Wheat and barley rank among the main crops cultivated on a global scale, providing the essential nutritional foundation for both humans and animals. Nevertheless, these crops are vulnerable to several fungal diseases, such as Septoria tritici blotch and net blotch, which significantly reduce yields by adversely affecting leaves and grain quality. To mitigate the effect of these diseases, chemical fungicides have proven to be genuinely effective; however, they impose a serious environmental burden. Currently, biocontrol agents have attracted attention as a sustainable alternative to fungicides, offering an eco-friendly option. The study aimed to assess the efficacy of Bacillus velezensis BE2 in reducing disease symptoms caused by Zymoseptoria tritici and Pyrenophora teres. This bacterium exhibited significant antagonistic effects in vitro by suppressing fungal development when pathogens and the beneficial strain were in direct confrontation. These findings were subsequently confirmed through microscopic analysis, which illustrated the strain’s capacity to inhibit spore germination and mycelial growth in both pathogens. Additionally, the study analysed the cell-free supernatant of the bacterium using UPLC-MS (ultra-performance liquid chromatography-mass spectrometry). The results revealed that strain BE2 produces, among other metabolites, different families of cyclic lipopeptides that may be involved in biocontrol. Furthermore, the beneficial effects of strain BE2 in planta were assessed by quantifying the fungal DNA content directly at the leaf level after bacterization, using two different application methods (foliar and drenching). The results indicated that applying the beneficial bacterium at the root level significantly reduced pathogens pressure. Finally, gene expression analysis of different markers showed that BE2 application induced a priming effect within the first hours after infection. • BE2 managed Z. tritici and P. teres by direct antagonism and induced systemic resistance. • Strain BE2 produced seven metabolite families, including three cyclic lipopeptides. • Application of strain BE2 at the root level triggered plant defense mechanisms.

Soil is a natural capital that provides several ecosystem services ensuring human well-being and sustainable socioeconomic development. The scarcity of soil information constitutes the main shortcoming to assess soil ecosystem services (SESs). The aim of this study is to test the hypothesis that using disaggregated soil information derived from Digital Soil Map techniques is more accurate rather than legacy soil data (at 1:250, 000 scale) in SESs assessment. However, three soil datasets differing by their accuracy were mobilizing in this study: (i) legacy soil properties maps, (ii) disaggregated soil properties maps at 50 m spatial resolution and (iii) field measurements (reference soil database). Overall, two regulating SES (Climate regulation and Water quality regulation) and four provisioning SES (N to plant provision, Water to plant provision, Plant biomass provision, and Groundwater recharge) were assessed using the multidisciplinary simulator for standard crops -STICS soil-crop model over 30 years. A total of 7437 STICS simulations were computed and six SESs indicators were estimated from daily STICS outputs to evaluate SES supplies over the baseline period. The main results show that i) SES provision depends on inherent and manageable soil properties and is marginally sensitive to the accuracy of soil information particularly, for climate regulation and N plant provision. ii) Disaggregating conventional soil map improves the accuracy of soil properties predictions and therefore, partially compensates the lack of soil information for SES assessment over large areas. iii) SES relationships were globally preserved regardless of soil dataset. These results clearly demonstrated that considering the pedological information in SES assessment approaches will deserve more work in the future.

Soil is natural capital that provides several ecosystem services that contribute to human well-being and sustainable socioeconomic development. The scarcity of soil information constitutes the main shortcomings for assessing soil ecosystem services (SESs). The aim of this study was to assess effects of the accuracy of soil information on estimates of SES in agricultural systems using a modeling approach. To this end, three soil datasets that differed in accuracy were used: (i) legacy maps of soil properties, (ii) maps of disaggregated soil properties at 50 m spatial resolution and (iii) field observations (reference soil database). The supply of two regulating SESs (climate regulation and water quality regulation) and four provisioning SES (nitrogen (N)-to-plant provision, water to plant provision, plant biomass provision and groundwater recharge) over 30 years was estimated from daily outputs of 7437 simulations of the STICS soil-crop model. The main results showed that i) estimated SES supply, particularly of climate regulation and N-to-plant provision, depended on both inherent and manageable soil properties and was marginally sensitive to the accuracy of soil information, ii) using disaggregated soil maps marginally increased the accuracy of soil property predictions and thus partially compensated for the lack of soil information when assessing SESs over large areas, and iii) relationships among SESs (i.e. correlation coefficients) generally remained the same regardless of the soil dataset used. The results demonstrated that considering the accuracy of soil information in SES assessment approaches deserves more research.

The efficiency of plant-growth-promoting rhizobacteria (PGPR) may not be consistently maintained under field conditions due to the influence of soil microbial communities. The present study aims to investigate their impact on three PGPR-based biofertilizers in wheat. We used the PGPR Paenibacillus sp. strain B2 (PB2), PB2 in co-inoculation with Arthrobacter agilis 4042 (Mix 2), or with Arthrobacter sp. SSM-004 and Microbacterium sp. SSM-001 (Mix 3). Inoculation of PB2, Mix 2, and Mix 3 into non-sterile field soil had a positive effect on root and aboveground dry biomass, depending on the wheat cultivar. The efficiency of the PGPR was further confirmed by the protection they provided against Mycosphaerella graminicola, the causal agent of Septoria leaf blotch disease. PB2 exhibited protection of ≥37.8%, while Mix 2 showed ≥47.9% protection in the four cultivars tested. These results suggest that the interactions between PGPR and native soil microbial communities are crucial for promoting wheat growth and protection. Additionally, high-throughput sequencing of microbial communities conducted 7 days after PGPR inoculations revealed no negative effects of PB2, Mix 2, and Mix 3 on the soil microbial community structure. Interestingly, the presence of Arthrobacter spp. appeared to mitigate the potential negative effect of PB2 on bacterial community and foster root colonization by other beneficial bacterial strains.

Background: Interest for the study of gut mycobiota in relation with human health and immune homeostasis has increased in the last years. From this perspective, new tools to study the immune/fungal interface are warranted. Systemic humoral immune responses could reflect the dynamic relationships between gut mycobiota and immunity. Using a novel flow cytometry technology (Fungi-Flow) to determine immunoglobulin (Ig) responses to fungi, we studied the relationships between gut mycobiota and systemic humoral anti-commensal immunity. Results: The Fungi-Flow method allows a sensitive and specific measurement of systemic IgG responses against 17 commensal and environmental fungi from the two main divisions; Ascomycota and Basidiomycota. IgG responses exhibited a high inter-individual variability. Anti-commensal IgG responses were contrasted with the relative abundance, alpha-diversity, and intra-genus richness of fungal species in gut mycobiota of twenty healthy donors. Categorization of gut mycobiota composition revealed two differentiated fungal ecosystems. Significant difference of anti-Saccharomyces systemic IgG responses were observed in healthy donors stratified according to the fungal ecosystem colonizing their gut. A positive and significant correlation was observed between the variety of IgG responses against fungal commensals and intestinal alpha-diversity. At the level of intra-genus species richness, intense IgG responses were associated with a low intra-genus richness for known pathobionts, but not commensals. Conclusions: Fungi-Flow allows an easy and reliable measure of personalized humoral responses against commensal fungi. Combining sequencing technology with our novel Fungi-Flow immunological method, we propose that there are at least two defined ecosystems in the human gut mycobiome associated with systemic humoral responses. Fungi-Flow opens new opportunities to improve our knowledge about the impact of mycobiota in humoral anti-commensal immunity and homeostasis.

The induction of plant defense mechanisms by resistance inducers is an attractive and innovative alternative to reduce the use of fungicides on wheat against Zymoseptoria tritici, the responsible agent of Septoria tritici blotch (STB). Under controlled conditions, we investigated the resistance induction in three wheat cultivars with different susceptible levels to STB as a response to a treatment with a sulfur, manganese sulfate, and protein-based resistance inducer (NECTAR Céréales). While no direct antigermination effect of the product was observed in planta, more than 50% reduction of both symptoms and sporulation were recorded on the three tested cultivars. However, an impact of the wheat genotype on resistance induction was highlighted, which affects host penetration, cell colonization, and the production of cell-wall degrading enzymes by the fungus. Moreover, in the most susceptible cultivar Alixan, the product upregulated POX2, PAL, PR1, and GLUC gene expression in both noninoculated and inoculated plants and CHIT2 in noninoculated plants only. In contrast, defense responses induced in Altigo, the most resistant cultivar, seem to be more specifically mediated by the phenylpropanoid pathway in noninoculated as well as inoculated plants, since PAL and CHS were most specifically upregulated in this cultivar. In Premio, the moderate resistant cultivar, NECTAR Céréales elicits mainly the octadecanoid pathway, via LOX and AOS induction in noninoculated plants. We concluded that this complex resistance-inducing product protects wheat against Z. tritici by stimulating the cultivar-dependent plant defense mechanisms.

Plant-growth-promoting rhizobacteria are known as potential biofertilizers and plant-resistance inducers. The current work aims to study the durability of the resistance induced as a response to the inoculation of wheat grains with Paenibacillus sp. strain B2 (PB2) and its influence by plant genotype, growth stage, and Mycosphaerella graminicola strain (the causal agent of Septoria tritici blotch or STB). The results of the plate-counting method showed that PB2 has high potential for wheat-root external colonization [>106 colony-forming unit (CFU)/g of root], and the quantitative real-time polymerase chain reaction (qPCR) analysis demonstrated its internal root-colonization capacity on all tested cultivars. However, the colonization seems to be dependent on wheat-growth stage. The durability of PB2-induced resistance (PB2-IR) was tested at the 3-leaf, tillering, and flag-leaf-growth stages. Additionally, the results showed that the PB2-IR is durable and able to protect the flag leaf, the most important leaf layer during grain fill. It conferred a high protection efficiency (55-94%) against four virulent strains of M. graminicola and over 11 wheat cultivars with different resistance levels to STB. Although, PB2-IR is dependent on M. graminicola strains, wheat genotypes and growth stages, its efficiency, under field conditions, at protecting the last wheat-leaf layers was not an influence. However, it showed 71-79% of protection and reached 81-94% in association with half of the recommended dose of Cherokee® fungicide. This may be explained using laboratory results by its direct impact on M. graminicola strains in these leaf layers and by the indirect reduction of the inoculum coming from leaves infected during the earlier growth stages. Gene expression results showed that PB2-IR is correlated to upregulation of genes involved in defense and cell rescue and a priming effect in the basal defense, jasmonic acid signaling, phenylpropanoids and phytoalexins, and reactive oxygen species gene markers. To conclude, PB2 induces a high and durable resistance against M. graminicola under controlled and field conditions. The PB2-IR is a pathogen strain and is plant-growth-stage and genotype dependent. These results highlight the importance of taking into consideration these factors so as to avoid losing the effectiveness of induced resistance under field conditions.

Septoria tritici blotch caused by the fungus Zymoseptoria tritici is one of the most devastating foliar diseases of wheat. Knowledge regarding mechanisms involved in resistance against this disease is required to breed durable resistances. This study compared the expression of defence and pathogenicity determinants in three cultivars in semicontrolled culture conditions. The most susceptible cultivar, Alixan, presented higher necrosis and pycnidia density levels than Altigo, the most resistant one. In Premio, a moderately resistant cultivar, necrosis developed as in Alixan, while pycnidia developed as in Altigo. In noninfectious conditions, genes coding for PR1 (pr1), glucanase (gluc) and allene oxide synthase (aos) were constitutively expressed at a higher level in both Altigo and Premio than in Alixan, while chitinase2 (chit2), phenylalanine ammonia‐lyase (pal), peroxidase (pox2) and oxalate oxidase (oxo) were expressed at a higher level in Premio only. Except for aos, all genes were induced in Alixan during the first steps of the symptomless infection phase. Only pox2, oxo, gluc and pal genes in Altigo and pal, chs and lox genes in Premio were up‐regulated at some time points. Basal cultivar‐dependent resistance against Z. tritici could therefore be explained by various gene expression patterns rather than high expression levels of given genes. During the necrotrophic phase, Z. tritici cell wall‐degrading enzyme activity levels were lower in Altigo and Premio than in Alixan, and were associated more with pycnidia than with necrosis. Similar tissue colonization occurred in the three cultivars, suggesting an inhibition of the switch to the necrotrophic lifestyle in Altigo.

Many of the non-pathogenic endophytic bacteria that reside in plant roots promote plant growth as well as protection against pathogens attack. However, little is known about their mode of action in wheat. We have previously demonstrated the potential of Paenibacillus sp. strain B2 (PB2) to stimulate plant defense mechanisms via its paenimyxin lipo-polypeptide elicitor. Recently, we isolated the Curtobacterium plantarum strain EDS (EDS) from seeds of almost all wheat cultivars. In the present work, the ability of PB2 and EDS to promote wheat growth and protection against Septoria leaf blotch (SLB) was investigated. Results showed that PB2 is a general root external colonizer and cultivar-dependent endophyte. In the endophytic state and only in co-inoculation, it significantly increased the internal root colonization by EDS, resulting in an increase of root and aerial part fresh weights. qPCR analysis showed that, in the endophytic and nonendophytic states, PB2 conferred >= 59% protection against SLB by inducing systemic resistance which is characterized by the over expression of the pr1, lox, Aos, peroxidase, oxo and gst genes. Paenimyxin conferred 76% local protection characterized by the overexpression of the glu, lox, aos, pal, chs, oxo, and gst genes, and 82% systemic protection by chs. It was concluded that PB2 is potentially very interesting in the biocontrol of SLB and, in a mixture with EDS, in the wheat growth promoting. Genes involved in the flavonoid, salicylic acid, jasmonic acid, reactive oxygen species and basal defense pathways seem to play an important role in the resistance against SLB.

Oligogalacturonides (OGs) are known for their powerful ability to stimulate the plant immune system but little is known about their mode of action in pea (Pisum sativum). In the present study, we investigated the elicitor activity of two fractions of OGs, with polymerization degrees (DPs) of 2–25, in pea against Aphanomyces euteiches. One fraction was nonacetylated (OGs − Ac) whereas the second one was 30% acetylated (OGs + Ac). OGs were applied by injecting the upper two rachises of the plants at three- and/or four-weeks-old. Five-week-old roots were inoculated with 105 zoospores of A. euteiches. The root infection level was determined at 7, 10 and 14 days after inoculation using the quantitative real-time polymerase chain reaction (qPCR). Results showed significant root infection reductions namely 58, 45 and 48% in the plants treated with 80 µg OGs + Ac and 59, 56 and 65% with 200 µg of OGs − Ac. Gene expression results showed the upregulation of genes involved in the antifungal defensins, lignans and the phytoalexin pisatin pathways and a priming effect in the basal defense, SA and ROS gene markers as a response to OGs. The reduction of the efficient dose in OGs + Ac is suggesting that acetylation is necessary for some specific responses. Our work provides the first evidence for the potential of OGs in the defense induction in pea against Aphanomyces root rot.

Mycosphaerella graminicola is a hemibiotrophic fungus that causes Septoria tritici blotch (STB), one of the most serious foliar diseases of wheat. STB can occur with a wide range of disease levels on the host, which depend not only on the pathogenicity of fungal strains, but also on the resistance of host cultivars. Here, we investigated the association between the disease level and fungal cell-wall degrading enzyme and protease activities in three wheat cultivars differing in their resistance levels against M. graminicola. The experiments were carried out in the greenhouse using artificial inoculations with the M. graminicola strain T01193. Disease symptoms scored at 21-day post-inoculation (dpi) were significantly higher on the susceptible and moderately resistant cultivars, Alixan and Premio (48% and 42% of diseased leaf area, respectively), than in the resistant one, Altigo (28% of diseased leaf area). Regarding sporulation, the rate of pycnidial density was significantly higher on Alixan (2.9) compared to Premio and Altigo (1.1 and 1.0, respectively). Further biochemical investigations revealed, by 17 dpi, significant fungal beta-1,4-endoxylanase, beta-1,4-endoglucanase and protease activities, whose amounts increased according to the pycnidial density recorded on the infected leaves. At 21 dpi, the amounts of these activities were significantly higher on Alixan compared to Premio and Altigo (0.36 U/mg, 0.63 U/mg and 2.70 mU/mg total proteins on Alixan, 0.09 U/mg, 0.19 U/mg and 0.72 mU/mg total proteins on Premio and 0.05 U/mg, 0.15 U/mg and 0.52 mU/mg total proteins on Altigo for beta-1,4-endoxylanase, beta-1,4-endoglucanase and protease activities, respectively). These results confirm the importance of CWDE and protease activities in the process of fungal sporulation during the necrotrophic phase of M. graminicola.

Seventeen Mycosphaerella graminicola isolates from Tunisia and two reference isolates from Europe (St-Q7-2 and IPO323) were examined for sensitivity to azoxystrobin and tebuconazole and for the importance of the drug transporter genes MgAtr3 (ABC transporter), MgMfs1 (MFS transporter), MgSlt2 (MAP Kinase), MgGpa1 and MgGpb1 (cyclic AMP) in the process of fungicide tolerance. All Tunisian isolates were sensitive to both fungicides, but considerable variability in sensitivity, and evidence for slight multidrug resistance toward both fungicides (r = 0.58), were observed. A gene expression assay revealed that MgAtr3 and MgMfs1 are involved in tolerance to both fungicides. MgAtr3 is likely involved in tolerance to tebuconazole, while MgMfs1 is likely required for tolerance to azoxystrobin. The other genes examined were found more likely to be pathogenicity factors rather than fungicide tolerance factors, except for MgSlt2 which was weakly induced by azoxystrobin treatment. This study has indicated that the Tunisian population of M. graminicola remains more sensitive to strobilurin and azole fungicides than European populations, and reports the importance of the ABC and MFS transporters MgAtr3 and MgMfs1 in the mechanism of fungicide tolerance.

Septoria tritici blotch caused by Mycosphaerella graminicola is one of the most devastating foliar diseases of wheat. Disease control relies heavily on fungicides, but frequent development of fungal resistance and the negative impact of their extensive use on the environment and human health increasingly compromise this control strategy. Plant resistance inducers could be an alternative to conventional fungicides to control in a more durable manner this pathogen. Here, we tested in the greenhouse two resistance inducers (FSOV7 and FSOV10) on two wheat cultivars, Alixan (susceptible) and Altigo (resistant), against M. graminicola. FSOV7 conferred a significant protection level on both cultivars, while FSOV10 conferred a significant protection level on the resistant cv. Altigo only. Furthermore, the modes of action of the two inducers were examined using cytological, biochemical and molecular approaches. In planta, investigation of the infection process showed that FSOV10 significantly reduced fungal spore germination, whereas FSOV7 did not. An association of protection efficacy with a decrease of fungal biomass and fungal β-1, 4-endoxylanase and protease activities was observed in both cultivars. However, no association of plant peroxidase activity with protection efficacy was recorded, whatever the cultivar and the resistance inducer. A RT-qPCR assay revealed significant inductions of the expression of genes involved in different defence pathways; further statistical analyses should determine which genes are associated with the observed protection efficacies. This study showed significant inducer-cultivar interactions on wheat against M. graminicola and allowed us to investigate the modes of action on wheat of the two studied resistance inducers.

BACKGROUND:Sterol 14α-demethylase inhibitors (DMIs) have been widely used for more than 20 years against wheat Septoria leaf blotch. However, resistance towards DMIs has increased in recent years. The objective of this study was to evaluate the effect of fungicide timing and persistence and wheat resistance varietal on Mycosphaerella graminicola and its DMI-resistant genotypes.RESULTS:Using qPCR, M. graminicola was detected 2 weeks later in the resistant cultivar than in the susceptible cultivar. A high proportion of DMI-moderate resistant genotypes (≥94%) was found in all samples, with an average of 74.2, 0.1 and 19.7% for R6, R7- and R7+ genotypes, respectively. Distribution of DMI-resistant genotypes was neither affected by different wheat cultivars nor by analysis dates. Electron microscopy coupled with qPCR analysis showed that the DMI fungicide prothioconazole had a significant inhibitive effect against spore germination and post-germination. However, the preventive treatment was the most effective, but it was affected strongly by fungicide persistence.CONCLUSION:Preventive fungicide applications are more effective against Septoria leaf blotch than the curative treatments, so persistence and wheat varietal resistance should be taken into account in the management of this disease. It would seem that none of the studied factors affect the frequency of DMI-resistant genotypes.

Septoria tritici blotch (STB) caused by Mycosphaerella graminicola (anamorph: Zymoseptoria tritici) is one of the most devastating foliar diseases on bread wheat (Triticum aestivum L.). Because of the emergence of fungal strains highly resistant to mainly used fungicides and the deleterious impacts of these fungicides on the environment, development of alternative control strategies to protect wheat crops against STB is needed. The induction of plant resistance by elicitors is likely to be a helpful alternative. Our study aims at characterizing the efficiency of potential resistance inducers towards STB in three bread wheat cultivars differing in their resistance levels to the pathogen: Alixan (susceptible), Premio (moderately resistant) and Altigo (resistant). These cultivars were inoculated under controlled and semi-controlled conditions with the pathogenic M. graminicolo strain T01193 in order to assess the protective effect of three potential resistance inducers against the disease. Moreover, the direct antifungal effect bf these products was evaluated in vitro at different concentrations in order to verify their potential biocide activity. Furthermore, cytological analyses were performed in order to determine the effects of these products on the fungal infection process and to compare these effects among the three wheat cultivars. Finally, reactive oxygen species metabolism was investigated in the three cultivars during their interaction with T01193 by measuring peroxidase activity.

BACKGROUNDSeptoria leaf blotch is the most important disease of wheat in Europe. To control this disease, fungicides of the 14α-demethylase inhibitor group (DMIs) have been widely used for more than 20 years. However, resistance towards DMIs has increased rather quickly in recent years. The objective of this study was to evaluate, on plants and under controlled conditions, the protective and curative efficacy of the DMI fungicide prothioconazole against three current isolates of M. graminicola, chosen to belong to different DMI-resistant phenotypes. Fungicide efficacy was assessed by visual symptoms and by quantitative real-time polymerase chain reaction (PCR).RESULTSWith a protective fungicide application, prothioconazole was always effective against each isolate. This was in accordance with the EC50 results. However, curative efficacy differed between the isolates. It remained at a good level, between 60 and 70% against one isolate, whereas it was strongly affected by late applications from 7 days post-inoculation with the two other isolates.CONCLUSIONA protective application of prothioconazole in wheat crops could be the best strategy to keep a high efficacy against Septoria leaf blotch.