Powdery mildew would be one of the most damaging wheat diseases without the extensive use of conventional fungicides. Some of the alternative control strategies currently emerging are based on the use of resistance inducers. The disacharride trehalose (TR) is classically described as an inducer of defenses in plants to abiotic stress. In this work, the elicitor or priming effect of TR was investigated in wheat both before and during a compatible wheat-powdery mildew interaction through molecular, biochemical, and cytological approaches. In noninoculated conditions, TR elicited the expression of genes encoding chitinase (chi, chi1, and chi4 precursor), pathogenesis-related protein 1, as well as oxalate oxidase (oxo). Moreover, lipid metabolism was shown to be altered by TR spraying via the upregulation of lipoxygenase (lox) and lipid-transfer protein (ltp)-encoding gene expression. On the other hand, the protection conferred by TR to wheat against powdery mildew is associated with the induction of two specific defense markers. Indeed, in infectious conditions following TR spraying, upregulations of chi4 precursor and lox gene expression as well as an induction of the LOX activity were observed. These results are also discussed with regard to the impact of TR on the fungal infectious process, which was shown to be stopped at the appressorial germ tube stage. Our findings strongly suggest that TR is a true inducer of wheat defense and resistance, at least toward powdery mildew.

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Following a request of the European Commission, EFSA and ANSES, beneficiary of the EFSA tasking grant on horizon scanning for plant pests (GP/EFSA/ALPHA/2017/02), developed a methodology to order by risk non-regulated pests recently identified through the monitoring of media and scientific literature. The ranking methodology proposed at the end of the pilot phase was based on the scoring of pests under evaluation following 16 criteria related to the steps of the pest risk assessment scheme. The multicriteria matrix of scores obtained was then submitted to the multicriteria analysis method PROMETHEE. The pilot methodology was tested on a limited number of pests (14 pests identified during the monitoring activity, and 4 'control' pests whose well-known risk should be reflected either in a positive or negative score), then applied on all non-regulated pests identified through the media and scientific literature monitoring in the first 2 years of the project. After having collected feedback from the targeted final users (EU risk managers), the methodology underwent a few refinements: (i) implementation of the methodology to a set of already assessed reference pests from EFSA opinions, (ii) exclusions of three criteria from the scoring phase, (iii) identification of pests proposed for further action ('positive' pests), using a threshold defined after scoring the reference pests.

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A review of existing ranking systems for plant threats developed by EU Member States and Third Countries is presented in this report. The analysis of these ranking systems is done according to six main topics: 1) purpose of the ranking, 2) characteristics of pests, 3) patterns and features of the systems, 4) structure of the systems in terms of point scales and score aggregation, 5) treatment of missing data, expression of uncertainty and validation of the system via comparison with expert ranking or judgments, and 6) possibility of running several scenarios and application of different weightings. Common features between these systems as well as their main differences are highlighted. General recommendations are put forward, especially with a view to the development of a future ranking system for new non‐regulated pests.

Activators of plant defence responses against pathogens are a potential alternative to fungicides, and the well-known resistance inducer salicylic acid (SA) protects wheat (Triticum aestivum L.) against powdery mildew. The aim of our work was to investigate through biochemical and molecular approaches whether lipid metabolism alteration could be considered as a characteristic feature of induced resistance in wheat upon SA infiltration. Expression levels of lox, PI-PLC2 and ltp genes encoding for a lipoxygenase (LOX), a phospholipase C2 and a lipid-transfer protein, respectively, were investigated. Increase of phosphatidic acid (PA) content 48 h after SA infiltration in wheat leaves, upregulation of PI-PLC2 gene expression and increased diacylglycerol content were recorded, indicating the involvement of the PLC pathway in the PA synthesis. The wheat octadecanoid pathway was shown to be highly responsive to SA infiltration through simultaneous increases in lox gene expression and LOX activity, as well as a reduction in the content of linolenic acid. Changes in several FA contents and increases of the ltp gene expression were also recorded during the latest hours after SA infiltration. The status of lipid metabolism, as well as the connections between its components as markers of SA-induced resistance in wheat, are discussed.