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1.
The total fatty acids (FA) composition of Blumeria graminis f.sp. tritici conidia, the causal agent of wheat powdery mildew, was analyzed as a function of their age. A total of 19 FA (C12-C24 saturated and unsaturated) and unusual methoxylated fatty acids (mFA) were detected in young, intermediate and old conidia. Two very long chain methoxylated FA were identified by GC-MS as 3-methoxydocosanoic and 3-methoxytetracosanoic acids. Medium chain FA were predominant in young conidia (75%, including 13% of mFA) while very long chain fatty acids constituted the major compounds in old conidia (74%, including 30% of mFA). We have shown for the first time that the total FA composition is strongly correlated with the age of B. graminis f.sp. tritici (Bgt) conidia.  相似文献   

2.
Prophylactic efficacies of Iodus 40 and salicylic acid (SA) against wheat powdery mildew caused by Blumeria graminis f. sp. tritici have been shown and compared with those of heptanoyl salicylic acid (HSA) and trehalose. Plantlets treated once exhibited 55%, 50%, 95%, and 38% protection levels, respectively. Two sprayings increased these levels up to 60%, 65%, 100%, and 60%, respectively. Biological effects of these resistance inducers on reactive oxygen species (ROS) metabolism and lipid peroxidation were also investigated. We found clear differences in the extent and the type of induced responses, with HSA exhibiting both the most numerous and the highest effects. HSA and SA induced a 5.5-fold increase of whole cell DAB staining due to hydrogen peroxide accumulation, whereas Iodus 40 and trehalose increased staining intensity at the penetration sites only. However, these effects were not correlated with any modification of catalase (CAT), oxalate oxidase (OXO) or lipoxygenase (LOX) activities, except for HSA which decreased CAT in non-inoculated conditions and increased LOX in infectious conditions. HSA also induced an increase in the rate of lipid peroxidation, whereas Iodus 40 induced a decrease. The effects of the inducers on germinating conidia and wheat epidermal cells responding to fungal penetration were also investigated. Papilla-linked autofluorescence was affected by SA and Iodus 40 whereas germination was slightly altered by Iodus 40. The newly described protective efficacies and the partial, distinct and non-overlapping activities of these inducers on the wheat/powdery mildew interaction are discussed.  相似文献   

3.
Blumeria (=Erysiphe) graminis f.sp. tritici (Bgt), the causal agent of wheat powdery mildew, is responsible for an important disease leading to considerable yield reductions in wheat worldwide. Conidia of the obligate plant pathogen Bgt were analysed for their total fatty acid (FA) composition as a function of their ontogeny. A total of 17 FAs were detected (C(12)-C(24) saturated and unsaturated ones), including the presence of unusual long-chain monoenoic FAs. In young conidia, the major FAs were C(18:2) (23%), C(16:0) (16%), C(18:0) (15.2%) and C(18:1) (14.3%). In old conidia, the main FAs were C(24:1) (20.7%), C(22:0) (15%), C(22:1) (13.5%) and C(24:0) (9.7%). The amount of total FA was about 39 microg.mg of dry weight(-1) in young conidia and decreased clearly to 18 microg.mg of dry weight(-1) in older conidia. For the first time, we have demonstrated that the FA composition of conidia changes greatly with age. Medium-chain FAs (C(12)-C(18)) are predominant in very young conidia (75%), whereas long-chain FAs (C(22)-C(24)) are the major compounds in old conidia (74%). This study showed a significant elongation of FAs and a drastic decrease in the total FA amount during the ontogeny of conidia.  相似文献   

4.
During primary infection by conidia ofErysiphe graminis f. sp.tritici, three mechanisms of resistance operate in first leaves of 8-day-old seedlings of both resistant and susceptible wheats. The first mechanism, operating at the penetration site, is responsible for the failure of penetrations attempted by primary germ tubes (PGT). The second mechanism is concerned with the abortion of haustoria in normal-appearing host cells. The third mechanism relates to the abortion of haustoria and the hypersensitivity of the penetrated host cells.With the inoculum-level of 19–24 conidia/mm2, the three mechanisms together prevented 89.3 % of the attempted penetrations by PGT from producing normal haustoria in resistant wheat Purdue 5752C1-7-5-1 and 37.4 % in the susceptible wheat Vermillion. The first mechanism accounted for the prevention of 73.3 % of the attempted PGT penetrations on Purdue 5752C1-7-5-1 and 36 % on Vermillion. The second mechanism was responsible for stopping 19 % of all the successful penetrations in Purdue 5752C1-7-5-1 and 0.8 % in Vermillion. The third mechanism accounted for the failure of 41 % of all the successful penetrations in Purdue 5752C1-7-5-1 and 1.4% in Vermillion. Thirty-six hours after inoculation, 10.7% of all the attempted PGT penetrations appeared to be developing normally in first leaves of 8-day-old seedlings of resistant wheat Purdue 5752C1-7-5-1 as compared to 62.6 % in the susceptible wheat Vermillion.This appears to be the first report showing the relative effectiveness of various mechanisms of resistance concerning any powdery mildew fungus.  相似文献   

5.
Plant immunity against the majority of the microbial pathogens is conveyed by a phenomenon known as non-host resistance (NHR). This defence mechanism affords durable protection to plant species against given species of phytopathogens. We investigated the genetic basis of NHR in Arabidopsis against the wheat powdery mildew fungus Blumeria graminis f. sp. tritici (Bgt). Both primary and appressorial germ tubes were produced from individual Bgt conidia on the surface of the Arabidopsis leaves. Attempted infection occasionally resulted in successful penetration, which led to the development of an abnormal unilateral haustorium. Inoculation of a series of Arabidopsis defence-related mutants with Bgt resulted in the attenuation of reactive oxygen intermediate (ROI) production and salicylic acid (SA)-dependent defence gene expression in eds1, pad4 and nahG plants, which are known to be defective in some aspects of host resistance. Furthermore, Bgt often developed bilateral haustoria in the mutant Arabidopsis lines that closely resembled those formed in wheat. A similar decrease in NHR was observed following treatment of the wild-type Arabidopsis plants with cytochalasin E, an inhibitor of actin microfilament polymerisation. In eds1 mutants, inhibition of actin polymerisation severely compromised NHR in Arabidopsis against Bgt. This permitted completion of the Bgt infection cycle on these plants. Therefore, actin cytoskeletal function and EDS1 activity, in combination, are major contributors to NHR in Arabidopsis against wheat powdery mildew.  相似文献   

6.
7.
This work presents a global investigation of total fatty acid (FA) content in wheat in relation to treatment with four inducers of resistance and to powdery mildew infection. Linolenic acid (C18:3), linoleic acid (C18:2) and palmitic acid (16:0) were the most abundant FAs in wheat leaves. We investigated the effect of the following inducers of resistance: Iodus40, heptanoyl salicylic acid (HSA), Milsana and trehalose on FA accumulation. Previous studies established that lipid metabolism is altered by these compounds, and we therefore aimed to characterise their impact at the FA level. During a time course experiment, content (quantitative analysis) and percentage (qualitative analysis) of FAs were compared in treated plants and in controls, as well as in plants inoculated with Blumeria graminis f. sp. tritici (i) and non-inoculated (ni) plants. No change in C18:3 content was observed. C18:1 in Iodus 40-treated (ni) plants showed a quantitative 1.2-fold increase. Lauric acid (C12:0) content quantitatively increased after Iodus 40 (2.8-fold), Milsana (4.8-fold) and trehalose (4.0-fold) treatment in (i) plants. However, eicosadienoic acid (C20:2) quantitatively decreased in (ni) plants after Iodus 40 (1.5-fold) and Milsana (2.3-fold) treatment. The amount of C18:2 increased (1.6-fold) after HSA treatment in (i) plants. All these variations in FA content were correlated with variations in the corresponding relative percentages. Our work provides the first evidence for alterations in C12:0, C18:1, C18:2 and C20:2 FA content caused by four resistance inducers. We also compared the amount and percentage of each FA in untreated (i) and (ni) plants. In (i) plants, eicosadienoic acid (C20:2) increased and C18:2 decreased slightly. The potential involvement of these FAs during induced resistance and infection is discussed.  相似文献   

8.
Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most consistently damaging diseases of common wheat worldwide and greatly affects crop productivity. Recently, several plant microRNAs (miRNAs) have been reported as gene expression regulators related to various adverse environments. However, up to now, less is known on the roles of miRNAs in powdery mildew infection response of wheat. In this study, miRNA expression patterns were investigated for identifying Bgt‐responsive miRNAs in wheat leaves using a plant miRNA microarray platform. A total of 79 miRNAs from 24 families were detected in wheat leaves. Among those, seven miRNAs were further validated to be involved in wheat powdery mildew response and two of them have never been reported. In addition, their target expression profiles showed a negative correlation with that of the seven miRNAs in mock‐ and Bgt‐infected samples furtherly proved, which in turn as the robust evidence, that those seven powdery mildew‐responsive miRNAs are highly reliable. These findings could extend the current view about miRNAs as ubiquitous regulators under stress conditions.  相似文献   

9.
10.
用半定量RT-PCR方法分析小麦TaMlo-A1c基因的表达   总被引:8,自引:0,他引:8  
以小麦稳定表达的肌动蛋白基因(Actin)作为对照,利用半定量反转录聚合酶链式反应(Semi-QRT-PCR)技术,对与抗白粉病有关的小麦(TriticumaestivumL.)TaMlo-A1c基因的表达进行了研究。结果发现:TaMlo-A1c基因在小麦的叶、茎、根中均表达,穗中不表达,在白粉菌(Blumeriagraminis(DC.)E.O.Speerf.sp.triticiEm.Marchal,Bgt)诱导不同时间后小麦叶片中的表达稍微有所增强。研究表明,用半定量RT-PCR技术研究小麦基因表达,具有特异性高、操作简便和可靠性强的优点。  相似文献   

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