Richard N Strange

Ferhat Abbas University of Setif, Sétif, Wilaya de Setif, Algeria

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Publications (26)96.62 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Fluorescent Pseudomonad spp. were isolated from the rhizosphere of potato plants (Algeria) by serial dilutions of rhizosphere soils on Kings B medium and were tested for their antifungal activity. The antifungal activity of the Pseudomonas isolated from Potatoes rhizosphere was tested against Pythium ultimum, Rhizoctonia solani and Fusarium oxysporum in dual culture with bacteria on PDA. The Petri dish was divided into tow, on one the bacteria was spread and on the opposite side fungal plugs were inoculated and incubated for one week. Fourteen bacteria were isolated; only one isolate inhibited the growth of Pythium ultimum, Rhizoctonia solani, Fusarium solani; Fusarium oxysporum f.sp. albedinis and Fusarium oxysporum f. sp. Lycopersici with inhibition zones of 39.9, 33.7, 30.8, 19.9 and 22.5 mm respectively.
    Communications in agricultural and applied biological sciences 01/2010; 75(4):671-4.
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    ABSTRACT: Ascochyta rabiei, agent of Ascochyta blight of chickpea produces three toxins, Solanapyrones A, B and C of which solanapyrone A is the most toxic. All isolates of the fungus so far examined produce at least one of the Solanapyrone toxins, usually Solanapyrone A. The universality of solanapyrone production argues strongly for the importance of the toxins in virulence or pathogenicity. However, further evidence for this awaits the development of mutants lacking toxin production. Generation and isolation of fungal mutants defective in pathogenicity has been very useful for understanding the genetic and enzymatic processes responsible for infectivity in a number of pathosystems. Numerous tools have been used to transform plants and micro-organisms but the most widely micro-organism employed is Agrobacterium tumefaciens. In the present experiments, two strains of A. tumefaciens, AGL1 and LBA1126, harbouring two different plasmids, both encoding a gene for hygromycin resistance in the T-DNA region were used to transform isolate Tk21 of A. rabiei. The transformation of Ascochyta rabiei, gave rise to 498 colonies which grew on media supplemented with the selective agent; hygromycin B. The 30 sporulated transformants produced solanapyrone A on the specific medium at different rates. Solanapyrone A production, as demonstrated by the absorption of light at 327 nm, varied from 2.11 microg/ml to 4.32 microg/ml, representing a reduction of 74.11% to 46.99% in comparison with the wild type (8.15 microg/ml).
    Communications in agricultural and applied biological sciences 01/2010; 75(4):601-5.
  • M M Zerroug, H Laouer, R N Strange, J Nicklin
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    ABSTRACT: Biological control such as the use of plant extracts has emerged as promising option to the phenomena of fungi resistance to chemical. Several constituent of essential oil have been studied for their biological activity including antibacterial and antifungal activity. In this study the effect of Ammoides pusilla essential oil with different concentrations was test against the growth of Ascochyta rabiei and the production of solanapyrone A by the fungus. After 14 days the mycelium was collected and the dry weight measured. A. rabiei did not grow at a final concentration of 6 and 3 mg/ml, at 1.5 mg/ml and 0.625ml there was little growth of the fungus with a dry weight of 55 mg and 99 mg respectively compared to the control with 519 mg dry weight, but there was no solanapyrone A produced. However a new compound appeared at the HPLC at 10 min. 30 sec. compared with the solanapyrone A which elutes at nearly 14 minutes.
    Communications in agricultural and applied biological sciences 01/2010; 75(4):721-4.
  • P. Sankara, P. V. SubbaRao, R. N. Strange
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    ABSTRACT: The accumulation of phytoalexins in a rust-susceptible (KH 241-D) and a rust-resistant (PI 259747) genotype of groundnut 2,6, 15 and 25 days after inoculation with the rust pathogen, Puccinia arachidis Speg. was investigated. Within 2 days of inoculation of the resistant genotype, total phytoalexins reached 35 μg/g fresh weight, remained close to this level for a further 13 days but reached 104μg/g at 25 days after inoculation. In contrast, the susceptible genotype accumulated only 4μg/g fresh weight 2 days after inoculation and this increased gradually to 13, 23 and 52 μg/g fresh weight at 6, 15 and 25 days, respectively. Extracts from uninoculated leaves of both genotypes showed the presence of an antifungal compound which appeared as a diffuse spot in the Thin Layer Chromatography (TLC) bioassay, but this was essentially absent in inoculated leaves and did not correspond to any peak detected on High Performance Liquid Chromatography (HPLC). Compounds with UV spectra corresponding to isoflavanones were the major component of the phytoalexin response whereas other phytoalexins, formononetin, daidzein, and medicarpin comprised a minor component. A further compound with a retention time of 23.0 min on HPLC and a λ max of 280 nm only accumulated in inoculated leaves of the resistant genotype.
    Journal of Phytopathology 04/2008; 144(11‐12):527 - 532. · 1.00 Impact Factor
  • F. D. BEED, R. N. STRANGE, C. ONFROY, B. TIVOLI
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    ABSTRACT: The production of ascochitine by seven isolates of Ascochyta fabae accounted for the toxicity of culture filtrates of the fungus to cells isolated from leaves of Vicia faba. The LD50 value for cells from cultivars that were susceptible, tolerant or resistant to the fungus was similar i.e. 3·0 × 10−5m, 3·8 × 10−5m and 2·9 × 10−5 M, respectively. Ascochitine affected neither the germination of seeds nor the growth of mature plants at 5·17 × 10−4m but caused necrosis and wilting of plant cuttings at 2·5 × 10−4m and 5·10−4m. There was no association between virulence of 16 isolates of A. fabae for three cultivars of V.faba and the production of ascochitine in vitro. One isolate produced no ascochitine in vitro and yet was the most virulent for two of three cultivars. The toxin could not be extracted from infected plants.
    Plant Pathology 04/2007; 43(6):987 - 997. · 2.97 Impact Factor
  • Z LATIF, R. N. STRANGE, J. BILTON, S. RIAZUDDIN
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    ABSTRACT: Nine isolates of Ascochyta rabiei from Pakistan were grown in still culture on Czapek Dox liquid medium supplemented with aqueous extracts of the seed of one of two cultivars, a desi (6153) or a kabuli (Cypressa). Toxicity of the culture filtrates from both media was assayed with cells isolated from the leaves of both cultivars and concentrations of the phytotoxins. solanapyrone A and solanapyrone C, in the filtrates were determined by high-performance liquid chromatography (HPLC). For eight of the fungal isolates, toxicity and solanapyrone concentration were correlated, r varying from 0·383 to 0·859 according to medium and assay cultivar, but culture filtrates of another isolate, which was the most active by more than an order of magnitude, contained cytochalasin D but neither of the solanapyrones.
    Plant Pathology 04/2007; 42(2):172 - 180. · 2.97 Impact Factor
  • Y. M. CHEN, R. N. STRANGE
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    ABSTRACT: The phytotoxic solanapyrones A, B and C, were produced by Ascochyta rabiei when grown on Czapek Dox nutrients supplemented with an aqueous extract of chickpea seed but not when grown on Czapek Dox nutrients alone. Addition of amino acids, vitamins and inorganic ions to Czapek Dox nutrients allowed the production of the solanapyrones in good yields. By systematic elimination of components of this medium, the constituents essential for toxin production were identified as the divalent metal cations Zn2+, Ca2+, Mn2+ and Cu2+. When these ions were added to Czapek Dox nutrients in the same concentrations as those found in chickpea extract, concentrations of the phytotoxins similar to those found in Czapek Dox nutrients supplemented with chickpea extract were detected. Removal of cations from the chickpea supplement by a cation exchange resin did not affect the growth of the fungus compared with growth on the medium containing the complete supplement, but no toxin was produced. A defined medium and cultural conditions suitable for solanapyrone production by A. rabiei are described.
    Plant Pathology 04/2007; 40(3):401 - 407. · 2.97 Impact Factor
  • D. W. HOLDEN, R. N. STRANGE
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    ABSTRACT: The affinity of various lectins for protoplasts from isolines of wheat differing in their reaction to Puccinia graminis Pers. f. sp. tritici, Ericks and E. Henn. race 21 and for infection structures of the fungus was studied. Protoplasts of both isolines were agglutinated by concanavalin A and soybean lectin and lysed by wheat germ agglutinin. Pokeweed mitogen and wheat germ agglutinin bound to fungal germ tubes and appressoria but not to uredospore walls, substomatal vesicles or infection hyphae.Viability of protoplasts from either isoline was not affected when they were incubated with uredospores, germlings with and without infection structures or with an extract of the susceptible line, heavily infected by the fungus. No differences between polypeptide fractions prepared from protoplasts of the isolines were detected by sodium dodecyl sulphate polyacrylamide gel electrophoresis.
    Plant Pathology 04/2007; 33(2):233 - 243. · 2.97 Impact Factor
  • Y.-M. CHEN, R. N. STRANGE
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    ABSTRACT: Production of the solanapyrone toxins by Ascochyta rabiei is nutrient dependent. When grown on a medium consisting entirely of expressed sap from the aerial parts of young chickpea plants (PSM). only low concentrations of the solanapyrones were produced (< 24 μM). However, toxicity of 4-day-old culture filtrates to isolated cells of chickpea leaflets was comparable with that obtained from 12-day-oId culture filtrates on Czapek Dox nutrients supplemented with chickpea seed extract or cations—media that are conducive to solanapyrone production. The additional toxic component which peaked at 4 days in culture was heat labile, losing about 50% of its activity on boiling for 10 min. Affinity for solid-phase extraction media, precipitation with ammonium sulphate and acetone, ionization properties and UV absorption characteristics suggested that the toxin was a polypeptide. The toxin was purified by solid-phase extraction, acetone precipitation and high performance liquid chromatography (HPLC) on a C2 column. Hydrolysis of the purified toxin yielded 14 amino acids, and calculation of the numbers of residues of each amino acid suggested a molecular mass of 7, 551 Da, A band corresponding to this molecular mass was present on SDS-PAGE gels. However, both the native peptide and its hydrolysate contained a compound that reacted with p-anisaldehyde suggesting the possibility of a glycosidic moiety.
    Plant Pathology 04/2007; 43(2):321 - 327. · 2.97 Impact Factor
  • Richard N Strange
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    ABSTRACT: Phytotoxic compounds produced by plant pathogens are often crucial determinants of plant disease. Knowledge of them provides insights into disease syndromes and may be exploited by conventional breeding and biotechnology to obtain resistant crops.
    Natural Product Reports 03/2007; 24(1):127-44. · 10.18 Impact Factor
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    ABSTRACT: SUMMARY Cultures, designated Ag1, Ag2 and Ag3, of a fungus resembling Ascochyta rabiei, Didymella rabiei (teleo- morph), were isolated from blighted chickpea plants growing in three regions of Algeria. The isolates were shown to be the cause of the disease by fulfilling Koch's postulates and were identified as A. rabiei by sequenc- ing ribosomal DNA. When grown on a defined liquid medium, consisting of Czapek Dox nutrients and five cations, the filtrates inhibited germination of chickpea seed, and elongation of hypocotyls and radicles of seedlings. All three isolates produced the phytotoxin solanapyrone A in culture and maximal concentrations in the culture filtrates, recorded after incubation for 14 days were 15.1 ± 1.29 µg/ml, 8.4 ± 1.19 µg/ml and 7.4 ± 0.85 mg/ml for Ag 1 Ag2 and Ag3, respectively. ED 50 values were 7.15 ± 1.77, 5.87 ± 1.40 and 3.60 ± 1.47 µg solanapyrone A/ml for inhibition of germination, hypocotyl elongation and radicle elongation, respective- ly. Concentrations of solanapyrone A in dilutions of cul- ture filtrates that caused 50% inhibition of these three parameters were sufficient to explain their inhibitory ef- fects in all cases except the inhibition of germination and hypocotyl elongation by filtrates of Ag2 and Ag3. Here they were only 65% and 58% of the amount re- quired to cause the inhibition of germination, respec- tively and 60% and 63% of the amount required to in- hibit hypocotyl elongation, respectively, suggesting that other factors may be involved.
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    ABSTRACT: Agrobacterium tumefaciens was used to transform Ascochyta rabiei, the causal agent of chickpea blight. Employing a T-DNA containing a hygromycin resistance gene (hph), 908 transformants were obtained from germinated pycnidiospores on a selective medium containing hygromycin. Transformants were confirmed using PCR and Southern analyses and of four of these that were tested, two had integrated multicopies of the hph gene, one had two copies and one had a single insertion. Transformants were tested for the production of solanapyrone A toxin using a microtitre plate assay. Loss of toxin production by transformants was confirmed by reversed phase high-performance liquid chromatography. Sixteen transformants out of 668 tested produced significantly less solanapyrone A than the wild-type strain.
    FEMS Microbiology Letters 03/2006; 255(2):255-61. · 2.05 Impact Factor
  • Richard N. Strange
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    ABSTRACT: Grain legumes, in common with all other plants, are subject to biotic constraints of which pathogens form an important group. They are variable in type, number, space and time and, most insidiously, in genetic constitution. Consequently, resistance in the plant to a given pathogen may be quickly nullified by genetic alteration of the pathogen, particularly where this is conferred by a single resistance gene. The products of such resistance genes usually recognise, directly or indirectly, a component of the pathogen, which is encoded by a corresponding avirulence gene. Thus resistance and avirulence genes are specific and complementary and the arrangement is referred to as a gene-for-gene relationship. It follows that alteration of the avirulence gene of the pathogen to give a product that is no longer recognised by the product of the resistance gene of the plant gives rise to a susceptible reaction. A possible solution to this problem is to pyramid several resistance genes, a procedure now facilitated by the techniques of genetic modification. In other interactions genes that reduce susceptibility rather than confer complete resistance have been found and in some cases the loci (quantitative trait loci) responsible have been mapped to specific regions of particular chromosomes. The mechanisms by which these genes limit the virulence of the pathogen are generally unknown. However, by gaining an understanding of the fundamental properties of a pathogen that are necessary for pathogenicity or virulence it may be possible to counteract them. Candidates for such properties are toxins, enzymes and mechanisms that interfere with constitutive or active defence of the plant. Reciprocally, understanding the properties of the plant that confer susceptibility may allow selection of germplasm that lacks such properties. Among the candidates here are germination stimulants of pathogen propagules and signals that promote the formation of infection structures.
    Euphytica 01/2006; 147(1):49-65. · 1.64 Impact Factor
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    ABSTRACT: A linkage map in a population of recombinant inbred lines (RILs) derived from an interspecific cross between Cicer arietinum (ILC72) Cicer reticulatum (Cr5-10), resistant and susceptible to blight, caused by Ascochyta rabiei, respectively, was obtained using RAPD, ISSR, STMS, isozyme (Pdf6) and flower colour (pink/white) markers. The map comprised ten linkage groups and covered a distance of 601.2 cM. When the population was evaluated for reaction to Ascochyta blight under field conditions by determining the Area Under the Disease Progress Curve (AUDPC), the distribution of frequencies was bimodal: most of the lines had an intermediate reaction, fewer were nearly as susceptible as the susceptible parent and none had values close to the resistant parent. A QTL explaining 28% of the variation in resistance was located in linkage group 2 (LG2). Five RAPD markers on this linkage group showed significant association with resistance (OPX04372, UBC881621, OPAI09746, OPAI09352 and OPAC12700) and the major QTL peak lay midway between OPAI09746 and UBC881621 which are 14.1 cM apart. Contrary to other studies, no association of linkage group 4 with resistance was found. The QTL for resistance to Ascochyta blight in this study is therefore different from QTLs for this character reported in other interspecific crosses and may be the same as that reported in linkage group 2 in intraspecific crosses where genes for resistance to races of Fusarium oxysporum f. sp. ciceri, causing wilt, are also located.
    Euphytica 01/2006; 149(1):105-111. · 1.64 Impact Factor
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    ABSTRACT: Fusarium acutatum was isolated from wilting chickpea plants in Pakistan. Filtrates from cultures grown on a defined liquid medium caused permanent wilting of chickpea cuttings and killed cells, isolated enzymically from healthy plants, in a bioassay. Toxic activity was retained by a cyano solid phase extraction cartridge and the toxin was isolated by elution from the cartridge in acetonitrile and Si-gel thin layer chromatography of the eluate. Analytical HPLC of the compound on a cyano column with diode array detection gave a single peak with a homogeneous spectrum and lambda(max) at 224 and 281 nm. NMR and mass spectral studies showed that the toxin was 8-O-methyl-fusarubin. The pure compound caused permanent wilting of chickpea cuttings and the LD50 value in the cell bioassay was 327 ng/ml.
    Phytochemistry 08/2005; 66(13):1536-9. · 3.35 Impact Factor
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    ABSTRACT: SummaryA total of 188 fungal isolates was obtained from the rhizosphere of Vicia faba grown in an Egyptian soil heavily infested with Orobanche species. Agar cultures of 58 isolates inhibited the germination of conditioned seed of Orobanche crenata exposed to the germination stimulant, GR24. Filtrates of inhibitory fungi grown in liquid medium for 9–15 days were also assayed and those of five isolates, which were morphologically similar, inhibited germination even when diluted 16-fold. The fungus was identified as Myrothecium verrucaria (Alb. & Schwein.) Ditmar by its morphology and the nucleotide sequence of the ITS1 and ITS2 regions of the ribosomal repeat unit. Purification of the inhibitor to homogeneity was accomplished by solvent partitioning, flash chromatography on silica gel, semi-preparative HPLC on a reversed phase C18 column, solid phase extraction and tlc on silica gel. The inhibitor was identified as verrucarin A by nuclear magnetic resonance spectroscopy and comparison of the spectra with those of an authentic sample of the compound. A preliminary experiment demonstrated that infection of V. faba by O. crenata could be prevented by addition of spores of the fungus to soil infested by the parasite.
    Weed Research 04/2005; 45(3):212 - 219. · 2.05 Impact Factor
  • Richard N Strange, Peter R Scott
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    ABSTRACT: A vast number of plant pathogens from viroids of a few hundred nucleotides to higher plants cause diseases in our crops. Their effects range from mild symptoms to catastrophes in which large areas planted to food crops are destroyed. Catastrophic plant disease exacerbates the current deficit of food supply in which at least 800 million people are inadequately fed. Plant pathogens are difficult to control because their populations are variable in time, space, and genotype. Most insidiously, they evolve, often overcoming the resistance that may have been the hard-won achievement of the plant breeder. In order to combat the losses they cause, it is necessary to define the problem and seek remedies. At the biological level, the requirements are for the speedy and accurate identification of the causal organism, accurate estimates of the severity of disease and its effect on yield, and identification of its virulence mechanisms. Disease may then be minimized by the reduction of the pathogen's inoculum, inhibition of its virulence mechanisms, and promotion of genetic diversity in the crop. Conventional plant breeding for resistance has an important role to play that can now be facilitated by marker-assisted selection. There is also a role for transgenic modification with genes that confer resistance. At the political level, there is a need to acknowledge that plant diseases threaten our food supplies and to devote adequate resources to their control.
    Annual Review of Phytopathology 02/2005; 43:83-116. · 10.23 Impact Factor
  • M M Zerroug, Z Bouznad, L Larous, R N Strange
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    ABSTRACT: Three Algerian isolates of A. rabiei (72, Mat 1.2 and 9216) were grown on Czapek Dox medium supplemented with cations and incubated for 14 days. After incubation, the mycelium of the fungus was removed by filtration through four layers of muslin cloth and spores were removed from the filtrate by centrifugation at 10,000 g for 20 min. Solanapyrone A was partially purified by liquid phase extraction into ethyl acetate and, after removal of the ethyl acetate, the toxin samples were dissolved in methanol and quantified by analytical High Performance Liquid Chromatography (HPLC). Solanapyrone A was identified by superimposition of its UV spectrum, obtained from the diode array detector of the HPLC, on the spectrum of an authentic sample. The action of solanapyrone A solution on seed germination and elongation of radicles and hypocotyls was tested using a concentration of 18.2 microg/ml and a two-fold dilution series of this solution in distilled water. The three Isolates, 72, Mat1.2 and 9216 produced solanapyrone A at concentrations of 37.2, 14.2 and 11.09 microg/ml, respectively. When probit % inhibition of seed germination was plotted against log2 of solanapyrone A concentration, there was a linear relationship and the EC50 concentration was determined as 7.2 microg/ml. Similarly, when radicle and hypocotyl elongation was plotted against log2 of solanapyrone A concentration, both gave linear relationships and the EC50 concentrations were determined as 5.37 and 6.02 microg/ml, respectively. It was concluded that solanapyrone A has a considerable inhibition of chickpea. However radicles and hypocotyls were susceptible than seed germination.
    Communications in agricultural and applied biological sciences 02/2004; 69(4):625-30.
  • Pazilat Bahti, Richard N Strange
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    ABSTRACT: The absence of solanapyrone A in chickpea plants infected by Ascochyta rabiei or fed the toxin was investigated. Toxin disappeared when incubated with protein extracts of chickpea, either in the presence or absence of NADPH or even if the extracts were boiled. When solanapyrone A was incubated with proteins precipitated by ammonium sulphate (30–70% saturation fraction) a new compound was detected on reversed phase HPLC with a longer retention time than solanapyrone A. This was identified as demethylated solanapyrone A and was subsequently shown to be formed as a result of the reaction of the toxin with residual ammonium sulphate. When ammonium sulphate was rigorously removed from the protein fraction, solanapyrone A still disappeared but the demethylated compound was not found. Incubation with other proteins also caused the disappearance of the toxin as did incubation with NaCl and Tris–HCl. In the latter instance, when the reaction mixture was separated by reversed phase chromatography another compound appeared on the HPLC trace with a λ max of 321 which eluted later than solanapyrone A. These data show that solanapyrone A is a labile compound, reacting with proteins, possibly by binding to them, and with low molecular weight compounds. It is not surprising therefore that it is neither recovered from infected plants nor from plants fed the toxin, where its reactivity is likely to be the reason for its toxicity.
    Physiological and Molecular Plant Pathology - PHYSIOL MOLEC PLANT PATHOL. 01/2004; 64(1):9-15.
  • Christine Edwards, Richard N. Strange
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    ABSTRACT: Leaves of groundnut, Arachis hypogaea, infected with the early leaf spot fungus, Cercospora arachidicola, were extracted in aqueous ethanol and the phytoalexins partitioned into ethyl acetate. Flash chromatography of the ethyl acetate extract on silica gel yielded fractions with one to five compounds from which the phytoalexins could be isolated by semipreparative reversed-phase high-performance liquid chromatography (HPLC). The major phytoalexins were demethylmedicarpin, formononetin, 7,4′-dimethoxy-2′-hydroxyisoflavanone and medicarpin. Minor components were 7,2′-dihydroxy-4′-methoxyisoflavanone and daidzein. Compounds were identified by cochromatography and comparison of their ultraviolet and mass spectra with authentic samples using an HPLC system equipped with a diode-array detector, HPLC mass spectrometry and gas chromatography—mass spectrometry of their trimethylsilyl derivatives. A solid-phase extraction method was developed for processing large numbers of samples. Acetonitrile eluates from C18 cartridges were separated by reversed-phase HPLC and the phytoalexins quantified by reference to external standards of the authentic compounds.
    Journal of Chromatography A 06/1991; 547:185-193. · 4.61 Impact Factor