Elicitation Of Resistance Research Articles

Induction of resistance in tomato against buckeye rot (Phytophthora nicotianae var. parasitica)

Buckeye rot disease of tomato caused by Phytophthora nicotianae var. parasitica is the most destructive disease for reducing tomato yields especially in those regions where fruiting coincides with rainy season. In the present study, the pathogen was characterized by sequencing the DNA region coding for internal transcribed spacer (ITS) region and sequence was deposited in NCBI with accession no. MF398189. The phylogenetic analysis using the Maximum Composite Likelihood (MCL) approach revealed that the isolated pathogen clustered together with P. nicotianae with high bootstrap value of 99%. Incubation period of 120 h was observed in pin-prick method of pathogen inoculation compared to 168 h in surface inoculation method. Further, the disease resistance induced by nine different elicitors of induced resistance against buckeye rot disease of tomato were studied under field conditions for two consecutive years 2016 and 2017. Minimum disease incidence of 9.57% and 7.93% was observed with foliar spray of ß-aminobutyric acid (2 mM) for 2016 and 2017, respectively. It was followed by potassium chloride (100 mM) with disease incidence of 11.32% and 8.85% for year 2016 and 2017, respectively. Maximum fruit yield of 7.02 kg and 8.12 kg was found in treatment with ß-aminobutyric acid as compared to 2.61 kg and 2.55 kg in control for year 2016 and 2017, respectively.

RESISTANCE ELICITORS ON PRODUCTION AND POST-PRODUCTION PERFORMANCE OF POTTED LISIANTHUS

ABSTRACT Lisianthus is an important ornamental species, whose cultivation in pot still requires studies, mainly regarding the use of alternative management. Thus, the aim of this work was to evaluate the influence of resistance elicitors on the production and post-production quality of potted lisianthus. Plants grown in pots were treated with two elicitors: (E1) phosphorylated mannano-oligosaccharide and (E2) citric bioflavonoids and phytoalexins, in the doses (D) of 1 and 2pL.L-1 (E1D1 1pL.L-1, E1D2 2pL.L-1, E2D1 1pL.L-1, E2D2 2pL.L-1 and control), with 5 replications, in a completely randomized design. After opening the first flower buds, the plants remained in the greenhouse for 15 days, until they reached at least 3 open flowers, when were transferred to the room conditions (24 ± 2 oC and 72 ± 2%) for another 15 days. The application of elicitors did not influence the culture cycle or the size of the stem. There was an increase, however, in the number of viable buds and open flowers, in addition to an increase in flower’s useful life paralleled to the reduction of senescent flowers, in relation to the control. The dose of 2pL.L-1 of the E2 kept the percentage of viable open flowers in relation to the control for at least another 5 days, reducing the percentage of senescent flowers. Together, with the application of the E2 elicitor in potted lisianthus, the viability of the flowers can be prolonged, maintaining quality and delaying senescence, and, in this way, increasing the market period.

Elicitors of Plant Immunity Triggered by Beneficial Bacteria.

The molecular basis of plant immunity triggered by microbial pathogens is being well-characterized as a complex sequential process leading to the activation of defense responses at the infection site, but which may also be systemically expressed in all organs, a phenomenon also known as systemic acquired resistance (SAR). Some plant-associated and beneficial bacteria are also able to stimulate their host to mount defenses against pathogen ingress via the phenotypically similar, induced systemic resistance phenomenon. Induced systemic resistance resembles SAR considering its mechanistic principle as it successively involves recognition at the plant cell surface, stimulation of early cellular immune-related events, systemic signaling via a fine-tuned hormonal cross-talk and activation of defense mechanisms. It thus represents an indirect but efficient mechanism by which beneficial bacteria with biocontrol potential improve the capacity of plants to restrict pathogen invasion. However, according to our current vision, induced systemic resistance is specific considering some molecular aspects underpinning these different steps. Here we overview the chemical diversity of compounds that have been identified as induced systemic resistance elicitors and thereby illustrating the diversity of plants species that are responsive as well as the range of pathogens that can be controlled via this phenomenon. We also point out the need for further investigations allowing better understanding how these elicitors are sensed by the host and the diversity and nature of the stimulated defense mechanisms.

Combined use of a resistance inducer (Agro-Mos®) and micronutrients for the control of Meloidogyne javanica in soybean

Elicitors of plant resistance are compounds that activate enzymatic processes involved in plant defense. Micronutrients also play an important role in plant responses against pathogens because they function as enzyme cofactors. Despite their well-known benefits, elicitors and micronutrients have been little investigated in nematode control. This study aimed to assess the effects of Agro-Mos® (a commercial biostimulant) and micronutrients (Zn and Mn), alone and combined, on soybean inoculated with Meloidogyne javanica. Seeds of soybean were sown in trays, treated 15 days after germination, and inoculated with 2000 eggs and juveniles of M. javanica at the time of transplanting. Treatments were as follows: 1 L/ha Agro-Mos®, 2 L/ha Metalosate® Zinc, 1.5 L/ha Metalosate® Manganese, Agro-Mos® + Zn, Agro-Mos® + Mn, and Agro-Mos® + Zn + Mn. Untreated inoculated and uninoculated plants were used as controls. At 60 days after inoculation, plants were harvested and evaluated for vegetative growth, nutrient content, and nematode parameters. All treatments were effective in reducing M. javanica population density in roots compared to the control. Agro-Mos®, Agro-Mos® + Zn, and Agro-Mos® + Zn + Mn were the most effective, reducing total nematode number and population density by 55–78% (P ≤ 0.05) in relation to the control. Agro-Mos® + Zn increased shoot dry weight. The results show that balanced fertilization can be used as part of an integrated nematode control strategy.

The Molecular Priming of Defense Responses is Differently Regulated in Grapevine Genotypes Following Elicitor Application against Powdery Mildew.

Molecular changes associated with response to powdery mildew (PM) caused by Erysiphe necator have been largely explored in Vitis vinifera cultivars, but little is known on transcriptional and metabolic modifications following application of resistance elicitors against this disease. In this study, the whole transcriptome sequencing, and hormone and metabolite analyses were combined to dissect long-term defense mechanisms induced by molecular reprogramming events in PM-infected ‘Moscato’ and ‘Nebbiolo’ leaves treated with three resistance inducers: acibenzolar-S-methyl, potassium phosphonate, and laminarin. Although all compounds were effective in counteracting the disease, acibenzolar-S-methyl caused the most intense transcriptional modifications in both cultivars. These involved a strong down-regulation of photosynthesis and energy metabolism and changes in carbohydrate accumulation and partitioning that most likely shifted the plant growth-defense trade-off towards the establishment of disease resistance processes. It was also shown that genotype-associated metabolic signals significantly affected the cultivar defense machinery. Indeed, ‘Nebbiolo’ and ‘Moscato’ built up different defense strategies, often enhanced by the application of a specific elicitor, which resulted in either reinforcement of early defense mechanisms (e.g., epicuticular wax deposition and overexpression of pathogenesis-related genes in ‘Nebbiolo’), or accumulation of endogenous hormones and antimicrobial compounds (e.g., high content of abscisic acid, jasmonic acid, and viniferin in ‘Moscato’).

Onion dry scales extract induce resistance against bacterial wilt in eggplant through improving polyamines and antioxidant metabolism

Abstract Nowadays there is an urgent need for using the natural resistance elicitors due to the numerous problems caused by the chemical ones and these natural elicitors can be used in organic agriculture. This study examines the ability of onion dry scale extract to enhance the resistance in eggplant against bacterial wilt. This evaluation was performed through studying the change in polyamines and antioxidant metabolism in two groups of eggplant seedling (the first treated with prepared onion dry scale extract and the other non-treated) are infected with Ralstonia solanacearum. The onion dry scales extract enhanced the polyamines content. In treated infected (TI) plants the polyamine oxidase (PAO) activity significantly increased only on the 7th day after infection. On the 14th day after infection, the PAO activity and H2O2 significantly decreased. In the TI group, the activity of the antioxidant enzymes significantly increased in the two stages, consequently, the lipid peroxidation decreased in the TI group, which appeared in decreasing the activity of lipoxygenase activity at the 14th day after infection and decreasing the content of malonyl dialdehyde. Moreover, exogenous application of onion dry scales extract completely suppressed the percentage of dead plants due to wilt disease 14 days after sowing in non-sprayed plants in comparison with the sprayed plants being 84.37%. The study confirmed that onion dry scales extract spray can be considered as an organic method for fighting bacterial wilt in eggplant through the improvement of polyamine metabolism and the antioxidant machinery.

Bacillus strain selection with plant growth-promoting mechanisms as potential elicitors of systemic resistance to gray mold in pepper plants.

Certain soil bacteria produce beneficial effects on the growth and health of plants; hence, their use is steadily increasing. Five strains of Bacillus with plant growth-promoting potential were selected in this study, which produced indole-3-acetic acid levels below 50µg.mL-1. On the other hand, while only strains M8 and M15 dissolved phosphorus, the latter was the only strain that did not produce siderophores. Only strains M8 and M16 significantly inhibited the in vitro growth of Botrytis cinerea and Fusarium solani phytopathogens, whose inhibition ranges fluctuated between 60% and 63% for strains M8 and M16 against B. cinerea and between 40% and 53% for strains M8 and M16 against F. solani. Based on these results, the need to implement resistance induction against gray mold on pepper plants was determined using strains M8 and M16. In this case, strain M16 inhibited the propagation of the necrotic spot by approximately 70%, whereas strain M8 significantly reduced the superoxide dismutase activity in systemic leaves, which substantially increased in plants inoculated with strain M8 and infected with the pathogen. Accordingly, the use of native rhizobacteria may entail biotechnological progress for the integrated management of crops in agriculture industry.

Physiological Responses to the Foliar Application of Synthetic Resistance Elicitors in Cape Gooseberry Seedlings Infected with Fusarium oxysporum f. sp. physali.

Vascular wilt caused by Fusarium oxysporum is the most limiting disease that affects cape gooseberry (Physalis peruviana L.) crops in Colombia. The use of synthetic elicitors for vascular wilt management is still scarce in Andean fruit species. The objective of the present study was to evaluate the effect and number of foliar applications of synthetic elicitors such as jasmonic acid (JA), salicylic acid (SA), brassinosteroids (BR), or a commercial resistance elicitor based on botanical extracts (BE) on disease progress and their effect on the physiology of cape gooseberry plants inoculated with F. oxysporum f. sp. physali. Groups of ten plants were separately sprayed once, twice, or three times with a foliar synthetic elicitor, respectively. Elicitor applications were performed at the following concentrations: JA (10 mL L−1), SA (100 mg L−1), BR (1 mL L−1) and BE (2.5 mL of commercial product (Loker®) L−1). The results showed that three foliar BR, SA, or BE applications reduced the area under the disease progress, severity index, and vascular browning in comparison to inoculated plants without any elicitor spray. Three BR, SA, or BE sprays also favored stomatal conductance, water potential, growth (total dry weight and leaf area) and fluorescence parameters of chlorophyll compared with inoculated and untreated plants with no elicitor sprays. Three foliar sprays of SA, BR, or BE enhanced photosynthetic pigments (leaf total chlorophyll and carotenoid content) and proline synthesis and decreased oxidative stress in Foph-inoculated plants. In addition, the effectiveness of three foliar BR, SA, or BE sprays was corroborated by three-dimensional plot and biplot analysis, in which it can evidence that stomatal conductance, proline synthesis, and efficacy percentage were accurate parameters to predict Foph management. On the hand, JA showed the lowest level of amelioration of the negative effects of Foph inoculation. In conclusion, the use of the synthetic elicitors BR, SA, or BE can be considered as a tool complementary for the commercial management of vascular wilt in areas where this disease is a limiting factor.

Natural Compounds as Elicitors of Plant Resistance Against Diseases and New Biocontrol Strategies

The goal of sustainable and organic agriculture is to optimize the health and productivity of interdependent communities of soil life, plants, animals, and people. Organic plant production uses natural products and natural self-regulation processes occurring in the ecosystem. The availability of innovative applications and molecular techniques opens up new possibilities in the approach to plant protection for sustainable and organic agriculture. New strategies not only directly protect plants against pathogens but can also induce enhanced immunity that permanently protects against pathogenic strains. This review focuses on the bioactive properties of selected natural compounds (of plant and animal origin), their action on pathogens, and their roles in the mechanism of inducing plant resistance. The author presents selected activities of organic bioactive compounds, such as allicin, naringin, terpenes, laminarin, carrageenans, chitin and chitosan, and outlines the possibilities for their application in protecting crop plants against diseases. In addition, this mini review describes the mechanism of action of the above compounds as elicitors of defense reactions in the plant and the possibility of their utilization in the production of biological preparations as elements of a new plant protection strategy.

Changes of lipid metabolism of Arabidopsis thalianain response to oligochitosan treatment

Lipids are vital cellular constituents in plant, and lipid peroxidation metabolites are critical defence substances in plants. In this study, mass spectrometry along with projections to latent structures discriminant analysis (PLS-DA) was used to detect lipid metabolism changes in Arabidopsis thaliana in response to oligochitosan (an effective resistance elicitor for the control of plant diseases). The PLS-DA showed that lipid metabolites of Arabidopsis thaliana were influenced by oligochitosan treatment. The total content of oxylipin containing monogalactosyldiacylglycerols, oxylipin-containing digalactosyldiacylglycerols, and oxylipin-containing phosphatidylglycerols increased firstly (after 1 h), and then decreased with the increase of oligochitosan treatment duration. In contrast, the total content of monogalactosyldiacylglycerols, phosphatidylcholines, phosphatidyl-ethanolamine, and phosphatidylglycerols decreased firstly, and then increased with the increase of oligochitosan treatment duration. The amounts of free fatty acids (C16:2, C16:3, C18:2, and C18:3) were lower after treatment with oligochitosan for 1, 3, and 6 h than in the control, while the production of volatile organic compounds such as 2-hexenal (except for 3 h) and nonanal was higher than in the control. In conclusion, lipid metabolites of Arabidopsis thaliana were influenced by oligochitosan treatment, and the synthesized lipids and oxylipin-containing lipids were remodelled and free fatty acids was metabolized to volatile organic compounds.

Selection and Formulation of Endophytic Bacteria as Plant Resistance Elicitor against Wilt Disease of Tomato

<p>Wilt disease of <em>Solanaceae</em> caused by <em>Ralstonia solanacearum</em> reduce the crop quality and negatively affect the crop product. The objective of this research was to discover of endophytic bacteria formulation that effectively decreases bacterial which cause wilt disease on <em>Solanaceae</em>. The research consisted of purification of <em>Ralstonia solanacearum</em>, endophytic bacteria were obtained from the sample and the screening of endophytic bacteria using this following assay: antagonist assay, seedling assay and <em>in planta</em> assay. The results showed that in antagonist assay, the bacterial isolate code PS<sub>1</sub>, PS<sub>2</sub>, and PS<sub>8 </sub>could inhibit growth of <em>R. solanacearum. </em>From the seedling assay, it obtained that all of the isolates increased of percentage of germination, seed coating and powder formulation can decrease disease incidence of bacterial wilt disease.</p>

Grapevine Phyllosphere Community Analysis in Response to Elicitor Application against Powdery Mildew.

The reduction of antimicrobial treatments and mainly the application of environmentally friendly compounds, such as resistance elicitors, is an impelling challenge to undertake more sustainable agriculture. We performed this research to study the effectiveness of non-conventional compounds in reducing leaf fungal attack and to investigate whether they influence the grape phyllosphere. Pathogenicity tests were conducted on potted Vitis vinifera “Nebbiolo” and “Moscato” cultivars infected with the powdery mildew agent (Erysiphe necator) and treated with three elicitors. Differences in the foliar microbial community were then evaluated by community-level physiological profiling by using BiologTM EcoPlates, high throughput sequencing of the Internal Transcribed Spacer (ITS) region, and RNA sequencing for the viral community. In both cultivars, all products were effective as they significantly reduced pathogen development. EcoPlate analysis and ITS sequencing showed that the microbial communities were not influenced by the alternative compound application, confirming their specific activity as plant defense elicitors. Nevertheless, “Moscato” plants were less susceptible to the disease and presented different phyllosphere composition, resulting in a richer viral community, when compared with the “Nebbiolo” plants. The observed effect on microbial communities pointed to the existence of distinct genotype-specific defense mechanisms independently of the elicitor application.

Cucumber mosaic virus 2b proteins inhibit virus-induced aphid resistance in tobacco.

SummaryCucumber mosaic virus (CMV), which is vectored by aphids, has a tripartite RNA genome encoding five proteins. In tobacco (Nicotiana tabacum), a subgroup IA CMV strain, Fny‐CMV, increases plant susceptibility to aphid infestation but a viral mutant unable to express the 2b protein (Fny‐CMV∆2b) induces aphid resistance. We hypothesized that in tobacco, one or more of the four other Fny‐CMV gene products (the 1a or 2a replication proteins, the movement protein, or the coat protein) are potential aphid resistance elicitors, whilst the 2b protein counteracts induction of aphid resistance. Mutation of the Fny‐CMV 2b protein indicated that inhibition of virus‐induced resistance to aphids (Myzus persicae) depends on amino acid sequences known to control nucleus‐to‐cytoplasm shuttling. LS‐CMV (subgroup II) also increased susceptibility to aphid infestation but the LS‐CMV∆2b mutant did not induce aphid resistance. Using reassortant viruses comprising different combinations of LS and Fny genomic RNAs, we showed that Fny‐CMV RNA 1 but not LS‐CMV RNA 1 conditions aphid resistance in tobacco, suggesting that the Fny‐CMV 1a protein triggers resistance. However, the 2b proteins of both strains suppress aphid resistance, suggesting that the ability of 2b proteins to inhibit aphid resistance is conserved among divergent CMV strains.

Phytohormones (Auxin, Gibberellin) and ACC Deaminase In Vitro Synthesized by the Mycoparasitic Trichoderma DEMTkZ3A0 Strain and Changes in the Level of Auxin and Plant Resistance Markers in Wheat Seedlings Inoculated with this Strain Conidia.

Both hormonal balance and plant growth may be shaped by microorganisms synthesizing phytohormones, regulating its synthesis in the plant and inducing plant resistance by releasing elicitors from cell walls (CW) by degrading enzymes (CWDE). It was shown that the Trichoderma DEMTkZ3A0 strain, isolated from a healthy rye rhizosphere, colonized the rhizoplane of wheat seedlings and root border cells (RBC) and caused approximately 40% increase of stem weight. The strain inhibited (in over 90%) the growth of polyphagous Fusarium spp. (F. culmorum, F. oxysporum, F. graminearum) phytopathogens through a mechanism of mycoparasitism. Chitinolytic and glucanolytic activity, strongly stimulated by CW of F. culmorum in the DEMTkZ3A0 liquid culture, is most likely responsible for the lysis of hyphae and macroconidia of phytopathogenic Fusarium spp. as well as the release of plant resistance elicitors. In DEMTkZ3A0 inoculated plants, an increase in the activity of the six tested plant resistance markers and a decrease in the concentration of indoleacetic acid (IAA) auxin were noted. IAA and gibberellic acid (GA) but also the 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase (ACCD) enzyme regulating ethylene production by plant were synthesized by DEMTkZ3A0 in the liquid culture. IAA synthesis was dependent on tryptophan and negatively correlated with temperature, whereas GA synthesis was positively correlated with the biomass and temperature.

Potassium Silicate, Against Water Stress, in Sweet Corn Plant Growth Traits

Water stress in sweet corn plants due effect of climatic events, such as El Niño, is difficult to monitor, leading to considerable losses. Silicon (Si) as an exogenous resistance elicitor may reduce water stress effects. The relationship between sweet corn plant age and its development, under induced water stress and leaf potassium silicate applications were evaluated. This work was carried out with the hybrid Tropical Plus®, in a randomized factorial block design with 15, 30, 45 and 60 kPa as soil water tensions in plots and potassium silicate doses (0, 6, 12 and 24 L ha-1) in subplots. Stem diameter, plant height and leaf number per plant were evaluated at 30, 45, 60, 75 and 90 days after seeding. Root length was measured on the 90th day after seeding. Sweet corn plants submitted to water stress conditions and Si application showed an age-dependent response. Water stress did not decrease stem diameter, plant height and number of leaves per plant sprayed with Si. Root length was longer with 60 kPa soil water tension. Silicon reduced negative impacts of water stress on sweet corn plants.

A Disease Resistance Elicitor Laminarin Enhances Tea Defense against a Piercing Herbivore Empoasca (Matsumurasca) onukii Matsuda

The tea plant (Camellia sinensis) suffers heavily from a harmful piercing pest, the tea green leafhopper (TLH) Empoasca (Matsumurasca) onukii Matsuda. In the present study, we studied the effect of an efficient elicitor of plant disease resistance, the β-1,3-glucan laminarin, on the induced defense against TLH in tea plants. Defense responses elicited by laminarin in tea include the activation of mitogen-activated protein kinases and WRKY, the burst of H2O2, salicylic acid, and abscisic acid, and the accumulation of direct-defense chemicals (including chitinase, phenylalanine ammonia lyase, callose, polyphenol oxidase, and flavonol synthase), as well as the production of volatile compounds. The laminarin-treated tea plants reduced the performance of TLH and enhanced the attractiveness to the egg parasitoid wasp of TLH, Stethynium empoascae Subba Rao. In the field experiment, laminarin application effectively reduced the number of TLH by attracting parasitoids. These results suggest that laminarin can induce protection against TLH by regulating signaling pathways in tea plant. Our study also proposes an environment friendly strategy for the integrated management of an economically important piercing pest.

Potassium silicate as a resistance elicitor in sweet corn yield traits under water stress

Plant water stress is a major problem in the Cerrado biome of Brazil. Dry periods and random climatic events cause quality and yield losses in sweet corn plants. Compounds, such as silicon (Si), are being studied to reduce the negative impacts of water stress on agricultural crops. Further tests may allow farmers to increase the use of silicon-based compounds. The objective of this study was to evaluate the production parameters of the sweet corn (Zea mays var. saccharata) (Poaceae) Tropical Plus® hybrid with water stress and potassium silicate doses applied with foliar spraying. A randomized block design with four soil water tensions (15, 30, 45 and 60 kPa) and four potassium silicate doses (0, 6, 12 and 24 L ha-1) was used in a greenhouse. The studied factors, alone or in interaction with each other, did not affect most of the sweet corn yield parameters. The hypothesis that these results may have been partially affected by the presence of silicon are discussed. The sweet corn plant yield was affected mainly by the soil water tension of 60 kPa.

Tomato 14-3-3 Proteins Are Required for Xv3 Disease Resistance and Interact with a Subset of Xanthomonas euvesicatoria Effectors.

The 14-3-3 phospho-binding proteins with scaffolding activity play central roles in the regulation of enzymes and signaling complexes in eukaryotes. In plants, 14-3-3 isoforms are required for disease resistance and key targets of pathogen effectors. Here, we examined the requirement of the tomato (Solanum lycopersicum) 14-3-3 isoform (TFT) protein family for Xv3 disease resistance in response to the bacterial pathogen Xanthomonas euvesicatoria. In addition, we determined whether TFT proteins interact with the repertoire of X. euvesicatoria type III secretion effector proteins, including AvrXv3, the elicitor of Xv3 resistance. We show that multiple TFT contribute to Xv3 resistance. We also show that one or more TFT proteins physically interact with multiple effectors (AvrXv3, XopE1, XopE2, XopN, XopO, XopQ, and XopAU). Genetic analyses indicate that none of the identified effectors interfere with AvrXv3-elicited resistance into Xv3 tomato leaves; however, XopE1, XopE2, and XopO are required to suppress symptom development in susceptible tomato leaves. Phospho-peptide mapping revealed that XopE2 is phosphorylated at multiple residues in planta and residues T66, T131, and S334 are required for maximal binding to TFT10. Together, our data support the hypothesis that multiple TFT proteins are involved in immune signaling during X. euvesicatoria infection.

The eggplant AG91-25 recognizes the Type III-secreted effector RipAX2 to trigger resistance to bacterial wilt (Ralstonia solanacearum species complex).

To deploy durable plant resistance, we must understand its underlying molecular mechanisms. Type III effectors (T3Es) and their recognition play a central role in the interaction between bacterial pathogens and crops. We demonstrate that the Ralstonia solanacearum species complex (RSSC) T3E ripAX2 triggers specific resistance in eggplant AG91-25, which carries the major resistance locus EBWR9. The eggplant accession AG91-25 is resistant to the wild-type R.pseudosolanacearum strain GMI1000, whereas a ripAX2 defective mutant of this strain can cause wilt. Notably, the addition of ripAX2 from GMI1000 to PSS4 suppresses wilt development, demonstrating that RipAX2 is an elicitor of AG91-25 resistance. RipAX2 has been shown previously to induce effector-triggered immunity (ETI) in the wild relative eggplant Solanum torvum, and its putative zinc (Zn)-binding motif (HELIH) is critical for ETI. We show that, in our model, the HELIH motif is not necessary for ETI on AG91-25 eggplant. The ripAX2 gene was present in 68.1% of 91 screened RSSC strains, but in only 31.1% of a 74-genome collection comprising R.solanacearum and R.syzygii strains. Overall, it is preferentially associated with R.pseudosolanacearum phylotype I. RipAX2GMI1000 appears to be the dominant allele, prevalent in both R.pseudosolanacearum and R.solanacearum, suggesting that the deployment of AG91-25 resistance could control efficiently bacterial wilt in the Asian, African and American tropics. This study advances the understanding of the interaction between RipAX2 and the resistance genes at the EBWR9 locus, and paves the way for both functional genetics and evolutionary analyses.

Selenium Nanoparticles-an Inducer of Tomato Resistance to the Root-Knot Nematode Meloidogyne incognita (Kofoid et White, 1919) Chitwood 1949.

We investigated the mechanisms of action of selenium nanoparticles obtained by laser ablation for their use as an abiogenic elicitor of tomato resistance to parasitic nematodes. Selenium nanoparticles induced systemic resistance of tomatoes to the root-knot nematode, stimulated plant growth and development, was involved in the PR-6 gene expression in the roots and leaves of plants subjected to invasion, and increased the activity of proteinase inhibitors (markers of systemic resistance of plants to infection). Exogenous treatment of plants with solutions of selenium nanoparticles reduced the invasion of plants by affecting the morphological and physiological parameters of the parasites in the roots.