Resistance-inducing Chemicals Research Articles

Cultivar Variation in Tomato Seed Coat Permeability Is an Important Determinant of Jasmonic Acid Elicited Defenses Against Western Flower Thrips.

Induction of defenses is one of the most widely accepted eco-friendly approaches for management of pests and diseases. Seeds are receptive to resistance-inducing chemicals and could offer broad-spectrum protection at the early stages of development. However, seed treatment with elicitors has previously been shown to differentially influence induced defense responses among cultivars and thus, could hamper commercial exploitation. In this context, the objective of the present study was to evaluate the genotype-dependent ability of jasmonic acid (JA) to induce resistance against western flower thrips (WFT) at the seed stage. We examined the variation in inducibility of resistance in eight commercial tomato cultivars. Causal factors accounting for discrepancies in JA-induced responses at the seed stage were phenotypically and biochemically evaluated. Seed receptivity to exogenous JA appeared to be cultivar dependent. Thrips associated silver damage was only reduced in JA seed-treated plants of cultivar Carousel. Enhancement of resistance, was not associated with activation of defense-related traits such as polyphenol oxidase activity (PPO), trichomes or volatiles. Sulfuric acid scarification, prior to JA seed incubation, significantly augmented the embryonic responsiveness to JA in cv. Moneymaker without an adverse effect on growth. Hence, these results support the hypothesis that seed coat permeability is a key factor for successfully inducing JA mediated thrips defenses. The outcome of our study is of translational value as it creates opportunities for the seed industry to perform pre-treatments on non-responsive cultivars as well as for tomato breeding programs to select for genetic traits that affect seed permeability.

Influence of Resistance-Inducing Chemical Elicitors against Pine Wilt Disease on the Rhizosphere Microbiome.

Pine wilt disease (PWD) caused by Bursaphelenchus xylophilus is a major threat to pine forests worldwide. Induction of resistance is a promising and safe management option that should be investigated in relation to its possible influence on the pine tree ecosystem, including the surrounding microbial communities. In this study, two main resistance-inducing chemical elicitors, methyl salicylic acid (MeSA) and acibenzolar-s-methyl (ASM), were tested for their control efficiency against PWD and their influence on the rhizosphere microbial composition. Foliar treatment of pine seedlings with the chemical elicitors resulted in a reduction in PWD severity, with ASM showing better control efficacy, reaching up to 73% compared to the untreated control. Moreover, bacterial community analysis of the rhizosphere revealed significant changes in several microbial taxa that were present at low relative abundance. In particular, ASM treatment resulted in a significant increase in specific microbial taxa, including members of the Rhodanobacter, Devosia, Bradyrhizobium, Acidibacter, Mesorhizobium, and Hyphomicrobium genera, which are known to play ecological and plant growth-promoting roles. Furthermore, chitinolytic bacteria were shown to be reduced in response to treatment with both MeSA and ASM. Altogether, the present findings demonstrate the occurrence of significant alterations in several ecologically important microbial taxa after treatment with resistance-inducing chemicals. As compared to MeSA treatment, ASM treatment was more effective at suppressing PWD and resulted in more beneficial changes in rhizosphere microbial composition.

EVALUATION OF CERTAIN BIOCIDES AND CHEMICALS INDUCING RESISTANCE IN MANAGEMENT OF CUCUMBER DOWNY MILDEW UNDER PROTECTED CULTIVATION

Downy mildew of cucumber is caused by the fungus-like pathogen Pseudoperonospora cubensis (Berk and Curtis), which causes loss in the yield in Egypt especially under protected cultivation where low temperature and high humidity are prevalent. The efficiency of two Bio-control agents i.e. T34 (Trichoderma asperellum, 109 spore/cm3) and Bio-Cure-B (Pseudomonas fluorescens, 108 spore/cm3) as well as three resistance inducing chemicals (RICs), i.e. potassium dihydrogenphosphate (K2HPO4), salicylic acid (C7H6O3), and potassium nitrate (KNO3) were evaluated for controlling cucumber downy mildew under greenhouse and plastic house conditions. Greenhouse experiment data revealed that, spraying cucumber plants with either biocontrol agent or tested RICs two times i.e. 5 days before and/or nine days after artificially inoculated by the P. cubensis significantly reduced percentage of disease severity, meanwhile plant length and foliage fresh weight were increased in comparison with control treatments. The treatments increased the activity of peroxidase, β-1,3-glucanase, beside increase in total carbohydrates and total phenolic contents. Under plastic house, all tested biocides and/or RICs either alone or double combinations caused significant reduction in disease severity associated with significant increment in some growth parameter of cucumber plants (plant length and fruit yield) when compared with control treatments in both seasons. However, application of tested RICs mixture with tested biocides was more effective in this regard than the only application of them individually. In this respect, tested biocides were also more efficient than resistance inducing chemicals (RICs).

Induction of Systemic Resistance against Charcoal-Rot of Cowpea Caused by Macrophomina phaseolina using Some Inducer Resistance Chemicals

Induction of Systemic Resistance against Charcoal-Rot of Cowpea Caused by Macrophomina phaseolina using Some Inducer Resistance Chemicals

INDUCTION OF SYSTEMIC DISEASE RESISTANCE IN CUCUMBER PLANTS TREATED BY THE SPRAY OF SOME BIOTIC AND ABIOTIC AGENTS TO CONTROL DOWNY MILDEW DISEASE

Certain amounts of inducers, i.e Salicylic acid, Oxalic acid, and yeast extract as biocontrol agent as well as the fungicide Aquacid, used as foliar spray treatments proved to be effective in reducing downy mildew severity (DS) caused by ( P s e u d o p e r o n o s p o r a c u b e n sis ) on cucumber plants under greenhouse and field condition. In vitro , the tested fungicide, resistance inducing chemicals (RIC) and biocontrol agent highly inhibited sporangial germination of P . cubensis fungus compared with the control, Aquacid fungicide and the biocontrol agent were more effective on sporangial germination than chemicals RIC. Under greenhouse condition, severity of downy mildew disease decreased, significantly. Some Plant growth parameters i.e Plant length and fresh weight were significantly increased when the fungicide and RIC were applied as compared with the control. In field experiments, foliar application with fungicide Aquacid (2.5g/L) as a comparison treatment, Salicylic acid, Oxalic acid, and the yeast extract in concern, significantly reduced the disease severity of downy mildew with the averages of 7.25, 25.43, 30.0 and 16.40 %, respectively compared with untreated plants in the first season 2016 and the same trend was cleared in the second season 2017 with the averages of 6.50, 24.15, 25.45and 13.33%, respectively. Moreover, all exercised treatments significantly increased all of the studied growth parameters, i.e. plant length, leaves number, number of flowers, fresh and dry weight/plant. The treatments showed remarkable increase physiological aspects (Peroxidase activity and total phenol content) and similar reduction in disease severity of downy mildew revealing the most superior positively correlation with both peroxidase activity and total phenol content.

Management of pepper verticillium wilt by combinations of inducer chemicals for plant resistance, bacterial bioagents and compost

Inducer resistance chemicals (IRCs) Bion (BTH), chitosan and salicylic acid, bacterial bioagents, i.e. Bacillus chitinosporus, B. megaterium, B. pumilus, B. subtilis, B. thuringiensis, Pseudomonas fluorescens and P. putida and compost tea caused a reduction to the linear growth of the fungus Verticillium dahliae, in culture plates. In general, P. fluorescens followed by B. subtilis were the most efficient in reducing the linear growth of V. dahliae. The viability of microsclerotia of V. dahliae was greatly reduced by the tested bacterial bioagents. In addition, B. megaterium, B. subtilis, P. fluorescens and P. putida were the most efficient bioagents, where no microsclerotia germinated three weeks after treatment with these bioagents. In addition, few of microsclerotia germinated when treated with B. chitinosporus, B. pumilus and B. thuringiensis. However, all the microsclerotia of the control treatment were viable even three weeks after treatment with bioagents. The combination and use singly of BTH, B. subtilis, P. fluorescens and compost resulted in a reduction of verticillium wilt in pepper and increase of fruit, photosynthetic pigments, and vitamin-C compared with the control treatment (infested with the causal fungus). Compost was the most efficient of single tactics in disease management. Moreover, no apparent infection was detected when BTH, the two bioagents B. subtilis and P. fluorescens and compost were used together and the fruit yield, photosynthesis pigments and vitamin-C were, similar to the control treatment (un-infested soil). Photosynthesis pigments including chlorophyll a, chlorophyll b and carotenoids as well as free and total ascorbic acid (vitamin-C) were greatly increased due to the tested treatments, i.e. BTH, both bioagents and compost in pepper plants grown in infested soil compared with those of untreated plants (grown in infested soil only). Compost was the best single treatment for minimizing the reduction in photosynthesis pigments in plants grown in infested soil with V. dahliae, as well as free and total ascorbic acid compared with plants grown in soil infested with the causal fungus without any another treatment.

Management of Damping-Off and Root-Rot Diseases of Faba bean by Bioproducts and Inducer Resistance Chemicals

This study was carried out to evaluate the efficiency of Plant Guard (Trichoderma harzianum) and Rhizo-N (Bacillus subtilis) as bioproducts in combination with ascorbic and shikimic acid as inducer resistance chemicals in management of faba bean damping-off and root-rot diseases caused by Fusarium moniliforme, F. solani and Macrphomina phaseolina under greenhouse and field conditions. In vitro using the tested two bioagents as well as the two inducer resistance chemicals (IRCs) and the fungicide Rizolex-T, significantly reduced the linear growth of the tested three pathogenic fungi. Rizolex-T followed by T. harzianum then ascorbic acid were the most effective treatments in reducing the linear growth of the tested fungi. Meanwhile, shikimic acid followed by B. subtilis were the lowest efficient ones in this regard. Under greenhouse conditions, soaking faba bean seeds in ascorbic acid then coating with Plant Guard (after adding talc powder) or Rhizo-N were the most effective treatments in managing the tested fungi. However, dressing faba bean seeds with the fungicide Rizolex-T was the superior treatment in this regard. In field experiments, soaking faba bean seeds in ascorbic or shikimic acid then coating with Plant Guard were the most effective treatments in reducing the natural infection by damping-off and root-rot diseases. Moreover, these treatments improved the estimated crop parameters as well as increased the percentages of total nitrogen and protein constitute of the dry seeds compared with the control treatment. Also, dressing faba bean seeds with the fungicide Rizolex-T was the superior treatment in this respect.

Effect of resistance inducing chemicals and seaweed extracts on defence enzymes in Xanthomonas oryzae pv. oryzae (Xoo) challenged paddy plants

Several chemicals, including salicylic acid, acibenzolar-S-methyl, acetylsalicylic acid, nicotinic acid, jasmonic acid, and oxalic acid, have been shown to induce resistance in various crops. Marine algae, with their vast array of complex natural products, represent a promising source of novel bioactive compounds that can enhance plant resilience by providing protection against stress induced by pathogens. This study aimed to evaluate the effects of various resistance-inducing chemicals and seaweed extracts on the activation of defense enzymes in Xanthomonas oryzae pv. oryzae (Xoo)-challenged paddy plants. The findings may contribute to the development of eco-friendly strategies for managing bacterial diseases in rice cultivation

Potentiality of Inducer Resistance Chemicals and Bioagents in Managing Lettuce Downy Mildew

The tested inducer resistance chemicals (IRCs) bion (BTH), chitosan and salicylic acid as well as the bacterial bioagents Bacillus pumilus B. subtilis, B. thuringiensis and Pseudomonas fluorescens and the fungal bioagents Trichoderma album, T. harzianum and T. viride resulted in significant reduction to the germinated sporangia (conidia) of the fungus like Bremia lactucae Regel, the causal of lettuce downy mildew. This reduction was gradually increased by increasing the used concentration. The role of the tested IRCs and bioagents on management of the disease under greenhouse was evaluated. Under greenhouse conditions, spraying of lettuce plants artificially inoculted with the causal fungus like resulted in significant reduction to the severity of the disease compared with control treatment. Moreover, the IRC bion as well as P. fluorescens and T. harzianum were the most efficient treatments in this regard. Two field experiments were carried out during 2016/ 2017 growing season under natural infection by the disease to evaluate the efficacy of spraying of lettuce plants with any of the IRC bion and the bioagents P. fluorescens and T. harzianum on plants previously soaked or not in bion just before transplanting on the severity of the disease and weight of the grown plants. Data revealed that there was significant reduction to the severity of the disease with considerable increase to the average weight of each plant compared with control treatment due to sprying of these treatments. However, the fungicide Ridomil Gold MZ was the superior treatment in reducing the disease and increasing the weight of the foliage growth of lettuce plants. In addition, spraying of the IRC bion on plants soaked in bion just before transplanting ranked the second in this regarad followed by spraying of any of the two bioagents. Considerable increase in the activity of the oxidative reductive enzymes, i.e phenylalanine ammonia lyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO), due to spraying of lettuce plants with bion, the bioagents P. fluorescens and T. harzianum as well as the fungicide Ridomil Gold MZ compared with unsprayed plants (control).

Optimizing Chemically Induced Resistance in Tomato Against Botrytis cinerea.

Resistance-inducing chemicals can offer broad-spectrum disease protection in crops, but can also affect plant growth and interactions with plant-beneficial microbes. We have evaluated different application methods of β-aminobutyric acid (BABA) and jasmonic acid (JA) for long-lasting induced resistance in tomato against Botrytis cinerea. In addition, we have studied nontarget effects on plant growth and root colonization by arbuscular mycorrhizal fungi (AMF). Germinating seeds for 1 week in BABA- or JA-containing solutions promoted seed germination efficiency, did not affect plant growth, and induced resistance in 4-week-old plants. When formulating BABA and JA in carboxymethyl cellulose seed coating, only BABA was able to induce resistance in 4-week-old plants. Root treatment of 1-week-old seedlings with BABA or JA also induced resistance in 4-week-old plants. However, this seedling treatment repressed plant growth at higher concentrations of the chemicals, which was particularly pronounced in hydroponically grown plants after BABA treatment. Both seed coating with BABA, and seedling treatments with BABA or JA, did not affect AMF root colonization in soil-grown tomato. Our study has identified commercially feasible application methods of BABA and JA, which induce durable disease resistance in tomato without concurrent impacts on plant growth or colonization by plant-beneficial AMF.

PR-Proteins Accumulation in Tomato Plant Due to Application of Resistance Inducing Chemicals During Period of Induced Resistance Against Alternaria Leaf Blight

Background: Resistance Inducing Chemicals (RIC) viz., Salicylic Acid (SA), $-aminobutyric acid (BABA), chitosan (CHT) and 2, 6-dichloroisonicotinic acid (INA) are known to play an important role in induction of resistance by increasing the activity of PR-proteins. Therefore the study was done to test these RIC’s for accumulation of PR-proteins in tomato plant to confer resistance against Alternaria blight disease. Methods: The activity of PR-proteins viz., chitinase and $ 1,3-glucanase in tomato leaves were measured in response to treatment of these RIC’s at different concentrations as seed dip treatment for 8 h, seedling dip treatment for 2 h and seed+seedling treatment. The RIC treated plants were challenged inoculated with Alternaria alternata, a tomato leaf blight pathogen at 10 days interval from germination and observed for disease development. Chitinases and $ 1,3-glucanase activity was determined spectronically by quantifying the release of mg of N-acetylglucosamine and of glucose, respectively at 30 days of RIC treatment as the persistence of resistance induced by RIC was up to 50 days. Results: Maximum activity of chitinase and $ 1,3-glucanase was observed in seed+seedling treatment with BABA at 15 mM concentration and the increase in chitinase and $ 1,3-glucanase activity was 32.00 and 56.59% more, respectively over control and was followed by treatment with salicylic acid at 1.5 mM concentration. Conclusion: The application of RIC SA and BABA elicits the increased activity of PR-proteins viz., chitinase and $ 1,3-glucanase which inhibit the process of pathogenesis in susceptible tomato cultivars to exhibit the resistance.

A Protocol Suggested for Management of Cantaloupe Downy Mildew

The inhibitory effect of the fungicides Acrobat copper, Previcure-N and Unilax, the inducer resistance chemicals (IRCs) bion, chitosan, salicylic acid and zinc sulphate and the bioagents Bacillus polymyxa, B. subtilis and Pseudomonas fluorescens on sporangial germination of fungus like Pseudoperonospora cubensis, the causal of cantaloupe downy mildew was tested in vitro. The role of the tested fungicides, IRCs and bioagents on management of cantaloupe downy mildew was evaluated under greenhouse conditions. In addition, the alternation between the sprayed tested fungicide Unilax, IRC chitosan and bioagent P.fluorescens on management of the disease under field conditions was investigated. The inhibitory effect of the tested fungicides, IRCs and bioagents on sporangial germination of P. cubensis revealed that they caused significant reduction to the germinated sporangia. The tested fungicides were the most efficient ones followed by the bioagents then IRCs. Disease management showed the same trend of in vitro experiment when they sprayed on artificially inoculated cantaloupe plants with the sporangia of the causal fungus like under greenhouse conditions. Under field conditions, spraying cantaloupe plants with the tested fungicide Unilax still the most efficient trial for management the disease during 2012 and 2013 growing seasons compared with spraying any of IRC (chitosan) and the bioagent (P. fluorescens) alone . However, spraying the tested fungicide in alternation with the tested IRC and the bioagent ranked the second efficiency of disease management. Meanwhile, spraying the tested fungicide in alternation with any of the tested IRC and bioagent was of moderate efficiency.

Effect of Combination between Bioagents and Antioxidants on Management of Tomato Powdery Mildew

Isolation of microorganisms occurring on the phyllopane of tomato leaves yielded many Basillus and Trichoderma strains. The isolated Bacillus spp. were purified and identified as B. chitinosporus, B. megaterium, B. pumilus, B. subtilis and B. thuringiensis and the isolated Trichoderma spp. were, T. album, T. hamatum, T. koningii, T. harzianum and T.veredi. All the tested Bacillus and Trichoderma strains caused significant inhibition to the germinated conidia of Leveillula taurica (imperfect stage = Oidiopsis taurica) the causal of tomato powdery mildew compared with control treatment. In addition, B. thuringiensis B. subtilis and B. chitinosporus were the most efficient bacteria in this regard and T. harzianum and T. veredi were the most efficient fungi. The inducer resistance chemicals (IRCs) bion, chitosan, humic acid, salicylic acid and zinc sulphate resulted in significant reduction to the germinated conidia of the causal fungus compared with control treatment. This reduction was gradually increased by increasing the tested concentration. In plastic house experiments, spraying tomato plants with the tested bioagents B. thuringiensis and T. harzianum and the IRC salicylic acid resulted in significant reduction to powdery mildew severity during 2012/2013 and 2013/ 2014 growing seasons. Spraying of the bioagents B.thuringiensis and T. harzianum and the IRC salicylic acid, each alone or in different combinations, resulted in significant reduction to the severity of the disease with significant increase to the produced fruit yield. Furthermore, spraying any of these compounds alone was of less effect in this regard compared with spraying their combinations. However, the fungicide Sumi-8 was the superior in this regard, being 3.7 % disease severity and fruit yield 16.2 k g. / plant followed by the mixture of the three treatments, being 4.6% disease severity and fruit yield 13.7 kg. / plant. The three oxidative-reductive enzymes, i.e. PAL, PO and PPO were greatly increased in the leaves of all sprayed treatments compared with control treatment. In addition, plants sprayed with salicylic acid recorded the highest activity of the three enzymes followed by that sprayed with B. thuringiensis then T. harzianum. Meanwhile, untreated leaves (control) recorded the lowest activity followed by that sprayed with Sumi-8.

Effect of combination between inducer resistance chemicals and systemic fungicides on management of sweet melon downy mildew

The efficiency of some inducer resistance chemicals (IRCs) like bion, chitosan, humic acid and salicylic acid as well as the fungicides like Folu-Gold, Galben Copper, Previcure-N and Redomil Gold Mancozeb on management of sweet melon downy mildew, caused by Pseudoperonospora cubensis was evaluated in vitro and in vivo. Also, the efficiency of the alternation between the sprayed two fungicides and IRCs on management of the disease and the produced fruit yield and its total soluble solids (TSS) under field conditions were assessed. The inhibitory effect of the IRCs and the tested fungicides on sporangial germination of P. cubensis resulted in a significant reduction in the germinated sporangia. In addition, IRCs were less effective than the fungicides. Disease management revealed the same trend of the in vitro experiment when they sprayed fungicides on sweet melon plants artificially inoculated with the sporangia of the causal fungus under greenhouse conditions. Furthermore, under field conditions, spraying sweet melon plants with the two tested fungicides was the most efficient in decreasing the disease and increasing fruit yield and its TSS, to somewhat, followed by the alternation between them and the tested IRCs. In addition, IRCs treatments showed the lowest efficiency in this regard.

Management of cucumber powdery mildew by certain biological control agents (BCAs) and resistance inducing chemicals (RICs)

The efficiency of some commercial biological control agents (BCAs), Bio Zaid and Bio Arc, and resistance inducers chemicals (RICs) (salicylic acid and Bion) on management of cucumber powdery mildew, caused by Sphaerotheca fuliginea, was evaluated in vitro and in vivo. In vitro experiments revealed that application of the tested BCAs and RICs significantly reduced the disease severity, number of conidia per leaf area unit (cm) and reduced germination of conidiospores of the causal pathogen. Under field conditions, application of BCAs and RICs caused significant decrement in the disease severity with significant increment in the fruit yield compared with check treatments. On the average, application of Bion recorded the highest values, either in reducing the disease severity or in raising the average fruit yield followed by Bio Arc. On the other hand, applying salicylic acid (SA) recorded, on the average, the lowest efficiency in reducing disease severity and low values of fruit yield in both growing seasons.

Resistance against various fungal pathogens and reniform nematode in transgenic cotton plants expressing Arabidopsis NPR1

Cotton is an economically important crop worldwide that suffers severe losses due to a wide range of fungal/bacterial pathogens and nematodes. Given its susceptibility to various pathogens, it is important to obtain a broad-spectrum resistance in cotton. Resistance to several fungal and bacterial diseases has been obtained by overexpressing the Non-expressor of Pathogenesis-Related genes-1 (NPR1) in various plant species with apparently minimal or no pleiotropic effects. We examined the efficacy of this approach in cotton by constitutive expression of the Arabidopsis (Arabidopsis thaliana) NPR1 gene. The results show that NPR1-expressing lines exhibited significant resistance to Verticillium dahliae isolate TS2, Fusarium oxysporum f. sp. vasinfectum, Rhizoctonia solani, and Alternaria alternata. Interestingly, the transformants also showed significant resistance to reniform nematodes. Analysis of defense-related, biochemical and molecular responses suggest that when challenged with pathogens or certain systemic acquired resistance-inducing chemicals, the transgenic lines respond to a greater degree compared to the wild-type plants. Importantly, the basal activities of the defense-related genes and enzymes in uninduced transformants were no different than those in their non-transgenic counterparts. The results provide additional evidence supporting the role of NPR1 as an important part of the plant defense system and suggest a means to achieve broad-spectrum resistance to pathogens via genetic engineering.

Induction of systemic resistance in blackgram (Vigna mungo) against urdbean leaf crinkle virus by chemicals

The effect of chemicals on the induction of systemic resistance in blackgram (Vigna mungo) against urdbean leaf crinkle virus (ULCV) was studied. Pre-inoculation spraying of blackgram plants with resistance-inducing chemicals, namely salicylic acid and benzothiadiazole at 100 ppm concentration was found to be effective in reducing ULCV infection and increasing the incubation period of the virus under controlled conditions. The treatment of blackgram plants with salicylic acid and benzothiadiazole significantly increased the phenylalanine ammonialyase (PAL), peroxidase (PO) and polyphenol oxidase (PPO) activities. New isoforms of peroxidase and polyphenol oxidase were also induced by these treatments. A two-fold increase in accumulation of total phenol was observed in plants treated with salicylic acid and benzothiadiazole.

Compuestos químicos inductores de resistencia contra Colletotrichum gloeosporioides en mangó

Se evaluaron varios compuestos químicos inductores de resistencia en la interacción entre mangó (Mangifera indica L.) y el patógeno, agente causal de la antracnosis, Colletotrichum gloeosporioides. Los compuestos evaluados fueron ácido salicílico, ácido isonicotínico, ácido benzo (1,2,3) tiadiazol-7-carbotiónico áster de S-metilo (Actigard®) y otros compuestos químicos estructuralmente similares como el ácido nicotínico, el dinucleótido de adenina de ácido nicotínico, el áster de etilo del ácido isonicotínico, el N-óxido de ácido isonicotínico, el ácido benzoico y el benzoato de sodio. En el laboratorio antes de la inoculación, estos compuestos se asperjaron hasta la saturación sobre pedazos de hojas y frutas de mangó. En condiciones de laboratorio, el tamaño de las lesiones causadas por C. gloeosporioidesen pedazos de hojas y frutas de mangó se redujo significativamente (P < 0.10) a concentraciones que fluctuaron entre 10-12 M a 10-6 M de ácido salicílico (SA), 10-18 M y 10-14 M de ácido isonicotínico (INA), 10-17 M a 10-2 M de Actigard® y 10-10 M de ácido benzoico (BA). El ácido salicílico, INA y BA causaron toxicidad en las hojas a concentraciones que fluctuaron entre 10-1 a 10-3 M. Los compuestos químicos que indujeron resistencia en condiciones de laboratorio se evaluaron en árboles de mangó de seis meses de edad en condiciones de umbráculo. Ninguno de los compuestos químicos evaluados redujo significativamente (P < 0.05) el tamaño de la lesión causada por C. gloeosporioides. Otros agentes químicos inductores de resistencia que no fueron evaluados durante estos estudios, tales como probenazol, derivados ciclopropanos de ácido carboxílico, aminoácidos no-proteícos [β-ácido aminobutírico (BABA) y Ï’-ácido aminobutírico (GABA)] y Phytogard®, se deben evaluar individualmente y en combinación para clarificar la ausencia de inducción de resistencia en los tejidos del mangó.