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Trichoderma longibrachiatum is a filamentous fungus used as a biological control agent against different plant diseases. The multifunctional secondary metabolites synthesized by Trichoderma , called peptaibols, have emerged as key elicitors in plant innate immunity. This study obtained a high-quality genome sequence for the T. longibrachiatum strain 40418 and identified two peptaibol biosynthetic gene clusters using knockout techniques. The two gene cluster products were confirmed as trilongin AIV a (11-residue) and trilongin BI (20-residue) using liquid chromatography coupled with tandem mass spectrometry. Further investigations revealed that these peptaibols induce plant resistance to Pseudomonas syringae pv tomato ( Pst ) DC3000 infection while triggering plant immunity and cell death. Notably, the two peptaibols exhibit synergistic effects in plant-microbe signaling interactions, with trilongin BI having a predominant role. Moreover, the induction of tomato resistance against Meloidogyne incognita showed similarly promising results.

Phytopathogen cell wall polysaccharides have important physiological functions. In this study, we isolated and characterized the alkali-insoluble residue on the inner layers of the Rhizoctonia solani AG1 IA cell wall (RsCW-AIR). Through chemical composition and structural analysis, RsCW-AIR was mainly identified as a complex of chitin/chitosan and glucan (ChCsGC), with glucose and glucosamine were present in a molar ratio of 2.7:1.0. The predominant glycosidic bond linkage of glucan in ChCsGC was β-1,3-linked Glcp, both the α and β-polymorphic forms of chitin were presented in it by IR, XRD, and solid-state NMR, and the ChCsGC exhibited a degree of deacetylation measuring 67.08 %. RsCW-AIR pretreatment effectively reduced the incidence of rice sheath blight, and its induced resistance activity in rice was evaluated, such as inducing a reactive oxygen species (ROS) burst, leading to the accumulation of salicylic acid (SA) and the up-regulation of SA-related gene expression. The recognition of RsCW-AIR in rice is partially dependent on CERK1., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

Background: Soybean cyst nematodes (SCN) as animal parasites of plants are not usually interested in killing the host but are rather focused on completing their life cycle to increase population, resulting in substantial yield losses. Remarkably, some agricultural soils after long-term crop monoculture show a significant decline in SCN densities and suppress disease in a sustainable and viable manner. However, relatively little is known about the microbes and mechanisms operating against SCN in such disease-suppressive soils., Results: Greenhouse experiments showed that suppressive soils (S) collected from two provinces of China and transplantation soils (CS, created by mixing 10% S with 90% conducive soils) suppressed SCN. However, SCN suppressiveness was partially lost or completely abolished when S soils were treated with heat (80 °C) and formalin. Bacterial community analysis revealed that the specific suppression in S and CS was mainly associated with the bacterial phylum Bacteroidetes, specifically due to the enrichment of Chitinophaga spp. and Dyadobacter sp., in the cysts. SCN cysts colonized by Chitinophaga spp. showed dramatically reduced egg hatching, with unrecognizable internal body organization of juveniles inside the eggshell due to chitinase activity. Whereas, Dyadobacter sp. cells attached to the surface coat of J2s increased soybean resistance against SCN by triggering the expression of defence-associated genes. The disease-suppressive potential of these bacteria was validated by inoculating them into conducive soil. The Dyadobacter strain alone or in combination with Chitinophaga strains significantly decreased egg densities after one growing cycle of soybeans. In contrast, Chitinophaga strains alone required more than one growing cycle to significantly reduce SCN egg hatching and population density., Conclusion: This study revealed how soybean monoculture for decades induced microbiota homeostasis, leading to the formation of SCN-suppressive soil. The high relative abundance of antagonistic bacteria in the cyst suppressed the SCN population both directly and indirectly. Because uncontrolled proliferation will likely lead to quick demise due to host population collapse, obligate parasites like SCN may have evolved to modulate virulence/proliferation to balance these conflicting needs. Video Abstract., (© 2024. The Author(s).)

Plant defence peptides are paramount endogenous danger signals secreted after a challenge, intensifying the plant immune response. The peptidic hormone Systemin (Sys) was shown to participate in resistance in several plant pathosystems, although the mechanisms behind Sys-induced resistance when exogenously applied remain elusive. We performed proteomic, metabolomic, and enzymatic studies to decipher the Sys-induced changes in tomato plants in either the absence or the presence of Botrytis cinerea infection. Sys treatments triggered direct proteomic rearrangement mostly involved in carbon metabolism and photosynthesis. However, the final induction of defence proteins required concurrent challenge, triggering priming of pathogen-targeted proteins. Conversely, at the metabolomic level, Sys-treated plants showed an alternative behaviour following a general priming profile. Of the primed metabolites, the flavonoids rutin and isorhamnetin and two alkaloids correlated with the proteins 4-coumarate-CoA-ligase and chalcone-flavanone-isomerase triggered by Sys treatment. In addition, proteomic and enzymatic analyses revealed that Sys conditioned the primary metabolism towards the production of available sugars that could be fuelling the priming of callose deposition in Sys-treated plants; furthermore, PR1 appeared as a key element in Sys-induced resistance. Collectively, the direct induction of proteins and priming of specific secondary metabolites in Sys-treated plants indicated that post-translational protein regulation is an additional component of priming against necrotrophic fungi., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

Terpenoids are defense metabolites that are induced upon infection or wounding. However, their role in systemic-induced resistance (SIR) is not known. Here, we explored the role of terpenoids in this phenomenon at a very early stage in the interaction between Austrian pine and the tip blight and canker pathogen Diplodia pinea. We induced Austrian pine saplings by either wounding or inoculating the lower stems with D. pinea. The seedlings were then challenged after 12 h, 72 h, or 10 days with D. pinea on the stem 15 cm above the induction. Lesion lengths and terpenoids were quantified at both induction and challenge locations. Key terpenoids were assayed for antifungal activity in in vitro bioassays. SIR increased with time and was correlated with the inducibility of several compounds. α-Pinene and a cluster of β-pinene, limonene, benzaldehyde, dodecanol, and n-dodecyl acrylate were positively correlated with SIR and were fungistatic in vitro, while other compounds were negatively correlated with SIR and appeared to serve as a carbon source for D. pinea. This study shows that, overall, terpenoids are involved in SIR in this system, but their role is nuanced, depending on the type of induction and time of incubation. We hypothesize that some, such as α-pinene, could serve in SIR signaling., (© 2024 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Gray mold caused by Botrytis cinerea is a major cause of economic losses during tomato production. In this study, we obtained 23 Trichoderma strains from tomato rhizosphere soil and their inhibitory effects on B. cinerea and the promoting effects on tomato growth were determined. Among them, the inhibition rate of strain DQ-1 on B. cinerea was 88.56%; compared with the control group, after treatment with strain DQ-1, the seeds germination rate and root length of tomato increased by 5.55 and 37.86%. The induced disease resistance of strain DQ-1 was evaluated by pot experiments. The disease incidence (DI) and disease severity index (DSI) of tomato pre-inoculated with strain DQ-1 and then inoculated with B. cinerea were reduced by 38 and 64% compared with the control. Furthermore, we detected the expression levels of tomato disease resistance related genes PR2 and TPX, ethylene pathway related genes ETR1 and CTR1 and jasmonic acid pathway related genes LOX1 and PAL in challenging and non-challenging inoculation treatments. The results showed that the tomato treated with strain DQ-1 triggered the system acquired resistance (SAR) and induced systemic resistance (ISR) pathway, thereby enhancing the disease resistance of tomato. Then the strain DQ-1 was identified as Trichoderma asperellum based on morphological characteristics and phylogenetic information. This study suggests that the novel T. asperellum strain DQ-1 can be a potential candidate for the biological control of gray mold in tomato., (© The Author(s) 2021. Published by Oxford University Press on behalf of FEMS. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Sulfur has been previously reported to modulate plant growth and exhibit significant anti-microbial activities. However, the mechanism underlying its diverse effects on plant pathogens has not been elucidated completely. The present study conducted the two-year field experiment of sulfur application to control kiwifruit canker from 2017 to 2018. For the first time, our study uncovered activation of plant disease resistance by salicylic acid after sulfur application in kiwifruit. The results indicated that when the sulfur concentration was 1.5-2.0 kg m - 3 , the induced effect of kiwifruit canker reached more than 70%. Meanwhile, a salicylic acid high lever was accompanied by the decline of jasmonic acid. Further analysis revealed the high expression of the defense gene, especially AcPR-1 , which is a marker of the salicylic acid signaling pathway. Additionally, AcICS1, gene was marked up-regulated. Thereafter, accumulation of lignin content in the kiwifruit stem and the higher deposition of lignin were visible in histochemical analysis. Moreover, the activity of the endochitinase activity of kiwifruit leaves increased significantly. We suggest that the sulfur-induced resistance against AcPAL gene was marked up-regulated. Thereafter, accumulation of lignin content in the kiwifruit stem and the higher deposition of lignin were visible in histochemical analysis. Moreover, the activity of the endochitinase activity of kiwifruit leaves increased significantly. We suggest that the sulfur-induced resistance against Pseudomonas syringae pv. actinidiae via salicylic activates systemic acquired resistance to enhance plant immune response in kiwifruit.

The soft rot disease caused by Rhizopus stolonifer is an important disease in cherry tomato fruit. In this study, the effect of iturin A on soft rot of cherry tomato and its influence on the storage quality of cherry tomato fruit were investigated. The results showed that 512 μg/mL of iturin A could effectively inhibit the incidence of soft rot of cherry tomato fruit. It was found that iturin A could induce the activity of resistance-related enzymes including phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO), peroxidase (POD), glucanase (GLU), and chitinase (CHI), and active oxygen-related enzymes including ascorbate peroxidases (APX), superoxide dismutases (SOD), catalases (CAT), and glutathione reductase (GR) of cherry tomato fruit. In addition, iturin A treatment could slow down the weight loss of cherry tomato and soften the fruit. These results indicated that iturin A could retard the decay and improve the quality of cherry tomato fruit by both the inhibition growth of R. stolonifera and the inducing the resistance.

Bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) has led to considerable losses in all major kiwifruit-growing areas. There are no commercial products in the market to effectively control this disease. Therefore, the defense resistance of host plants is a prospective option. In our previous study, sulfur could improve the resistance of kiwifruit to Psa infection. However, the mechanisms of inducing resistance remain largely unclear. In this study, disease severity and protection efficiency were tested after applying sulfur, with different concentrations in the field. The results indicated that sulfur could reduce the disease index by 30.26 and 31.6 and recorded high protection efficiency of 76.67% and 77.00% after one and two years, respectively, when the concentration of induction treatments was 2.0 kg/m 3 . Ultrastructural changes in kiwifruit stems after induction were demonstrated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the activities of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and polyphenol oxidase (PPO), and the accumulation of lignin were determined by biochemical analyses. Our results showed that the morphological characteristics of trichomes and lenticels of kiwifruit stem were in the best defensive state respectively when the sulfur concentration was 3.0 kg/m 3 and 1.5 kg/m 3 . Meanwhile, in the range of 0.5 to 2.0 kg/m 3 , the sulfur could promote the chloroplast and mitochondria of kiwifruit stems infected with Psa to gradually return to health status, increasing the thickness of the cell wall. In addition, sulfur increased the activities of PAL, POD and PPO, and promoted the accumulation of lignin in kiwifruit stems. Moreover, the sulfur protection efficiency was positively correlated with PPO activity ( p < 0.05) and lignin content ( p < 0.01), which revealed that the synergistic effect of protective enzyme activity and the phenolic metabolism pathway was the physiological effect of sulfur-induced kiwifruit resistance to Psa. This evidence highlights the importance of lignin content in kiwifruit stems as a defense mechanism in sulfur-induced resistance. These results suggest that sulfur enhances kiwifruit canker resistance via an increase in phenolic components and morphology structure modification in the kiwifruit stems. Therefore, this study could provide insights into sulfur to control kiwifruit canker caused by Psa.

To support the search for alternative, nonchemical plant disease control strategies, we present a review of the pathogen-suppressive effects of biochar, a product derived from agricultural and other organic wastes, used as a soil amendment. A wide range of biochar effects contribute to the control of root or foliar fungal pathogens through modification of root exudates, soil properties, and nutrient availability, which influence the growth of antagonist microorganisms. The induction of systemic plant defenses by biochar in the roots to reduce foliar pathogenic fungi, the activation of stress-hormone responses, as well as changes in active oxygen species are indicative of a coordinated hormonal signaling within the plant. Although scarce data are available for oomycetes and bacterial pathogens, reports indicate that biochar promotes changes in the soil microbiota influencing pathogen motility and colonization, and the induction of plant systemic defenses, both contributing to disease suppression. Biochar also suppresses nematode and insect pests. For plant-parasitic nematodes, the primary modes of action are changes in soil microbial community diversity, the release of nematicidal compounds, and the induction of plant defenses. Use of biochar-based soil amendments is a promising strategy compatible with a circular economy, based on zero waste, as part of integrated pathogen and pest management. Since biochars exert complex and distinct modes of action for the control of plant pathogens, its nature and application regimes should be designed for particular pathogens and its effects studied locally.

Host mixtures are a promising method for agroecological plant disease control. Plant immunity is key to the success of host mixtures against polymorphic pathogen populations. This immunity results from priming-induced cross-protection, whereby plants able to resist infection by specific pathogen genotypes become more resistant to other pathogen genotypes. Strikingly, this phenomenon was absent from mathematical models aiming at designing host mixtures. We developed a model to specifically explore how priming affects the coexistence of two pathogen genotypes in host mixtures composed of two host genotypes and how it affects disease prevalence. The main effect of priming is to reduce the coexistence region in the parameter space (due to the cross-protection) and to generate a singular mixture of resistant and susceptible hosts corresponding to the maximal reduction disease prevalence (in absence of priming, a resistant pure stand is optimal). The epidemiological advantage of host mixtures over a resistant pure stand thus appears as a direct consequence of immune priming. We also showed that there is indirect cross-protection between host genotypes in a mixture. Moreover, the optimal mix prevents the emergence of a resistance-breaking pathogen genotype. Our results highlight the importance of considering immune priming to design optimal and sustainable host mixtures.

Litchis are tasty fruit with economic importance. However, the extreme susceptibility of harvested litchis to litchi downy blight caused by Peronophythora litchii leads to compromised quality. This study aimed to study the effects of melatonin on postharvest resistance to P. litchii in 'Feizixiao' litchis. Results showed that melatonin restricted lesion expansion in litchis after P. litchi inoculation. Melatonin enhanced the activities of phenylalanine ammonia-lyase, cinnamate-4-hydroxylase and 4-hydroxycinnamate CoA ligase while promoting the accumulations of phenolics and flavonoids. Nicotinamide adenine dinucleotide phosphate content and glucose-6-phosphate dehydrogenase and 6-phosphogluconic acid dehydrogenase activities were higher in treated fruit than control fruit. Higher energy status along with elevated H + -ATPase, Ca 2+ -ATPase, succinate dehydrogenase and cytochrome C oxidase activities were observed in treated fruit. Ultrastructural observation showed reduced damage in mitochondria in treated fruit. The results suggest that melatonin induced resistance in litchis by modulating the phenylpropanoid and pentose phosphate pathways as well as energy metabolism. ., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Iron (Fe) is a poorly available mineral nutrient which affects the outcome of many cross-kingdom interactions. In Arabidopsis thaliana, Fe starvation limits infection by necrotrophic pathogens. Here, we report that Fe deficiency also reduces disease caused by the hemi-biotrophic bacterium Pseudomonas syringae and the biotrophic oomycete Hyaloperonospora arabidopsidis, indicating that Fe deficiency-induced resistance is effective against pathogens with different lifestyles. Furthermore, we show that Fe deficiency-induced resistance is not caused by withholding Fe from the pathogen but is a plant-mediated defense response that requires activity of ethylene and salicylic acid. Because rhizobacteria-induced systemic resistance (ISR) is associated with a transient up-regulation of the Fe deficiency response, we tested whether Fe deficiency-induced resistance and ISR are similarly regulated. However, Fe deficiency-induced resistance functions independently of the ISR regulators MYB72 and BGLU42, indicating that both types of induced resistance are regulated in a different manner. Mutants opt3 and frd1, which display misregulated Fe homeostasis under Fe-sufficient conditions, show disease resistance levels comparable with those of Fe-starved wild-type plants. Our results suggest that disturbance of Fe homeostasis, through Fe starvation stress or other non-homeostatic conditions, is sufficient to prime the plant immune system for enhanced defense., (© The Author(s) 2020. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.)

Current crop protection strategies against the fungal pathogen Botrytis cinerea rely on a combination of conventional fungicides and host genetic resistance. However, due to pathogen evolution and legislation in the use of fungicides, these strategies are not sufficient to protect plants against this pathogen. Defence elicitors can stimulate plant defence mechanisms through a phenomenon known as defence priming. Priming results in a faster and/or stronger expression of resistance upon pathogen recognition by the host. This work aims to study defence priming by a commercial formulation of the elicitor chitosan. Treatments with chitosan result in induced resistance (IR) in solanaceous and brassicaceous plants. In tomato plants, enhanced resistance has been linked with priming of callose deposition and accumulation of the plant hormone jasmonic acid (JA). Large-scale transcriptomic analysis revealed that chitosan primes gene expression at early time-points after infection. In addition, two novel tomato genes with a characteristic priming profile were identified, Avr9/Cf-9 rapidly elicited protein 75 (ACRE75) and 180 (ACRE180). Transient and stable over-expression of ACRE75, ACRE180 and their Nicotiana benthamiana homologs, revealed that they are positive regulators of plant resistance against B. cinerea. This provides valuable information in the search for strategies to protect Solanaceae plants against B. cinerea., (© 2020 The Authors. Plant, Cell & Environment published by John Wiley & Sons Ltd.)

Systemic acquired resistance (SAR) is a broad-spectrum disease resistance response that can be induced upon infection from pathogens or by chemical treatment, such as with benzo-(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH). SAR involves priming for more robust activation of defence genes upon pathogen attack. Whether priming for SAR would involve components of RNA silencing remained unknown. Here, we show that upon leaf infiltration of water, BTH-primed Arabidopsis thaliana plants accumulate higher amounts of mRNA of ARGONAUTE (AGO)2 and AGO3, key components of RNA silencing. The enhanced AGO2 expression is associated with prior-to-activation trimethylation of lysine 4 in histone H3 and acetylation of histone H3 in the AGO2 promoter and with induced resistance to the yellow strain of cucumber mosaic virus (CMV[Y]). The results suggest that priming A. thaliana for enhanced defence involves modification of histones in the AGO2 promoter that condition AGO2 for enhanced activation, associated with resistance to CMV(Y). Consistently, the fold-reduction in CMV(Y) coat protein accumulation by BTH pretreatment was lower in ago2 than in wild type, pointing to reduced capacity of ago2 to activate BTH-induced CMV(Y) resistance. A role of AGO2 in pathogen-induced SAR is suggested by the enhanced activation of AGO2 after infiltrating systemic leaves of plants expressing a localized hypersensitive response upon CMV(Y) infection. In addition, local inoculation of SAR-inducing Pseudomonas syringae pv. maculicola causes systemic priming for enhanced AGO2 expression. Together our results indicate that defence priming targets the AGO2 component of RNA silencing whose enhanced expression is likely to contribute to SAR., (© 2020 The Authors. Molecular Plant Pathology published by British Society for Plant Pathology and John Wiley & Sons Ltd.)

Indian mustard (Brassica juncea L.) is an important edible oilseed crop in India. Low productivity is the major concern which is adversely affected by biotic stresses. Alternaria blight (Alternaria brassicae) is one among major diseases that has no resistant cultivar until now. Keeping in view, an experiment was conducted for isolation of Alternaria blight-tolerant mutants in Indian mustard using gamma radiation and EMS mutagens during four consecutive years in Rabi (winter season). Furthermore, the morphologically and economically superior mutants of Brassica juncea were screened artificially at cotyledonary and adult stage against Alternaria blight. Tolerance to Alternaria blight is observed in DRMR-M-163 (11.7%), DRMR-M-158 (13.1%), DRMR-M-174 (13.8%) and DRMR-M-177 (18.6%) with minimum conidia in infected cotyledons. Mutant DRMR-M-178 (19.8%) had the highest radical scavenging activity, while DRMR-M-162 (104.9 mg/g AAE), DRMR-M-169 (96.9) and DRMR-M-161 (96.9) had higher antioxidant capacity that appears to act as defence to pathogen. DRMR-M-168 (8.4%), DRMR-M-173 (8.3), DRMR-M-171 (7.9), DRMR-M-165 (7.4), DRMR-M-175 (7.2) and DRMR-M-172 (6.9) had higher phenol content which may be responsive for resistance, although DRMR-M-161 (192.7 mg/g), DRMR-M-163 (187.7 mg/g), DRMR-M-164 (132.7 mg/g), DRMR-M-167 (149.3 mg/g), DRMR-M-173 (196.0 mg/g) and DRMR-M-178 (192.7 mg/g) mutants are found to contain low levels of total soluble sugar compared with susceptible Rohini (379.3). Based on biochemical parameter's similarity, mutants are grouped in 4 major clusters. Cluster 4 contained significantly different mutant DRMR-M-172. Relative expression of mitogen-activated protein kinase 3 (MAPK3) gene was found highest in DRMR-M-177, DRMR-M-174, DRMR-M-175, DRMR-M-178, DRMR-M-170, DRMR-M-176, DRMR-M-172 and DRMR-M-173 which resulted the better response to AB stress. Based on biochemical analysis, realtime PCR and cluster analysis, DRMR-M-172 mutant appears more tolerant to Alternaria. DRMR-M-178, DRMR-M-167 and DRMR-M-177 mutants seem tolerant and could be utilized for further breeding programme.

Flowers are the most vulnerable plant organ to infection by the necrotrophic fungus Botrytis cinerea. Here we show that pre-treatment of chrysanthemum (Chrysanthemum morifolium) flowers with phenylalanine (Phe) significantly reduces their susceptibility to B. cinerea. To comprehend how Phe treatment induces resistance, we monitored the dynamics of metabolites (by GC/LC-MS) and transcriptomes (by RNAseq) in flowers after Phe treatment and B. cinerea infection. Phe treatment resulted in accumulation of 3-phenyllactate and benzaldehyde, and in particular induced the expression of genes related to Ca 2+ signaling and receptor kinases, implicating an induction of the defense response. Interestingly, the main effects of Phe treatment were observed in flowers exposed to B. cinerea infection, stabilizing the global fluctuations in the levels of metabolites and transcripts while reducing susceptibility to the fungus. We suggest that Phe-induced resistance is associated to cell priming, enabling rapid and targeted reprogramming of cellular defense responses to resist disease development. After Phe pre-treatment, the levels of the anti-fungal volatiles phenylacetaldehyde and eugenol were maintained and the level of coniferin, a plausible monolignol precursor in cell wall lignification, was strongly increased. In addition, Phe pre-treatment reduced ROS generation, prevented ethylene emission, and caused changes in the expression of a minor number of genes related to cell wall biogenesis, encoding the RLK THESEUS1, or involved in Ca 2+ and hormonal signaling processes. Our findings point to Phe pre-treatment as a potential orchestrator of a broad-spectrum defense response which may not only provide an ecologically friendly pest control strategy but also offers a promising way of priming plants to induce defense responses against B. cinerea., (© 2020 Society for Experimental Biology and John Wiley & Sons Ltd.)

Natural rhamnolipids are potential biocontrol agents for plant protection against bacterial and fungal diseases. In this work, we synthetized new synthetic mono-rhamnolipids (smRLs) consisting in a rhamnose connected to a simple acyl chain and differing by the nature of the link and the length of the lipid tail. We then investigated the effects of these ether, ester, carbamate or succinate smRL derivatives on Botrytis cinerea development, symptoms spreading on tomato leaves and immune responses in tomato plants. Our results demonstrate that synthetic smRLs are able to trigger early and late immunity-related plant defense responses in tomato and increase plant resistance against B. cinerea in controlled conditions. Structure-function analysis showed that chain length of the lipidic part and type of acyl chain were critical to smRLs immune activity and to the extent of symptoms caused by the fungus on tomato leaves.

Biological control agents including microbes and their products have been studied as sustainable crop protection strategies. Although aquatic microalgae have been recently introduced as a biological control agent, the underlying molecular mechanisms are largely unknown. The aim of the present study was to investigate the molecular mechanisms underlying biological control by microalga Chlorella fusca. Foliar application of C. fusca elicits induced resistance in Arabidopsis thaliana against Pseudomonas syringae pv. tomato DC3000 that activates plant immunity rather than direct antagonism. To understand the basis of C. fusca-triggered induced resistance at the transcriptional level, we conducted RNA sequencing (RNA-seq) analysis. RNA-seq data showed that, upon pathogen inoculation, C. fusca treatment primed the expression of cysteine-rich receptor-like kinases, WRKY transcription factor genes, and salicylic acid and jasmonic acid signalling-related genes. Intriguingly, the application of C. fusca primed pathogen-associated molecular pattern -triggered immunity, characterized by reactive oxygen species burst and callose deposition, upon flagellin 22 treatment. The attempts to find C. fusca determinants allowed us to identify d-lactic acid secreted in the supernatant of C. fusca as a defence priming agent. This is the first report of the mechanism of innate immune activation by aquatic microalga Chlorella in higher plants., (© 2019 The Authors. The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.)

Jasmonates (JAs), the group of lipid-derived hormones, were found to control the defense responses in a myriad of plants. Meaningfully, the macrolactones of 12-hydroxy jasmonate isoleucine (12OH-JA-Ile) were reported to induce the defensive response of wild tobacco. However, little to nothing has been known about the elicitation effect of JA-Ile-macrolactones on woody plants to harmful organisms, let alone its underlying mechanisms. Here, we first optimized the synthetic routine using mild toxic reagent isobutyl chloroformate instead of ethyl chloroformate for conjugation, and we used acetonitrile (MeCN) instead of ethyl alcohol for the better dissolution of p -toluenesulfonic acid ( p -TsOH) to gain JA-Ile-macrolactones. JA-Ile-macrolactone 5b -treated tea plants significantly inhibited the larvae weight gain of Ectropis obliqua larvae and the lesions caused by Colletotrichum camelliae . Furthermore, the expression level of CsOPR3 was significantly upregulated in 5b -treated leaves. Meanwhile, 5b reduced the accumulation of eriodictyol 7-O-glucuronide (EDG) in tea plants, which was confirmed to promote the growth rate of E. obliqua larvae by artificial diet assay. In conclusion, our study proved that the exogenous application of 5b could induce the tea plant resistance both to herbivore E. obliqua and pathogen C. camelliae , and EDG was identified as one of the secondary metabolites that could influence the growth rate of E. obliqua , but it did not directly influence the infection of C. camelliae in vitro . Further research should be carried out to clarify the mechanism through which 5b induces tea plant resistance to C. camelliae .

The pink ear rot is one of the most damaging maize diseases, caused by the mycotoxigenic fungal pathogen, Fusarium verticillioides. The application of biological control agents, like antagonistic and/or resistance inducer microorganisms, is an option to reduce fungal infection and kernel contamination in a sustainable and environmentally friendly way. It is well known that Trichoderma species are non-pathogenic fungi able to antagonize plant pathogens and to induce systemic resistance in plants. The present work aimed to verify if Trichoderma spp., applied to maize kernels, affect the plant growth and induce systemic responses to F. verticillioides. Besides, the capability to reduce fumonisin concentration in liquid cultures was investigated. Two T. gamsii (IMO5 and B21), and one T. afroharzianum (B75) isolates, selected both for antagonism and for the ability to reduce root infections, significantly reduced the endophytic development of the stem-inoculated pathogen, compared to the control. The mechanisms of action appeared to be strain-specific, with IMO5 enhancing transcript levels of marker genes of Induced Systemic Resistance (ZmLOX10, ZmAOS, and ZmHPL) while B21 enhancing marker genes of Systemic Acquired Resistance (ZmPR1 and ZmPR5), as evinced by measuring their expression profiles in the leaves. Moreover, IMO5 promoted plant growth, while B21 was able to significantly reduce the fumonisin content in a liquid medium. The results of this work give new evidence that the seed application of T. gamsii is a promising tool for controlling F. verticillioides to be integrated with breeding and the adoption of good agricultural practices., (Copyright © 2019 Elsevier GmbH. All rights reserved.)

Root-knot nematodes (RKNs) severely affect plants growth and productivity, and several commercial biocontrol bacteria can improve plants resistance to RKNs. Pseudomonas putida Sneb821 isolate was found to induce tomatoes resistance against Meloidogyne incognita . However, the molecular functions behind induced resistance remains unclear. Long non-coding RNA (lncRNA) is considered to be a new component that regulates the molecular functions of plant immunity. We found lncRNA was involved in Sneb821-induced tomato resistance to M. incognita . Compared with tomato inoculated with M. incognita , high-throughput sequencing showed that 43 lncRNAs were upregulated, while 35 lncRNAs were downregulated in tomatoes previously inoculated with Sneb821. A regulation network of lncRNAs was constructed, and the results indicated that 12 lncRNAs were found to act as sponges of their corresponding miRNAs. By using qRT-PCR and the overexpression vector pBI121, we found the expression of lncRNA44664 correlated with miR396/GRFs (growth-regulating factors) and lncRNA48734 was correlated with miR156/SPL (squamosal promoter-binding protein-like) transcription factors. These observations provided a novel molecular model in biocontrol bacteria-induced tomato resistance to M. incognita .

Compounds that establish induced resistance (IR) in plants are promising alternatives for the pesticides that are progressively being banned worldwide. Screening platforms to identify IR-establishing compounds have been developed, but none were specifically designed for monocot plants. Here, we propose the use of an RT-qPCR screening platform, based on conserved immunity marker genes of rice as proxy for IR induction. Central regulators of biotic stress responses of rice were identified with a weighted gene co-expression network analysis (WGCNA), using more than 350 microarray datasets of rice under various sorts of biotic stress. Candidate genes were narrowed down to six immunity marker genes, based on consistent association with pattern-triggered immunity (PTI), both in rice plants as in rice cell suspension cultures (RCSCs). By monitoring the expression of these genes in RCSCs upon treatment with candidate IR-inducing compounds, we showed that our marker genes can predict IR induction in rice. Diproline, a novel IR-establishing compound for monocots that was detected with these marker genes, was shown to induce rice resistance against root-knot nematodes, without fitness costs. Gene expression profiling of the here-described PTI-marker genes can be executed on fully-grown plants or in RCSCs, providing a novel and versatile tool to predict IR induction.

The effects of exogenous polyamines treatment on reactive oxygen species (ROS) metabolism in apricot fruits were systematically analyzed through the investigation of their curative and preventive effects on black spot disease. Results showed that 1.5 mM spermine (Spm), 1.5 mM spermidine (Spd) and 10 mM putrescine (Put) treatment significantly inhibited black spot development, additionally, the efficacy of this control was dependent upon the type of polyamines used and concentration level applied. Further studies have shown that exogenous polyamines treatments significantly improved production of O 2 - and H 2 O 2 , and increased the activities and gene expression levels of NADPH oxidase (NOX), super oxide dismutase (SOD), catalase (CAT) ascorbate peroxidase (AXP) and glutathione reductase (GR) in apricot fruit. Increased ascorbic acid (AsA) and reduced glutathione (GSH) content were also observed after exogenous polyamines treatment. These results have revealed that postharvest polyamines treatment effectively enhanced disease resistance through the maintenance of homeostasis in apricot fruits., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Several elicitors, stimulating induced resistance mechanisms, have potential in preventing or mitigating pathogen infections. Some of these compounds, triggering the production of jasmonic acid (JA), a precursor of herbivore-induced plant volatiles, could also play a central role in indirect resistance to pest species, by improving beneficial arthropod performance, and necrotrophic pathogens. In the current work, Trichoderma gamsii/T. asperellum and silica gel treatments - alone and in combination - were studied to evaluate the plant defence mechanism on grapevines (Vitis vinifera L.) by laboratory and field trials. JA production level was measured before and after Plasmopara viticola infection on potted vines. JA production induced by silica gel was higher than that caused by Trichoderma before infection. In Trichoderma-treated plants, JA production increased after P. viticola inoculation. In vineyard field trials, Mymaridae (Hymenoptera: Chalcidoidea) showed higher captures in transparent sticky traps on silica gel-treated plants, in comparison with control. On the other hand, no significant attraction was detected for Ichneumonoidea and other Chalcidoidea in silica gel and T. gamsii/T. asperellum-treated plants. The potential effects of elicitors are discussed, in the frame of attract and reward strategy.

Laminaran, a β-(1→3)-glucan extracted from Laminaria digitata, is a known elicitor of plant defenses, but provides only low level of disease control in vineyard trials. In this context, laminaran was partly hydrophobized by grafting from 1.6 to 7.6 lauryl chains to the native saccharidic chain and the impact of sulfation of the hydrophobized glucans was studied. The activity of the different synthetized laminaran derivatives as antimicrobial agents against Plasmopara viticola, the causal agent of grape downy mildew, and as elicitors of defense reactions in planta, was evaluated. Our results showed that acylation imparts an antimicrobial activity to laminaran which is related to the degree of acylation, AL3, with 7.6 lauryl chains, being the most effective derivative. Sulfation of the acylated laminarans did not further increase the antimicrobial activity. Our results also demonstrated that the efficacy of AL3 against Plasmopara viticola was most likely due to the direct antimicrobial activity of the lauryl chains rather than to an elicitation of plant defenses., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Alternaria tenuissima infects stored potatoes, and causes tuber rot, resulting in significant economic losses. As a naturally-occurring polysaccharide (poly-β-(1 → 4) N-acetyl-D-glucosamine), chitosan has been reported to be an eco-friendly alternative to synthetic fungicides for the control of postharvest diseases on agricultural commodities. In this study, application of 0.25-1.25 g/L chitosan significantly inhibited spore germination and mycelial growth of A. tenuissima in vitro, with the greatest inhibitory effect observed at the highest concentration. Cytological and biochemical analysis of A. tenuissima spores indicated that exposure to 1.25 g/L chitosan significantly damaged the plasma membrane and increased the level of lipid oxidation. Gene expression analysis in potato tuber revealed that an application of 1.25 g/L chitosan induced the expression of defense-related genes, including catalase, peroxidase, polyphenol oxidase, chitinase and β-1,3-glucanase, and the level of flavonoids and lignin. Chitosan effectively controlled tuber rot caused by A. tenuissima. Collectively, results of the current study indicate that the ability of chitosan to reduce Alternaria rot in stored potato tubers is due to its direct antifungal activity and its ability to induce defense responses in potato tuber tissues. Chitosan may have the potential as a substitute for synthetic fungicides to reduce postharvest losses in potato., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Gray mold caused by Botrytis cinerea is the most important disease in postharvest tomato fruit. Inducing resistance to fungal pathogens in the harvested fruit and vegetable is a promising approach to control postharvest losses. In the present study, the effect of l-glutamate on induction of resistance to B. cinerea and the underlying mechanisms were investigated. The results indicated that l-glutamate at 100 ppm was effective in reducing the gray mold of tomatoes after inoculation of the pathogen. Gene expressions of nine glutamate receptors, four pathogenesis-related proteins and the content of amino acids were affected by l-glutamate treatment. Furthermore, the metabolites of l-glutamate, including GABA, Met, Lys and Arg, could also induce significant resistance against B. cinerea in tomato fruit. Our findings suggested that l-glutamate treatment may represent a promising method for managing postharvest decay of tomato fruit., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Improving plant resistance against systemic diseases remains a challenging research topic. In this study, we developed a dual-action pesticide-loaded hydrogel with the capacity to significantly induce plant resistance against tobacco mosaic virus (TMV) infection and promote plant growth. We produced an alginate-lentinan-amino-oligosaccharide hydrogel (ALA-hydrogel) by coating the surface of an alginate-lentinan drug-loaded hydrogel (AL-hydrogel) with amino-oligosaccharide using electrostatic action. We determined the formation of the amino-oligosaccharide film using various approaches, including Fourier transform infrared spectrometry, the ζ potential test, scanning electron microscopy, and elemental analysis. It was found that the ALA-hydrogel exhibited stable sustained-release activity, and the release time was significantly longer than that of the AL-hydrogel. In addition, we demonstrated that the ALA-hydrogel was able to continuously and strongly induce plant resistance against TMV and increase the release of calcium ions to promote Nicotiana benthamiana growth. Meanwhile, the ALA-hydrogel maintained an extremely high safety to organisms. Our findings provide an alternative to the traditional approach of applying pesticide for controlling plant viral diseases. In the future, this hydrogel with the simple synthesis method, green synthetic materials, and its efficiency in the induction of plant resistance will attract increasing attention and have good potential to be employed in plant protection and agricultural production.

Seven isolates of Trichoderma spp. (T1 to T7) from Egypt were evaluated in vitro by bioassay for their potential to antagonize Fusarium oxysporum f.sp. lycopersici (FOL, the causal pathogen of tomato wilt disease). The highest percentage of inhibition against the tested pathogenic isolate were obtained with Trichoderma isolate (T7) followed by Trichoderma isolate (T3). In greenhouse experiments, the application of the highly antagonistic isolates of Trichoderma spp. (T3 and T7) led to a significant decrease of disease severity compared to the untreated control treatment. The lowest severity was achieved with the T3 isolate (24.8%) followed by isolate T7 (34.6%) compared with the other tested isolates. To understand the ability of Trichoderma isolates to protect against wilt disease, its induced systemic resistance in tomato plants has been studied. The expression of a defense-related gene (β-1,3-glucanase gene) was assessed by real-time RT-PCR in tomato plants to test the accumulation kinetics of transcripts encoding PR proteins in the roots of tomato in control (only with the pathogen), T3&FOL, and T7&FOL treatments. The highest degree of gene expression was found in tomato plants which were treated with T3&FOL compared with control (pathogen only). Two species of antagonistic Trichoderma (T3& T7) were characterized based on molecular tools using internal transcribed spacers (ITS1 and ITS4). The results of genetic characterization identified two different species of Trichoderma (T. atroviride and T. longibrachiatum).

Cytosinpeptidemycin (CytPM) is a microbial pesticide that displayed broad-spectrum antiviral activity against various plant viruses. However, the molecular mechanism underlying antiviral activity of CytPM is poorly understood. In this study, the results demonstrated that CytPM could effectively delay the systemic infection of tobacco mosaic virus (TMV) in Nicotiana benthamiana and significantly inhibit the viral accumulation in tobacco BY-2 protoplasts. Results of RNA-seq indicated that 210 and 120 differential expressed genes (DEGs) were significantly up- and down-regulated after CytPM treatment in BY-2 protoplasts, respectively. In addition, KEGG analysis indicated that various DEGs were involved in endoplasmic reticulum (ER) protein processing, suggesting a possible correlation between ER homeostasis and virus resistance. RT-qPCR was performed to validate the gene expression of crucial DEGs related with defense, stress responses, signaling transduction, and phytohormone, which were consistent with results of RNA-seq. Our works provided valuable insights into the antiviral mechanism of CytPM that induced host resistance to viral infection.

The esterified fraction of jujube ( Ziziphus jujuba Mill.) peel extract showed strong antifungal activity on Alternaria alternata. p-Coumaric acid (pCA) was found to be the most predominant individual phenolic acid that was correlated highly with the antifungal activity of the esterified fraction. Thus, effects of postharvest treatments with pCA and its simplest esterified derivative methyl p-coumarate (MeCA) against black spot rot on jujube fruit caused by A. alternata were investigated. pCA and MeCA strongly suppressed in vitro growth of the fungus and significantly reduced postharvest Alternaria rot on fresh jujubes. Biochemical and transcriptional analysis revealed that pCA and MeCA regulated the expression of some genes encoding antioxidant enzymes and their enzymatic activities, enhanced the phenylpropanoid pathway metabolism, and activated the expression of genes encoding pathogenesis-related proteins. These results suggested that, apart from its direct antifungal activity, pCA and MeCA induced defense responses in jujube fruit against postharvest Alternaria rot.

Bacterial wilt is a devastating disease of tomato caused by soilborne pathogenic bacterium Ralstonia solanacearum . Previous studies found that silicon (Si) can increase tomato resistance against R. solanacearum , but the exact molecular mechanism remains unclear. RNA sequencing (RNA-Seq) technology was used to investigate the dynamic changes of root transcriptome profiles between Si-treated (+Si) and untreated (-Si) tomato plants at 1, 3, and 7 days post-inoculation with R. solanacearum . The contents of salicylic acid (SA), ethylene (ET), and jasmonic acid (JA) and the activity of defense-related enzymes in roots of tomato in different treatments were also determined. The burst of ET production in roots was delayed, and SA and JA contents were altered in Si treatment. The transcriptional response to R. solanacearum infection of the +Si plants was quicker than that of the untreated plants. The expression levels of differentially-expressed genes involved in pathogen-associated molecular pattern-triggered immunity (PTI), oxidation resistance, and water-deficit stress tolerance were upregulated in the Si-treated plants. Multiple hormone-related genes were differentially expressed in the Si-treated plants. Si-mediated resistance involves mechanisms other than SA- and JA/ET-mediated stress responses. We propose that Si-mediated tomato resistance to R. solanacearum is associated with activated PTI-related responses and enhanced disease resistance and tolerance via several signaling pathways. Such pathways are mediated by multiple hormones (e.g., SA, JA, ET, and auxin), leading to diminished adverse effects (e.g., senescence, water-deficit, salinity and oxidative stress) normally caused by R. solanacearum infection. This finding will provide an important basis to further characterize the role of Si in enhancing plant resistance against biotic stress.

In order to define the role of oxalic acid (OA) in the invasion of Botrytis cinerea in tomato plants, the OA induction of resistance related to oxalate oxidase (O×O) and germin was examined. In greenhouse experiments, OA at 3 mmol/L significantly induced resistance in tomato plants against B. cinerea strains B05.10 and T4, reducing lesion size of 37.55% and 24.91% by compared with distilled water control, respectively, while 20 mmol/L OA increasing by 36.14% and 41.48%. OA contents were 98 and 46 µg/mL when tomato plants were infected by B. cinerea strains B05.10 and T4, respectively. To define the molecular-genetic mechanisms, we compared the gene expression under four different conditions: 3 mmol/L OA-treated plants, 20 mmol/L OA-treated plants, B. cinerea strain B05.10-infected plants (B05.10 Inf plants) and B. cinerea strain T4-infected plants (T4 Inf plants). In 3 mmol/L OA-treated plants, the expressions of O×O and Germin peaked at 48 h after spraying, with approximate threefold and 18-fold increase compared with the control expression, respectively. In T4 Inf plants, the expression (mRNA accumulation) of O×O and Germin reached the highest levels at 24 h after inoculation, with 3- and 13-times that immediately after inoculation, respectively. In total, these findings suggest that elevated levels of OA correlated with increased fungal invasion and lower OA induced resistance in tomato plants by increasing expressions of O×O and Germin.

Capsicum annuum L. is infected by Fusarium Wilt and causes significant yield losses in Pakistan. Biological control is an excellent and environment friendly way. Presently, the biocontrol assays were conducted in pot trials using methanolic leaf extract of Eucalyptus citriodora L. where spray of extract prior to infection provided better protection from pathogen with maximum disease control. Further, Native page electrophoresis was performed to find out difference in expression profile of enzyme which revealed that control and T2 (Plant sprayed with Eucalyptus extract) did not exhibit any difference in their isozyme profile signifying no extra load of biological control measure on plant for the production of defense elements until the pathogen arrived. While in case of T3 （Protective treatment） and T4 (Curative treatment) extra isozyme (PO1) was observed in T4 only, PPO1 and PPO5, and PAL 2 and PAL 3 were comprised in higher quantities in T3 and T4 over control exposing the expression of plant metabolism under pathogen attack. The study concludes that the organic extract of E. citriodora have the potential to restrain the disastrous effects of pathogenic fungi. It will lead to the different aspect of biocontrol to suppress the plant pathogenic fungi in a broad spectrum.

Background: Phytopathogenic problems caused by the bacterial pathogen Pseudomonas syringae in tomato are becoming more serious due to the emergence of strains resistant to classical pesticides. This has led to research into new formulations with lower environmental problems. One of the most promising alternatives to the use of classical pesticides is the induction of natural plant defences. New formulations based on Cu complexed with heptagluconic acid induce plant innate defences and could be an alternative to classical treatments based on inorganic Cu against bacterial speck. To study the efficacy of this compound in tomato against P. syringae, we tested its systemic effect Applying the treatments via radicular., Results: Treated plants showed less infection development and lower number of viable bacteria in leaves. We also observed better performance of parameters involved in plant resistance such as the antioxidant response and the accumulation of phenolic compounds., Conclusion: Results showed that soil drench applications can be highly effective for the prevention and control of bacterial speck in tomato plants, showing a reduction in symptoms of ∼ 50%. Moreover, application of Cu heptagluconate induced accumulation of the plant polyphenols caffeic and chlorogenic acids, and reduced the amount of reactive oxygen species in infected plants. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

The present study characterized a cell wall chitin from Saccharomyces cerevisiae and investigated the effect of a postharvest chitin treatment on disease resistance against Botrytis cinerea infection in tomato fruit and the possible mechanisms involved. The results indicated that treatment with chitin could effectively induce strong resistance against gray mold rot caused by B. cinerea in tomato fruit. Moreover, chitin treatment promoted the accumulation of ROS and callose deposition. The activities of six defense-related enzymes, including superoxide dismutase, catalase, peroxidase, phenylalanine ammonia-lyase, β-1,3-glucanase and chitinase, along with the expression of these corresponding genes, were markedly enhanced in the chitin-treated fruit. Meanwhile, the key enzyme genes of SA biosynthesis and signal transduction pathway were found up-regulated in the chitin treatment. Therefore, these results suggest that the increased disease resistance of tomato fruit after chitin treatment during storage might be attributed to an elicitation of defense response as mentioned above in fruit., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Background: Blue mould caused by Penicillium expansum comprises a notable disease of apple fruit during storage. ϵ-Poly-l-lysine (PL) consists of ϵ-amino and α-hydroxyl and has been used in food preservation. In the present study, apple fruits (cv. Fuji) were used to investigate the effects of PL dipping treatment, at different concentrations of PL, on the lesion diameter of fruit inoculated with P. expansum, aiming to screen the optimal concentration for controlling blue mould. The effects of PL at the optimal concentration on reactive oxygen species (ROS) metabolism and the phenylpropanoid pathway were also investigated., Results: The results indicated that 25, 50, 100 and 200 µL L -1 PL treatment significantly decreased the lesion diameter in apple fruit inoculated with P. expansum and the smallest lesion diameter was determined for 50 µL L -1 PL-treated fruits. The results also indicated that 50 µL L -1 PL treatment increased the hydrogen peroxide content and the activities of enzymes involved in ROS metabolism, including superoxide dismutase, catalase, ascorbate peroxidase, glutathione reductase and peroxidase in apple fruit. The activity of phenylalanine ammonia-lyase and the contents of lignin, total phenolic compounds and flavonoids were also enhanced by PL treatment., Conclusion: The disease resistance to P. expansum in apple fruits enhanced by PL treatment is related to activating ROS metabolism and the phenylpropanoid pathway and the accumulation of antifungal compounds. © 2018 Society of Chemical Industry., (© 2018 Society of Chemical Industry.)

The results from this study showed that cell wall prepared from Rhodosporidium paludigenum induced strong disease resistance against blue mold rot caused by Penicillium expansum in pear fruit. Yeast cell wall reduced germination of P. expansum in vitro and in fruit wounds after 24h of treatment. Moreover, the cell wall treatment significantly enhanced the activities of defense-related enzymes (β-1,3-glucanase and chitinase) and the genes expression of PR proteins (PR1-like, endoGLU9, endoCHI-like and PR4), which may be an important mechanism by which cell wall reduces the fungal disease of pear fruit caused by P. expansum. These findings suggest that the mechanism by which R. paludigenum induced fruit resistance was linked to the function of its cell wall and application of cell wall might be a useful strategy for the control of postharvest disease in pear fruit., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Sulfur dioxide (SO 2 ) is a common air pollutant that has complex impacts on plants. The effect of prior exposure to 30mgm -3 SO 2 on defence against Botrytis cinerea (B. cinerea) in Arabidopsis thaliana and the possible mechanisms of action were investigated. The results indicated that pre-exposure to 30mgm -3 SO 2 resulted in significantly enhanced resistance to B. cinerea infection. SO 2 pre-treatment significantly enhanced the activities of defence-related enzymes including phenylalanine ammonia-lyase (PAL), polyphenol oxidase (PPO), β-1,3-glucanase (BGL) and chitinase (CHI). Transcripts of the defence-related genes PAL, PPO, PR2, and PR3, encoding PAL, PPO, BGL and CHI, respectively, were markedly elevated in Arabidopsis plants pre-exposed to SO 2 and subsequently inoculated with B. cinerea (SO 2 + treatment group) compared with those that were only treated with SO 2 (SO 2 ) or inoculated with B. cinerea (CK+). Moreover, SO 2 pre-exposure also led to significant increases in the expression levels of MIR393, MIR160 and MIR167 in Arabidopsis. Meanwhile, the expression of known targets involved in the auxin signalling pathway, was negatively correlated with their corresponding miRNAs. Additionally, the transcript levels of the primary auxin-response genes GH3-like, BDL/IAA12, and AXR3/IAA17 were markedly repressed. Our findings indicate that 30mgm -3 SO 2 pre-exposure enhances disease resistance against B. cinerea in Arabidopsis by priming defence responses through enhancement of defence-related gene expression and enzyme activity, and miRNA-mediated suppression of the auxin signalling pathway., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Lentinan (LNT), a complex polysaccharide with a β-(1→3)-linked backbone of d-glucose residues, has been reported to inhibit plant diseases. Our objective was to explore the efficacy and action mechanism of LNT used as a seed dressing to control sharp eyespot of wheat. Seed dressing promoted wheat growth. At control germination rates of 50%, 8 g of LNT/100 kg of seeds of the Jimai 22, Shannong 23, and Luyuan 502 cultivars significantly increased seed germination to 54%, 52%, and 51%, respectively. Seven days after emergence, the heights and root activity of wheat treated with LNT were significantly greater than those of controls. These effects were dose-dependent. At this time, the plant heights of Jimai 22, Shannong 23, and Luyuan 502 cultivars were 9.52, 8.52, and 10.52 cm, respectively, significantly higher than that of the controls. LNT prevented the development of wheat sharp eyespot. In the highly susceptible Jimai 22 cultivar, sharp eyespot development was reduced by 33.7%, 31.9%, and 30.4% at 7, 14, and 21 days after germination. LNT somewhat increased phenylalanine ammonia-lyase, peroxidase, and superoxide dismutase activity; reduced the malondialdehyde content; increased chlorophyll a and b levels; and enhanced the root vigor of wheat. These effects peaked 7 days after germination. LNT increased transcription of the genes encoding alternative oxidase (AOX) and β-1,3-glucanase (GLU), the salicylic acid signaling pathway-related gene NbPR1a, and the sharp eyespot resistance-related gene RS33. A significant dose-effect relationship was evident in terms of AOX transcription; we thus speculate that AOX may be the target gene.

The antifungal properties and the induction of resistance by ε-poly-l-lysine (ε-PL) were examined to reveal its potential in protecting tomato plants against Botrytis cinerea. As presented herein, ε-PL at 1200mg/L was found to have optimal in vitro antifungal activities, achieving an inhibition rate of 94.96%. In first-year field tests, ε-PL (1200mg/L) had a control effect of up to 79.07% against tomato grey mould. Similar results were obtained in the second year. In greenhouse experiments, ε-PL was observed to effectively reduce leaf infection, with an observed control rate at 89.22%. To define the molecular-genetic mechanisms, we compared the gene expression under four different conditions: sterile water sprayed plants (Control), Botrytis-infected plants (Inf), ε-PL-treated plants (ε-PL) and ε-PL-treated+infected plants (ε-PL+Inf). Quantitative PCR analysis at 36h after inoculation revealed that ε-PL+Inf plants exhibited significant expression and priming of several key Botrytis-induced genes in tomato. The results indicate that ε-PL promoted plant capacity of tomato to activate defense mechanisms upon pathogen attack. In total, these findings revealed that ε-PL should be an excellent biocontrol agent candidate that combined direct antifungal activity against B. cinerea and plant resistance capacity., (Copyright © 2017. Published by Elsevier Inc.)

Main Conclusion: Endogenous levels of β-aminobutyric acid (BABA) increase after the molecular recognition of pathogen presence. BABA is accumulated differently during resistance or susceptibility to disease. The priming molecule β-aminobutyric acid has been recently shown to be a natural product of plants, and this has provided significance to the previous discovery of a perception mechanism in Arabidopsis. BABA levels were found to increase after abiotic stress or infection with virulent pathogens, but the role of endogenous BABA in defence has remained to be established. To investigate the biological significance of endogenous BABA variations during plant-pathogen interactions, we investigated how infections with virulent, avirulent (AvrRpt2), and non-pathogenic (hrpA) strains of Pseudomonas syringae pv. tomato DC3000 (Pst DC3000), as well as treatment with defence elicitors (Flg22 and AtPep2), affect the accumulation of BABA in Arabidopsis plants. We found that BABA levels increased more rapidly during resistance than susceptibility to Pst DC3000. In addition, BABA was accumulated during PAMP-triggered immunity (PTI) after infection with the non-pathogenic Pst DC3000 hrpA mutant, or treatment with elicitors. Importantly, treatment with Flg22 induced BABA rise in Columbia-0 plants but not in Wassilewskija-0 plants, which naturally possess a non-functional flagellin receptor. These results indicate that BABA levels are controlled by the plant's immune system, thus advancing the understanding of the biological role of plant produced BABA.

Although numerous studies have reported the involvement of glutamate in plant abiotic stress, relatively little is known about the role of glutamate in plant defence against pathogens. To gain further knowledge, we investigated the effect of glutamate on Alternaria alternata in tomato fruit. A multidisciplinary approach was pursued, combining exogenous glutamate applications, enzymatic activity measurements and real-time quantitative PCR analysis. The results showed glutamate significantly reduced the disease incidence in tomato caused by A. alternata, by inducing resistance (Duncan's test, p<0.05). A large variety of defence-related enzymes and genes involved in the glutamine synthetase/glutamate synthase cycle, energy-generated metabolism, such as the γ-aminobutyric acid shunt, glycolysis and the tricarboxylic acid cycle, and the salicylic acid signalling pathway were activated by glutamate. The activation of these pathways as mentioned above might play a potential role in the resistance mechanisms underpinning glutamate-induced plant immunity., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

The study investigated the effect of γ-aminobutyric acid (GABA) on the control of alternaria rot in tomato fruit and the possible mechanism involved. Our results showed exogenous GABA could stimulate remarkable resistance to the alternaria rot, while it had no direct antifungal activity against Alternaria alternata. Moreover, the activities of antioxidant enzymes, including peroxidase, superoxide dismutase and catalase, along with the expression of these corresponding genes, were significantly induced in the GABA treatment. The obtained data suggested GABA induced resistance against the necrotrophic pathogen A. alternata, at least in part by activating antioxidant enzymes, restricting the levels of cell death caused by reactive oxygen species. Meanwhile, the key enzyme genes of GABA shunt, GABA transaminase and succinic-semialdehyde dehydrogenase, were found up-regulated in the GABA treatment. The activation of the GABA shunt might play a vital role in the resistance mechanism underpinning GABA-induced plant immunity., (Copyright © 2016 Elsevier Ltd. All rights reserved.)

Elicitors are known to trigger plant defenses in response to biotic stress, but do not systematically lead to effective resistance to pathogens. The reasons explaining such differences remain misunderstood. Therefore, elicitation and induced resistance (IR) were investigated through the comparison of two modified β-1,3 glucans applied on grapevine (Vitis vinifera) leaves before and after inoculation with Plasmopara viticola, the causal agent of downy mildew. The sulfated (PS3) and the shortened (H13) forms of laminarin are both known to elicit defense responses whereas only PS3 induces resistance against downy mildew. The analysis of the 2-DE gel electrophoresis revealed that PS3 and H13 induced distinct proteomic profiles after treatment and pathogen inoculation. Our results point out that the PS3-induced resistance is associated with the activation of the primary metabolism especially on amino acids and carbohydrates pathways. In addition, few proteins, such as the 12-oxophytodienoate reductase (OPR-like) related to the OPDA pathway, and an Arsenite-resistance protein (Serrate-like protein) could be considered as useful markers of induced resistance., Significance: One strategy to reduce the application of fungicides is the use of elicitors which induce plant defense responses. Nonetheless, the elicitors do not systematically lead to resistance against pathogens. The lack of correlation between plant defense activation and induced resistance (IR) requires the investigation of what makes the specificity of elicitor-IR. In this study, the two β-glucans elicitors, sulfated (PS3) and short (H13) laminarins, were used in the grapevine/Plasmopara viticola interaction since only the first one leads to resistance against downy mildew. To disclose IR specificity, proteomic approach has been employed to compare the two treatments before and after P. viticola inoculation. The analysis of the 2-DE revealed that PS3 and H13 induced distinct proteomic profiles after treatment and pathogen inoculation. Significant increase of the number of proteins regulated by PS3, relative to both H13 and time-points, is correlated with the resistance process establishment. Our results point that the PS3-induced resistance requires the activation of the primary metabolism especially on amino acids and carbohydrates pathways. In addition, few proteins, such as the 12-oxophytodienoate reductase (OPR-like) related to the OPDA pathway, and an Arsenite-resistance protein (Serrate-like protein) could constitute useful markers of PS3 induced resistance., (Copyright © 2017 Elsevier B.V. All rights reserved.)

White rot caused by Sclerotinia sclerotiorum (SS) is one of the most devastating plant diseases of sunflower. Controlling this pathogen by available tools hardly result in acceptable control. The aim of this study was to elucidate the effects of plant resistance inducers, BTH (benzothiadiazole in Bion 50 WG) and arbuscular mycorrhizal fungi (AMF) on disease development of white rot in three sunflower genotypes. Defence responses were characterized by measuring the disease severity and identifying cellular/histological reactions (e.g. autofluorescence) of host plants upon infection. Depending on the host genotype, a single application of inducers reduced disease symptoms. Histological examination of host responses revealed that BTH and/or AMF pre-treatments significantly impeded the development of pathogenic hyphae in Iregi szürke csíkos and P63LE13 sunflower plants and it was associated with intensive autofluorescence of cells. Both localized and systemic induction of resistance was observed. Importantly, the frequency of mycorrhization of hybrid P63LE13 and PR64H41 was significantly increased upon BTH treatment, so it had a positive effect on the formation of plant-mycorrhiza interactions in sunflower. To our knowledge, this is the first report on the additive effect of BTH on mycorrhization and the positive effect of these inducers against SS in sunflower.

Background: Several diseases threaten cereal production, and fungicides are therefore widely used. Biological control is an environmentally friendly alternative, and the fungus Clonostachys rosea is a versatile antagonist, effective against several plant diseases. We studied the ability of C. rosea to control barley leaf pathogens and the mechanisms behind the inhibition, emphasising induced resistance., Results: Under controlled conditions, spray application of C. rosea isolate IK726 to barley leaves reduced Bipolaris sorokiniana severity by up to 70% when applied 24 h before or simultaneously with the pathogen, whereas application 24 h after the pathogen had no effect. IK726 also reduced the sporulation capacity of B. sorokiniana. Microscopy of B. sorokiniana infection revealed that IK726 primarily inhibited conidial germination and appressorium formation, while further pathogen development and host defence reactions (papillae and fluorescent epidermal cells) were unaffected. Likewise, expression of defence-related genes encoding PR proteins was unaltered. In addition to B. sorokiniana, IK726 also reduced infection by Drechslera teres and Rhynchosporium commune., Conclusion: C. rosea acted as a protectant against three barley leaf pathogens. B. sorokiniana was directly inhibited by IK726, whereas induced resistance appeared not to be involved. Quantitative microscopy is a powerful tool for elucidating mechanisms involved in disease control. © 2016 Society of Chemical Industry., (© 2016 Society of Chemical Industry.)

This is the first report that paromomycin, an antibiotic derived from Streptomyces sp. AG-P 1441 (AG-P 1441), controlled Phytophthora blight and soft rot diseases caused by Phytophthora capsici and Pectobacterium carotovorum, respectively, in chili pepper (Capsicum annum L.). Chili pepper plants treated with paromomycin by foliar spray or soil drenching 7 days prior to inoculation with P. capsici zoospores showed significant (p < 0.05) reduction in disease severity (%) when compared with untreated control plants. The disease severity of Phytophthora blight was recorded as 8% and 50% for foliar spray and soil drench, respectively, at 1.0 ppm of paromomycin, compared with untreated control, where disease severity was 83% and 100% by foliar spray and soil drench, respectively. A greater reduction of soft rot lesion areas per leaf disk was observed in treated plants using paromomycin (1.0 μg/ml) by infiltration or soil drench in comparison with untreated control plants. Paromomycin treatment did not negatively affect the growth of chili pepper. Furthermore, the treatment slightly promoted growth; this growth was supported by increased chlorophyll content in paromomycin-treated chili pepper plants. Additionally, paromomycin likely induced resistance as confirmed by the expression of pathogenesis-related (PR) genes: PR-1, β-1,3-glucanase, chitinase, PR-4, peroxidase, and PR-10, which enhanced plant defense against P. capsici in chili pepper. This finding indicates that AG-P 1441 plays a role in pathogen resistance upon the activation of defense genes, by secretion of the plant resistance elicitor, paromomycin.

Glomerella leaf spot (GLS) caused by Glomerella cingulata is a newly emergent disease that results in severe defoliation and fruit spots in apple. Currently, there are no effective means to control this disease except for the traditional fungicide sprays. Induced resistance by elicitors against pathogens infection is a widely accepted eco-friendly strategy. In the present study, we investigated whether exogenous application of salicylic acid (SA) could improve resistance to GLS in a highly susceptible apple cultivar (Malus domestica Borkh. cv. 'Gala') and the underlying mechanisms. The results showed that pretreatment with SA, at 0.1-1.0 mM, induced strong resistance against GLS in 'Gala' apple leaves, with SA treated leaves showing significant reduction in lesion numbers and disease index. Concurrent with the enhanced disease resistance, SA treatment markedly increased the total antioxidant capacity (T-AOC) and defence-related enzyme activities, including catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO). As expected, SA treatment also induced the expression levels of five pathogenesis-related (PR) genes including PR1, PR5, PR8, Chitinase and β-1,3-glucanase. Furthermore, the most pronounced and/or rapid increase was observed in leaves treated with SA and subsequently inoculated with G. cingulata compared to the treatment with SA or inoculation with the pathogen. Together, these results suggest that exogenous SA triggered increase in reactive oxygen species levels and the antioxidant system might be responsible for enhanced resistance against G. cingulata in 'Gala' apple leaves., (Copyright © 2016 Elsevier Masson SAS. All rights reserved.)