Application Of Resistance Inducers Research Articles

Organic vs. Integrated-Production Agriculture Farming: Which Grapevine Stress-Responsive Genes Are Affected by the Application of Resistance Inducers and Elicitors?

With the rising prominence of organic farming systems in European Union countries, motivated by agricultural policies, there is pressure for effective disease management strategies. To address this challenge, the use of plant resistance inducers (PRIs) and elicitors has emerged as a promising approach. In this study, we compared the impact of integrated production with organic agriculture farming practices, specifically applying PRIs and elicitors in the latter, on the expression levels of stress-responsive genes in two grapevine cultivars, ‘Alicante Bouschet’ and ‘Trincadeira’. Our findings revealed that the organic farming system led to upregulation of eight of the 12 studied genes in at least one cultivar, indicating a significant influence of production mode. The upregulated genes were associated with plant stress-responsive genes (PR1, PR2, PR4, and TLP9), sugar metabolism (HT5), phenylpropanoids (STS1), enzymes related to jasmonic acid synthesis and response to biotic stresses, respectively (LOX, PER42). Also, the ‘Alicante Bouschet’ cultivar consistently displayed significantly higher levels of transcript accumulation on most of the stress-related genes compared to the ‘Trincadeira’ cultivar in both production modes. Our study provides valuable insights into the effectiveness of PRIs and elicitors in increasing plant expression levels of stress-responsive genes, leading to greater resilience to pathogen attacks and emphasizing their position in organic agriculture.

The Effect of Benzo(1,2,3)-thiadiazole-7-carbothioic Acid S-Methyl Ester (BTH) and Its Cholinium Ionic Liquid Derivative on the Resistance Induction and Antioxidant Properties of Tomato (Solanum lycopersicum L.).

Tomatoes are one of the most important vegetables thanks to their taste attributes and nutritional value. Their cultivation is threatened by various pathogens including viruses. The application of resistance inducers (RI), such as benzo(1,2,3)-thiadiazole-7-carbothioic acid S-methyl ester (BTH) may be used to enhance plant performance against viruses. Here we aimed to compare the impact of BTH and its choline derivative (Chol-BTH) on resistance induction and antioxidant properties of healthy plants and tomato mosaic virus (ToMV)-infected ones. The response of tomato plants to treatment with BTH or Chol-BTH was manifested by increased expression of not only pathogenesis-related (PR) genes but also WRKY and Jasmonate Zim-domain protein (JAZ) genes and increased jasmonic acid (JA) levels. The effect of BTH as a resistance inducer was observed early after application, while with Chol-BTH the plant defense system reacted more strongly after 8 days. The antioxidant properties of RI-treated tomatoes are related to both glutathione content and peroxidase activity. In the case of BTH, an increase in these activities occurred early after application, while in the case of Chol-BTH, the glutathione level was particularly high in the plant early after treatment, and high peroxidase activity was observed 8 days post-treatment. Overall, the collected results indicate that Chol-BTH, due to its physicochemical parameters (e.g., good solubility) and biological activity (increased expression of lignification-related genes, supported by increases in peroxidase activity and total phenolic compounds levels), can also be a very useful agent inducing tomato resistance against viral pathogens.

Management of Lettuce Bacterial Soft Rot Disease Using Biotic and Abiotic Agents under Field Conditions

The current investigation was planned to apply some biotic and abiotic treatments singlely and/or combined to control bacterial soft rot diseases of lettuce under field conditions in Qaha region, Qalyubia Governorate, Egypt. The application of resistance inducers (jasmonic acid and salicylic acid), antibiotics (norfloxacin and tetracycline) and bio-agents (isolates of B. subtilis and Ps. fluorescens) significantly reduced the disease severity as a single treatment compared to the control treatment. Obtained results indicated that resistance inducers appeared to be most effective against bacterial soft rot disease of lettuce compared with other treatments, while antibiotics were less effective at controlling the disease. However, the interaction between bio-agents as soil drench treatment, antibiotics, or resistance inducers as foliar treatment significantly reduced the severity of lettuce bacterial soft rot disease compared with the control treatment. Furthermore, the interaction between disease severity was more reducted with interaction treatments between Ps. fluorescens isolate rather than interact with treatments between B. subtilis isolate and other treatments. However, the interaction between the isolate of Ps. fluorescens as bio-agent treatment or norfloxacin as antibiotic or salicylic acid as a plant resistance inducer, were the most effective methods to control the disease compared with other treatments. Meanwhile, the interaction between resistance inducers and antibiotics as foliar treatments were significantly reduced from the severity of lettuce bacterial soft rot disease compared with the control treatment. Disease severity was more reduced with the application of interaction between norfloxacin and resistance inducers than the interaction between tetracycline and resistance inducers. Meanwhile, the severity of the disease decreased more with the application of interaction between salicylic acid and antibiotics than the interaction between jasmonic acid and antibiotics. Generally, all combination treatments were more efficient than single treatments alone to significantly manage the spread and the infection of the disease compared to the untreated control.

Systemic resistance induction in ‘Ortanique’ tangor

Abstract This study aimed to evaluate the quality of ‘Ortanique’ tangor, in the post-harvest and refrigerated storage after application of pre-harvest resistance inducers, in the 2015 and 2016 crops. The experimental design in the field was in completely randomized blocks, in a single factorial scheme. The treatment factor was composed of the following resistance inducers [without inducer, selenium (Se), silicon (Si), acibenzolar-s-methyl (ASM), methyl jasmonate (MeJa), thiamethoxam (TMT) and imidacloprid (IMI)]. In the laboratory, the design used was the same as that established in the field, but in a two-factorial scheme, where factor A was composed of the same inducers and factor B, for the storage period [zero (fruits that were not submitted to storage) and 30 days (Cold chamber 5±1°C, relative humidity 85 to 95%)], with simulation of the commercialization time (7 days at 20±1°C). The following analysis were performed: coloration (L *, a *, b * and hue), fresh mass loss, rot index, soluble solids (SS), pH, titratable acidity (TA), SS/TA ratio, ascorbic acid, phenolic compounds and antioxidant capacity. The application of resistance inducers reduces the percentage of fresh mass loss and fruit rot after 30 days of refrigerated storage. Inducers keep phenolic compounds and antioxidant capacity, both in pulp and fruit peel, over the storage period. The inducers Si, MeJa and IMI provide phytochemicals improvement, when compared to the control.

Effects of chitosan treatment on avocado postharvest diseases and expression of phenylalanine ammonia-lyase, chitinase and lipoxygenase genes

Stem-end rot (Lasiodiplodia theobromae) and anthracnose (Colletotrichum gloeosporioides) are major postharvest diseases in avocado that cause severe postharvest losses throughout the supply chain. One of the strategies to reduce development of such decay agents resides in the application of resistance inducers (e.g. chitosan), capable of reducing fungal growth and inducing resistance in fruit tissues.The influence of chitosan treatment (1% or 1.5% w/v) was investigated on decay incidence, gene expression of phenylalanine ammonia-lyase (PAL), chitinase (CHI) and lipoxygenase (LOX) and antioxidant enzyme activity [superoxide dismutase (SOD) and catalase (CAT)] in i) drop-inoculated (without wounding) or ii) artificially infected (with wounding) avocado (cv. ‘Hass’) with L. theobromae or C. gloeosporioides pathogens and also in iii) naturally infected (natural inoculum) avocado. Fruit were dipped in 1% or 1.5% w/v chitosan dissolved in water for 3 min, followed by storage for 14 d and 28 d respectively at 7.5 °C, and thereafter for 5 d at 18 °C to simulate market shelf conditions.Chitosan at 1.5% significantly reduced the incidence of stem-end rot and anthracnose in both inoculated and naturally infected avocados. The up-regulation of PAL and down-regulation of LOX genes moderately allowed higher epicatechin contents (90 mg kg−1 FW) in the exocarp, which could have contributed to improved anthracnose control. The up-regulation of CHI genes and higher SOD activity could have contributed to control of stem-end rot. Chitosan solution (1.5%) retained moderate levels of C7 sugars and firmness up to 5 d shelf life. The control of stem-end rot and anthracnose of avocados obtained with 1.5% chitosan can be ascribed to a combination of its antifungal and eliciting properties.

Chitosan treatment elicited defence mechanisms, pentacyclic triterpenoids and stilbene accumulation in grape (Vitis vinifera L.) bunches

The stimulation of the plant response to pathogen attack by the application of resistance inducers, called elicitors, could represent an environmentally and commercially viable alternative or complement to existing pathogen control methods. In this work, the elicitor chitosan was sprayed on grape (Vitus vinifera L.) berries growing on the vine to shed light into the elicitation mechanisms underlying its application, with untreated bunches as controls. To gain a more comprehensive picture of the complex molecular processes elicited by chitosan, a proteomic approach was complemented by target and untargeted mass spectrometric analyses. The treatment altered the regulation of reactive oxygen species, with Cu/Zn superoxide dismutase and glyoxal oxidase showing up-accumulation. This might lead to an increased lignification via hypersensitive response mechanisms. Furthermore, enzymes involved in anthocyanin rather than stilbene phytoalexins accumulated in treated bunches. Stilbenes increased from 1.6 times (resveratrol) up to 3.8 times (piceid) over untreated bunches. The up accumulation of hydroperoxide lyase might lead to accumulation of oxylipins. Furthermore, the pentacyclic triterpenoids ursolate, oleanoate and betulinate increased by 1.25, 1.47 and 3.68 times in treated grape bunches (p < 0.01). Hence, the main processes underlying the response of grape fruits to chitosan treatment involved the accumulation of phenylpropanoid and triterpenoids phytoalexins, as well as the modulation of oxidative stress–related enzymes.

Abiotic Stresses Affect Trichoderma harzianum T39-Induced Resistance to Downy Mildew in Grapevine

Enhancement of plant defense through the application of resistance inducers seems a promising alternative to chemical fungicides for controlling crop diseases but the efficacy can be affected by abiotic factors in the field. Plants respond to abiotic stresses with hormonal signals that may interfere with the mechanisms of induced systemic resistance (ISR) to pathogens. In this study, we exposed grapevines to heat, drought, or both to investigate the effects of abiotic stresses on grapevine resistance induced by Trichoderma harzianum T39 (T39) to downy mildew. Whereas the efficacy of T39-induced resistance was not affected by exposure to heat or drought, it was significantly reduced by combined abiotic stresses. Decrease of leaf water potential and upregulation of heat-stress markers confirmed that plants reacted to abiotic stresses. Basal expression of defense-related genes and their upregulation during T39-induced resistance were attenuated by abiotic stresses, in agreement with the reduced efficacy of T39. The evidence reported here suggests that exposure of crops to abiotic stress should be carefully considered to optimize the use of resistance inducers, especially in view of future global climate changes. Expression analysis of ISR marker genes could be helpful to identify when plants are responding to abiotic stresses, in order to optimize treatments with resistance inducers in field.

Atividades de quitinase e beta-1,3-glucanase após eliciação das defesas do tomateiro contra a mancha-bacteriana

O objetivo deste trabalho foi avaliar a influência de eliciadores biológicos e químicos sobre as atividades de duas proteínas relacionadas à patogênese (PR), quitinase e beta-1,3-glucanase, em folhas de tomateiro, e avaliar o potencial desses eliciadores na redução do progresso da mancha-foliar causada por Xanthomonas campestris pv. vesicatoria. Plantas de tomateiro da cultivar Santa Cruz Kada foram pulverizadas com: acibenzolar-S-metil (ASM; 0,2 g L-1); formulação biológica proveniente de biomassa cítrica, denominada Ecolife (5 mL L-1); suspensão de quitosana (MCp; 200 g L-1), proveniente de micélio de Crinipellis perniciosa; extrato aquoso de ramos de lobeira (Solanum lycocarpum) infectados por C. perniciosa (VLA; 300 g L-1). As plantas foram desafiadas com um isolado virulento da bactéria, quatro dias depois das pulverizações. Plantas pulverizadas com extratos biológicos mostraram redução da mancha-bacteriana. ASM proporcionou 49,3% de proteção, e foi igual à MCp e Ecolife e superior ao VLA. Este último não diferiu significativamente de MCp e Ecolife. Observou-se maior atividade das duas enzimas nas plantas tratadas, principalmente nas primeiras horas após as pulverizações.

History and Perspectives on the Use of Disease Resistance Inducers in Horticultural Crops

A major challenge facing horticultural crop production is the need to provide field and postharvest disease control measures that help maintain high quality plant products. Producers and consumers also expect high quality produce with minimal or no pesticide residues and competitive prices. The chemical management of disease is further complicated by the development of fungicide resistance in many important pathogens. Because of these concerns, an alternative or complementary approach is the use of disease resistance inducers that activate the natural defenses of the plant. Induced disease resistance in plants has been studied in many different pathosystems for nearly a century. Resistance to plant disease can be induced systemically by prior infection with pathogens, by certain non-pathogenic microbes that colonize the surface of roots and leaves, or by chemicals. The application of resistance inducers should protect plants through the induction of defenses that are effective against a broad spectrum of pathogens. Over the last few years, a number of materials that could potentially be used as inducers of resistance in horticultural crops have been identified. Some of these materials are already commercially available. Although induced resistance is known to provide a broad spectrum of disease suppression, it may not be a complete solution because variation in the efficacy of disease resistance induction has been observed. The variation in the response may be dependent on the plant species and even cultivars, as well as variability in the spectrum of pathogens that resistance can be induced against. Induction of resistance depends on the activation of biochemical processes that are triggered in the plant, and therefore a lag time between treatment and expression of resistance occurs. This lag effect may limit the practical application of disease resistance inducers. Since the efficacy of the inducers also depends on the part of the plant that was treated, the product delivery (i.e., how the inducers would be applied in order to optimize their action) is another factor to be considered. Some studies have shown that there may be side effects on growth or yield characteristics when certain inducers are used. Understanding the biochemical interactions occurring between plants, pathogens and the inducers will provide information that may be useful for the optimization of this new approach on disease control. Approaches to integrate induced resistance with other management practices need to be investigated as a means to aid the development of sustainable disease management programs that are effective as well as economically and environmentally sound.