Rhizoctonia solani, the rice sheath blight pathogen, produces a toxin that reproduces all symptoms of the disease. The toxin has been partially purified and it was found to be a carbohydrate containing glucose, mannose, N-acetylgalactosamine, and N-acetylglucosamine. The toxin was also detected in infected leaves. Highly virulent isolates produced more toxin than less virulent isolates. Several R. solani isolates from rice and one each from cotton and tomato produced a similar toxin. All rice cultivars tested were susceptible to the pathogen and sensitive to the toxin. Host specificity of the toxin has been demonstrated using hosts and nonhosts of the pathogen.

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The effectiveness of aqueous extracts of various medicinal plants in detoxification of aflatoxin B1 (AFB1) was tested in vitro by thin-layer chromatography and enzyme-linked immunosorbent assay (ELISA). Among the different plant extracts, the leaf extract of Vasaka (Adhatoda vasica Nees) showed the maximum degradation of AFB1 (≥ 98%) after incubation for 24h at 37 °C. The aflatoxin detoxifying activity of the A. vasica leaf extract was significantly reduced by heating to 100 °C for 10 min or autoclaving at 121 °C for 20 min. Dialysis had no effect on aflatoxin detoxifying ability of A. vasica extract and the dialyzed extract showed similar level of detoxification of AFB1 as that of the untreated extract. A time course study of aflatoxin detoxification by A. vasica extract showed that 69% of the toxin was degraded within 6h and ≥ 95% degradation was observed after 24h of incubation. Detoxification of AFB1 by A. vasica extract was further confirmed by liquid chromatography-mass spectrometry (LC-MS) analysis. Phytochemical analysis revealed the presence of alkaloids in methanolic extract of A. vasica leaves. A partially purified alkaloid from A. vasica leaves by preparative TLC exhibited strong AFB1 detoxification activity.

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.

Yellow mosaic disease (YMD) is the major constraint of mungbean for realizing high productivity worldwide. Moreover, management of disease using YMD‐resistant genotypes is the simplest approach. Therefore, based on a preliminary screening of 220 genotypes during the year 2010 and 2011 at 17 locations, a set of 25 genotypes was further selected to evaluate at six locations over 2 years for identification of more stable resistant genotypes. The genotype and genotype × environment (GGE) analysis indicated that the genotypes and environment effects were significant (P < 0.001) for YMD incidence. Interestingly, the GGE biplot analysis successfully accounted for 74.71 per cent of the total variation with three genotypes (ML 818, ML 1349 and IPM 02‐14) showing high degree of resistance and stability over the locations. Notably, a strong positive association was observed between disease reaction and temperature, relative humidity and rainfall. As crop is grown in diverse growing environments, aforementioned genotypes can be used as stable/durable sources for future breeding programme to develop YMD‐resistant cultivars.

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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...