Application Of acibenzolar-S-methyl Research Articles

Local Application of Acibenzolar-S-Methyl Treatment Induces Antiviral Responses in Distal Leaves of Arabidopsis thaliana.

Systemic acquired resistance (SAR) is a plant defense mechanism that provides protection against a broad spectrum of pathogens in distal tissues. Recent studies have revealed a concerted function of salicylic acid (SA) and N-hydroxypipecolic acid (NHP) in the establishment of SAR against bacterial pathogens, but it remains unknown whether NHP is also involved in SAR against viruses. We found that the local application of acibenzolar-S-methyl (ASM), a synthetic analog of SA, suppressed plantago asiatica mosaic virus (PlAMV) infection in the distal leaves of Arabidopsis thaliana. This suppression of infection in untreated distal leaves was observed at 1 day, but not at 3 days, after application. ASM application significantly increased the expression of SAR-related genes, including PR1, SID2, and ALD1 after 1 day of application. Viral suppression in distal leaves after local ASM application was not observed in the sid2-2 mutant, which is defective in isochorismate synthase 1 (ICS1), which is involved in salicylic acid synthesis; or in the fmo1 mutant, which is defective in the synthesis of NHP; or in the SA receptor npr1-1 mutant. Finally, we found that the local application of NHP suppressed PlAMV infection in the distal leaves. These results indicate that the local application of ASM induces antiviral SAR against PlAMV through a mechanism involving NHP.

Evaluation of systemic acquired resistance inducers for the management of copper and streptomycin resistant strains of Xanthomonas perforans on tomato

Bacterial spot (Xanthomonas spp.) is one of the most detrimental diseases of tomato (Solanum lycopersicum L.) worldwide. Bacterial spot Xanthomonads are either endemic or spread by contaminated seed or transplant material into tomato production areas. Due to limited disease management options, transplant producers rely on copper- and streptomycin-based bactericides that are often ineffective due to the predominance of resistant Xanthomonas strains. In this study, transplant production facilities located across eight counties in western North Carolina were surveyed for bacterial spot symptoms from 2018 to 2019. In total, 29 strains (n = 6 in 2018 and n = 23 in 2019) were isolated and identified as Xanthomonas perforans. All strains were resistant to copper, while only 24% of the strains were resistant to streptomycin. Therefore, the ability of three systemic acquired resistance (SAR) inducers, methyl salicylate, Bacillus mycoides isolate J, and acibenzolar-S-methyl (ASM), alone or in combination with copper or streptomycin were evaluated as potential alternatives to copper-mancozeb (grower standard) to manage bacterial spot under greenhouse and field conditions. Under greenhouse conditions, applications of ASM at 0.4 g/L alone, or in combination with copper or streptomycin, significantly reduced bacterial spot disease severity when compared to the grower standard and nontreated controls (P < 0.05). However, none of the SAR inducers significantly reduced disease severity or improved yield when compared to copper-mancozeb-ASM under field conditions (P < 0.05). This study highlights the potential of using ASM for the management of bacterial spot of tomato transplant production to reduce bacterial spot introduction into the field.

Effect of Acibenzolar-S-Methyl on severity of Fusarium wilt and fruit yield of two tomato cultivars

Tomato wilt caused by Fusarium oxysporum f.sp. lycopersici (Fol) is one of the limiting factors to tomato production in the whole world because of its negative effect on the fruit yield of tomato. The study investigated the application of Acibenzolar-S-Methyl (ASM), a plant activator that stimulates plants’ defence mechanisms, at different concentrations (0, 25, 35 and 45 mg/L) on two tomato genotypes (Delila and Kerewa) using drenching method. Factorial experiments were laid out in a randomized complete block design and completely randomized design in both field and the screenhouse, respectively. Results showed that the application of ASM significantly reduced (p≤0.05) disease severity. At 9 weeks after transplanting Delila recorded severity scores of 3.00 and 3.33(screenhouse) and 0.33 (field) while Kerewa had severity scores of 1.33 and 1.50 (screenhouse) and 0.33 (field) when ASM was apllied at 35 and 45 mg/L concentrations, respectively. These values were significantly lower (p≤0.05) than those recorded in untreated plots. Delila yielded 151.23 and 151.73 kg/ha (screenhouse), and 754.70 and 795.8 kg/ha (field) while Kerewa yielded 109.60 and 124.03 kg/ha (screenhouse) and 601.10 and 279.8 kg/ha (field) when ASM was apllied at 35 and 45 mg/l concentrations, respectively. Yields in both screenhouse and the field were significantly higher (p≤0.05) than yields in the untreated control plots. The study concluded that application of ASM at 35 and 45 mg/L to tomato could enhance its resistance which would translate to fruit yield increase.

Optimizing the application of acibenzolar-S-methyl and copper to control bacterial spot on fresh-market tomato

This study aimed to adjust the number of applications of acibenzolar-S-methyl (ASM) and copper in an integrated program for the control of bacterial spot on fresh-market tomato. Two field trials were carried out during 2018 and 2019. Four sets of number of weekly applications of ASM were evaluated (7, 9, 11, and 13 applications). In addition to these, four other treatments were included: two as a tank mixture compound [13 weekly applications of ASM + biostimulant and nine applications of ASM + copper oxychloride]. Copper oxychloride was applied after ASM treatments in order to complete 13 applications per growing season. Copper oxychloride and untreated plots were used as a control. The variables evaluated were bacterial spot severity, total yield, and yield per classes of fruit according to the Brazilian market standards. Benefit-cost ratio (B/C) was calculated considering the income increase of a given treatment in relation to the untreated control. The disease ratings and yield data were subjected to ANOVA and the means tested for significance by Fisher, Dunnett, and orthogonal contrasts comparison tests. Regression analysis were carried out with the disease ratings to evaluate the ASM number of applications. As the number of ASM applications increased, disease severity decreased, although, the best B/C was obtained with seven applications of ASM, followed by copper applications until the end of the cycle. The tank mixture compound treatments did not result in economic gain increase. Moreover, disease severity was significantly high when ASM was applied in tank mixture with copper.

Effects of Acibenzolar-S-methyl on the Probing Behaviour and Mortality of Cacopsylla pyri on Pear Plants.

European pear psylla, Cacopsylla pyri, is one of the worst pests of pear in Europe. We investigated whether acibenzolar-S-methyl (ASM) application on pear plants might affect the behaviour in C. pyri. The elicitor was applied on pear potted plants, and after 48 h, we confirmed the ASM-mediated induction of several Pathogenesis-Related protein (PR) coding genes. At the same time, an in-depth analysis was performed on the probing behaviour of adults and nymphs of C. pyri on ASM-treated pear plants by the EPG-DC system, as well as the assessment of young nymphs' survival 7 days after the ASM application. The elicitor application weakly interfered with C. pyri nymphs probing behaviour and survival, while it did not affect adult stages. These data confirm previous observations obtained on C. pyricola and suggest that the elicitor does not represent a viable tool in the control of pear psylla species, especially if used alone, but it might be used in integrated management strategies focused on other plant pathogens such as Erwinia amylovora.

Postharvest application of acibenzolar-S-methyl and plant extracts affect physicochemical properties of blueberry (Vaccinium corymbosum L.) fruits

The demand for fruits with high anthocyanin content, such as blueberries, has increased in recent years due to their health benefits. However, few studies are known on the postharvest behavior of blueberry fruits subjected to the application of plant extracts and acibenzolar-S-methyl (ASM). The objective of this research was to investigate the effect of the application of ASM and vegetable extracts (mint and coriander) on the organoleptic characteristics of blueberry fruits stored at 16°C during postharvest through a completely randomized design with five treatments. The contents of total anthocyanins in fruits (TA) did not differ between treatments, with values that ranged between 74.1 mg and 83.9 mg 100 g-1 of fresh weight. The TA tended to increase during storage and then to decrease during senescence. The firmness of blueberry fruits increased during storage, but hardness did not increase, since the fruits are softer and show wrinkling over time, indicating that the epidermis of the fruits has great elasticity. The fruits with the application of vegetable extracts showed the highest total soluble solids and total titratable acidity. The values of red/green and yellow/blue ratio increased, so the blueberry fruits slightly lost their blue hue during postharvest. Fruits with ASM application reached a postharvest life of 15 d after harvest (dah) while the other treatments only maintained quality for 13 dah.

Impact of Foliar Application of Acibenzolar-S-Methyl on Rose Rosette Disease and Rose Plant Quality.

Rose rosette disease (RRD) caused by rose rosette emaravirus (RRV) is a major issue in the U.S. rose industry with no effective method for its management. This study evaluated the effect of foliar application of acibenzolar-S-methyl (ASM), a plant systemic acquired resistance inducer, in reducing RRD disease severity on Rosa species cv. Radtkopink ('Pink Double Knock Out') under greenhouse conditions, and the effect of ASM on plant growth under commercial nursery production conditions. ASM at 50- or 100-mg/liter concentrations at weekly intervals significantly reduced RRD severity compared with the untreated control in two of the three greenhouse trials (P < 0.05). The plants in these trials were subsequently pruned and observed for symptoms, which further indicated that application of ASM at 50- or 100-mg/liter concentrations lowered disease severity compared with the untreated control (P < 0.05) in these two trials. Plants treated with ASM at 50- or 100-mg/liter concentrations had delayed incidence of RRD compared with the nontreated controls. Plants treated with ASM at the 50- or 100-mg/liter rate in all three trials either did not have RRV present or the virus was present in fewer leaf samples than untreated controls as indicated by quantitative reverse transcription PCR analysis. Overall, plants treated with ASM at the 50-mg/liter concentration had 36 to 43% reduced RRD incidence compared with the water control. The treatment of two cultivars of rose, 'Radtkopink' and 'Meijocos' ('Pink Drift'), with weekly foliar applications of ASM at the three rates (0.5, 0.75, and 1.0 oz/A) indicated that ASM had no negative effect on flowering or plant growth at even the highest rate of application.

Transient Changes in Defence Gene Expression and Phytohormone Content Induced by Acibenzolar-S-Methyl in Glasshouse and Orchard Grown Kiwifruit

Acibenzolar-S-methyl (ASM), the active ingredient in Actigard® (Syngenta), is a plant defence elicitor used for the management of bacterial canker caused by Pseudomonas syringae pv. actinidiae (Psa) in kiwifruit. We examined changes in gene expression and phytohormone content in two kiwifruit cultivars, ‘Hayward’ (Actinidia chinensis var. deliciosa) and ‘Zesy002’ (A. chinensis var. chinensis), following ASM application. In glasshouse studies, ASM-induced resistance to stem inoculation with Psa was accompanied by upregulation of salicylic acid (SA) defence pathway genes (PR1, PR2, and PR5) in stems and leaves. The expression of PR1 in ASM-treated plants increased by c. 5-fold in ‘Hayward’ and by over 15-fold in ‘Zesy002,’ relative to the untreated controls, whereas PR2 and PR5 increased by up to 4-fold in both cultivars. Orchard studies over three seasons confirmed the utility of PR1, PR2, and PR5 for monitoring ASM-induced responses in mature vines. PR1 and PR5 were more strongly induced by ASM than PR2 and gene upregulation in ‘Hayward,’ was accompanied by a reduction in Psa leaf spotting; no such relationship was measurable for ‘Zesy002’ because leaf spot symptoms are rarely expressed. In the third season, six additional gene candidates, BAD, Gluc2, Class IV Chit, EDS1A, NPR3, and NIMIN2, were responsive to ASM in ‘Hayward’ and ‘Zesy002.’ Gene upregulation was transient, with expression levels increasing by 1 d after ASM application and declining to control levels between 7 and 14 days. Moreover, the amplitude of gene upregulation depended on leaf developmental stage and was greater in the first true leaf and the youngest mature leaves than in immature leaves along the same shoot. Phytohormone content did not show a repeatable response pattern to ASM in potted plants or in vines possibly as a consequence of their wider role in regulating plant growth and mediating environmental responses. In conclusion, this study demonstrates that defence gene expression can be used to monitor responsiveness to ASM in two genetically distinct mature kiwifruit cultivars (‘Hayward’ and ‘Zesy002’) under orchard conditions. The use of defence marker genes could be of broader utility across kiwifruit species and could be used to guide ASM application schedules in the orchard.

Antifungal effects of low environmental risk compounds on development of pear postharvest diseases: Orchard and postharvest applications

In the main productive area of Argentina, decays caused by Botrytis cinerea, Alternaria alternata, and Alternaria spp. lead to important postharvest losses in pears during medium- and long-term storage. In view of the problems associated with the use of chemical synthetic fungicides, and attending to current demands for global production of safe food, in this work we evaluated the antimicrobial effect of different low-toxicity compounds, also known as ‘biorationals’ in the control of B. cinerea, A alternata, and Alternaria spp, postharvest diseases in pear (Pyrus communis L.). Commercial formulations of acibenzolar-s-methyl (ASM), algae extract (AE) from Ascophyllum nodosum, chitosan (CH), and potassium phosphite (KPhi) were evaluated after application on orchards (30, 60, and 90 days after full flower, and 10 days prior to harvest) and postharvest (to assess possible curative and preventive effects) in ‘Beurrè d'Anjou’ and ‘Packham's Triumph’ pear cultivars. Additionally, the antimicrobial behavior of the above biorationals was evaluated in vitro by determining their inhibitory activity (EC50) on B. cinerea and A alternata mycelial growth. Water was used as negative control, while the chemical fungicide fludioxonil was included in postharvest application experiments as positive control. Both postharvest decay control efficacy and effects on fruit quality parameters varied substantially among the biorationals assayed, depending on cultivar, time of application, and pathogen evaluated. In ‘Beurrè d'Anjou’, both in-orchard and curative postharvest applications of CH controlled the incidence of B. cinerea decays, while orchard applications of KPhi effectively controlled Alternaria spp decay incidence. In the ‘Packham's Triumph’ cultivar, both orchard and postharvest applications of ASM were effective in controlling decays caused by Alternaria spp and A. alternata, whereas orchard application of AE was effective in controlling B. cinerea incidence. Meanwhile, postharvest application of CH provided a curative effect for both B. cinerea and A. alternata infections and exhibited also preventive efficacy against the latter pathogen. ‘Beurrè d'Anjou’, but not ‘Packham's Triumph’, fruit firmness was increased (by 4–7 N) by all the compounds when applied postharvest. In most assay types and for the two cultivars, control fludioxonil treatment outperformed the efficacy of the compounds against both pathogens. For both B. cinerea and A. alternata spp, the EC50 values of the biorational compounds were considerably higher than those of fludioxonil, and in some cases they could not be determined. Thus, that although orchard control results were variable, the postharvest behavior of the biorationals evaluated was generally uniform, affording good control efficiency against A. alternata and exerting clear preventive effects in the two cultivars. The studied compounds might hence represent a useful alternative to traditional agrochemical postharvest practices, leading to a meaningful reduction in the use of chemical fungicides.

Combination of yeast antagonists and Acibenzolar-S-Methyl reduced the severity of Fusarium head blight of wheat incited by Fusarium graminearum sensu stricto

The combination of yeast antagonists and Acibenzolar-S-Methyl (ASM) was tested against Fusarium graminearum on a spring wheat cultivar PAN3471. Two strains of Papiliotrema flavescens (Strains WL3 and WL6) and a strain of Pseudozyma sp. (MGO1) were combined with full strength ASM at anthesis, half strength ASM at anthesis and quarter strength ASM at late boot stages. The yeast and ASM treatments were applied prior to F. graminearum inoculation and disease progress was assessed over time. The combination of yeast and ASM treatments effectively reduced Fusarium Head Blight (FHB) severity and deoxynivalenol (DON) concentration compared to when the treatments were used alone. A positive correlation was observed between the Area Under Disease Progress Curve (AUDPC) and Percentage Seed Infection (PSI) (r = 0.44) whereas a negative correlation was observed between AUDPC and Hundred Seed Weight (HSW) (r = -0.77) and PSI and HSW (r = -0.44). The best combination treatment providing the highest reduction in final disease severity (41.83%), high HSW and moderate PSI was 0.075 g/l ASM at anthesis plus P. flavescens strain WL3. The highest DON reduction (19.35%) was by the treatment 0.075 g/l ASM at anthesis plus P. flavescens strain WL6. The best treatment was P. flavescens combined with 0.075 g/l ASM at anthesis. Although Pseudozyma sp. strain MGO1 did not provide the best FHB and DON reduction, its combination with ASM application improved disease control efficacy. To the best of our knowledge, this study presents the first report of the combination of P. flavescens and ASM in the management of FHB caused by F. graminearum in wheat plants.

Soil application of acibenzolar-s-methyl and thiamethoxam for the management of citrus canker under subtropical conditions

Drench applications of systemic acquired resistance (SAR) inducing compounds acibenzolar-s-methyl (ASM) and thiamethoxam (THIA) may contribute for the control of citrus canker, caused by Xanthomonas citri subsp. citri. Here, we report the results of a 3-year field experiment on the effect of drench applications of two SAR-inducing compounds, applied alone or in combination with copper oxychloride (CuOX) foliar sprays, on citrus canker control, as well as tree growth and yield, of Natal sweet orange trees under Brazilian subtropical conditions. Leaf disease incidence, tree defoliation, and citrus leaf miner (Phyllocnistis citrella) attack were evaluated every 30 days for 16 months. Soil applications of ASM or THIA combined with foliar sprays of CuOX highly reduced citrus canker incidence on leaves. Effective control of the disease, comparable to regular foliar sprays of cupric bactericides, was obtained with two to four drench applications of SAR-inducing compounds. No differences among the treatments were observed in regard to tree height and canopy volume, and fruit yield of the young citrus trees. Soil applications of SAR-inducing compounds proved to be an important measure for the integrate management of citrus canker under the Brazilian subtropical conditions.

Elicitation of resistance through the exploration of acibenzolar-S-methyl (ASM) against Meloidogyne incognita in tomato under salt stress condition

Meloidogyne incognita is one of the prime restricting factors of yield in crops. Approaches to diminish the populations are consistently raised, and the application of elicitors as resistance inducers is an option for managing the disease. Thus, this study was conducted to examine the potential of acibenzolar-S-methyl (ASM), a chemical activator, as a soil drench to induce resistance against M. incognita infestation with and without salt stress. Results demonstrated that alone and under salt stress, ASM was able to reduce root-knot nematode population in tomato. The applied treatments significantly reduced the root-knot nematode reproduction, increased growth and phenolic compounds in the plants. Treatment of ASM (0.254 mM) with NaCl (100 mM), significantly reduced the root-knot index by 58.0% compared to untreated control. The same combination significantly enhanced the phenolic compounds and dry matter up to 60.6% and 59.0%, respectively, compared to inoculated control. However, the application of the highest concentration of ASM (1.019 mM) alone was the most potent in reducing the eggmasses and root-knot index by 74.4% and 68.0% respectively compared to inoculated control. Additionally, the lowest increase (23.0%) of phenol was observed in ASM (0.509 mM). NaCl alone also reduced the root-knot index by 32.0% and increased phenol accumulation by 47.5%. Moreover, lower concentration of ASM (0.254 mM) in combination with salt stress (NaCl 100 mM) showed significantly higher efficacy. The study revealed that application of ASM through stress modulation effect can activate the inherent M. incognita resistance in tomato, which could contribute substantially in sustainable management of nematode infestation.

Gene expression of salicylic acid and jasmonic acid pathways and photosynthesis parameters of sweet orange trees in response to acibenzolar-S-methyl

The use of resistance inducers may be a tool to assist in the management of citrus diseases. However, knowledge about how some inducers, such as the benzothiadiazoles, promote gene expression from the pathways involved in induced resistance and alter plant development are lacking. In this work, we evaluated the effect of the acibenzolar-S-methyl (ASM) on gene expression from the biosynthetic pathways of salicylic (SA) and jasmonic (JA) acids, as well as in physiological parameters of young sweet orange trees. After a single ASM application, gene expression assessed during six time points revealed no significant changes in the main pathway for SA synthesis: isochorismate synthases (ISC) 1 and ICS2 genes were up-regulated only at 6 days after treatment (dat). However, an increase in phenylalanine ammonia lyase (PAL) was observed. Salicylic acid carboxymethyl transferase (BSMT1) and salicylic acid glucosyltransferase I (SAGT1) were up-regulated, indicating expression of genes whose products modify SA. Pointedly up-regulation of lipoxygenase (LOX) and both up- and down-regulation of allene oxide synthase (AOS) and allene oxide cyclase (AOC) in biosynthetic pathways of JA was observed, while jasmonic acid methyl transferase (JMT), whose product modify JA, was consistently induced from three to 13 dat. Besides an increase in SA and JA modification enzymes, ASM reduced photosynthetic rate in treated plants, without affecting the stomatal conductance and the transpiration rate. Our results reveal how the SA and JA pathways are regulated soon after ASM treatment, in particular the up-regulation of BSTM1, SAGT1 and JMT.

Evaluation of integrated management of bacterial wilt of tomato using grafting, biofumigant and plant resistance activator under field conditions

Bacterial wilt, caused by Ralstonia solanacearum, is a major and constant constraint in the production of tomatoes worldwide. A two-season field experiments, laid out in two separate orchards in a randomized complete block design and a split-split plot arrangement with three replications, was conducted to evaluate the integrated effect of grafting, thymol and acibenzolar-S-methyl (ASM) in the management of tomato bacterial wilt disease in a naturally infested soil. Beske and UC82-B tomato cultivars, susceptible to the pathogen, were grafted on a resistant tomato rootstock (Tomachiva) while thymol (0.7% w/v) was applied as a pre-plant soil fumigant. Grafted and non-grafted tomato received ASM as foliar spray after transplanting. Sole or combined application of the enhancers (thymol and ASM) had significant reduction of bacterial wilt incidence in both seasons, from the second to eight weeks after transplanting. At eighth week after transplanting, the effect of combined application of thymol and ASM translated to 100% and 90.3% disease reduction in early and late planting seasons, respectively. Grafted tomato, thymol and ASM combination produced an average yield of 74.3 and 86.9 ton/ha in early and 65.3 and 58.1 ton/ha in late planting seasons respectively. The findings indicated that integrated use of grafting, thymol (0.7% w/v) and ASM (30 µg/ml) could be of great benefit in the control of bacterial wilt of tomato.

Inducers of resistance in potato and its effects on defoliators and predatory insects

The effects of chemical inducers of plant resistance on folivorous beetles and predatory insects in Sola- num tuberosum L. were evaluated. The effects of these chemical inducers on crop development and yield were also determined. The experiment was conducted with cv. Emeraude using a randomised complete-block design with four treatments and six replications: 1 - control; 2 - 1% silicic acid; 3 - 0.02% acibenzolar-S-methyl (ASM); and 4 - 1.15% diatomaceous earth (DE). Treatments 2, 3 and 4 were applied by spraying plant foliage every 10 days, total of five applications. The injuries and damages caused by beetles were evaluated. There were no significant differences in the presence of folivorous and predatory beetles in the aerial plant mass and the surrounding soil. However, the plants treated with silica or DE were less preferred by defoliators. Spraying with silicic acid, ASM and DE produced signifi- cant increases in plant diameter and height without affecting productivity. The application of silicic acid, ASM or DE increased protection against herbivorous insects and decreased tuber damage.

Postharvest acibenzolar-S-methyl treatment maintains storage quality and retards softening of apple fruit.

"Golden delicious" apples were dipped in 100mg/L acibenzolar-S-methyl (ASM) to investigate the fruit quality and softening during 12days of storage. Weight loss, flesh firmness, ethylene release, respiratory rate, content of total soluble solids and titratable acid, the activity of pectinase, cellulase, and β-glucosidase, and water-insoluble pectin and water-soluble pectin contents were investigated. The results demonstrated that ASM treatment inhibited ethylene release and respiratory rate, reduced titratable acidity, and enhanced total soluble solids content in apples. Moreover, application of ASM suppressed the reduction of flesh firmness, activity of pectin methylesterase, and polygalacturonase. Cellulase, β-glucosidase, and degradation of protopectin in apple fruit were also suppressed by ASM treatment during storage. In conclusion, ASM could maintain fruit quality by regulating cell wall-degrading enzymes during storage. PRACTICAL APPLICATIONS: Application of acibenzolar-S-methyl after harvest has the potential of delaying fruit softening by regulating cell wall-degrading enzymes, thus retain fruit quality.

Acibenzolar-S-methyl activates stomatal-based defense against Pseudomonas cannabina pv. alisalensis in cabbage

Pseudomonas cannabina pv. alisalensis (Pcal), which causes bacterial blight of brassicaceous plants, is an economically important pathogen worldwide. Copper fungicide and antibiotics are major strategies to manage the disease caused by Pcal; however, a Pcal strain resistant to these chemicals has already been found, and severe outbreaks of bacterial blight have been reported on cabbage in Japan. Therefore, there is an urgent need to develop new Pcal management strategies. Plant defense activators could be useful not only to protect plants against invading pathogens, but also to reduce the amount of copper fungicides and antibiotics applied. However, the mechanisms by which plant defense activators contribute to controlling diseases remains unclear. In this work, we focused on cabbage and acibenzolar-S-methyl (ASM), a well-known plant defense activator. Expression profiles revealed that ASM induced expression of systemic acquired resistance (SAR) marker genes including PR1, PR2, and PR5 in cabbage plants. We also demonstrated that a soil drench with ASM 2 h before transplanting clearly reduced bacterial blight symptoms and reduced Pcal bacterial populations in cabbage. ASM application was also able to prime cabbage for Pcal resistance by activating stomatal-based defense. Our findings highlight that ASM protects plants from bacterial pathogens by activating stomatal-based defense.

Resistance elicitors and defense response enhancers of maize to Spodoptera frugiperda (J.E.Smith) (Lepidoptera: Noctuidae)

The objective of this research was to assess the potential of abiotic compounds as defense response enhancers in maize using enzymatic quantification and their efficiency in reduction of damages caused by S. frugiperda. The experiment was laid out in a randomized complete block design with six treatments and five replications. The treatments were: T1: positive control (distilled water + infestation); T2: negative control (without product application, uninfested); T3: biofertilizer; T4: acibenzolar-S-methyl (ASM); T5: potassium silicate; T6: potassium silicate + ASM. The treatments were applied in V6 stage of maize plants. After five days, the plants were artificially infested with 2nd instar caterpillars of S. frugiperda. Damage assessments were carried out at 4, 8, 16 and 22 days after infestation using a scale of notes. To evaluate the enzymatic activity, one leaf of each plant was removed at 2, 4, 8, 16 and 22 days after infestation. The largest peroxidase activities were observed at two DAI (days after infestation) using the potassium silicate + ASM (2,344.12 UAE.mg-1 of proteína.min-1) treatment, while the larger polyphenol oxidase activity peaks were observed after treatment with ASM at 22 DAI. The application of potassium silicate + ASM in corn plants can promote peroxidase activity. The polyphenol oxidase activity was increased after application of ASM, whereas the presence of the pest (on positive control) could potentially increase the activity of phenylalanine ammonia-lyase. The applications of ASM alone and potassium silicate + ASM contributed to reduction of the foliar damage level caused by S. frugiperda in corn plants.

Postharvest longevity of 'BRS Vitória' seedless grapes subjected to cold storage and acibenzolar-S-methyl application

Abstract: The objective of this work was to evaluate cold storage periods and postharvest longevity of the seedless table grape 'BRS Vitória' subjected to the application of the disease-resistance inducer acibenzolar-S-methyl (ASM). Bunches were treated or not with 1% ASM, placed individually in plastic clamshell trays and stored in a cold chamber at 2±1ºC, at a high relative humidity, for three periods (30, 45, and 60 days), followed by a 5-day period of shelf life in plastic clamshells, at 22±2ºC. After each storage period, gray mold (Botrytis cinerea) incidence was evaluated, and the physicochemical analysis was performed. A completely randomized design, with four replicates, was used in two 2x3 factorial arrangements: one evaluating ASM application and cold storage periods; and another, ASM and cold storage + shelf-life periods. ASM did not change the physicochemical characteristics of the bunches, and the incidence of gray mold was lower than 1% in all treatments. Water loss from bunches increased with storage periods. Even without ASM application, 'BRS Vitória' grape can preserve its postharvest quality for up to 60 days of cold storage, plus five days of shelf life in plastic clamshells.

Soil applications of acibenzolar-S-methyl induce defense gene expression in tomato plants against bacterial spot

Acibenzolar-S-methyl (ASM), a plant activator known to induce plant resistance, has been used as foliar sprays to manage several plant diseases including bacterial spot on tomato caused by four distinct Xanthomonas species. This study aimed to investigate the effects of soil application rates of ASM on bacterial spot of tomato and the expression levels of the two pathogenesis-related (PR) genes, PR1a and PR1b, in leaf tissues. Tomato seedlings were leaf-applied with ASM at 18.8 mg/l corresponding to the labeled rate, soil-applied with ASM at 0.84 and 10 mg/l, and sprayed with water served as an untreated control. The soil application of ASM at 10 mg/l consistently reduced the final disease severity and disease progress compared to the untreated control in four growth chamber experiments, whereas the soil application of ASM at 0.84 mg/l and foliar spray of ASM significantly reduced the final disease severity and area under disease progress curve (AUDPC) in three out of the four experiments. The expression levels of PR1a and PR1b in the leaf tissues were significantly induced by both soil and foliar applications of ASM. In addition, field trial results suggested that the soil applications of ASM at 10 mg/l markedly reduced disease progress compared to the control and copper standard. Although the control efficiency of soil applications of ASM depends on rates used, this study suggests that ASM can be used as soil applications to induce tomato resistance against bacterial spot.