Application Of Methyl Jasmonate Research Articles

Improvement of the yield and essential oil of fennel (Foeniculum vulgare Mill.) using external proline, uniconazole and methyl jasmonate under drought stress conditions

Drought stress is a significant environmental constraint that seriously limits crop productivity. A two-year field study was carried out as a split plot based on a randomized complete block design (RCBD) with three replicates in the experimental station of the agricultural faculty of Azarbaijan Shahid Madani University, Tabriz, Iran. This study evaluated the impacts of various irrigation regimes and plant growth regulators/proline on yield, its components, and essential oil content. Water shortage led to considerable decreases in umbels per plant, umbellets per umbel, fruits per umbellet, 1000-fruit weight, biological yield, and finally, fruit yield, despite increases in fruit essential oil content under moderate drought stress conditions. External methyl jasmonate, uniconazole, and proline significantly increased these parameters measured in fennel plants compared with the control. Improved effects of external plant growth regulators/proline tended to be greater in drought-stress plants, as it enhanced yield, its components, and fruit essential oil content compared with control. Foliar spraying, particularly methyl jasmonate, and uniconazole, enhanced e- anethole content under drought stress. Fenchone and methyl chavicol contents increased in plant growth regulators/proline-treated plants when they were kept under moderate drought stress conditions; however, their contents decreased by the severity of drought stress apart from the application of methyl jasmonate. Hence, applying these PGRs or proline could be critical in cultivating fennel plants under water shortage conditions to achieve higher essential oils yield and its constituents, particularly anethole, compared with control.

Methyl jasmonate influences ethylene formation, defense systems, nutrient homeostasis and carbohydrate metabolism to alleviate arsenic-induced stress in rice (Oryza sativa)

The plant growth regulator, jasmonic acid (JA) has emerged as important molecule and involved in key processes of plants. In this study, we investigated the role of methyl jasmonate (MeJA) in achieving tolerance mechanisms against arsenic (As) stress in rice (Oryza sativa). Arsenic toxicity is a major global concern that significantly deteriorate rice production. The application of MeJA (20 μM) and ethylene (150 μL L−1) both individually and/or in combination were found significant in protecting against As-induced toxicity in rice, and significantly improved defense systems. The study shown that the positive influence of MeJA in promoting carbohydrate metabolism, photosynthesis and growth under As stress were the result of its interplay with ethylene biosynthesis and reduced oxidative stress-mediated cellular injuries and cell deaths. Interestingly, the use of JA biosynthesis inhibitor, neomycin (Neo) and ethylene biosynthesis inhibitor, aminoethoxyvinylglycine (AVG) overturned the effects of MeJA and ethylene on plant growth under As stress. From the pooled data, it may also be concluded that Neo treatment to MeJA- treated rice plants restricted JA-mediated responses, implying that application of MeJA modulated ethylene- dependent pathways in response to As stress. Thus, the action of MeJA in As tolerance is found to be mediated by ethylene. The study will shed light on the mechanisms that could be used to ensure the sustainability of rice plants under As stress.

Regulation of mycorrhizal colonization under stress in tomato depends on symbiotic efficiency

The mutualistic symbiosis between plants and arbuscular mycorrhizal (AM) fungi is based on a balanced nutrient exchange between both partners, with the plant achieving improved nutrition and stress tolerance. The symbiosis is finely-tuned according to plant’s needs and surrounding conditions, usually through phytohormonal signaling. Thus, environmental conditions or stress factors modulating phytohormone signaling may influence the symbiosis. This study compares the colonization abilities of 2 AM fungal species, Funneliformis mosseae and Rhizophagus irregularis, independently or in combination, in tomato plants subjected to different stress conditions. These included salt stress and systemic defense activation by aboveground application of the defense-related hormones methyl jasmonate, abscisic acid and salicylic acid. The results show that root colonization by the two fungal species differs depending on the stress treatment. Nutrient and transcriptional analyses revealed that changes in colonization correlated with differential regulation of nutrient exchange, plant defensive responses, and symbiosis regulatory genes. Specifically, under salt stress R. irregularis colonization decreased, while F. mosseae colonization was promoted. These differential regulation of colonization under stress positively correlated with changes in the functionality of the symbiosis. Overall, the results support that the benefits provided by each AM fungi influence carbon reward and determines the control of root colonization by the host plant.

The roles of brassinosteroids and methyl jasmonate on postharvest grape by regulating the interaction between VvDWF4 and VvTIFY 5 A

Brassinosteroids (BRs) and methyl jasmonate (MeJA) are known for the regulation of plant development, and the crosstalk between them is important for plant growth. However, the interaction between them in the development of postharvest fruit is unresolved. We found that BR treatment enhanced the accumulation of sugar composition and aroma content, reduced the content of organic acids (such as tartaric acid) and promoted the coloring of grape callus. After the application of MeJA, the acidity increased and the sugar content decreased. The physiological data showed that exogenous BR also attenuated the JA inhibition of postharvest ripening in grape. DWF4 is a key enzyme in the BR biosynthetic pathway, and it can effectively regulate the content of endogenous BRs. TIFY 5 A, which belongs to the Jasmonate ZIM-domain (JAZ) family, can be baited by DWF4 through the Y2H experiment. TIFY 5 A represses the expression of dihydroflavonol-4-reductase (DFR) which plays a key role in the synthesis of anthocyanins, while this will be alleviated by VvDWF4. The interaction between TIFY 5 A and DWF4 contributes to the cross talk between JA and BR signalling pathways. This is also verified by the transgenic experimental results. The results in this paper provides a new insight into the relationship between BR and JA signalling pathways, which is important to the regulation of the postharvest ripening of grape.

Alkane biosynthesis is promoted in methyl jasmonate-treated sweet cherry (Prunus avium) fruit cuticles.

The cuticle plays an important role in the survival of plants, and it is important to preserve the quality of fleshy fruits like sweet cherry. Plant hormones play a role in cuticle formation. In this sense, jasmonates have been shown to induce cuticle biosynthesis, but until today this has not been demonstrated in sweet cherry fruit. Therefore, the effect of exogenous methyl jasmonate (MeJA) application at the fruit set stage on the expression levels of cuticle synthesis-related genes and the wax composition of the isolated cuticle was studied in developing and ripe fruits of sweet cherry (Prunus avium 'Bing'), respectively. MeJA treatment resulted in up-regulation of the cuticle biosynthesis-related gene expression, such as PaWINA, PaWINB, PaKCS1, PaKCS6, PaLACS1, PaLACS2, PaWS, and PaWBC11. These genes play a vital role in the elongation and transport of fatty acids, and wax biosynthesis. Analysis of cuticular components in ripe fruit showed an increase in long-chain linear aliphatic wax compounds, particularly C27, C28, C29, C30, and C31 alkanes. Exogenous MeJA application at the fruit set stage of sweet cherry has a significant effect on the wax composition of the ripe fruit cuticle, particularly in terms of alkane biosynthesis. The results of this study may provide insights into the regulation of cuticle biosynthesis by jasmonates and be useful for improving fruit quality and storage life. © 2023 Society of Chemical Industry.

A metabolic reprogramming in Bacopa monnieri plants induced by methyl-jasmonate and enhanced biosynthesis of triterpene saponins

The bacoside-A is the main bioactive metabolite present in Bacopa monnieri L. The yield of bacoside-A from plant sources is too less to meet industrial demand. This study investigated the effect of methyl jasmonate (MeJA) on metabolic profiles and bacoside-A biosynthesis in greenhouse-grown plants of B. monnieri. The greenhouse-grown plants were kept inside a closed plastic container and then elicited with MeJA vapour. It was found that MeJA treatment (200 µM for 2 h on day zero) followed by harvesting leaves on day three was the optimum treatment, resulting in an increase of 1.8-fold, 2.2-fold, 3.1-fold, and 2.5-fold in bacoside A3, bacopaside II, bacopaside X, and bacopasaponin C in comparison with control plants, respectively. The transcript levels of squalene synthase (SQS), a key gene involved in bacoside-A biosynthesis was transiently induced by MeJA and reached a peak of up to 3.7-fold at 24 h. The relationships between bacosides content and primary metabolites in plants treated with MeJA were analyzed by gas chromatography-mass spectrometry. MeJA enhances glycolysis and TCA cycles, generating acetyl-CoA, which acts as a precursor for bacosides synthesis, as revealed by untargeted metabolomics. Therefore, in planta application of MeJA appears to have a great impact on enhanced bacoside-A accumulation, in the greenhouse-grown plants of B. monnieri. In this study, farmers and the pharmaceutical industry will have access to a simple and time-saving elicitation strategy for improving bacosides production from greenhouse-grown plants without the need for expensive and time-consuming in vitro culture techniques.

Alleviation of arsenic toxicity-induced oxidative stress in lemon grass by methyl jasmonate

Arsenic (As) is a toxic and non-essential metalloid, with known detrimental effects on sustainable agricultural production. Therefore, this study assessed the negative effects of As on lemon grass and how methyl jasmonate (MeJA) mitigated those effects. Interestingly, lemon grass showed no toxicity symptoms under mild As-stress, however plants under severe stress showed early senescence and chlorosis, indicating a decrease in nitrogen content under As-treatment. The results revealed that various physiological and biochemical mechanisms were negatively affected by As-induced oxidative stress. The high production of reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) (8.3-fold), hydroxide ion (OH−) (5.4-fold), superoxide radicals (O2−) (5.2-fold), malondialdehyde (MDA) (2.9-fold), and methylglyoxal (MG) (3.7-fold) caused oxidative injury to lemon grass undergoing As-stress (120 mM). To ameliorate the ROS- and MG-induced oxidative damages, the glutathione-ascorbate (GSH-AsA) cycle and its related antioxidants played a crucial role in ROS detoxification under high As stress. Furthermore, the results revealed that ROS- and MG-induced oxidative stress negatively impacted the metabolic profile of lemon grass under As stress. The ROS- and MG-induced oxidative damage resulted in lowering antioxidants, proline, organic acids, proteins, and amino acids content. Additionally, the current study demonstrated the usefulness of exogenous MeJA application, which considerably improved the plants’ antioxidant defense system and metabolic profile wgich resulted in the reduction of ROS and MG levels by neutralizing the ROS- and MG-induced oxidative damage under As-stress in lemon grass. Collectively, the current study provided insights into the physiological and biochemical pathways of the As-mediated ROS- and MG-induced oxidative damage in lemon grass and its mitigation through exogenous MeJA application.

Application of Methyl Jasmonate to Papaya Fruit Stored at Lower Temperature Attenuates Chilling Injury and Enhances the Antioxidant System to Maintain Quality.

Papaya fruit has a limited shelf life due to its sensitivity to decay and chilling damage during cold storage. The application of methyl jasmonate (MeJA) is known to reduce the incidence of disease and chilling injury, and to maintain the overall quality of the papaya fruit when stored at low temperature. Consequently, the effects of postharvest MeJA (1 mM) immersion on papaya fruits during low-temperature storage (10 °C ± 2 °C) for 28 days were studied. The experiment revealed that MeJA treatment significantly decreased the papaya fruit's weight loss, disease incidence, and chilling injury index. Furthermore, the accumulation of malondialdehyde and hydrogen peroxide was markedly lower after the application of MeJA. In addition, MeJA treatment exhibited significantly higher total phenols, ascorbic acid, antioxidant activity, and titratable acidity in contrast to the control. Similarly, MeJA-treated papaya fruits showed higher antioxidant enzymatic activity (superoxide dismutase, catalase, and peroxidase enzymes) with respect to the control fruits. In addition, MeJA reduced the soluble solids content, ripening index, pH, and sugar contents compared to the control fruits. Furthermore, MeJA-treated papaya fruit exhibited higher sensory and organoleptic quality attributes with respect to untreated papaya fruits. These findings suggested that postharvest MeJA application might be a useful approach for attenuating disease incidence and preventing chilling injury by enhancing antioxidant activities along with enhanced overall quality of papaya fruits during low-temperature storage.

Exogenous Application of Methyl Jasmonate Promotes Yield and Grain Quality of Rice under Terminal Drought Stress

Exogenous application of methyl jasmonate (MeJA) improves rice drought tolerance, but its effects on rice yield and quality under drought stress during the reproductive phase remain unclear. A pot experiment was conducted to measure rice yield, grain quality, and starch physicochemical properties under three treatments: continuous flooding irrigation throughout the whole growth season (CF), ten days of −40 kPa drought stress at the heading stage (DS), and foliar spraying 100 μmol L−1 MeJA on the first three days of the ten-day −40 kPa heading stage drought stress (DM). An inbred japonica rice variety, Huaidao 5, was the experimental material, and each treatment had 11 replicates for sampling. The results indicated that DS significantly reduced rice yield and quality compared to CF. With increases in superoxide dismutase (+22.2%), peroxidase activities (+10.5%), catalase (+5.0%), and proline content (+5.7%), DM significantly increased 1000-grain weight (+8.6%), filled grain percentage (+3.6%), and yield (+11.1%) compared with DS. Regarding grain quality, DM significantly decreased the chalkiness degree (−12.3%) and protein content (−3.9%) but increased the amylose content (+17.2%) and taste value (+7.3%) relative to DS. In addition, DM improved breakdown viscosity (+17.8%), gelatinization enthalpy (+17.2%), retrogradation enthalpy (+28.0%), 1045/1022 cm−1 ratio (+3.0%), and starch granule morphology compared to DS. In conclusion, exogenous application of 100 μmol L−1 MeJA enhanced the antioxidant capacity of rice leaves, and thus improved starch physicochemical properties to increase grain yield and quality under terminal drought stress.

Jasmonates regulate apical hook development by repressing brassinosteroid biosynthesis and signaling.

An apical hook is a special structure formed during skotomorphogenesis in dicotyledonous plant species. It is critical for protecting the shoot apical meristem from mechanical damage during seed germination and hypocotyl elongation in soil. Brassinosteroid (BR) and jasmonate (JA) phytohormones antagonistically regulate apical hook formation. However, the interrelationship between BRs and JAs in this process has not been well elucidated. Here, we reveal that JAs repress BRs to regulate apical hook development in Arabidopsis (Arabidopsis thaliana). Exogenous application of methyl jasmonate (MeJA) repressed the expression of the rate-limiting BR biosynthetic gene DWARF4 (DWF4) in a process relying on 3 key JA-dependent transcription factors, MYC2, MYC3, and MYC4. We demonstrated that MYC2 interacts with the critical BR-activated transcription factor BRASSINAZOLE RESISTANT 1 (BZR1), disrupting the association of BZR1 with its partner transcription factors, such as those of the PHYTOCHROME INTERACTING FACTOR (PIF) family and downregulating the expression of their target genes, such as WAVY ROOT GROWTH 2 (WAG2), encoding a protein kinase essential for apical hook development. Our results indicate that JAs not only repress the expression of BR biosynthetic gene DWF4 but, more importantly, attenuate BR signaling by inhibiting the transcriptional activation of BZR1 by MYC2 during apical hook development.

PpMYB105 inhibits chilling injury by regulating PpMsrA1 in peach fruit.

MeJA supplementation enhanced the chilling tolerance and gene expression of PpMsrA1. PpMYB105 protein positively regulated the PpMsrA1 promoter. PpMYB105 mediated the MeJA-boosted chilling tolerance by regulating PpMsrA1. Cold storage can maintain the quality of postharvest fruit. However, peaches easily suffer from chilling injury (CI) during cold storage, leading to economic loss. Results showed that methyl jasmonate (MeJA) supplementation reduced the CI severity, and enhanced the gene expression of methionine sulfoxide reductase A1 (PpMsrA1). It was found that MeJA application elevated the MsrA activity and methionine (Met) content, and reduced the methionine-S-sulfoxide (Met-S-SO) content and reactive oxygen species (ROS) production afterwards. Moreover, PpMYB105 could activate the transcription of PpMsrA1 by binding to the MYB binding element in its promoter. The gene expression of PpMYB105 was up-regulated by MeJA application. Overexpression of PpMYB105 in tomatoes enhanced the chilling tolerance and gene expression of SlMsrA1. Virus-induced gene silencing of PpMYB105 in peaches resulted in the increase in CI severity and the decrease in gene expression of PpMsrA1. Thus, PpMYB105 was involved in the MeJA-boosted chilling tolerance by regulating PpMsrA1.

Healing of bark wounds in Norway spruce seedlings can be negatively affected by treatment with methyl jasmonate

Key messageTreatment with methyl jasmonate can slow down the healing of stem bark wounds in Norway spruce seedlings.In woody plants, healing of bark wounds is a tolerance trait involved in recovery from stem damage. Yet, little is known on how wound healing may be affected by plant protection treatments such as methyl jasmonate application (MeJA, a plant hormone triggering increased resistance to pests). Here, we examined if MeJA can affect healing of an existing and a subsequently inflicted stem wound on Norway spruce (Picea abies) seedlings, the effect of treatment on plant growth, and potential trade-offs between healing and resistance to insect damage. Seedlings from 18 full-sib families were mechanically wounded (or not) on the lower stem and treated with MeJA (or water) one week after. Two months later, another wound was inflicted and wound area was measured during six months. Growth of non-wounded and wounded seedlings were compared, and correlations between family estimates of healing rates and field insect damage were examined. We found that MeJA slowed down wound healing. For the first and second wound, respectively, MeJA-treated seedlings experienced 15% and 9% slower healing rates, and wounds remained 58% and 69% larger in size compared to water-treated seedlings. Stem wounding and MeJA together were more detrimental to seedling diameter than height growth, relative to each treatment alone. Finally, resistance to field insect damage and wound healing rates were not significantly correlated. We conclude that MeJA-mediated seedling protection may trade-off with bark wound healing, which may be negative for seedling vigor. However, further studies are needed to evaluate if such effects outweigh the benefits that MeJA provides.

Effect of Methyl Jasmonate Plus Urea Foliar Application on the Polysaccharide and Monosaccharide Composition of Tempranillo Grapes and Wines and on the Wine’s Quality

Polysaccharides are the main group of macromolecules in wines. Climate change is a major problem for viticulturists as it leads to the production of unbalanced grapes. This is attributed to a mismatch between the technological maturity and phenolic maturity of grapes, which can negatively impact the production of high quality wines. To mitigate this effect, biostimulants can be applied to grapevines. For the first time in the literature, this work studied the foliar application of methyl jasmonate plus urea (MeJ + Ur) on the vineyard and its effect on the monosaccharide and polysaccharide composition of Tempranillo grapes and wines over two consecutive seasons. To achieve this, the extraction and precipitation of polysaccharides was conducted, and the identification and quantitation of monosaccharides was performed via GC–MS. The effect of MeJ + Ur foliar treatment in both the grapes and wines was season-dependent. The MeJ + Ur treatment had a slight impact on the monosaccharide composition of the grapes and also demonstrated a small effect on the wines. Multifactor and discriminant analysis revealed that the season had a greater influence on the monosaccharide and polysaccharide composition of grapes and wines compared to the influence of MeJ + Ur treatment. Interestingly, the MeJ + Ur-treated wines exhibited a higher sensory evaluation than the control wines in the second vintage. To gain further insights into the effect of MeJ + Ur foliar application on the monosaccharide and polysaccharide composition of grapes and wines, further investigations should be conducted.

Methyl jasmonate, salicylic acid, and oxalic acid affects growth, inducible defenses, and pine weevil resistance in Norway spruce.

The large pine weevil (Hylobius abietis) is a major regeneration pest in commercial forestry. Pesticide application has historically been the preferred control method, but pesticides are now being phased out in several countries for environmental reasons. There is, thus, a need for alternative plant protection strategies. We applied methyl jasmonate (MeJA), salicylic acid (SA) or oxalic acid (OxA) on the stem of 2-year-old Norway spruce (Picea abies) plants to determine effects on inducible defenses and plant growth. Anatomical examination of stem cross-sections 9 weeks after application of 100 mM MeJA revealed massive formation of traumatic resin ducts and greatly reduced sapwood growth. Application of high concentrations of SA or OxA (500 and 200 mM, respectively) induced much weaker physiological responses than 100 mM MeJA. All three treatments reduced plant height growth significantly, but the reduction was larger for MeJA (~55%) than for SA and OxA (34-35%). Lower MeJA concentrations (5-50 mM) induced comparable traumatic resin duct formation as the high MeJA concentration but caused moderate (and non-significant) reductions in plant growth. Two-year-old spruce plants treated with 100 mM MeJA showed reduced mortality after exposure to pine weevils in the field, and this enhanced resistance-effect was statistically significant for three years after treatment.

Jasmonate biosynthesis enzyme allene oxide cyclase 2 mediates cold tolerance and pathogen resistance.

Allene oxide cyclase (AOC) is a key enzyme in the biosynthesis of jasmonic acid (JA), which is involved in plant growth and development as well as adaptation to environmental stresses. We identified the cold- and pathogen-responsive AOC2 gene from Medicago sativa subsp. falcata (MfAOC2) and its homolog MtAOC2 from Medicago truncatula. Heterologous expression of MfAOC2 in M. truncatula enhanced cold tolerance and resistance to the fungal pathogen Rhizoctonia solani, with greater accumulation of JA and higher transcript levels of JA downstream genes than in wild-type plants. In contrast, mutation of MtAOC2 reduced cold tolerance and pathogen resistance, with less accumulation of JA and lower transcript levels of JA downstream genes in the aoc2 mutant than in wild-type plants. The aoc2 phenotype and low levels of cold-responsive C-repeat-binding factor (CBF) transcripts could be rescued by expressing MfAOC2 in aoc2 plants or exogenous application of methyl jasmonate. Compared with wild-type plants, higher levels of CBF transcripts were observed in lines expressing MfAOC2 but lower levels of CBF transcripts were observed in the aoc2 mutant under cold conditions; superoxide dismutase, catalase, and ascorbate-peroxidase activities as well as proline concentrations were higher in MfAOC2-expressing lines but lower in the aoc2 mutant. These results suggest that expression of MfAOC2 or MtAOC2 promotes biosynthesis of JA, which positively regulates expression of CBF genes and antioxidant defense under cold conditions and expression of JA downstream genes after pathogen infection, leading to greater cold tolerance and pathogen resistance.

Methyl jasmonate and selenium synergistically mitigative cadmium toxicity in hot pepper (Capsicum annuum L.) plants by improving antioxidase activities and reducing Cd accumulation.

Methyl jasmonate (MeJA) or selenium (Se)-mediated response to cadmium (Cd) stress in plant has been widely reported, but the combined effects both on plant growth in response to Cd stress and the underlying mechanisms remain obscure. Here, we showed the combined effects of MeJA (2.5μM) and Se (7μM) on hot pepper growth under Cd stress (CdCl2, 5μM). The results showed Cd suppressed the accumulation of total chlorophyll and carotenoid and reduced the photosynthesis, while it increased the content of endogenous signaling molecules, e.g. nitric oxide (NO) and hydrogen peroxide (H2O2), as well as Cd content in leaves. The combined application of MeJA and Se significantly decreased the malondialdehyde (MDA) accumulation and improved the activities of antioxidant enzymes (AOEs, e.g. SOD and CAT) and defense-related enzymes (DREs, POD and PAL). Additionally, the synergistic application of MeJA and Se also obviously improved photosynthesis in hot pepper plants under Cd stress compared with those treated with MeJA or Se respectively or not. Moreover, the treatment of MeJA associated with Se also effectively reduced the Cd accumulation in hot pepper leaves under Cd stress compared with the plants treated with MeJA or Se separately, which implied a potentially synergistic role of MeJA and Se in alleviating Cd toxicity in hot pepper plants. This study provides a theoretical reference for the further analysis of the molecular mechanism of MeJA and Se in jointly mediating the response to heavy metals in plants.

Inducing the Production of Secondary Metabolites by Foliar Application of Methyl Jasmonate in Peppermint.

Mentha x piperita is a major source of secondary metabolites (SMs), and developing tools to enhance these compounds would be beneficial to meet the increasing demand in the industry. Elicitation by plant hormones became a new strategy to reach this goal. Three experiments in a climatic chamber and two experiments in an open field were conducted with peppermint to explore the effect of methyl jasmonate (MeJa) on the essential oil (EO) content, EO composition, and the total phenolic content (TPC). The treatment was applied for all experiments by spraying the aerial parts of the plants with a dosage of 2 mM MeJa twice. The treatment influenced all the parameters studied in the trials. The volatile content increased by 9-35%; however, in one trial it remained unchanged. The treatment also affected the main compounds of the EO. Menthone increased significantly in two trials while pulegone and menthofuran decreased. In the case of menthol, the change may also be influenced by the phenological and developmental stages of the plants. In the majority of cases, the TPC was also elevated considerably due to the treatments. MeJa treatments may have promising effects in influencing the accumulation of biologically active compounds and the quality of the drug; therefore, further systematic studies are needed to optimize the technology in vivo.

Sweet Cherry (Prunus avium L.) Cracking during Development on the Tree and at Harvest: The Impact of Methyl Jasmonate on Four Different Growing Seasons

Rainfall occurring during the developmental stages of sweet cherries on the tree can lead to significant preharvest losses, primarily due to fruit cracking. Certain cultivars exhibit a higher susceptibility to such losses, particularly when persistent rains coincide with advanced phenological stages. The current study aims to investigate the efficacy of preharvest methyl jasmonate (MeJA) applications at harvest and during distinct developmental ripening stages in mitigating sweet cherry cracking at harvest and on-tree ripening. Preharvest foliar applications of 0.5 mM MeJA were applied across various sweet cherry cultivars, including ‘Prime Giant’, ‘Early Lory’, ‘Sweetheart’, and ‘Staccato’. By conducting this experiment over four growing seasons, we evaluated the impact of this natural elicitor on the cracking tolerance of these cultivars. The results of our analysis indicate that MeJA preharvest treatments effectively reduce fruit cracking, enhancing abiotic stress tolerance. Additionally, these treatments induce a general delay in fruit ripening on the tree across the examined cultivars. This delayed ripening effect is reflected in several quality parameters at harvest, such as the fruit firmness, external colour, total soluble solids, and total acidity. These parameters in the MeJA-treated fruit were delayed compared to the control fruit or remained unaffected for the total acidity. Conversely, the MeJA treatments delayed the accumulation of total polyphenols, exhibiting a minimal impact on reducing pedicel browning. The enhanced tolerance to cracking and delayed ripening attributed to the MeJA preharvest treatments could be helpful for plot management. Consequently, these MeJA-based preharvest treatments hold potential as valuable tools in adapting to climate change and mitigating abiotic stress in sweet cherry.

Foliar application of methyl jasmonate affects impatiens walleriana growth and leaf physiology under drought stress

ABSTRACT In this study, the effects of foliar applied methyl jasmonate (MeJA) on drought-stressed Impatiens walleriana growth and leaf physiology parameters: stomatal conductance, chlorophyll, flavonoid, anthocyanin, and nitrogen balance index (NBI), were evaluated. These parameters could serve as indicators of drought tolerance of I. walleriana, a popular horticultural plant worldwide that is very sensitive to drought. The experiment included four treatments: control, drought-stressed plants sprayed with distilled water, drought-stressed plants sprayed with 5 µM MeJA, and drought-stressed plants sprayed with 50 µM MeJA. Foliar spraying with MeJA was performed twice: seven days before and on the day of drought induction. The stressed plant groups were non-irrigated to achieve soil water contents (SWC) of 15 and 5%, while control plants were well-watered throughout the experiment (35–37% SWC). The results of this study showed that drought significantly reduced I. walleriana fresh and dry shoot weight, as well as total leaf area, but did not impact on dry matter content. The foliar application of MeJA improved growth parameters of I. walleriana, depending on the elicitor concentration and drought intensity. Stomatal conductance was slightly reduced at 5% SWC, and foliar applied MeJA at both concentrations. The flavonoid index was slightly reduced at 15 and 5% SWC when 50 µM MeJA was foliar applied, while there were no observed changes in the anthocyanin index in any treatments. The foliar application of 50 µM MeJA increased the chlorophyll index and NBI of I. walleriana at 5% SWC, indicating a contribution of the elicitor to plant drought tolerance at the physiological level.

Synergistic effects of methyl jasmonate treatment and propagation method on Norway spruce resistance against a bark-feeding insect.

Utilizing plants with enhanced resistance traits is gaining interest in plant protection. Two strategies are especially promising for increasing resistance against a forest insect pest, the pine weevil (Hylobius abietis): exogenous application of the plant defense hormone methyl jasmonate (MeJA), and production of plants through the clonal propagation method somatic embryogenesis (SE). Here, we quantified and compared the separate and combined effects of SE and MeJA on Norway spruce resistance to pine weevil damage. Plants produced via SE (emblings) and nursery seedlings (containerized and bare-root), were treated (or not) with MeJA and exposed to pine weevils in the field (followed for 3 years) and in the lab (with a non-choice experiment). Firstly, we found that SE and MeJA independently decreased pine weevil damage to Norway spruce plants in the field by 32-33% and 53-59%, respectively, compared to untreated containerized and bare-root seedlings. Secondly, SE and MeJA together reduced damage to an even greater extent, with treated emblings receiving 86-87% less damage when compared to either untreated containerized or bare-root seedlings in the field, and by 48% in the lab. Moreover, MeJA-treated emblings experienced 98% lower mortality than untreated containerized seedlings, and this high level of survival was similar to that experienced by treated bare-root seedlings. These positive effects on survival remained for MeJA-treated emblings across the 3-year experimental period. We conclude that SE and MeJA have the potential to work synergistically to improveplants' ability to resist damage, and can thus confer a strong plant protection advantage. The mechanisms underlying these responses merit further examination.