Moyen-Orient : Revue de presse du 17 au 23 mai 2021

Israël : vers la fin des hostilités ou une guerre à outrance ? - 17 mai 2021 Depuis la semaine dernière, les heurts entre l'État d'Israël et le Hamas ont fait près de 212 morts, dont 61 enfants à Gaza et 10 morts côté israélien. Lundi soir, Benyamin Netanyahou s'entretenait avec son homologue américain, Joe Biden, affirmant être en faveur d'un cessez-le-feu, sans nécessairement demander la fin des hostilités. Un cessez-le-feu donne de faibles espoirs car il ne permettrait pas d'engager un pro..

Phloridzin and phloretin are differentially converted during the Erwinia amylovora/apple tree interaction according to the susceptibility of genotypes

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Acibenzolar-S-methyl and resistance quantitative trait loci complement each other to control apple scab and fire blight

International audienceDiversifying disease control methods is a key strategy to sustainably reduce pesticides. Plant genetic resistance has long been used to create resistant varieties. Plant resistance inducers (PRI) are also considered to promote crop health, but their effectiveness is partial and can vary according to the environment and the plant genotype. We investigated the putative interaction between intrinsic (genetic) and PRI-induced resistance in apple when affected by scab and fire blight diseases. A large F1 mapping population was challenged by each disease after a pre-treatment with acibenzolar-S-methyl (ASM) and compared with the water control. Apple scab and fire blight resistance quantitative trait loci (QTLs) were detected in both conditions and compared. ASM exhibited a strong effectiveness in reducing both diseases. When combined, QTL-controlled and ASM-induced resistance acted complementarily to reduce the symptoms from 85% to 100% depending on the disease. In our conditions, resistance QTLs were only slightly or rarely affected by ASM treatment, despite their probable implication in various stages of the resistance build-up. Implications of these results are discussed considering already known results, the underlying mechanisms, cross-protection of both types of resistance against pathogen adaptation, and practical application in orchard conditions

The constitutive phenolic composition of two Malus x domestica genotypes is not responsible for their contrasted susceptibilities to fire blight

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699International audienceApple (Malus x domestica) leaf phenolics, in particular the three major dihydrochalcones, phloridzin, trilobatin and sieboldin, were studied for their potential contribution to the resistance to Erwinia amylovora, the causative agent of fire blight. The constitutive phenolic compositions of part of a progeny resulting from a cross between two apple genotypes, displaying contrasted susceptibilities to fire blight, were investigated by RP-HPLC-DAD. With regards to the major dihydrochalcones, offsprings were found to display the parent profile: either phloridzin alone or a combination of phloridzin, trilobatin and sieboldin. Despite a strong antioxidant activity that could interfere with the oxidative burst triggered by the bacteria, sieboldin did not segregate with resistance even though it was strongly associated with a high constitutive antioxidant capacity of leaf extracts. Several hydroxycinnamic acids and flavonols were identified in the progeny but profiles were very similar. However, concentrations of several flavonols positively correlated with resistance in the genotypes that possessed trilobatin and sieboldin. The major dihydrochalcones that represent more than 200 mg/g of leaf DW are not directly responsible for resistance to fire blight in this system. In addition, a high constitutive antioxidant activity is unlikely to be sufficient to block bacterial sprea

When a Plant Resistance Inducer Leaves the Lab for the Field: Integrating ASM into Routine Apple Protection Practices

Plant resistance inducers, also called elicitors, could be useful to reduce the use of pesticides. However, their performance in controlling diseases in the field remains unsatisfactory due to lack of specific knowledge of how they can integrate crop protection practices. In this work, we focused on apple crop and acibenzolar-S-methyl (ASM), a well-known SAR (systemic acquired resistance) inducer of numerous plant species. We provide a protocol for orchard-effective control of apple scab due to the ascomycete fungus Venturia inaequalis, by applying ASM in combination with a light integrated pest management program. Besides we pave the way for future optimization levers by demonstrating in controlled conditions (i) the high influence of apple genotypes, (ii) the ability of ASM to prime defenses in newly formed leaves, (iii) the positive effect of repeated elicitor applications, (iv) the additive effect of a thinning fruit agent

An Erwinia amylovora inducible promoter for improvement of apple fire blight resistance

International audienceAbstract Key message pPPO16, the first Ea-inducible promoter cloned from apple, can be a useful component of intragenic strategies to create fire blight resistant apple genotypes. Abstract Intragenesis is an important alternative to transgenesis to produce modified plants containing native DNA only. A key point to develop such a strategy is the availability of regulatory sequences controlling the expression of the gene of interest. With the aim of finding apple gene promoters either inducible by the fire blight pathogen Erwinia amylovora ( Ea ) or moderately constitutive, we focused on polyphenoloxidase genes ( PPO ). These genes encode oxidative enzymes involved in many physiological processes and have been previously shown to be upregulated during the Ea infection process. We found ten PPO and two PPO-like sequences in the apple genome and characterized the promoters of MdPPO16 ( pPPO16 ) and MdKFDV02 PPO -like ( pKFDV02 ) for their potential as Ea -inducible and low-constitutive regulatory sequences, respectively. Expression levels of reporter genes fused to these promoters and transiently or stably expressed in apple were quantified after various treatments. Unlike pKFDV02 which displayed a variable activity, pPPO16 allowed a fast and strong expression of transgenes in apple following Ea infection in a Type 3 Secretion System dependent manner. Altogether our results does not confirmed pKFDV02 as a constitutive and weak promoter whereas pPPO16 , the first Ea -inducible promoter cloned from apple, can be a useful component of intragenic strategies to create fire blight resistant apple genotypes

An Erwinia amylovora inducible promoter for intragenic improvement of apple fire blight resistance

Intragenesis is an important alternative to transgenesis to produce modified plants 27 containing native DNA only. A key point to develop such a strategy is the availability of 28 regulatory sequences controlling the expression of the gene of interest. With the aim of 29 finding apple gene promoters either inducible by the fire blight pathogen Erwinia amylovora 30 (Ea) or moderately constitutive, we focused on polyphenoloxidase genes (PPO). These genes 31 encode oxidative enzymes involved in many physiological processes and have been 32 previously shown to be up-regulated during the Ea infection process. We found ten PPO and 33 two PPO-like sequences in the apple genome and characterized the promoters of MdPPO16 34 (pPPO16) and MdKFDV02 PPO-like (pKFDV02) for their potential as Ea-inducible and low-35 constitutive regulatory sequences respectively. Expression levels of reporter genes fused to 36 these promoters and transiently or stably expressed in apple were quantified after various 37 treatments. Unlike pKFDV02 which displayed a variable activity, pPPO16 allowed a fast and 38 strong expression of transgenes in apple following Ea infection in a Type 3 Secretion System 39 dependent manner. Altogether our results indicate that pKFDV02 did not keep its promises as 40 a constitutive and weak promoter whereas pPPO16, the first Ea-inducible promoter cloned 41 from apple, can be a useful component of intragenic strategies to create fire blight resistant 42 apple genotypes

Using Molecular Tools To Decipher the Complex World of Plant Resistance Inducers: An Apple Case Study

Exogenous application of plant resistance inducers (PRIs) able to activate plant defenses is an interesting approach for new integrated pest management practices. The full integration of PRIs into agricultural practices requires methods for the fast and objective upstream screening of efficient PRIs and optimization of their application. To select active PRIs, we used a molecular tool as an alternative to methods involving plant protection assays. The expressions of 28 genes involved in complementary plant defense mechanisms were simultaneously determined by quantitative real-time PCR in PRI-treated tissues. Using a set of 10 commercial preparations and considering the pathosystem apple/Erwinia amylovora, this study shows a strong correlation between defense activation and protection efficiency in controlled conditions, thus enabling the easy identification of promising PRIs in fire blight protection. Hence this work clearly highlights the benefits of using a molecular tool to discriminate nonactive PRI preparations and provides useful molecular markers for the optimization of their use in orchard

Hydroxycinnamic acid amide accumulation and PR-protein encoding gene expressionare major responses of wheat during the early stages of powdery mildew infection

International audienceBlumeria graminis f.sp. tritici (Bgt) is an obligate biotrophic fungal pathogen responsible for powdery mildew in bread wheat (Triticum aestivum L.). During the firststeps of this pathogenic interaction, basal defense mechanisms take place in wheat leaves. We used RT-qPCR and metabolomic approaches to analyze these earlystages of the interaction between Bgt and the moderately susceptible wheat cultivar Pakito. The expression of genes encoding pathogenesis-related (PR) proteins (PR1,PR4, PR5 and PR8), known to target the pathogen, increased during the first 48 hours post-inoculation. Moreover, RT-qPCR and metabolomic analyses pointed out theimportance of the phenylpropanoid pathway in quantitative resistance against Bgt. Among metabolites of this pathway, hydroxycinnamic acid amides containing agmatineand putrescine as amine components accumulated from the second to the fourth day after inoculation. This suggests the involvement of these metabolites in quantitativeresistance via cross-linking processes in cell wall for reinforcement, what is supported by the up-regulation of PAL (phenylalanine ammonia-lyase), PR15 (encoding anoxalate oxidase) and POX (peroxidase) further inoculation. This study increases knowledge on basal resistance in wheat, giving new targets to investigate inducedresistance in wheat towards Bgt

Analysis of defense-related gene expression and leaf metabolome in wheat during the early infection stages of Blumeria graminis f.sp. tritici

International audienceBlumeria graminis f.sp. tritici (Bgt) is an obligate biotrophic fungal pathogen responsible for powdery mildew in bread wheat (Triticum aestivum L.). Upon Bgt infection, the wheat plant activates basal defense mechanisms namely PAMP-triggered immunity (PTI) in the leaves during the first few days. Understanding this early stage of quantitative resistance is crucial for developing new breeding tools and evaluating plant resistance inducers for sustainable agricultural practices. In this sense, we used a combination of transcriptomic and metabolomic approaches to analyze the early steps of the interaction between Bgt and the moderately susceptible wheat cultivar Pakito. Bgt infection resulted in an increasing expression of genes encoding pathogenesis-related proteins (PR-proteins, PR1, PR4, PR5 and PR8), known to target the pathogen, during the first 48 hours post-inoculation. Moreover, RT-qPCR and metabolomic analyses pointed out the importance of the phenylpropanoid pathway in quantitative resistance against Bgt. Among metabolites linked to this pathway, hydroxycinnamic acid amides containing agmatine and putrescine as amine component accumulated from the second to the fourth day after inoculation. This suggests their involvement in quantitative resistance via cross-linking processes in cell wall for reinforcement, what is supported by the up-regulation of PAL (phenylalanine ammonia-lyase), PR15 (encoding an oxalate oxidase) and POX (peroxidase) after inoculation. Finally, pipecolic acid, which is considered as a signal involved in systemic acquired resistance (SAR), accumulated after inoculation. These new insights lead to a better understanding of basal defense in wheat leaves after Bgt infection