the pathogen's linear growth (40 to 60%), whereas their exudates were ultimately ineffective. Bacillus spp. isolates, except for B. megaterium, were more effective against spore germination, giving 80 to 90% reduction on average. Among the examined plant extracts, garlic sap gave 98.67% reduction of linear growth followed by artemisia (15.5%) and camphor (24.8%). The extraction methods greatly influenced the antifungal efficiency of each extract because exposure to organic solvents significantly decreased the efficiency of all extracts, whereas hot water extraction negatively affected garlic sap only. Successful bioagents and plant extracts were further assayed for the suppression of heart rot disease on date palms. Both T. album and T. harzianum gave comparable degrees of suppression as by commercial fungicides. In addition, treatment before or during pathogen inoculation was the most effective because it significantly enhanced the expression of defense-related enzymes. Our findings suggest biopesticides possess a dual role in disease suppression and defense boosters for date palms suffering heart rot disease.

Black shank-mediated alteration of the community assembly of rhizosphere soil bacteria in tobacco.

There is a close and complex interaction between the elements in the aboveground-underground ecosystem during the growth and development of plants. Specifically, when the aboveground part of plants is infected by pathogens, it induces the plant rhizosphere to synthesize specific root exudates. Consequently, a group of beneficial rhizosphere soil bacteria is recruited to help plants resist diseases. However, the changes in the rhizosphere soil bacterial community of plants under infection by oomycete pathogens remain unknown. Three experimental treatments were set up in this experiment: soils inoculated with P. nicotianae, no-inoculation with P. nicotianae, and a control. The control treatment was composed of soils without transplanted tobacco plants, with the pathogen inoculated twice at an interval of eight days to ensure a successful P. nicotianae infection. P. nicotianae inoculation treatments were designed using the hyphal block inoculation method. In the non-inoculation treatment, tobacco plants were grown normally without pathogen inoculation. The tobacco plants were grown in a greenhouse. This study demonstrates that tobacco plants recruit microorganisms at the rhizosphere level as a defense mechanism against disease after infection by the oomycete pathogen Phytophthora nicotianae. Specific rhizosphere soil bacteria were screened in vitro to promote tobacco growth in a biofilm-forming manner, which induced the systemic resistance of the plants to P. nicotianae. The recruitment of rhizosphere soil bacteria to the inter-root zone of tobacco plants after infection by P. nicotianae can help subsequently cultivated tobacco plants in the same soil resist pathogen infestation. In conclusion, the present study confirms that infestation caused by oomycete pathogens alters the composition of the plant rhizosphere soil bacterial community and recruits a specific group of beneficial microorganisms that induce disease resistance and promote plant growth, thereby maximizing the protection of progeny grown in the same soil against the disease.

Poplar Adventitious Roots Induced by Stem Canker Pathogens: An Experimental System for Studying Roots Biology and Light Response-Related Processes.

Valsa sordida and Botryosphaeria dothidea are two crucial necrotrophic fungal pathogens that damage many plant hosts, particularly species in the genus Populus. These two fungal pathogens occur mainly in poplar branches, stems, and twigs, causing classic symptoms such as canker lesions, canopy dieback, and wilting. Pathogen inoculation is the most efficient pathway to study the mechanism of plant disease. Besides the canker lesions around the inoculation sites on the stems, a novel developmental phenomenon, copious adventitious roots (ARs) with bright red color, were observed in poplar species after stem canker pathogen inoculations. In this study, we described the method for inducing ARs using fungal pathogens in poplar trees. The crucial step of this method is the pathogen inoculation after (phloem or epidermis) girdling manipulation. The second crucial step is the application of the moisturizing material. Compared to the moisturizing manipulation with Parafilm, wrapping the inoculated sites with household polyethylene (PE) plastic wrap can produce colorful, numerous, and robust ARs in 20 days after girdling-inoculation. Finally, white ARs sprouted from the inoculated rings in the poplar stems after shading treatment (wrapping the stems with aluminum foil). This method introduces a novel experimental system for studying root development and morphogenesis, which is crucial for understanding the biology of root development, morphogenesis, and response under disease stress. Furthermore, when combined with shading treatment, this study can provide a convenient experimental system for investigating light response-related processes, for example, the biosynthesis of flavonoids, anthocyanins, or other related metabolites, and genes or transcription factors involved in these processes.

Natural Defense: The Inhibitory Effects of Endophytic Bacillus and Xylaria sp. against Rice Pathogens

Aim: Endophytes living inside the plant tissues are known to play a crucial role in the physiology and developmental functioning of host plants. Rice is the major food crop that feeds half of the world population. But pest and diseases lead to drastic yield reduction in rice. Sustainable and eco-friendly disease management strategies are urgently needed to reduce the reliance on chemical pesticides and mitigate the environmental impact of intensive agriculture.The aim of the study was the selection of natural suppressors of the brown spot and sheath blight diseases in rice. In this study, three bacterial endophytes viz., Bacillus subtilis isolate PAL 11, B. altitudins isolate TSL-4 and B. altitudinis isolate KAM-11 and one endophytic fungal isolate Xylaria sp. isolate KTD-2 were tested for their potential to inhibit Bipolaris oryzae and Rhizoctonia solani under in vitro conditions. Methodology: In vitro evaluation of endophytes against two major rice pathogens viz., Rhizoctonia solani and Bipolaris oryzae causing sheath blight and brown leaf spot respectively were tested by dual culture technique. Results: All the tested bacterial and fungal endophytes significantly inhibited both the pathogens under in vitro conditions. Among the bacterial endophytes, B. subtilis isolate PAL-11 exhibited highest inhibition of both the pathogens. The mycelial inhibition of B. oryzae was 56.04 and 74.48 per cent respectively at 5 and 8 days after dual culturing whereas the inhibition of R. solani was 80.31 and 80.22 per cent respectively at 3 and 5 days after dual culturing. The fungal endophyte Xylaria sp. isolate KTD-2 exhibited 63.2 and 67.95 per cent inhibition of mycelial growth of B. oryzae at 5 and 8 days respectively after the pathogen inoculation. The mycelial growth of R. solani was also significantly inhibited (54.95 %) by the fungal endophyte at 5 days after pathogen inoculation. Conclusion: This research highlights the potential role of endophytes in sustainable agriculture and suggests that integrating beneficial microbes into rice disease management strategies could help enhance plant health, increase crop yields, and contribute to global food security.

Evaluating Treatments for the Protection of Grapevine Pruning Wounds from Natural Infection by Trunk Disease Fungi.

Infection of grapevines by fungal pathogens causing grapevine trunk diseases (GTDs) primarily arises from annual pruning wounds made during the dormant season. While various studies have showcased the efficacy of products in shielding pruning wounds against GTD infections, most of these investigations hinge on artificial pathogen inoculations, which may not faithfully mirror real field conditions. This study aimed to evaluate and compare the efficacy of various liquid formulation fungicides (pyraclostrobin + boscalid) and paste treatments, as well as biological control agents (BCA: Trichoderma atroviride SC1, T. atroviride I-1237, and T. asperellum ICC012 + T. gamsii ICC080), for their potential to prevent natural infection of grapevine pruning wounds by trunk disease fungi in two field trials located in Samaniego (Northern Spain) and Madiran (Southern France) over three growing seasons. Wound treatments were applied immediately after pruning in February. One year after pruning, canes were harvested from vines and brought to the laboratory for assessment of Trichoderma spp. and fungal trunk pathogens. More than 1,200 fungal isolates associated with five GTDs (esca, Botryosphaeria, Diaporthe and Eutypa diebacks, and Cytospora canker) were collected from the two vineyards each growing season. Our findings reveal that none of the products under investigation exhibited complete effectiveness against all the GTDs. The efficacy of these products was particularly influenced by the specific year of study. A notable exception was observed with the biocontrol agent T. atroviride I-1237, which consistently demonstrated effectiveness against Botryosphaeria dieback infections throughout each year of the study, irrespective of the location. The remaining products exhibited efficacy in specific years or locations against particular diseases, with the physical barrier (paste) showing the least overall effectiveness. The recovery rates of Trichoderma spp. in treated plants were highly variable, ranging from 17 to 100%, with both strains of T. atroviride yielding the highest isolation rates. This study underscores the importance of customizing treatments for specific diseases, taking into account the influence of environmental factors for BCA applications.

Identification of Magnaporthe oryzae candidate secretory effector proteins through standardizing the filtering process of the canonical parameters

AbstractThe virulence of Magnaporthe oryzae largely hinges on its secretory effectors. Therefore, identification and thorough understanding of the effector functionality is crucial for unravelling the pathogenicity of the pathogen. In the present study, we employed a modified computational pipeline with deep machine learning techniques with an integration of Magnaporthe effector reference datasets (MOED) that predicted 434 M. oryzae candidate secretory effector proteins (MoCSEPs) from the genomic data. The reliability of the modified CSEP prediction workflow through utilization of precise parametric filtering is considered valid as it predicted 100 functional effectors (97.08%) out of 103 previously identified effector proteins within the Magnaporthe genus. Insights into secretion patterns and subcellular localization elucidated the role of these proteins in host cell recognition. Furthermore, structural classification of MoCSEPs, based on conserved motifs, combined with an exploration of their biological functions, revealed their significance in host adaptability and localization. Experimental validation done through examining expression of the MoCSEPs revealed varied secretion patterns in the resistant (40 expressed) and susceptible (92 expressed) rice cultivars at different time intervals after pathogen inoculation owing to different degrees of resistance by the host cultivars. The present work thus provides the strategic model of canonical parametric evaluation within the MOED and deepens the understanding on the role of secretory proteins of M. oryzae in establishing successful parasitic infection in rice. The predicted MoCSEPs could be used as biomarkers for disease diagnosis and tracking evolutionary shifts in M. oryzae.

Combined application of the endophyte Bacillus K1 and sodium dehydroacetate alleviates postharvest gray mold in grapes

Botrytis cinerea, which causes postharvest gray mold, is a primary pathogen that limits grape shelf-life and consumption and causes substantial yield loss worldwide. The combined use of biocontrol agents and food additives has attracted increasing interest. The effects of combined treatment with the endophyte Bacillus subtilis K1 and sodium dehydroacetate (SD) on the occurrence of gray mold and maintenance of grape fruit quality were studied. Treatment with a K1 suspension (1 × 108 CFU/ml) combined with 0.32 g/L SD resulted in markedly improved control of B. cinerea on grapes. The disease incidence and severity in the groups treated with K1 alone or in combination with SD were significantly lower than those in the control groups (P < 0.05) when the mixtures were applied 2 h after pathogen inoculation. Moreover, application of the mixture could maintain the appearance, firmness, total soluble solid (TSS) content and titratable acidity (TA) of grape fruit. Furthermore, the combination triggered increases in the activities of defense-related enzymes such as peroxidase (POD), phenylalanine ammonia lyase (PAL), catalase (CAT), superoxide dismutase (SOD) and polyphenol oxidase (PPO). Additionally, it could increase the vitamin C content. Thus, appropriate combinations of biocontrol agents and chemical reagents can provide effective protection against postharvest decay.

Unravelling the Complexity of Ginger Rhizome Rot Disease: A Focus on Pathogen Interactions

ABSTRACTRhizome rot poses a significant threat to ginger cultivation, caused by a complex interaction of pathogens such as Pythium aphanidermatum, Fusarium oxysporum, Ralstonia solanacearum, Sclerotium rolfsii and Meloidogyne incognita. The pathogens were individually inoculated at 75, 105 and 135 days after planting (DAP), as well as in various combinations, to evaluate disease severity and symptom development. Results revealed that R. solanacearum exhibited the highest disease severity and fastest symptom development across all stages of inoculation, followed by P. aphanidermatum, F. oxysporum, S. rolfsii and M. incognita. The combined inoculation of pathogens significantly increased disease incidence and rhizome rot compared to individual inoculations, indicating synergistic interactions among the pathogens. Sequential inoculation experiments demonstrated that pre‐infection by M. incognita exacerbated disease severity, highlighting the role of nematodes in predisposing plants to secondary infections.

Aqueous Chromolaena Odorata Leaf Extracts Induce Rice Resistance against Bacterial Leaf Blight

Aqueous Chromolaena odorata leaf extracts enhanced rice seed germination and seedling growth. Five extract concentrations (1, 2, 3, 4, and 5%, w/v) applied as seed soaking and foliar spraying were tested for their disease-reducing effects against rice bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae. For foliar sparying, the extracts were applied using three different methods, i.e., at 7 days before inoculation, at 14 days before inoculation and their combination. It was efficient to apply the 3% extract by seed soaking and foliar spraying at 14 days before inoculation to control BLB as it was the lowest concentration where the disease-reducing effects were observed until 21 DAI. The effects involved induced resistance. Indeed, activities of the four defense-related and antioxidant enzymes, i.e., peroxidase (POX), catalase (CAT), polyphenol oxidase (PPO), and phenylalanine ammonia lyase (PAL), increased after extract application and reached higher levels with both extract application and pathogen inoculation. Activities of POX and CAT were induced earlier and stronger using seed soaking than foliar spraying while those of PPO and PAL increased earlier using foliar spraying than seed soaking. This suggests a combination of both application methods to obtain coordinate increases in activities of the four defense-related and antioxidant enzymes which could provide sufficiently protection to rice plants again the disease.

Impact of E. muris infection on B. burgdorferi-induced joint pathology in mice.

Tick-borne infections are increasing in the United States and around the world. The most common tick-borne disease in the United States is Lyme disease caused by infection with the spirochete Borrelia burgdorferi (Bb), and pathogenesis varies from subclinical to severe. Bb infection is transmitted by Ixodes ticks, which can carry multiple other microbial pathogens, including Ehrlichia species. To address how the simultaneous inoculation of a distinct pathogen impacted the course of Bb-induced disease, we used C57BL/6 (B6) mice which are susceptible to Bb infection but develop only mild joint pathology. While infection of B6 mice with Bb alone resulted in minimal inflammatory responses, mice co-infected with both Bb and the obligate intracellular pathogen Ehrlichia muris (Em) displayed hematologic changes, inflammatory cytokine production, and emergency myelopoiesis similar to what was observed in mice infected only with Em. Moreover, infection of B6 mice with Bb alone resulted in no detectable joint inflammation, whereas mice co-infected with both Em and Bb exhibited significant inflammation of the ankle joint. Our findings support the concept that co-infection with Ehrlichia can exacerbate inflammation, resulting in more severe Bb-induced disease.