Inoculation with the virulence factor deoxynivalenol (DON) can induce disease symptoms in wheat ( Triticum aestivum L.) spikelets, even though it is not needed for the initial invasion by Fusarium graminearum Schwabe, thus the mechanism of plant defense against both the pathogen and DON, was investigated. Wheat cultivars that are resistant (‘Sumai3’) or susceptible (‘Roblin’) to fusarium head blight (FHB) were inoculated with F. graminearum, DON, or water. Inoculated spikelets were harvested 48 h after inoculation, the metabolites were extracted in methanol–water and chloroform, then derivatized and analyzed by gas chromatography – mass spectrometry. The metabolite peaks were deconvoluted and identified by manually matching the mass spectra with those in the NIST and GMD libraries. The peaks were aligned, and abundances were measured. A total of 117 metabolites were tentatively identified, including several antimicrobial metabolites and signal molecules or their precursors. Out of these 117 metabolites, 15 and 18 were identified as possible resistance-related (RR) metabolites, following F. graminearum (RRIF) and DON (RRID) inoculations, respectively, with 4 metabolites common to both. Canonical discriminant analysis of marginally significant metabolites (105) identified those with constitutive and induced resistance functions. The metabolites with high canonical loading to the canonical vectors were used to explain these functions. The putative roles of these RR metabolites in plant defense, their metabolic pathways, and their potential application for screening of wheat breeding lines for resistance to FHB are discussed.

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Metabolite profiles based on GC/MS were used to study the temporal dynamics of metabolites in potato leaves following pathogen inoculation. In the polar and non-polar plant extracts a total of 106 consistent peaks were detected, of which 95 metabolites were tentatively identified. Following pathogen inoculation, the abundances of 42 metabolites were significantly increased or decreased, and these metabolites were designated as Pathogenesis-Related (PR) Metabolites. Factor analysis of the abundance of 106 metabolites identified four plant-pathogen interaction functions: (i) homeostasis; (ii) primary defence; (iii) secondary defence; (iv) collapse of primary and secondary defence responses. During the primary and secondary defence phases, dramatic changes in the amino acids, known precursors of several plant defence-related metabolites, were observed. Plausible satellite-networks of metabolic pathways leading to the up-regulation of these families of amino acids and other secondary metabolites, and their potential application for the evaluation of horizontal resistance in potato against the late blight pathogen is discussed.

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. 2008. Metabolic profiling to discriminate wheat near isogenic lines, with quantitative trait loci at chromosome 2DL, varying in resistance to fusarium head blight. Can. J. Plant Sci. 88: 789Á797. The resistance in wheat to fusarium head blight (FHB) is controlled by several quantitative trait loci (QTLs), which are mainly expressed as two different types of resistance. The objective of this study was to assess the potential of a metabolomics approach to identify resistance-related metabolites associated with a QTL that confers resistance to FHB. Two near isogenic lines (NIL), with alternate alleles for the FHB resistance/ susceptibility QTL on chromosome 2DL, were grown under greenhouse conditions and spikelets were inoculated with F. graminearum. Metabolites were extracted from the rachis and spikelets using a mixture of methanol-water and chloroform, and subsequently analyzed using GC/MS. Compound identification and quantification were achieved using AMDIS, GMD and NIST libraries, and MET-IDEA as the software platform. A total of 182 components were detected. A t-test of the quantities of these metabolites identified 27 resistance-related (RR) metabolites, including 22 constitutive (RRC) and 8 induced (RRI), with three common metabolites. Canonical discriminant analysis was used to classify treatments and to identify the associated metabolic functions. The putative metabolic pathways linking the RR-metabolites identified here are discussed. Key words: Functional genomics, metabolomics, fusarium head blight, Triticum aestivum, Fusarium graminearumHamzehzarghani, H., Paranidharan, V., Abu-Nada, Y., Kushalappa, A. C., Mamer, O. et Somers, D. 2008. Discrimination des ligne´es de ble´quasi isoge´niques pre´sentant des locus quantitatifs de re´sistance variable a`la bruˆlure de l'e´pi cause´e par fusarium sur le chromosome 2DL par profilage du me´tabolisme. Can. J. Plant Sci. 88: 789Á797. Plusieurs locus quantitatifs codent la re´sistance du ble´a`la bruˆlure de l'e´pi cause´e par Fusarium (BEF). Ces locus expriment surtout deux formes de re´sistance. L'e´tude devait servir a`e´valuer si on peut identifier les me´tabolites lie´s a`cette re´sistance et les associer a`un des locus quantitatifs qui codent la re´sistance a`la BEF par la me´tabolomique. À cette fin, les auteurs ont cultive´en serre deux ligne´es presque isoge´niques mais pre´sentant des alle`les diffe´rents aux locus quantitatifs de re´sistance/sensibilite´a`la BEF sur le chromosome 2DL, puis ont inocule´les e´pillets avec F. graminearum. Ils ont extrait les me´tabolites du rachis et des e´pillets avec un me´lange d'eau-me´thanol et de chloroforme, puis analyse´la solution par CG-SM. Les compose´s ont e´teí dentifie´s et quantifie´s graˆce aux re´pertoires AMDIS, GMD et NIST sur la plateforme logicielle MET-IDEA. En tout, 182 compose´s ont e´te´de´cele´s. Le test t effectue´sur leur quantite´a permis d'en identifier 27 lie´s a`la re´sistance, dont 22 constitutifs et 8 induits, y compris 3 communs. Les traitements ont e´te´classe´s par analyse de discri...

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Abstract:Metabolic profiles were developed for potato leaves, cvs. Caesar and AC Novachip, inoculated with water (CW and AW) or Phytophthora infestans (CP and AP), using gas chromatography/mass spectrometry (GC/MS). The level of horizontal resistance was higher for cv. Caesar than for AC Novachip with an area under the lesion expansion curve (AULEC) of 334 and 857, lesion area of 86 and 224 mm 2 , and sporulation of 4.4 × 10 3 and 13.7 × 10 3 sporangia lesion -1 , respectively. A total of 51 metabolites were detected consistently in all the four replicates of at least one treatment. Of the 51 relatively consistent metabolites, 33 were unique to a treatment and 18 were common to two or more treatments. A total of 7 and 29 PR-metabolites were identified, respectively, in Caesar and AC Novachip cultivars. Most of the phenolic compounds were associated with the AP. The metabolite heptadecanoic acid, 16-methy was detected only in the CP. In response to the P. infestans attack, the two cultivars appear to follow two different pathways. The susceptible cv. AC Novachip appears to follow the Shikimic acid-phenylpropanoid pathway as we have detected many phenolic metabolites and benzoic acids, the latter is a precursor of the signal molecule salicylic acid (SA), known to trigger phenolic compounds. On the other hand, the resistant cv. Caesar appears to follow mevalonic acid-methylerythritol pathway as we have detected heptadecanoic acid, a probable derivative of linolenic acid that is a precursor of a signal molecule jasmonic acid (JA), known to trigger terpenes. The factor analysis using principal components discriminated all the four treatments and the factor loading indicated which compound loaded significantly to a treatment. The possible function of these compounds in plant defense against biotic stress is discussed.