The Elicitor Protein AsES Induces a Systemic Acquired Resistance Response Accompanied by Systemic Microbursts and Micro-Hypersensitive Responses in Fragaria ananassa

A type II secreted subtilase from commensal rhizobacteria cleaves immune elicitor peptides and suppresses flg22-induced immune activation

Plant roots grow in association with a community of microorganisms collectively known as the rhizosphere microbiome. Immune activation in response to elicitors like the flagellin-derived epitope flg22 restricts bacteria on plant roots but also inhibits plant growth. Some commensal root-associated bacteria are capable of suppressing the plant immune response to elicitors. In this study, we investigated the ability of 165 root-associated bacteria to suppress flg22-induced immune activation and growth restriction. We demonstrate that a type II secreted subtilase, which we term immunosuppressive subtilase A (IssA), from Dyella japonica strain MF79 cleaves the immune elicitor peptide flg22 and suppresses immune activation. IssA homologs are found in other plant-associated commensals, with particularly high conservation in the order Xanthomonadales. This represents a novel mechanism by which commensal microbes modulate flg22-induced immunity in the rhizosphere microbiome.

PeVL1 Novel Elicitor Protein, from Verticillium lecanii 2, Enhances Systemic Resistance against Rice Leaf Roller (Marasmia ruralis Wlk.) in Rice (Oryza sativa L.)

The hazardous pest known as rice leaf roller (Marasmia ruralis Wlk.) (Lepidoptera: Pyralidae), which undermines rice (Oryza sativa L.) output globally, folds the leaves of the rice plant. Protein elicitors are thought to be biological elements that causes the rice to become resistant to herbivores. The potential for biocontrol of the emerging elicitor protein evaluated from Verticillium lecanii 2 (PeVL1) was evaluated against M. ruralis. To assess the impact of PeVL1 on immature development, survival, and lifetime, four different PeVL1 concentrations were allocated. Electrical penetration graphs (EPGs) against M. ruralis were used to evaluate adult reproductive efficiency and the interaction between the pest and the pathogen. Furthermore, the characterization of active substances in PeVL1 with multi-acting entomopathogenic effects looked into the direct interactions of PeVL1 with temperature and climatic change in rice (O. sativa) plants. PeVL1 treatments reduced the population increase of second and third generation M. ruralis compared to controls. In a test of host selection, M. ruralis colonized control plants more quickly than PeVL1-treated O. sativa plants. PeVL1 concentrations prolonged the M. ruralis larval stage. Similar to fecundity, PeVL1-treated seedlings produced fewer offspring than control seedlings. On PeVL1-treated leaves, trichomes and wax production created an unfavorable habitat for M. ruralis. PeVL1 changed the surface structure of the leaves, which inhibited colonization and decreased M. ruralis reproduction. The activation of pathways was another aspect of systemic defense activities including jasmonic acid (JA), salicylic acid (SA), and ethylene (ET). Based on these results against M. ruralis, the use of PeVL1 in the agroecosystem with integrated pest management and biocontrol seems appropriate. Our research provides a novel insight into a cutting-edge biocontrol method utilizing V. lecanii 2.

Biocontrol Potential of PeBL2, a Novel Entomopathogenic Bacterium from Brevibacillus laterosporus A60, Induces Systemic Resistance against Rice Leaf Folder Cnaphalocrocis exigua (Butler) in Rice (Oryza sativa L.)

The dangerous insect pest known as rice leaf folder Cnaphalocrocis exigua (Butler), which reduces rice output globally, twists and feeds on the young rice plant's leaves. Protein elicitors are hypothesized to be biological components that promote rice in becoming herbivore resistant. The evolving elicitor protein PeBL2, obtained from Brevibacillus laterosporus A60, was tested for biocontrol against C. exigua. Four distinct PeBL2 doses (74.23, 45.53, 22.26, and 11.13 μg mL^-1) were assigned to evaluate the impact of PeBL2 on immature growth, survivability, and lifespan. Adult reproductive efficiency and the interaction between the pest and the disease were assessed against C. exigua. Further, the assessment of active compounds in PeBL2 with multi-acting entomopathogenic effects investigated the direct correlations of PeBL2 with temperature and climatic change in plants of rice (Oryza sativa L.). When compared to controls, PeBL2 treatments reduced the growing population of second- and third-generation C. exigua. Cnaphalocrocis exigua colonized control plants faster than PeBL2-treated O. sativa plants in a host selection test. PeBL2 doses delayed the development of the larval stage of C. exigua. PeBL2-treated seedlings generated less offspring than control seedlings, identical to fecundity. Trichomes and wax formation on PeBL2-treated leaves generated an adverse environment for C. exigua. PeBL2 altered the surface topography of the leaves, preventing colonization and reducing C. exigua reproduction. PeBL2-treated O. sativa seedlings exhibited somewhat increased amounts of jasmonic acid (JA), salicylic acid (SA), and ethylene (ET). Systemic defensive processes also included the activation of pathways (JA, SA, and ET). Following these results versus C. exigua, the use of PeBL2 in an agroecosystem with integrated pest management and biocontrol appears to be reasonable. These findings shed new light on a cutting-edge biocontrol technique based on B. laterosporus A60.

Identification of Key Residues Essential for the Activation of Plant Immunity by Subtilisin From Bacillus velezensis LJ02

Subtilisin, a serine protease, can trigger defense responses in a wide variety of plants, both locally and systemically, to protect against pathogens. However, key residues of subtilisin to improve resistance to plant diseases remain unknown. In this study, Nicotiana benthamiana (N. benthamiana) leaves expressing subtilisin from Bacillus velezensis LJ02 were shown to improve protection against Botrytis cinerea (B. cinerea). Furthermore, the underlying mechanism that LJ02 subtilisin improved the protective effect was explored, and the direct inhibitory effect of subtilisin on B. cinerea was excluded in vitro. Subsequently, reactive oxygen species (ROS) burst and upregulation of resistance-related genes in systemic leaves of N. benthamiana further verified that subtilisin could induce systemic protection against B. cinerea. G307A/T308A and S213A/L214A/G215A subtilisin significantly reduced the ability to resist B. cinerea infection in N. benthamiana. Furthermore, the ROS content and expression levels of resistance-related genes of both mutants were significantly decreased compared with that of wild-type subtilisin. This work identified key residues essential for the activation function of subtilisin plant immunity and was crucial in inducing plant defense responses against B. cinerea.

Hrip1 Induces Systemic Resistance against Bean Aphid (Megoura japonica Matsumura) in Common Beans (Phaseolus vulgaris L.)

The emerging elicitor protein Hrip1 was evaluated for sublethal effects and biocontrol potential in the common bean Phaseolus vulgaris. In Megoura japonica Matsumura, purified elicitor protein Hrip1 was investigated for impacts on endurance, life expectancy, juvenile expansion, fully grown procreative performance, and pathogen–pest interface. The multi-acting entomopathogenic effects of the active compounds of Alternaria tenuissima active on Hrip1 in common bean (Phaseolus vulgaris L.) plants were also investigated. Megoura japonica population expansion was reduced by Hrip1 treatments (second and third generations). In a host selection test, control plants colonized quicker than Hrip1-treated P. vulgaris plants. Hrip1 influenced the longevity, development, and fertility of insects. Hrip1-elicitor protein concentrations aided M. japonica nymph development. Similarly, seedlings treated with Hrip1 generated fewer offspring than seedlings not treated with Hrip1. Hrip1 altered plant height and leaf surface structure, reducing M. japonica reproduction and colonization. Hrip1-treated P. vulgaris seedlings exhibited somewhat increased amounts of jasmonic acid, salicylic acid, and ethylene (ET). The integrated management of insect pests and biocontrol with Hrip1 in the agroecosystem appears to be suitable against M. japonica based on these findings.

A fungal protease named AsES triggers antiviral immune responses and effectively restricts virus infection in arabidopsis and Nicotiana benthamiana plants

BACKGROUND AND AIMS

Plants have evolved complex mechanisms to fight against pathogens. Among these mechanisms, pattern-triggered immunity (PTI) relies on the recognition of conserved microbe- or pathogen-associated molecular patterns (MAMPs or PAMPs, respectively) by membrane-bound receptors. Indeed, PTI restricts virus infection in plants and, in addition, BRI1-associated kinase 1 (BAK1), a central regulator of PTI, plays a role in antiviral resistance. However, the compounds that trigger antiviral defences, along with their molecular mechanisms of action, remain mostly elusive. Herein, we explore the role of a fungal extracellular subtilase named AsES in its capacity to trigger antiviral responses.

METHODS

In this study, we obtained AsES by recombinant expression, and evaluated and characterized its capacity to trigger antiviral responses against Tobacco mosaic virus (TMV) by performing time course experiments, analysing gene expression, virus movement and callose deposition.

KEY RESULTS

The results of this study provide direct evidence that exogenous treatment with recombinant AsES increases a state of resistance against TMV infection, in both arabidopsis and Nicotiana benthamiana plants. Also, the antiviral PTI response exhibited by AsES in arabidopsis is mediated by the BAK1/SERK3 and BKK1/SERK4 co-receptors. Moreover, AsES requires a fully active salicylic acid (SA) signalling pathway to restrict the TMV movement by inducing callose deposition. Additionally, treatment with PSP1, a biostimulant based on AsES as the active compound, showed an increased resistance against TMV in N. benthamiana and tobacco plants.

CONCLUSIONS

AsES is a fungal serine protease which triggers antiviral responses relying on a conserved mechanism by means of the SA signalling pathway and could be exploited as an effective and sustainable biotechnology strategy for viral disease management in plants.

Pectin Microspheres: Synthesis Methods, Properties, and Their Multidisciplinary Applications

There is great contemporary interest in using cleaner technologies through green chemistry and utilizing biopolymers as raw material. Pectin is found on plant cell walls, and it is commonly extracted from fruit shells, mostly apples or citrus fruits. Pectin has applications in many areas of commercial relevance; for this reason, it is possible to find available information about novel methods to transform pectin and pursuing enhanced features, with the structuring of biopolymer microspheres being highly cited to enhance its activity. The structuring of polymers is a technique that has been growing in recent decades, due to its potential for diverse applications in various fields of science and technology. Several techniques are used for the synthesis of microspheres, such as ionotropic gelation, extrusion, aerosol drying, or emulsions, with the latter being the most commonly used method based on its reproducibility and simplicity. The most cited applications are in drug delivery, especially for the treatment of colon diseases and digestive-tract-related issues. In the industrial field, it is used for protecting encapsulated compounds; moreover, the environmental applications mainly include the bioremediation of toxic substances. However, there are still many possibilities for expanding the use of this biopolymer in the environmental field.

Biocontrol Potential of Novel Emerging Multiacting Bacterium Bacillus amyloliquefaciens NC6 against Brevicoryne brassicae in Brassica rapa ssp. Pekinensis

The emerging elicitor protein PeBA1, extracted from Bacillus amyloliquefaciens NC6, was tested against the cabbage aphid (Brevicoryne brassicae) for its biocontrol potential. Its effects on the survival, lifespan, immature development, adult reproductive performance, and pest–pathogen interaction were assessed using electrical penetration graphs (EPGs) against B. brassicae. Furthermore, the direct effects of PeBA1 with temperature and climate change in Brassica rapa ssp. Pekinensis plants were investigated by the characterization of active compounds in B. amyloliquefaciens with multi-acting entomopathogenic effects. Compared with controls, PeBA1 treatments decreased (second- and third-generation) B. brassicae population growth rates. In a host selection test, control plants were colonized faster by B. brassicae than PeBA1-treated B. rapa plants. The B. brassicae nymphal development was extended by PeBA1 concentrations. Likewise, fecundity was reduced in PeBA1-treated seedlings compared with control, with fewer offspring produced. The trichomes and wax production on PeBA1-treated leaves resulted in a hostile environment for B. brassicae. PeBA1 altered the surface structure of the leaves, reducing B. brassicae reproduction and preventing colonization. Systemic defensive processes also included the activation of pathways (JA, SA, and ET). Based on these findings against B. brassicae, integrated pest management and bio control with PeBA1 in the agroecosystem appears to be suitable.

Reactive oxygen species and nitric oxide as mediators in plant hypersensitive response and stomatal closure

Nitric oxide (NO) and reactive oxygen species (ROS) have attracted considerable interest from plant pathologists since they regulate plant defenses via the hypersensitive response (HR) and stomatal closure. Here, we introduce the regulatory mechanisms of NO and ROS bursts and discuss the role of such bursts in HR and stomatal closure. It showed that epidermal sections of leaves respond to pathogens by the rapid and intense production of intracellular ROS and NO. Oxidative stress and H₂O₂ induce stomatal closure. Catalase and peroxidase-deficient plants are also hyperresponsive to pathogen invasion, suggesting a role for H₂O₂ in HR-mediated cell death. The analysis reveals that ROS and NO play important roles in stomatal closure and HR that involves multiple pathways. Therefore, multi-disciplinary and multi-omics combined analysis is crucial to the advancement of ROS and NO research and their role in plant defense mechanism.

PeaT1 and PeBC1 Microbial Protein Elicitors Enhanced Resistance against Myzus persicae Sulzer in Chili Capsicum annum L

The green peach aphid (Myzus persicae Sulzer), a major and harmful chili aphid usually managed using chemical pesticides, is responsible for massive annual agricultural losses. The efficacy of two protein elicitors, PeaT1 and PeBC1, to stimulate a defensive response against M. persicae in chili was studied in this study. When compared to positive (water) and negative (buffer, 50 mM Tris-HCl, pH 8.0) controls, the rates of population growth (intrinsic rate of increase) of M. persicae (second and third generations) were lower with PeaT1- and PeBC1-treated chilli seedlings. M. persicae demonstrated a preference for colonizing control (12.18 ± 0.06) plants over PeaT1- (7.60 ± 0.11) and PeBC1 (6.82 ± 0.09) treated chilli seedlings in a host selection assay. Moreover, PeaT1- and PeBC1-treated chilli seedlings, the nymphal development period of the M. persicae was extended. Similarly, fecundity was lowered in the PeaT1- and PeBC1-treated chilli seedlings, with fewer offspring produced compared to the positive (water) and negative controls (50 mM Tris-HCl, pH 8.0). The trichomes and wax production on the PeaT1 and PeBC1-treated chilli leaves created a disadvantageous surface environment for M. persicae. Compared to control (30.17 ± 0.16 mm^-2), PeaT1 (56.23 ± 0.42 mm^-2) and PeBC1 (52.14 ± 0.34 mm^-2) had more trichomes. The levels of jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) were significantly higher in the PeaT1- and PeBC1-treated chili seedlings, indicating considerable accumulation. PeaT1 and PeBC1 significantly affected the height of the chili plant and the surface structure of the leaves, reducing M. persicae reproduction and preventing colonization, according to the data. The activation of pathways was also part of the defensive response (JA, SA, and ET). This present research findings established an evidence of biocontrol for the utilization of PeaT1 and PeBC1 in the defence of chili plants against M. persicae.

Do microbial protein elicitors PeaT1 obtained from Alternaria tenuissima and PeBL1 from Brevibacillus laterosporus enhance defense response against tomato aphid (Myzus persicae)?

Tomato aphid (Myzus persicae) is a destructive insect pest of tomato responsible for huge losses in the production as well in the vegetable industry. In the present in vitro study two protein elicitors, PeaT1 and PeBL1 were considered to study their efficacies to exhibit defense response against tomato aphid. Three different concentrations of both protein elicitors were applied on the tomato seedlings. After the application of PeaT1 and PeBL1, population growth rates of tomato aphid were decreased as compared to the control treatment. In host preference assay, the tomato aphid showed a preference to build a colony on the control as compared to the treated tomato plant, because tomato leaves provided hazardous surface for aphid after the formation of wax and trichome. The concentrations of protein showed significant (p < 0.05) results in life-history traits of the aphid. Jasmonic acid (JA), salicylic acid (SA) and ethylene (ET) showed significant accumulation in tomato seedlings treated with PeaT1 and PeBL1. Elicitors treated plants produced resistance against M. persicae. Our finding suggests that PeaT1 and PeBL1 have shown high potentials against the damage of M. persicae, and both elicitors could be used as novel biological tools against tomato aphid.

The fungal elicitor AsES requires a functional ethylene pathway to activate the innate immunity in strawberry

Acremonium strictum Elicitor Subtilisin (AsES) is a fungal elicitor that activates innate immunity, conferring disease resistance in strawberry (Fragaria × ananassa Duch.), Arabidopsis and other plant species. The aim of the present work was to evaluate the involvement of the ethylene (ET) signalling pathway in AsES-mediated immune response in strawberry. Ethylene production and expression of the genes responsible for ET synthesis, perception and response were measured after AsES treatment. ROS (H₂ O₂ ) accumulation and immunity induced by AsES were studied after ET perception was blocked by 1-methylcyclopropene (1-MCP). Biochemical and molecular results showed that AsES induced a marked increase in local and systemic biosynthesis of ET, both in a biphasic manner. Blocking of ET perception by 1-MCP prior to AsES induction reduced production of ROS (H₂ O₂ ) and prevented AsES from eliciting defence against fungal pathogens having different lifestyles, such as Botrytis cinerea (necrotrophic) and Colletotrichum acutatum (hemibiotrophic). These findings contribute to elucidate the mode of action of the novel elicitor subtilase, AsES, specifically regarding the role of ET signalling in the activation of plant innate immunity, in addition to the multitude of processes regulated by ET in plants.

Biocontrol Potential of Purified Elicitor Protein PeBL1 Extracted from Brevibacillus laterosporus Strain A60 and Its Capacity in the Induction of Defense Process against Cucumber Aphid (Myzus persicae) in Cucumber (Cucumis sativus)

The Cucumber aphid (Myzus persicae), a destructive cucumber aphid usually managed by chemical pesticides, is responsible for enormous annual agricultural losses. A protein elicitor, PeBL1, was investigated in the present work for its ability to induce a defense response against M. persicae in cucumber. The rates of population growth (Intrinsic rate of increase) of M. persicae (second and third generations) decreased with PeBL1-treated cucumber seedlings as compared to positive (water) and negative 70.58 μg mL^-1 controls (50 mM Tris-HCl, pH 8.0). In an assay on host selection, M. persicae had a preference for colonizing control plants as compared to the PeBL1-treated cucumber seedlings. The nymphal development time of the aphid was extended with the PeBL1-treated cucumber seedlings. Likewise, fecundity was reduced, with less offspring produced in the PeBL1-treated cucumber seedlings as compared to the positive (water) and negative 70.58 μg mL^-1 controls (50 mM Tris-HCl, pH 8.0). The cucumber leaves treated with PeBL1 had a hazardous surface environment for M. persicae, caused by trichomes and wax formation. Jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) levels were significantly higher, exhibiting significant accumulation in the PeBL1-treated cucumber seedlings. The following results showed that PeBL1 considerably altered the height of the cucumber plant and the surface structure of the leaves to minimize M. persicae reproduction, and it prevented colonization. Defensive processes also included the activation of pathways (JA, SA, and ET). This study provides evidence of biocontrol for the use of PeBL1 in cucumber defense against M. persicae.

Protein Elicitor PeBL1 of Brevibacillus laterosporus Enhances Resistance Against Myzus persicae in Tomato

Myzus persicae, a destructive aphid of tomato usually managed by chemical pesticides, is responsible for huge annual losses in agriculture. In the current work, a protein elicitor, PeBL1, was investigated for its capacity to induce a defense response against M. persicae in tomato. Population growth rates of M. persicae (second and third generation) decreased with PeBL1 treatments as compared with controls. In a host selection assay, M. persicae showed preference for colonizing control plants as compared to tomato seedlings treated with PeBL1. Tomato leaves treated with PeBL1 gave rise to a hazardous surface environment for M. persicae due to formation of trichomes and wax. Jasmonic acid (JA), salicylic acid (SA), and ethylene (ET) showed significant accumulation in tomato seedlings treated by PeBL1. The following results showed that PeBL1 significantly modified the tomato leaf surface structure to reduce reproduction and deter colonization by M. persicae. Defense processes also included activation of JA, SA, and ET pathways. The study provides evidence for use of PeBL1 in the protection of tomato from M. persicae.

Protein elicitor PeaT1 enhanced resistance against aphid (Sitobion avenae) in wheat

BACKGROUND

Sitobion avenae, a dominant aphid in wheat that causes huge annual losses in agriculture, is mainly controlled using chemical pesticides. In this study, we investigated a protein elicitor, PeaT, for its induction of the defense response in wheat against Sitobion avenae.

RESULTS

Intrinsic rates of increase in second and third generations of S. avenae decreased in the PeaT1 (second generation 0.31 ± 0.01, third generation 0.28 ± 0.01) treatment compared with controls (second generation 0.28 ± 0.01, third generation 0.26 ± 0.01). S. avenae preferred to colonize control rather than PeaT1-treated wheat seedlings in a host selection test. PeaT1-treated wheat leaves possessed more trichomes and wax that formed a disadvantageous surface environment for S. avenae. Both salicylic acid (SA) and jasmonic acid (JA) accumulated significantly in PeaT1-treated wheat seedlings.

CONCLUSION

These results showed that PeaT1 modified physical surface structures in wheat to reduce reproduction and deter colonization by S. avenae. SA and JA were involved in the induced physical defense process. This study provided evidence for use of PeaT1 as a 'vaccine' to protect wheat from Sitobion avenae. © 2019 Society of Chemical Industry.

Colletotrichum acutatum M11 can suppress the defence response in strawberry plants

Colletotrichum acutatum M11 produces a diffusible compound that suppresses the biochemical, physiological, molecular and anatomical events associated with the defence response induced by the plant defence elicitor AsES. The fungal pathogen Colletotrichum acutatum, the causal agent of anthracnose disease, causes important economical losses in strawberry crop worldwide and synthetic agrochemicals are used to control it. In this context, the control of the disease using bioproducts is gaining reputation as an alternative of those toxic and pollutant agrochemicals. However, the success of the strategies using bioproducts can be seriously jeopardized in the presence of biological agents exerting a defence suppression effect. In this report, we show that the response defence induced in plant by the elicitor AsES from the fungus Acremonium strictum can be suppressed by a diffusible compound produced by isolate M11 of C. acutatum. Results revealed that strawberry plants treated with conidia of the isolated M11 or the culture supernatant of the isolate M11 suppress: ROS accumulation (e.g., H₂O₂, O₂^·- and NO), cell wall reinforcement (e.g., lignin and callose), and the up-regulation of defence-related genes (e.g., FaPR1, FaCHI23, FaPDF1.2, FaCAT, FaCDPK, FaCML39) induced by the elicitor AsES. Additionally, we show that the defence suppressing effect causes a systemic sensitization of plants. Results presented here highlights the necessity to make an integral study of the microbiome present in soils and plant biosphere before applying defence activation bioproducts to control crop diseases.

Development of PSP1, a Biostimulant Based on the Elicitor AsES for Disease Management in Monocot and Dicot Crops

In this work, we present a novel biostimulant for sustainable crop disease management, PSP1, based on the plant defense-elicitor AsES, an extracellular protease produced by the strawberry fungal pathogen Acremonium strictum. Fungal fermentation conditions and downstream processing were determined to maximize extracellular protein production, product stability and a high plant defense-eliciting activity, as monitored by anthracnose resistance in supernatant-treated strawberry plants subsequently infected with a virulent strain of Colletotrichum acutatum. Fermentation batches were shown to reduce anthracnose development by 30-60% as compared to infected non-treated plants. Product formulation was shown to be stable for 6 months when stored at temperatures up to 45°C and toxicological tests showed that PSP1 was harmless to beneficial organisms and non-toxic to mammalian species at concentrations 50 times higher than those used in plant experiments. Furthermore, disease protection studies using dilutions of PSP1 indicated that there is a minimum threshold protease activity needed to induce pathogen defense in strawberry and that this induction effect is dose-independent. A significant characteristic of PSP1 is its broad-range protection against different diseases in various crop species. In soybean, PSP1 reduced the symptomatology by 70% of Corynespora cassiicola, etiological agent of the target spot. This protection effect was similar to the commercial inducer BION 500 WG based on BTH, and both products were shown to induce an oxidative burst and up-regulated PR1-gene expression in soybean. Furthermore, a double PSP1-treatment on greenhouse-grown sugarcane plants provided protection against bacterial red stripe disease caused by Acidovorax avenae and a double foliar application of PSP1 on field-grown wheat plants significantly increased resistance against Fusarium graminearum, causal agent of head blight disease, manifested mainly in an increased seed germination rate. In summary, these disease protection studies demonstrated an effective control against both bacterial and fungal pathogens in both monocot and dicot crop species, which together with its low production cost, effectiveness at low concentrations, long shelf-life, tolerance to high temperatures, harmlessness to non-target organisms and simple handling and application, make PSP1 a very promising candidate for effective and sustainable disease management in many crop species.

Elicitor-Based Biostimulant PSP1 Protects Soybean Against Late Season Diseases in Field Trials

Currently, fungicide application in soybean production accounts for an important amount of global pesticide use, and it is therefore most desirable to find new healthier and more environmental friendly alternatives for the phytosanitary management in this crop. In this study, we present convincing evidence for effective induction of disease protection by the agricultural biostimulant PSP1, a formulation based on the plant-defense eliciting activity of the fungal protease AsES (Acremonium strictum elicitor subtilisin), in multiple field trials in Argentina. PSP1 was shown to combine well with commercial spray adjuvants, an insecticide, a herbicide and fungicides used in Argentinian soybean production without losing any defense-inducing activity, indicating an easy and efficient adaptability to conventional soybean production and disease management in the region. Results from multiple soybean field trials conducted with different elite genotypes at several locations during two consecutive growing seasons, showed that PSP1 is able to induce an enhanced pathogen defense which effectively reduced late season disease (LSD) development in field-grown soybean. This defense response seems to be broad-range as disease development was clearly reduced for at least three different fungi causing LSDs in soybean (Septoria glycines, Cercospora kikuchii and Cercospora sojina). It was noteworthy that application of PSP1 in soybean alone gave a similar protection against fungal diseases as compared to the commercial fungicides included in the field trials and that PSP1 applied together with a fungicide at reproductive stages enhanced disease protection and significantly increased grain yields. PSP1 is the first example of an elicitor-based strategy in order to efficiently control multiple fungal diseases under field conditions in the soybean crop. These results show the feasibility of using induced resistance products as complements or even full-good replacements to currently used chemical pesticides, fulfilling a role as important components of a more sustainable crop disease management system.

Soft mechanical stimulation induces a defense response against Botrytis cinerea in strawberry

Genes associated with plant mechanical stimulation were found in strawberry genome. A soft mechanical stimulation (SMS) induces molecular and biochemical changes in strawberry plants, conferring protection against Botrytis cinerea. Plants have the capacity to induce a defense response after exposure to abiotic stresses acquiring resistance towards pathogens. It was reported that when leaves of Arabidopsis thaliana were wounded or treated with a soft mechanical stimulation (SMS), they could resist much better the attack of the fungal pathogen Botrytis cinerea, and this effect was accompanied by an oxidative burst and the expression of touch-inducible genes (TCH). However, no further work was carried out to better characterize the induced defense response. In this paper, we report that TCH genes were identified for first time in the genomes of the strawberry species Fragaria ananassa (e.g. FaTCH2, FaTCH3, FaTCH4 and FaCML39) and Fragaria vesca (e.g. FvTCH2, FvTCH3, FvTCH4 and FvCML39). Phylogenetic studies revealed that F. ananassa TCH genes exhibited high similarity with the orthologous of F. vesca and lower with A. thaliana ones. We also present evidence that after SMS treatment on strawberry leaves, plants activate a rapid oxidative burst, callose deposition, and the up-regulation of TCH genes as well as plant defense genes such as FaPR1, FaCHI2-2, FaCAT, FaACS1 and FaOGBG-5. The latter represents the first report showing that TCH- and defense-induced genes participate in SMS-induced resistance in plants, bringing a rational explanation why plants exposed to a SMS treatment acquired an enhance resistance toward B. cinerea.