Induction of Resistance in Melon to Didymella bryoniae and Sclerotinia sclerotiorum by Seed Treatments with Acibenzolar-S-methyl and Methyl Jasmonate but not with Salicylic Acid

The plant resistance activator acibenzolar‐S‐methyl (BTH), the signalling molecules salicylic acid (SA) and methyl jasmonate (MeJA) were tested by seed treatment for their ability to protect melon seedlings from gummy stem blight and white mould disease caused by the soil‐borne fungal pathogens Didymella bryoniae and Sclerotinia sclerotiorum, respectively. Didymella bryoniae infection on melon seedlings was completely suppressed by MeJA treatment. Necrotic lesions akin hypersensitive response occurred on all inoculated seedlings and prevented pathogen diffusion into healthy tissues. Didymella bryoniae infection was restricted following BTH seed treatment as well, although the percentage of necrotic lesions in comparison with the water soaked lesions was significantly lower than that from MeJA‐induced seedlings. BTH protected melon seedlings against S. sclerotiorum by the occurrence of a high percentage of necrotic lesions. A lower level of resistance was also achieved by MeJA seed treatment. The augmented level of resistance of tissues from BTH and MeJA‐treated seeds was associated with rapid increases in the activity of the pathogenesis‐related proteins chitinase and peroxidase. MeJA also determined a rapid and transient accumulation of lipoxygenase. Moreover, BTH and MeJA treatments determined the differential induction of particular de novo synthesized isoenzymes of these proteins. Results indicate that BTH and MeJA applied to melon seeds may activate on seedlings diverse metabolic pathways leading to the enhancement of resistance against distinct pathogens.     

Depressed performance and detoxification enzyme activities of Helicoverpa armigera fed with conventional cotton foliage subjected to methyl jasmonate exposure

Methyl jasmonate (MeJA)‐mediated defense in conventional cotton, Gossypium hirsutum L. (Malvaceae), against cotton bollworm, Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), was investigated with respect to the activities of the detoxification enzymes acetylcholinesterase (AChE), carboxylesterase (CarE), and glutathione S‐transferases (GST) in pupae as well as the performance of larvae. The results suggested that exogenous application of MeJA to cotton leaves depressed the activities of AChE, CarE, and GST of cotton bollworm pupae. Both the absolute and protein‐specific AChE activities of pupae were depressed at all three MeJA concentrations applied as compared with a control, and the effects of 0.4 mM MeJA were significantly higher than those of 0.1 and 0.2 mM. A marked reduction in absolute CarE activity was observed at the 0.4 mM MeJA treatment, whereas the protein‐specific activity was increased by 0.2 and 0.4 mM. Absolute GST activity was significantly depressed only by the 0.4 mM MeJA treatment, whereas protein‐specific GST activity was not markedly affected by MeJA. Protein content of pupae was reduced by 0.4 mM MeJA‐induced defense in cotton leaves. The development time of larvae was protracted and pupal weight was reduced by 0.1 and 0.4 mM MeJA‐treated cotton leaves. Larval weight gain was inhibited significantly on 0.2 and 0.4 mM MeJA‐treated cotton leaves. The results suggested that MeJA‐induced plant defense may have adverse effects on H. armigera. In addition to the inhibition of growth and development, induced defense may also impair the insect's ability to detoxify toxic plant secondary metabolites.     

Anatomy Of The Genus Mesembryanthemum. I. Root Structures

Summary

Caesium cation toxicity observed previously in light- and dark-germinated tomato seedlings Lycopersicon esculentum L.) without calcium cation supplementation in the germination media was also observed here in tomato seedlings germinated in light and dark environments on mixtures of caesium and calcium cations. This non-amelioration of caesium cation-induced toxicity by externally supplied calcium cations in light- and dark- germinated tomato seedlings was evident in five cultivars, thus demonstrating that this phenomenon was not cultivar specific.     

Treatment with acetyl salicylic acid protects muskmelon seedlings against drought stress

Salicylic acid (SA) is a common plant-produced signal molecule that is responsible for inducing tolerance to a number of biotic and abiotic stresses. An experiment was, therefore, conducted to test whether acetyl salicylic acid (ASA) application at various concentrations through seed soaking or foliar spray would protect muskmelon [Cucumis melo L. (reticulatus group)] seedlings, subjected to drought stress. Twenty-three-day-old plants pre-treated with ASA (0, 0.1, 0.25, 0.50 or 1.0 mM) were subjected to drought stress for 1 week in a greenhouse. ASA applied either through seed soaking or through foliar spray was effective within the range of 0.1–1 mM in providing drought stress protection in muskmelon seedlings; however, there was no difference between application methods indicating that both methods provided similar levels of protection. ASA significantly affected all seedling growth and stress indicator variables measured except leaf number and root dry weight. The best protection appeared to be obtained from seedlings pre-treated with lower concentrations of ASA. Even though both methods provided similar means of protection, due to its simplicity and practicality, soaking muskmelon seeds prior to sowing in up to 0.5 mM ASA would be a more desirable method.     

茉莉酸甲酯诱导邻近番茄植株抗斜纹夜蛾的浓度和距离效应

茉莉酸甲酯(Methyl jasmonate, MeJA)与植物间的防御通讯密切相关,其挥发性强,可以在空气中传播而诱导邻近植物产生防御反应,为探明MeJA诱导邻近植株抗虫性的浓度和距离效应,本研究在大棚(长4 m×宽1 m×高1 m)进口处喷以不同浓度MeJA,检测离气味源60 cm、120 cm、180 cm、240 cm和300 cm远的番茄植株叶片多酚氧化酶(Polyphenol oxidase, PPO),过氧化物酶(Peroxidase, POD)和脂氧合酶(Lipoxygenase, LOX)的活性以及斜纹夜蛾幼虫取食不同处理番茄植株叶片后的体重增长率,研究结果表明1 mmol/L和10 mmol/L MeJA挥发物可以显著诱导增强邻近番茄植株叶片PPO,POD和LOX酶的活性,以离10 mmol/L MeJA气味源60 cm处植株叶片的酶活性最高,并随着距离的增加而呈降低的趋势;取食60 cm和300 cm对照组植株叶片的斜纹夜蛾幼虫其体重增长率没有显著差异,然而1 mmol/L和10 mmol/L MeJA处理下,取食300 cm处植株叶片的斜纹夜蛾幼虫其体重增长率显...     

<Emphasis Type="Italic">Fusarium sambucinum</Emphasis> isolate FS-94 induces resistance against fusarium wilt of tomato via activation and priming of a salicylic acid-dependent signaling system

The wheat rhizosphere-inhabiting nonpathogenic Fusarium sambucinum isolate FS-94 protected tomato from Fusarium wilt (F. oxysporum f. sp. lycopersici) in laboratory experiments. Seed soaking or immersion of seedling roots in a FS-94 spore suspension prior to inoculation with the pathogen delayed the appearance of wilt symptoms and significantly reduced disease severity in plants of a susceptible tomato cultivar. Quantification of fungal ergosterol in infected tomato showed that protection against wilt agent was related to limitation of the pathogen growth in plants exposed to FS-94. Incubation of tomato seedlings in a FS-94 spore suspension for 48 or 72 h led to plant protection and increased the salicylic acid (SA) concentration in their roots, suggesting that this isolate was involved in a plant-mediated mode of action and induced resistance. Soaking tomato seeds in the spore suspension did not induce SA accumulation in seedling roots, but nevertheless resulted in a significant reduction in wilt severity when the seedlings were challenged with the pathogen. In response to pathogen attack, the SA content in susceptible seedlings grown from FS-94-treated seeds started to increase within 1 day and remained elevated for 72 h. This suggests that F. sambucinum isolate FS-94 primed a SA-dependent signaling system in tomato.     

Methyl jasmonate stimulates polyamines biosynthesisand resistance against leaf rust in wheat plants

Abstract

Leaf rust of wheat (Triticum aestivum L.), incited by Puccinia recondita ex Desm. f. sp. tritici Eriks, is one of the most important wheat diseases in Egypt. Methyl jasmonate (MJ) is a potential plant elicitor which induces a wide range of chemical and anatomical defense reactions in conifers and might be used to increase systemic resistance against biotic damage. In the greenhouse, different concentrations of MJ (10, 20 and 30 mM) were applied as seed soaking plus foliar spray or only as foliar spray to control leaf rust and induction of secondary compound production in leaves of wheat plants. Foliar spray was applied after 30 and 50 days of sowing. Results indicated that all concentrations and treatments reduced the severity of rust disease caused by P. recondita f. sp. tritici in wheat leaves during 45 days of inoculations. Disease incidence was decreased significantly in MJ-treated plants as seed soaking plus foliar spray with 20 and 30 mM when compared to 10 mM MJ or control plants. The study revealed that, with increasing concentrations of MJ, the secondary metabolites were greatly increased. Endogenous levels of both free and conjugated putrescine, spermidine and spermine increased in response to the elicitor. Activities of polyamine biosynthetic enzymes of ornithine decarboxylase (ODC) and polyamine oxidase (PAO) displayed up to threefold increases relative to untreated control. Moreover, significant increases in activities of plant defense-related protein, enzymes as peroxidase and chitinase as well as free and conjugated phenols contents were recorded in treated plants compared with untreated and infected plants. Furthermore, MJ treatment increased the chlorophyll-a, chlorophyll-b and carotenoids pigments contents, the higher increase was obtained with combined treatment between seeds soaking plus foliar spray at 20 and 30 mM of MJ. Under field conditions, three concentrations of MJ, i.e. 10, 20 and 30 mM as combined treatment between seeds soaking plus foliar spray or only as foliar spray were applied to study their effect against rust disease. Foliar spray was applied after 30 and 80 days of sowing. Results showed that the high reduction in disease severity was obtained with combined treatments between seeds soaking plus foliar spray with MJ at 20 and 30 mM compared with other treatments and control. At the same time, all treatments increased the growth and grain yield of wheat plants. It could be suggested that combination treatment between seeds soaking plus foliar spray with methyl jasmonate might be used commercially for controlling rust disease of wheat plants under field conditions.     

Direct Delivery of Inoculum to Shoot Tissue Interferes with Genotypic Resistance to Ralstonia solanacearum in Tomato Seedlings

Employing known susceptible and resistant genotypes and pure bacterial inoculum (0.1 OD; 10⁸ CFU/ml^?1), five different inoculation methods were tried to assess the response of tomato genotypes to Ralstonia solanacearum. This included seed‐soaking inoculation, seed‐sowing followed by inoculum drenching, or at 2‐week stage through petiole‐excision inoculation, soaking of planting medium with inoculum either directly or after imparting seedling root‐injury. Seed‐based inoculations or mere inoculum drenching at 2 weeks did not induce much disease in seedlings. Petiole inoculation induced 90–100% mortality in susceptible checks but also 50–60% mortality in normally resistant genotypes within 7–10 days. Root‐injury inoculation at 2‐week seedling stage appeared the best for early and clearer distinction between resistant and susceptible lines. The observations suggest a role played by the root system in governing genotypic resistance to the pathogen. Direct shoot inoculation is to be adopted only for selecting highly resistant lines or to thin down segregating populations during resistance breeding.     

Effect of salicylic acid and methyl jasmonate on phenylalanine ammonia-lyase activity and total phenol in wheat infected by Pratylenchus thornei

The effect of biochemical responses in wheat seedlings cultivar Falat against lesion nematode (Pratylenchus thornei) was investigated by two factors inducer resistance salicylic acid (SA) and methyl jasmonate (MeJA). Foliar sprays with 1?ml SA 1?mM and 1?ml MeJA 100?μM was conducted on 20-day-old wheat (cv. Falat) seedlings. About 24?h after foliar sprays, plants were inoculated by root lesion nematode. Phenylalanine ammonia-lyase (PAL) activity was increased significantly in all treatments two days after inoculation over control. However, PAL activity was decreased in all treatments five days after inoculation in compared to control. What is more, in both time points, total phenol increased in all treatments over control. The comparison of both inducers SA and MeJA on total phenol in healthy and infected wheat seedlings in both days two and five after inoculation of nematode indicated that total phenol has decreased significantly in all treatments in the fifth day.     

不同BR施用方式诱导黄瓜幼苗对Ca(NO_3)_2胁迫抗性的研究

为探讨外源油菜素内酯(brassinosteroid,BR)诱导黄瓜幼苗对Ca(NO3)2胁迫抗性的效果,研究了3种外源BR施用方法(0.01mg·L-1 BR浸种、0.1mg·L-1 BR喷叶及其二者结合施用)对Ca(NO3)2胁迫(60mmol·L-1)下黄瓜幼苗生长、生理活动以及光合作用的影响。结果表明:(1)3种外源BR方法处理后,Ca(NO3)2胁迫下的黄瓜幼苗株高、茎粗、展开叶片数、叶面积、干重含水量均显著提高,同时其叶片游离脯氨酸和可溶性糖含量上升,过氧化物酶活性提高,而其丙二醛(MDA)含量趋于无Ca(NO3)2胁迫对照的水平;(2)外源BR处理还提高了Ca(NO3)2胁迫下黄瓜幼苗的净光合速率、蒸腾速率和气孔导度,却抑制了Ca(NO3)2胁迫下胞间CO2浓度的升高。研究认为,适宜浓度的外源BR浸种和喷叶处理均可有效增强黄瓜幼苗渗透调节能力,降低细胞膜质过氧化伤害程度,提高抗氧化酶活性和光合效率,从而表现出对Ca(NO3)2胁迫的抗性,并以操作简便、用量极低的0.01mg·L-1 BR浸种方法效果最佳。     

Free and glucosylated phenolics, phenol β-glucosyltransferase activity and membrane permeability in cucumber roots affected by derivatives of cinnamic and benzoic acids

Seven-day-old seedlings of cucumber (Cucumis sativus L.) cv. Wisconsin were treated with 0.01, 0.1 and 0.5 mM solutions of derivatives of cinnamic acid (ferulic and p-coumaric acids) and benzoic acid (p-hydroxybenzoic and vanillic acids) as stress factors. In cucumber roots phenolics (free and glucosylated), phenol β-glucosyltransferase (E.C. 2.4.1.35) activity as well as membrane permeability were examined. The most intensive glucosylation took place in the first hour of stress duration in roots treated with 0.01 mM ferulic and p-coumaric acids and with 0.01 and 0.1 mM p-hydroxybenzoic and vanillic acids. At these concentrations a high phenol β-glucosyltransferase activity was found. The deterioration of capacity for phenolic glucosylation as well as the decrease of the phenol β-glucosyltransferase was observed at the higher concentrations. It was associated with increased membrane permeability.     

Spider mites (Tetranychus urticae) perform poorly on and disperse from plants exposed to methyl jasmonate

Jasmonates are plant hormones involved in wound and defense responses against herbivorous arthropods. Methyl jasmonate (MeJA) is used experimentally to induce defense responses in plants. In experiments outlined here we utilized a novel preference assay with unwounded plants that allowed us to study the impact of a MeJA spray on subsequent Tetranychus urticae Koch (Acari: Tetranychidae) proliferation and preference. Spraying plants with 100 μm MeJA 1 day before infestation caused mites to disperse within 2 days from treated impatiens [Impatiens wallerana Hook f., ‘Super Elfin Pink’ (Balsaminaceae)], pansy [Viola × wittrockiana Gams, ‘Imperial Beaconsfield’ (Violaceae)], and tomato [Solanum lycopersicum L., ‘Big Boy’ (Solanaceae)] plants. In addition, MeJA application reduced mite proliferation rate on impatiens and pansy by 60% (measured 22–34 days after infestation). Proteinase inhibitor (PI) assays suggested that MeJA‐induced PIs alone were not responsible for the observed results in pansy and impatiens but may have been a factor in tomato. Implications of these results in the context of MeJA‐induced resistance responses and possible directions for future research and application are discussed.     

Enhancement of root hydraulic conductivity by methyl jasmonate and the role of calcium and abscisic acid in this process

The role of jasmonic acid in the induction of stomatal closure is well known. However, its role in regulating root hydraulic conductivity (L) has not yet been explored. The objectives of the present research were to evaluate how JA regulates L and how calcium and abscisic acid (ABA) could be involved in such regulation. We found that exogenous methyl jasmonate (MeJA) increased L of Phaseolus vulgaris, Solanum lycopersicum and Arabidopsis thaliana roots. Tomato plants defective in JA biosynthesis had lower values of L than wild‐type plants, and that L was restored by addition of MeJA. The increase of L by MeJA was accompanied by an increase of the phosphorylation state of the aquaporin PIP2. We observed that MeJA addition increased the concentration of cytosolic calcium and that calcium channel blockers inhibited the rise of L caused by MeJA. Treatment with fluoridone, an inhibitor of ABA biosynthesis, partially inhibited the increase of L caused by MeJA, and tomato plants defective in ABA biosynthesis increased their L after application of MeJA. It is concluded that JA enhances L and that this enhancement is linked to calcium and ABA dependent and independent signalling pathways.     

Bacillus halotolerans strain LYSX1-induced systemic resistance against the root-knot nematode Meloidogyne javanica in tomato

Purpose

Determination of the nematicidal potential and mode of action of bacteria isolated from tobacco rhizosphere soil against the root-knot nematode Meloidogyne javanica in tomato plants.

Methods

Antagonistic bacteria were isolated from rhizosphere soil of tobacco infested with root-knot nematodes. Culture filtrate was used to examine nematicidal activity and ovicidal action of bacterial strains. Biocontrol of M. javanica and growth of treated tomato plants were assessed in pot experiments. To clarify whether secondary metabolites of bacteria in tomato roots induced systemic resistance to M. javanica, bacterial culture supernatants and second-stage juvenile nematodes were applied to spatially separated tomato roots using a split-root system. Bacterial strains were identified by 16S rDNA and gyrB gene sequencing and phylogenetic analysis.

Results

Of the 15 bacterial strains isolated, four (LYSX1, LYSX2, LYSX3, and LYSX4) demonstrated nematicidal activity against second-stage juveniles of M. javanica, and strain LYSX1 showed the greatest antagonistic activity; there was dose-dependent variability in nematicidal activity and inhibition of egg mass hatching by strain LYSX1. In vivo application of LYSX1 to tomato seedlings decreased the number of egg masses and galls and increased the root and shoot fresh weight. Treatment of half of the split-root system with LYSX1 reduced nematode penetration to the other half by 41.64%. Strain LYSX1 was identified as Bacillus halotolerans.

Conclusion

Bacillus halotolerans LYSX1 is a potential microbe for the sustainable biocontrol of root-knot nematodes through induced systemic resistance in tomato.

     

番茄内生菌的分离鉴定及菌株FQ-G3抗病促生特性

由灰葡萄孢(Botrytis cinerea)引起的灰霉病是番茄生产中最重要的病害之一,当前使用的杀菌剂因药物残留、病原菌抗药性及食品安全等原因逐渐受到限制。因此,利用拮抗微生物的生物防治逐渐成为灰霉病防控的有效策略。【目的】从番茄植株体内筛选具有抗病促生特性内生菌株并对其生防潜力进行评估,为开发番茄灰霉病生物防治新策略提供理论依据。【方法】采用组织分离法在番茄植株不同部位分离出内生细菌、真菌,结合16SrRNA和ITS序列分析,对候选菌株进行初步鉴定;通过菌株对峙培养、果实离体接种筛选对灰葡萄孢具有拮抗活性的内生菌;进一步测定菌株分泌生长素、嗜铁素的能力及其对拟南芥和番茄幼苗生长的促生特性。【结果】从番茄植株不同部位共分离出72株内生细菌和31株内生真菌,通过平板对峙法筛选出1株对多种病原菌具有较好抑菌活性的内生细菌FQ-G3,分子鉴定为Bacillus velezensis。FQ-G3对灰葡萄孢抑菌率达80.93%,并显著抑制灰葡萄孢在番茄果实上的扩展。该菌株能够分泌生长素、蛋白酶和嗜铁素,且对拟南芥、番茄幼苗具有明显的促生效果。【结论】本研究表明分离自番茄植株的内生菌FQ-G3具...     

Import of polyphenol oxidase by chloroplasts is enhanced by methyl jasmonate

Polyphenol oxidase (PPO; EC 1.10.3.2 or EC 1.14.18.1) takes part in the response of tomato plants (Lycopersicon esculentum Mill.) to wounding and herbivore attack, mediated by the octadecanoid wound-signaling pathway. Wounding and methyl jasmonate (MeJA) induce expression of ppo genes and markedly increase the level of the enzyme. We report that pretreatment with MeJA also markedly increased the ability of isolated tomato chloroplasts to import and process PPO precursors (pPPO). Pea (Pisum sativum L.) chloroplasts showed no such response. Wounding or ethylene alone was ineffective but ethylene was synergistic with MeJA. Treatment with MeJA conferred a strong binding of pPPO, or its processing intermediate, to thylakoids and subsequent translocation into the lumen and processing to the mature protein. The effect on PPO import and translocation was evident after 8–16 h exposure to MeJA. Membrane-bound pPPO was cross-linked to a proteinaceous component of the thylakoid translocation apparatus, apparently induced by MeJA. The import and processing of other nuclear-encoded thylakoid proteins were not affected by MeJA in tomato. A 90-kDa protein that co-fractionated with thylakoids was induced along with the increase in competence for PPO import, and was identified as the proteinase-inhibitor multicystatin. It is concluded that the 90-kDa protein observed is part of the MeJA-induced defense response of tomato, not a component of the thylakoid translocation apparatus.Abbreviations Chl Chlorophyll - i and p Prefixes used to denote the intermediate and precursor forms of a protein, respectively - JA Jasmonic acid - LSU Large subunit of Rubisco - MeJA Methyl jasmonate - OE23 and OE33 23- and 33-kDa subunits of the oxygen-evolving complex of PSII - PC Plastocyanin - pPPO (iPPO, PPO) Precursor (intermediate, mature) form of polyphenol oxidase     

Specificity of 1-triacontanol as a plant growth stimulator and inhibition of its effect by other long-chain compounds

The effect of several analogs of 1-triacontanol (TRIA), differing in C-chain length (16–32), the position of the hydroxyl group and the terminal functional group, were tested alone and in combination with TRIA on the growth of rice (Oryza sativa L.), maize (Zea mays L.) and tomato (Lycopersicon esculentum Mill.) seedlings. Applied alone, none of the compounds caused an increase in growth; thus, chain length (30 C) and presence and position (terminal) of the hydroxyl group appear to be specific for the growth-promoting activity of TRIA. When applied simultaneously with TRIA, all analogs inhibited the response to the latter in all three test plants, whether applied in the nutrient solution, as foliar spray or by seed soaking. 1-Octacosanol inhibited the response of rice seedlings to 2.3 x 10^-8 M TRIA at concentrations as low as 2.4 x 10^-12 M. Thus preparations of TRIA and application equipment must be free from trace amounts of other long-chain compounds if they are to be used to increase plant growth.Abbreviation TRIA 1-triacontanol     

Marker Gene Overexpression in Flowers Treated with Resistance Inducers does not Correlate with Protection Against Flower‐Infecting Fungi in Tomato and Blueberry

Flowers can serve as infection courts for specialized and unspecialized plant pathogens, but little is known about the ability of floral tissues to undergo induced resistance (IR) responses against these pathogens. We studied the expression of IR marker genes in tomato and blueberry flowers treated with the inducers methyl jasmonate (MeJA), benzothiadiazole‐S‐methyl ester (BTH) and 2,6‐dichloroisonicotinic acid (INA). In tomato, spray application of MeJA and BTH (but not INA) to entire plants (leaves, stems and flowers) resulted in a significant (P < 0.05) overexpression of Pin2 (5.2‐fold) and PR‐4 (5.6‐fold) in pistil tissues, respectively. A statistically similar expression was obtained in pistils when flowers were protected from direct spray, indicating a systemic response. In blueberry, where information about IR marker genes is limited, PR‐3 and PR‐4 orthologs were first identified and characterized using in silico and wet‐laboratory techniques. In subsequent induction experiments, INA and BTH induced overexpression of PR‐4 in blueberry pistils by 3.2‐ and 1.8‐fold, respectively, when entire plants were treated. In blueberry flowers protected from spray applications, all chemicals applied to vegetative tissues led to significant overexpression of PR‐4 (MeJA: 1.4‐fold, BTH: 2.9‐fold and INA: 1.6‐fold), with BTH also inducing PR‐3 (1.7‐fold). The effect of these responses in protecting flowers was studied by inoculating treated tomato flowers with the necrotroph Botrytis cinerea and blueberry flowers with the hemi‐biotroph Monilinia vaccinii‐corymbosi. In both pathosystems, no significant disease suppression associated with resistance inducer application was observed under the conditions studied. Thus, although IR marker genes were shown to be inducible in floral tissue, the magnitude of this response was insufficient to suppress pathogen ingress.