Genetic, phenotypic and pathogenic diversity among xanthomonads isolated from pistachio (Pistacia vera) in Australia

Repetitive extragenic palindromic polymerase chain reaction (rep-PCR), sequencing of the 16S−23S rDNA internal transcribed spacer (ITS), biochemical and physiological tests, the Biolog microplate system, polyacrylamide gel electrophoresis (PAGE) of whole-cell proteins, and pathogenicity tests were used to characterize variability among xanthomonads isolated from pistachio trees suffering from bacterial dieback in four regions of Australia. ITS sequencing and rep-PCR revealed two distinct genotypes among the strains. The ITS sequencing suggested that the pistachio strains were closely related to Xanthomonas translucens pathovars, in particular X. translucens pv . poae . Results of physiological and biochemical tests, as well as Biolog microplate analysis and protein profiling, confirmed the existence of two groups. Furthermore, pathogenicity and host-range studies indicated that the two groups were biologically different. There was an association between the two groups and the geographical origin of the strains.     

Seed Development,Oil Accumulation and Fatty Acid Composition of Drought Stressed Rapeseed Plants Affected by Salicylic Acid and Putrescine

Two field experiments were carried out in 2017 and 2018 to evaluate the impacts of salicylic acid (1?mM SA) and putrescine (1?mM Put) on leaf osmolytes, seed reserve and oil accumulation and fatty acid composition of rapeseed (Brassica napus L.) under different watering levels (irrigations after 70 and 150?mm evaporation as normal irrigation and severe drought stress, and 70?→?90?→?110?→?130?→?150 and 70?→?100?→?130→150 as gradual and moderately gradual water deficits, respectively). The experiments were laid out as split plot on the bases of randomized complete block design in three replications. Water stress increased the contents of glycine betaine, proline, soluble sugars, and proteins. Application of SA and Put further enhanced the contents of glycine betaine and soluble sugars, while reduced proline content of leaves. Seed filling duration, seeds per plant, plant biomass and seed yield were decreased with increasing irrigation intervals. Exogenous SA and Put enhanced all of these parameters under different irrigation intervals. Oil accumulation in seeds was diminished as water stress severed. The gradual water deficit considerably reduced the impacts of drought stress on yield related traits and oil content per seed, due to stress acclimation of plants. Oil content of seeds was augmented by SA and Put treatments through prolonging seed filling duration, particularly under limited irrigations. Percentages of palmitic acid and stearic acid (saturated fatty acids) were not affected by water limitation. However, unsaturated fatty acids of linoleic and linolenic acids were reduced, and oleic acid was enhanced due to water shortage. Unsaturation index was improved by SA and Put treatments under severe water stress as a result of decreasing oleic acid and increasing linoleic and linolenic acids contents. The SA spray was the best treatment for improving rapeseed seed and oil production under normal and stressful conditions.

     

Physiochemical Responses of Stevia rebaudiana Bertoni Subjected to Sodium Chloride (NaCl) Salinity and Exogenous Salicylic Acid Application

Gesunde Pflanzen - Soil salinity is one of the ecological problems limiting plant growth and development, especially in semi-arid and arid regions where water availability is very limited. Stevia...     

Enhancement of Postharvest Disease Resistance in Ya Li Pear (Pyrus bretschneideri) Fruit by Salicylic Acid Sprays on the Trees during Fruit Growth

The Ya Li pear (Pyrus bretschneideri) trees were sprayed three times with 2.5 mM salicylic acid (SA) around 30, 60 and 90 days after full flowering. The fruit were harvested at commercial maturity (about 120 days after full flowering), inoculated with Penicillium expansum, and incubated at 20 °C, 95–100% RH. The results showed that resistance to the pathogen of the mature pear fruit was remarkably enhanced by the SA sprays. Disease incidence in the SA-treated fruit was 58.0% or 26.5%, and lesion diameter on SA-treated fruit was 58.4% or 29.0% lower than that in/on fruit without SA treatment (control) on day 12 or 17 after incubation, respectively. The SA spray applied to the trees around 30 days after full flowering notably enhanced accumulation of hydrogen peroxide in the young fruit. Meanwhile, activities of defense enzymes, including peroxidase, phenylalanine ammonia-lyase (PAL), chitinase or β-1,3-glucanase in the young fruit from SA-treated trees was 29.5%, 60.0%, 24.4% or 35.7% higher than that in the control fruit 4 days after the SA spraying. Furthermore, after harvest, activities of PAL, chitinase and β-1,3-glucanase were still significantly higher in the mature pear fruit from the trees sprayed three times with SA than those of the control fruit. Activities of the antioxidant enzymes including catalase and ascorbate peroxidase in the young fruit were significantly reduced by SA spraying. However, the activity of another antioxidant enzyme, glutathione reductase in the young fruit was significantly enhanced by SA spraying. These results suggest that enzymes exerting their functions in different ways may be coordinately regulated by SA in the pear fruit. Our study indicates that treatment of SA sprays on the trees may provide further protection against postharvest disease of Ya Li pear fruit in practice and could be used as an alternative and economical approach to reduce application of chemical fungicides.     

Grain Yield and Qualitative of Rapeseed Genotypes Change in Response to Exogenous Application of Salicylic Acid and Planting Density

Gesunde Pflanzen - A factorial split-plot experiment (2015–17) was carried out in a randomized complete block design with three replications at Karaj, Iran, to investigate...     

Attenuation of Negative Effects of Saline Stress in two Lettuce Cultivars by Salicylic Acid and Glycine Betaine

Reducing destructive effects of lettuce plants irrigated with saline water was investigated in two field experiments conducted at Ismailia Governorate in 2012–2013 and 2013–2014. Two lettuce (Lactuca sativa L.) cultivars, Great Lakes and Balady, irrigated with saline water (3.22 dS/m) were treated using two levels of salicylic acid (SA) and glycine betaine (GB) as a foliar application (200, 400 ppm and 15, 30 Mm, respectively). Generally, application of SA and GB enhanced growth parameters, i.?e. plant height; root length; number of leaves per plant; plant fresh and dry weight; leaf relative water content (LRWC); membrane permeability (MP); lipid peroxidation (MDA); chlorophyll a, b and carotenoid content in leaf; proline; total soluble sugars (TSS); superoxide dismutase (SOD) and peroxidase (POD) activity; and Na, K, Ca content. GB treatments significantly increased most recorded growth parameters, especially at 30 mM, while this treatment decreased values of MP, (MDA) and Na content in two lettuce cultivars.     

Role of Salicylic Acid in Systemic Resistance Induced by Pseudomonas spp. Against Pythium aphanidermatum in Cucumber Roots

Pseudomonas corrugata strain 13 and P. aureofaciens strain 63-28, applied to roots, induced systemic resistance against Pythium aphanidermatum in cucumber roots. Salicylic acid (SA) from bacterial culture or plant tissues was quantified by high performance liquid chromatography. Both strains produced SA in King's B broth and also induced cucumber root to accumulate endogenous SA one day after bacterial inoculation. Using a split root system, more SA accumulated in roots treated with bacteria than in distant roots on the opposite side of the root system in the first two days, but this difference disappeared after 3–4 days. SA levels were significantly higher in plants treated with bacteria compared to the split control, from one to five days after bacterization. SA did not inhibit mycelial growth of Pythium aphanidermatum at 100–200µgml^–1 in vitro, but higher levels inhibited mycelial growth. Zoospore germination increased at concentrations of 10–500µgml^–1, but decreased at 1000µgml^–1 compared to lower concentrations. Exogenously applied SA failed to induce local or systemic resistance against a challenge infection by the pathogen in planta. The results of this study show that exogenous applied SA does not induce systemic resistance to cucumber root rot caused by P. aphanidermatum, but endogenous SA accumulation in cucumber roots may be involved in induced systemic resistance.     

Impact of Exogenous Application of Salicylic Acid on Growth,Water Status And Antioxidant Enzyme Activity of Strawberry Plants (Fragaria vesca L.) Under Salt Stress Conditions

Irrigation with saline water can act as an alternate water resource and thus plays an important role in saving freshwater resources as well as promoting agriculture. Furthermore, salinity stress is considered one of the major abiotic stress factors, which strongly reduces crop productivity. In this context, the present work was conducted to examine the effect of exogenous salicylic acid (SA) application on salt stress tolerance of strawberry plants. For this purpose, strawberry plants (Fragaria vesca L.), three months old, were treated with three SA concentrations (0?mM, 0.25?mM and 0.5?mM), then subjected to 80?mM NaCl or not. After five weeks of treatment, growth responses, water status, photochemical efficiency and oxidative stress indicators were measured. The obtained results showed that irrigation with saline water negatively affected the growth parameters, the leaf water potential (LWP), the relative water content (RWC), the stomatal conductance (gs) and photochemical efficiency (Fv/Fm). While, the total protein content, the electrolyte leakage (EL), the malondialdehyde (MDA) and the hydrogen peroxide (H₂O₂) contents were increased in stressed plants compared to unstressed ones. Salt stress also leads to the activation of the antioxidant enzymes. However, the exogenous application of SA under salt stress conditions reduced the H₂O₂ accumulation, the electrolyte leakage and the MDA content. It has also improved the growth parameters, the LWP, the RWC, the gs, the Fv/Fm, the protein content and the antioxidant enzyme activities (POD, CAT and SOD) in the treated plants compared to those without SA application. Therefore, the beneficial effect of 0.25?mM SA on Fragaria vesca L. salinity tolerance may provide some practical basis for strawberry cultivation under saline conditions.

     

盐、旱及其交叉胁迫对银沙槐幼苗保护酶活性的影响

为了研究银沙槐[Ammodendron argenteum(Pall.)Kuntze]幼苗对盐、旱及其交叉胁迫的适应性,采用盆栽试验的方式研究盐、旱及其交叉胁迫对银沙槐幼苗保护酶活性的影响.结果显示:在轻度和中度干旱、盐分的单一胁迫处理下,银沙槐幼苗超氧歧化酶(SOD)、过氧化物酶(POD)和过氧化氢酶(CAT)活性均上升.盐、旱交叉胁迫时,T2D胁迫前,银沙槐幼苗的SOD,POD和CAT活性均上升,三者协调一致.重度盐分、重度盐旱交叉胁迫下,银沙槐幼苗体内的SOD,POD和CAT保护酶的活性不能维持较高水平.表明保护酶在银沙槐的抗逆性上起到了积极的调节作用,在盐、旱交叉胁迫下表现出适应性,适度的盐分胁迫可增强银沙槐的抗旱能力.该研究为深入了解不同胁迫下银沙槐生长发育特征提供了依据.     

Control of Loose Smut (Ustilago nuda and U. tritici) Infections in Barley and Wheat by Foliar Applications of Systemic Fungicides

Foliar application of a number of broad-spectrum systemic fungicides (particularly conazole fungicides) to loose smut-infected plants of wheat and barley in a 3-spray programme resulted in a marked reduction in the percentage of plants producing infected ears. Such foliar fungicides may have a previously unseen role in reducing the levels of loose smut infection in wheat and barley.     

灰色灾变理论在宁南山区干旱气候预测中的应用

在分析宁南山区干旱气候特征及其对农业生产影响的基础上 ,借助灰色灾变理论分别建立了春旱、夏旱、秋旱、春夏连旱、夏秋连旱、全年旱等六种干旱类型的 GM( 1 ,1 )预测模型 ,并对 2 0 0 0～ 2 0 2 0年的干旱气候做出预测。经对 2 0 0 0年和 2 0 0 1年预测结果验证 ,吻合性良好。此外 ,提出了宁南山区抗旱防旱的综合农业措施。研究结果可对广大旱区抗旱减灾 ,促进农业生产发展提供科学指导。     

Salicylic Acid Induced Insensitivity to Culture Filtrate of Fusarium oxysporum f.sp. zingiberi in the Calli of Zingiber officinale Roscoe

Salicylic acid (SA) was used to induce insensitivity in the callus cultures of Zingiber officinale against culture filtrate (CF) of Fusarium oxysporum f.sp. zingiberi. The treatment of callus cultures with SA (10⁴M) prior to selection with CF of the pathogen-increased callus survival. Exogenous application of SA resulted in increased activity of peroxidase and -1,3-glucanase enzymes in the callus cultures. No increase in the activity of phenylalanine ammonia lyase was obtained. Two new protein bands of 97 and 38kDa molecular weights were obtained by SDS-PAGE analysis of soluble proteins extracted from SA-treated calli. The PR-1 monoclonal antibody used for immunodetection of induced proteins cross-reacted with the 38kDa protein band. In vitro antifungal activity of protein extract of calli treated with SA tested against the spores of F. oxysporum f.sp. zingiberi showed significant reduction in spore germination and germ tube elongation. It is concluded that in ginger, SA may result in the induction of resistance to F. oxysporum f.sp. zingiberi by inducing increased activity of peroxidase, -1,3-glucanase and antifungal PR-proteins.     

朱砂叶螨酸性磷酸酯酶测定条件的研究

应用最优４因子组合测定朱砂叶螨（Ｔｅｔｒａｎｙｃｈｕｓｃｉｎｎａｂａｒｉｎｕｓ（Ｂｏｉｓｄｕｖａｌ）酸性磷酸酯酶，并进行了主因子效应分析。结果表明，在醋酸缓冲液ｐＨ值４．４、反应温度４２℃、温浴４０ｍｉｎ、底物８．５×１０^－３ｍｏｌ／Ｌ的组合条件，波长４０５ｎｍ下，该酶吸收值最大，其中温浴时间是影响朱砂叶螨酸性磷酸酯酶活性的关键因子     

Salicylic Acid Biosynthetic Genes Expressed in Pseudomonas fluorescens Strain P3 Improve the Induction of Systemic Resistance in Tobacco Against Tobacco Necrosis Virus

ABSTRACT Application of salicylic acid induces systemic acquired resistance in tobacco. pchA and pchB, which encode for the biosynthesis of salicylic acid in Pseudomonas aeruginosa, were cloned into two expression vectors, and these constructs were introduced into two root-colonizing strains of P. fluorescens. Introduction of pchBA into strain P3, which does not produce salicylic acid, rendered this strain capable of salicylic acid production in vitro and significantly improved its ability to induce systemic resistance in tobacco against tobacco necrosis virus. Strain CHA0 is a well-described biocontrol agent that naturally produces salicylic acid under conditions of iron limitation. Introduction of pchBA into CHA0 increased the production of salicylic acid in vitro and in the rhizosphere of tobacco, but did not improve the ability of CHA0 to induce systemic resistance in tobacco. In addition, these genes did not improve significantly the capacity of strains P3 and CHA0 to suppress black root rot of tobacco in a gnotobiotic system.     

Foliar absorption and translocation of 14C-dicamba into host (pearl millet and cowpea) and parasite plants of the genus Striga

The foliar absorption and translocation of ¹⁴C dicamba were investigated to determine the potential of this chemical as a selective herbicide for Striga control. After application of the labelled herbicide to the host, the uptake, measured 5 days after foliar treatment, reached 46 and 72% for cowpea (Vigna unguiculata) and pearl millet (Pennisetum glaucum), respectively. A high percentage of the herbicide was translocated into Striga plants, particularly into S. gesnerioides. The fraction recovered in this species reached 51.2% of the amount absorbed 5 days after foliar application. The distribution patterns of the herbicide after 1 and 5 days suggest that dicamba might be used as an effective pre-emergence spray for Striga control. Selective application to the parasite leaves showed that the bulk of the radioactivity remained in the parasites, a very low percentage of the amount absorbed (1.6 and 2.5% in pearl millet and cowpea, respectively) being translocated into the host, suggesting that post-emergence application of dicamba might also be useful in the control of Striga. Absorption foliaire et transport du dicamba ¹⁴C à Pintérieur de la plante-hôte (petit mil et Vigna) leurs parasites du genre Striga L'absorption foliaire et le transport du dicamba ¹⁴C ont étéétudiés en vue de déterminer le potentiel de cette molécule comme desherbant sé1ectif contre le Striga. Après application de ('herbicide marqué sur 1'hôte, 1'absorption, mesurée 5 jours aprés le traitement foliaire atteignait 46% et 72% pour Vigna unguiculata et le petit mil (Pennisetum glaucum) respective-ment. Un taux élevé d'herbicide était transporté dans les plantes de Striga, en particulier dans S. gesnerioides. La part retrouvée dans cette espéce a atteint 51,2% de la quantité absorbée, 5 jours après I'application foliaire. Les modèles de distribution de 1'herbicide après 1 et 5 jours conduisent à penser que le dicamba pourrait être utilisé efficacement comme un herbicide de prélevée contre Striga. Des applications sélectives sur les feuilles du parasite ont montré que la majeure partie de la radioactivité restait dans les parasites, un très faible pourcen-tage de la quantité absorbée (1,6 et 2,5% dans le petit mil et le pois à vache, respectivement) étant transporté dans 1'hôte suggérant qu'une application de post levée de dicamba peut aussi être utilisée pour lutter contre le Striga. Blattaufnahme und Translokation von ¹⁴C-Dicamba bei Wirtspflanzen (Perlhirse und Kuhbohne) und parasitischen Pflanzen der Gattung Striga Die Blattaufnahme und Translokation von ¹⁴C-Dicamba wurden untersucht, um die Möglichkeiten zur selektiven Bekämpfung von Striga-Arten mit diesem Wirkstoff zu bestimmen. 5 Tage nach der Applikation des radioaktiv markierten Herbizids wurde bei der Kuhbohne (Vigna unguiculata (L.) Walp.) eine Aufnahme von 46% und bei der Perlhirse (Pennisetum glaucum (L.) R.Br.) 72% gemessen. Eine große Menge des Herbizids wurde in die Striga-Pflanzen transloziert, besonders Striga gesnerioides, bei der zu dieser Zeit 51,2% der absorbierten Menge gefunden wurden. Das Verteilungsmuster des Herbizids nach l und 5 Tagen läßt vermuten, daß Dicamba als ein wirksames Vorauflaufmittel zur Striga-Bekämpfung genutzt werden kann. Nach Applikation auf die Blätter der parasitischen Pflanzen verblieb die Radioaktivität größtenteils in diesen Pflanzen, und in die Wirtspflanzen wurde davon nur ein sehr kleiner Teil transloziert (1,6% in die Perlhirse, 2,5% in die Kuhbohne), so daßStriga-Arten wohl auch im Nachauflauf mit Dicamba bekämpft werden können.     

Salicylic acid induced alleviation of oxidative stress caused by clethodim in maize (Zea mays L.) leaves

Salicylic acid is used for regulation of oxidative stress in plants subjected to unfavorable environmental conditions. Application of herbicides for the purpose of weed killing can affect not only the weeds but also the main crop as well. Many herbicides have the ability to cause oxidative stress and further degradation of cell components. In this work, SA was used to alleviate the oxidative stress caused in response to clethodim herbicide in maize leaves. The results demonstrated that, spraying of clethodim caused yellowing of leaves and sometimes browning or drying of leaf tips with high clethodim doses. Contrary, leaves showed no injuries when treated with 1 mM SA 3 days prior clethodim application. Elevated amounts of H₂O₂ and MDA were detected in clethodim treated leaves compared with control indicating ROS formation and lipid peroxidation. Excessive ROS formation led to oxidative stress which followed by degradation of membranous structures. In SA treated leaves, the contents of H₂O₂ and MDA were more or less similar to the corresponding controls. A change in the antioxidant enzymes activities due to clethodim and SA treatment was noticed. For example, the activities of POD and APX were induced while SOD and CAT were more or less reduced in response to clethodim. SA treatment prior clethodim application could induce POD but inhibit CAT. Moreover, SOD and APX activities were adjusted to be similar to those of the control. Another mechanism of SA regulation of the oxidative stress occurred through the formation of antioxidants in the form of phenolic compounds. For that, spraying SA with or without clethodim could accumulate phenolic compounds greatly. The DPPH free radical scavenging assay for leaf extracts had confirmed a change in antioxidant status. Furthermore, SA could enhance accumulation of total proteins and free amino acids in clethodim and SA treated leaves compared with the control. This work was to provide evidence for the ability of SA to regulate clethodim herbicide detoxification through regulation of the antioxidant status of maize leaf cells.