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At least 217 records · Page 12Linked to original sources
PubMed2001

A viral double-stranded RNA up regulates the fungal virulence of Nectria radicicola.

Double-stranded RNAs (dsRNAs) are widespread in plant pathogenic fungi, but their functions in fungal hosts remain mostly unclear, with a few exceptions. We analyzed dsRNAs from Nectria radicicola, the causal fungus of ginseng root rot. Four distinct sizes of dsRNAs, 6.0, 5.0, 2.5, and 1.5 kbp, were detected in 24 out of the 81 strains tested. Curing tests of individual dsRNAs suggested that the presence of 6.0-kbp dsRNA was associated with high levels of virulence, sporulation, laccase activity, and pigmentation in this fungus. The 6.0-kbp dsRNA-cured strains completely lost virulence-related phenotypes. This 6.0-kbp dsRNA was reintroduced by hyphal anastomosis to a dsRNA-cured strain marked with hygromycin resistance, which resulted in the restoration of virulence-related phenotypes. These results strongly suggest that 6.0-kbp dsRNA up regulates fungal virulence in N. radicicola. Sequencing of several cDNA clones derived from 6.0-kbp dsRNA revealed the presence of a RNA-dependent RNA polymerase (RDRP) gene. Phylogenetic analysis showed that this gene is closely related to those of plant cryptic viruses. Biochemical analyses suggested that the 6.0-kbp dsRNA may regulate fungal virulence through signal-transduction pathways involving cyclic AMP-dependent protein kinase and protein kinase C.

Amino Acid Sequence↗
PubMed2001

Phenazine-1-carboxamide production in the biocontrol strain Pseudomonas chlororaphis PCL1391 is regulated by multiple factors secreted into the growth medium.

Pseudomonas chlororaphis PCL1391 controls tomato foot and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici. The production of phenazine-1-carboxamide (PCN) is crucial for this biocontrol activity. In vitro production of PCN is observed only at high-population densities, suggesting that production is under the regulation of quorum sensing. The main autoinducer molecule produced by PCL1391 was identified structurally as N-hexanoyl-L-homoserine lactone (C6-HSL). The two other autoinducers that were produced comigrate with N-butanoyl-L-homoserine lactone (C4-HSL) and N-octanoyl-L-homoserine lactone (C8-HSL). Two PCL1391 mutants lacking production of PCN were defective in the genes phzI and phzR, respectively, the nucleotide sequences of which were determined completely. Production of PCN by the phzI mutant could be complemented by the addition of exogenous synthetic C6-HSL, but not by C4-HSL, C8-HSL, or any other HSL tested. Expression analyses of Tn5luxAB reporter strains of phzI, phzR, and the phz biosynthetic operon clearly showed that phzI expression and PCN production is regulated by C6-HSL in a population density-dependent manner. The introduction of multiple copies of the regulatory genes phzI and phzR on various plasmids resulted in an increase of the production of HSLs, expression of the PCN biosynthetic operon, and consequently, PCN production, up to a sixfold increase in a copy-dependent manner. Surprisingly, our expression studies show that an additional, yet unidentified factor(s), which are neither PCN nor C4-HSL or C8-HSL, secreted into the growth medium of the overnight cultures, is involved in the positive regulation of phzI, and is able to induce PCN biosynthesis at low cell densities in a growing culture, resulting in an increase of PCN production.

Antifungal Agents↗
PubMed2003

GacS sensor domains pertinent to the regulation of exoproduct formation and to the biocontrol potential of Pseudomonas fluorescens CHA0.

In the root-colonizing biocontrol strain CHA0 of Pseudomonas fluorescens, cell density-dependent synthesis of extracellular, plant-beneficial secondary metabolites and enzymes is positively regulated by the GacS/GacA two-component system. Mutational analysis of the GacS sensor kinase using improved single-copy vectors showed that inactivation of each of the three conserved phosphate acceptor sites caused an exoproduct null phenotype (GacS-), whereas deletion of the periplasmic loop domain had no significant effect on the expression of exoproduct genes. Strain CHA0 is known to synthesize a solvent-extractable extracellular signal that advances and enhances the expression of exoproduct genes during the transition from exponential to stationary growth phase when maximal exoproduct formation occurs. Mutational inactivation of either GacS or its cognate response regulator GacA abolished the strain's response to added signal. Deletion of the linker domain of the GacS sensor kinase caused signal-independent, strongly elevated expression of exoproduct genes at low cell densities. In contrast to the wild-type strain CHA0, the gacS linker mutant and a gacS null mutant were unable to protect tomato plants from crown and root rot caused by Fusarium oxysporum f. sp. radicis-lycopersici in a soil-less microcosm, indicating that, at least in this plant-pathogen system, there is no advantage in using a signal-independent biocontrol strain.

Amino Acid Sequence↗
PubMed1991

Indole-3-acetic acid (IAA) synthesis in the biocontrol strain CHA0 of Pseudomonas fluorescens: role of tryptophan side chain oxidase.

Pseudomonas fluorescens strain CHA0 is an effective biocontrol agent against soil-borne fungal plant pathogens. In this study, indole-3-acetic acid (IAA) biosynthesis in strain CHA0 was investigated. Two key enzyme activities were found to be involved: tryptophan side chain oxidase (TSO) and tryptophan transaminase. TSO was induced in the stationary growth phase. By fractionation of a cell extract of strain CHA0 on DEAE-Sepharose, two distinct peaks of constitutive tryptophan transaminase activity were detected. A pathway leading from tryptophan to IAA via indole-3-acetamide, which occurs in Pseudomonas syringae subsp. savastanoi, was not present in strain CHA0. IAA synthesis accounted for less than or equal to 1.5% of exogenous tryptophan consumed by resting cells of strain CHA0, indicating that the bulk of tryptophan was catabolized via yet another pathway involving anthranilic acid as an intermediate. Strain CHA750, a mutant lacking TSO activity, was obtained after Tn5 mutagenesis of strain CHA0. In liquid cultures (pH 6.8) supplemented with 10 mM-L-tryptophan, growing cells of strains CHA0 and CHA750 synthesized the same amount of IAA, presumably using the tryptophan transaminase pathway. In contrast, resting cells of strain CHA750 produced five times less IAA in a buffer (pH 6.0) containing 1 mM-L-tryptophan than did resting cells of the wild-type, illustrating the major contribution of TSO to IAA synthesis under these conditions. In artificial soils at pH approximately 7 or pH approximately 6, both strains had similar abilities to suppress take-all disease of wheat or black root rot of tobacco. This suggests that TSO-dependent IAA synthesis is not essential for disease suppression.

Bacterial Proteins↗
PubMed2005

Influence of fusaric acid on phenazine-1-carboxamide synthesis and gene expression of Pseudomonas chlororaphis strain PCL1391.

Production of the antifungal metabolite phenazine-1-carboxamide (PCN) by Pseudomonas chlororaphis strain PCL1391 is essential for the suppression of tomato foot and root rot caused by the soil-borne fungus F. oxysporum f. sp. radicis-lycopersici. The authors have shown previously that fusaric acid (FA), a phytotoxin produced by Fusarium oxysporum, represses the production of PCN and of the quorum-sensing signal N-hexanoyl-l-homoserine lactone (C(6)-HSL). Here they report that PCN repression by FA is maintained even during PCN-stimulating environmental conditions such as additional phenylalanine, additional ferric iron and a low Mg(2+) concentration. Constitutive expression of phzI or phzR increases the production of C(6)-HSL and abolishes the repression of PCN production by FA. Transcriptome analysis using P. chlororaphis PCL1391 microarrays showed that FA represses expression of the phenazine biosynthetic operon (phzABCDEFGH) and of the quorum-sensing regulatory genes phzI and phzR. FA does not alter expression of the PCN regulators gacS, rpoS and psrA. In conclusion, reduction of PCN levels by FA is due to direct or indirect repression of phzR and phzI. Microarray analyses identified genes of which the expression is strongly influenced by FA. Genes highly upregulated by FA are also upregulated by iron starvation in Pseudomonas aeruginosa. This remarkable overlap in the expression profile suggests an overlapping stress response to FA and iron starvation.

Fusaric Acid↗
PubMed2003

Molecular characterization of dsRNA segments 2 and 5 and electron microscopy of a novel reovirus from a hypovirulent isolate, W370, of the plant pathogen Rosellinia necatrix.

A hypovirulent isolate, W370, of the white root rot fungus Rosellinia necatrix has previously been shown to harbour 12 dsRNA segments. In this study, complete nucleotide sequences of segments 2 and 5 of W370 dsRNAs were determined. The nucleotide sequence of genome segment 2 was 3773 bases long with a single long open reading frame (ORF) encoding 1226 amino acid residues with a predicted molecular mass of approximately 138.5 kDa. The nucleotide sequence of segment 5 was 2089 bases long with a single long ORF, whose deduced polypeptide contained 646 amino acid residues with a predicted molecular mass of about 72 kDa. Comparative analysis showed that the deduced protein sequence of segment 2 had significant homology with the putative VP2 of Colorado tick fever virus (CTFV) and European Eyach virus (EYAV) in the genus Coltivirus, but the deduced protein sequence of segment 5 had no similarity with other virus proteins. Double-shelled spherical particles approximately 80 nm in diameter associated with W370 dsRNAs were observed in a preparation from the mycelial tissue of isolate W370. The results demonstrated that the virus associated with W370 dsRNAs is a novel reovirus of the family Reoviridae. The virus was named Rosellinia anti-rot virus (RArV).

Amino Acid Sequence↗
PubMed1999

Characterization of two novel type I ribosome-inactivating proteins from the storage roots of the andean crop Mirabilis expansa.

Two novel type I ribosome-inactivating proteins (RIPs) were found in the storage roots of Mirabilis expansa, an underutilized Andean root crop. The two RIPs, named ME1 and ME2, were purified to homogeneity by ammonium sulfate precipitation, cation-exchange perfusion chromatography, and C4 reverse-phase chromatography. The two proteins were found to be similar in size (27 and 27.5 kD) by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and their isoelectric points were determined to be greater than pH 10.0. Amino acid N-terminal sequencing revealed that both ME1 and ME2 had conserved residues characteristic of RIPs. Amino acid composition and western-blot analysis further suggested a structural similarity between ME1 and ME2. ME2 showed high similarity to the Mirabilis jalapa antiviral protein, a type I RIP. Depurination of yeast 26S rRNA by ME1 and ME2 demonstrated their ribosome-inactivating activity. Because these two proteins were isolated from roots, their antimicrobial activity was tested against root-rot microorganisms, among others. ME1 and ME2 were active against several fungi, including Pythium irregulare, Fusarium oxysporum solani, Alternaria solani, Trichoderma reesei, and Trichoderma harzianum, and an additive antifungal effect of ME1 and ME2 was observed. Antibacterial activity of both ME1 and ME2 was observed against Pseudomonas syringae, Agrobacterium tumefaciens, Agrobacterium radiobacter, and others.

Amino Acid Sequence↗
PubMed1999

Induced resistance to pathogenic fungi in norway spruce

Norway spruce (Picea abies) trees (approximately 16 m high) of a single clone were used to study the effects of fungal infection and wounding on induction of resistance to the bark beetle-associated bluestain fungus Ceratocystis polonica. A dose-response experiment was designed involving three different dosages of fungal (fungus and wound) and sterile agar (wound) pretreatment inoculations (10, 50, or 100 inoculations/m(2) on the stem between 0.8 and 2.0 m high). Three weeks after pretreatment, trees were challenged with a massive C. polonica inoculation (400 inoculations/m(2)). Control trees that received no pretreatment were heavily colonized and killed by the challenge inoculation. The high and medium fungal pretreatments reduced subsequent fungal colonization success by 76% to 97% relative to the control, and fungal pretreatments protected the trees much more efficiently than sterile agar pretreatments. The protection was demonstrated to be local and not systemic in a subsequent experiment, where trees were pretreated with the medium fungal dosage on the lower bole and challenge inoculated further up the stem. Protection was also demonstrated to be pathogen nonspecific, as trees that had been pretreated with a medium dosage of the root rot fungus Heterobasidion annosum showed enhanced resistance to challenge inoculation with C. polonica.

Journal Article↗
PubMed2000

Comparative analysis of expressed sequences in Phytophthora sojae.

Phytophthora sojae (Kaufmann and Gerdemann) is an oomycete that causes stem and root rot on soybean (Glycine max L. Merr) plants. We have constructed three cDNA libraries using mRNA isolated from axenically grown mycelium and zoospores and from tissue isolated from plant hypocotyls 48 h after inoculation with zoospores. A total of 3,035 expressed sequence tags (ESTs) were generated from the three cDNA libraries, representing an estimated 2,189 cDNA transcripts. The ESTs were classified according to putative function based on similarity to known proteins, and were analyzed for redundancy within and among the three source libraries. Distinct expression patterns were observed for each library. By analysis of the percentage G+C content of the ESTs, we estimate that two-thirds of the ESTs from the infected plant library are derived from P. sojae cDNA transcripts. The ESTs originating from this study were also compared with a collection of Phytophthora infestans ESTs and with all other non-human ESTs to assess the similarity of the P. sojae sequences to existing EST data. This collection of cDNA libraries, ESTs, and accompanying annotation will provide a new resource for studies on oomycetes and on soybean responses to pathogen challenge.

DNA, Complementary↗
PubMed1976

Host-Pathogen Interactions: XII. Response of Suspension-cultured Soybean Cells to the Elicitor Isolated from Phytophthora megasperma var. sojae, a Fungal Pathogen of Soybeans.

The glucan elicitor isolated from the mycelial walls of Phytophthora megasperma var. sojae, the fungus which causes stem and root rot in soybeans, stimulates the activity of phenylalanine ammonia-lyase and the accumulation of glyceollin in suspension-cultured soybean cells. Nigeran, a commercially available fungal wall glucan, was the only other compound tested which has any activity in this system. Glyceollin is a phenylpropanoid-derived phytoalexin which is toxic to P. megasperma var. sojae. Evidence is presented to support the hypothesis that the action of elicitors in stimulating phytoalexin synthesis is not species or variety specific but, rather, is part of a general defensive response of plants.

Journal Article↗
PubMed2004

Effects of Rhizoctonia infection and drought on peroxidase and chitinase activity in Norway spruce (Picea abies).

Seedlings of Norway spruce were exposed to fungal infection and drought in order to investigate differences in their stress responses on the enzymatic level. Six-week-old seedlings were infected with the root rot fungus Rhizoctonia, or subjected to drought, respectively. Changes at the enzymatic level were more rapid and significantly higher in infected plants in comparison with drought-stressed spruce plants. Rhizoctonia infection resulted in early local and systemic increase in peroxidase and chitinase activity. The most prominent isoforms responding were highly basic peroxidases and chitinases (pI 9-9.5) and several acidic chitinases (pI3-4). An increased intensity of similar peroxidase isoforms was found in drought-affected plants. Two peroxidase isoforms (with pI < 9) accumulated exclusively in response to drought. These results suggest that at an early stage of infection and drought stress, the two stresses can be distinguished by the temporal appearance and isoform profile of peroxidases and chitinases. Changes in enzyme activity appeared before changes in physiological parameters, thus these isoform profiles could be used as early markers of stress conditions in spruce.

Journal Article↗
PubMed2004

Genetic and functional characterization of a Bacillus sp. strain excreting surfactin and antifungal metabolites partially identified as iturin-like compounds.

AIMS: A bacterial strain producing antifungal compounds active against the plant pathogenic fungi Fusarium, Rhizoctonia and Sclerotinia has been characterized and shown to control Rhizoctonia root rot of soya bean. METHODS AND RESULTS: The metabolites excreted by Bacillus BNM 122 remained active after autoclaving, were resistant over a wide pH range and to hydrolytic enzymes. By (1)H-NMR and thin-layer chromatography analyses surfactin and iturin-like compounds were partially identified. Moreover, soya bean seeds bacterization with BNM 122 in a compost-based formulation was as effective controlling Rhizoctonia solani as pentachloronitrobenzene. According to its 16S rDNA sequence BNM 122 was closely related to Bacillus amyloliquefaciens and Bacillus subtilis. PCR analysis of the 16S-23S rRNA intergenic spacer region and repetitive sequence-based PCR (rep-PCR) genomic fingerprinting revealed a close genetic relationship to B. amyloliquefaciens. However, by physiological characterization using API tests, this strain resembled more B. subtilis. CONCLUSIONS: This is the first report describing the co-production of surfactin and iturin-like compounds by a putative strain of B. amyloliquefaciens. The synergistic effect of both lipopetides is a remarkable trait for a candidate biocontrol agent. SIGNIFICANCE AND IMPACT OF THE STUDY: This kind of research has relevance in order to minimize the use of synthetic fungicides and surfactants, contributing to the preservation of the environment.

Ascomycota↗
PubMed2026

The H3K27me3 reader GmLHP1 impairs Phytophthora sojae resistance by repressing ethylene precursor accumulation in soybean.

Phytophthora root rot, caused by Phytophthora sojae, is a devastating soilborne disease of soybean (Glycine max). However, the epigenetic regulation of soybean responses to P. sojae remains incompletely understood. Here, using genetic, molecular and biochemical approaches, we characterized the functions of LIKE HETEROCHROMATIN PROTEIN 1 (GmLHP1) and its downstream regulatory network. We demonstrated that GmLHP1, as a reader of H3K27me3, negatively regulates soybean resistance to P. sojae. GmLHP1 binds to H3K27me3 peptides in vitro and colocalizes with H3K27me3 marks genome-wide in vivo. The integrated chromatin immunoprecipitation sequencing and RNA sequencing analysis identified the ethylene biosynthesis pathway gene 1-AMINO-CYCLOPROPANE-1-CARBOXYLATE SYNTHASE 18 (GmACS18) as being enriched for H3K27me3 and bound by GmLHP1, leading to its transcriptional downregulation. Notably, GmLHP1 associates with the GmACS18 promoter by directly binding to AATTAA motifs and recognizing H3K27me3 marks. Moreover, GmACS18 enhances defense against P. sojae by accumulating the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC). Further analysis unveiled that recognition of H3K27me3 by GmLHP1 is essential for regulating soybean resistance to P. sojae through repressing GmACS18 transcription and decreasing ACC accumulation. Our findings reveal a novel epigenetic regulatory mechanism in which the H3K27me3 reader GmLHP1 blocks soybean resistance to P. sojae by repressing ethylene precursor ACC accumulation.

ACC accumulation↗
PubMed1993

Role of copper resistance in competitive survival of Pseudomonas fluorescens in soil.

A copper-resistant strain (09906) of Pseudomonas fluorescens that was isolated from a citrus grove soil is being investigated as a biological control agent for Phytophthora root rot. Since citrus grove soils in California are often contaminated with copper from many years of copper fungicide applications, the role of copper resistance in survival of strain 09906 was investigated. Three copper-sensitive Tn5 mutants were obtained with insertions in different chromosomal DNA regions. These insertions were not in the chromosomal region that hybridized with the copper resistance operon (cop) cloned from Pseudomonas syringae. A copper-sensitive mutant survived as well as the wild type in a sterile loamy sand without added copper, but with 10 and 15 micrograms of CuSO4 added per g of soil, populations of the copper-sensitive mutant were 27- and 562-fold lower, respectively, than that of the wild type after a 25-day period. In a sterilized citrus grove soil, populations of the copper-sensitive mutant and wild-type strain were similar, but in nonsterile citrus soil, populations of the copper-sensitive mutant were 112-fold lower than the wild type after 35 days. These data suggest that copper resistance genes can be important factors in persistence of P. fluorescens in soil contaminated with copper. In addition, these genes appear to play a role in competitive fitness, even in soils with a low copper content.

Agriculture↗
PubMed1994

Mutations Affecting Hyphal Colonization and Pyoverdine Production in Pseudomonads Antagonistic toward Phytophthora parasitica.

In previous studies, Pseudomonas putida 06909 and Pseudomonas fluorescens 09906 suppressed populations of Phytophthora parasitica in the citrus rhizosphere, suggesting that these bacteria may be useful in biological control of citrus root rot. In this study we investigated the mechanisms of antagonism between the bacteria and the fungus. Both bacteria colonized Phytophthora hyphae and inhibited the fungus on agar media. A hyphal column assay was developed to measure the colonization of bacteria on fungal hyphae and to enrich for colonization-deficient mutants. In this way we identified Tn5 mutants of each pseudomonad that were not able to colonize the hyphae and inhibit fungal growth in vitro. Colonization-deficient mutants were nonmotile and lacked flagella. Survival of nonmotile mutants in a citrus soil was similar to survival of a random Tn5 mutant over a 52-day period. Additional screening of random Tn5 mutants of both pseudomonads for loss of fungal inhibition in vitro yielded two distinct types of mutants. Mutants of the first type were deficient in production of pyoverdines and in inhibition of the fungus in vitro, although they still colonized fungal hyphae. Mutants of the second type lacked flagella and were not able to colonize the hyphae or inhibit fungal growth. No role was found for antibiotic production by the two bacteria in the inhibition of the fungus. Our results suggest that both hyphal colonization and pyoverdine production are important in the inhibition of Phytophthora parasitica by P. fluorescens and P. putida in vitro.

Journal Article↗
PubMed1995

Tn5-directed cloning of pqq genes from Pseudomonas fluorescens CHA0: mutational inactivation of the genes results in overproduction of the antibiotic pyoluteorin.

Pseudomonas fluorescens CHA0 produces several secondary metabolites, e.g., the antibiotics pyoluteorin (Plt) and 2,4-diacetylphloroglucinol (Phl), which are important for the suppression of root diseases caused by soil-borne fungal pathogens. A Tn5 insertion mutant of strain CHA0, CHA625, does not produce Phl, shows enhanced Plt production on malt agar, and has lost part of the ability to suppress black root rot in tobacco plants and take-all in wheat. We used a rapid, two-step cloning-out procedure for isolating the wild-type genes corresponding to those inactivated by the Tn5 insertion in strain CHA625. This cloning method should be widely applicable to bacterial genes tagged with Tn5. The region cloned from P. fluorescens contained three complete open reading frames. The deduced gene products, designated PqqFAB, showed extensive similarities to proteins involved in the biosynthesis of pyrroloquinoline quinone (PQQ) in Klebsiella pneumoniae, Acinetobacter calcoaceticus, and Methylobacterium extorquens. PQQ-negative mutants of strain CHA0 were constructed by gene replacement. They lacked glucose dehydrogenase activity, could not utilize ethanol as a carbon source, and showed a strongly enhanced production of Plt on malt agar. These effects were all reversed by complementation with pqq+ recombinant plasmids. The growth of a pqqF mutant on ethanol and normal Plt production were restored by the addition of 16 nM PQQ. However, the Phl- phenotype of strain CHA625 was due not to the pqq defect but presumably to a secondary mutation. In conclusion, a lack of PQQ markedly stimulates the production of Plt in P. fluorescens.

Amino Acid Sequence↗
PubMed1997

Molecular cloning, structural analysis, and expression in Escherichia coli of a chitinase gene from Enterobacter agglomerans.

The gene chiA, which codes for endochitinase, was cloned from a soilborne Enterobacter agglomerans. Its complete sequence was determined, and the deduced amino acid sequence of the enzyme designated Chia_Entag yielded an open reading frame coding for 562 amino acids of a 61-kDa precursor protein with a putative leader peptide at its N terminus. The nucleotide and polypeptide sequences of Chia_Entag showed 86.8 and 87.7% identity with the corresponding gene and enzyme, Chia_Serma, of Serratia marcescens, respectively. Homology modeling of Chia_Entag's three-dimensional structure demonstrated that most amino acid substitutions are at solvent-accessible sites. Escherichia coli JM109 carrying the E. agglomerans chiA gene produced and secreted Chia_Entag. The antifungal activity of the secreted endochitinase was demonstrated in vitro by inhibition of Fusarium oxysporum spore germination. The transformed strain inhibited Rhizoctonia solani growth on plates and the root rot disease caused by this fungus in cotton seedlings under greenhouse conditions.

Amino Acid Sequence↗
PubMed1998

Detoxification of Benzoxazolinone Allelochemicals from Wheat by Gaeumannomyces graminis var. tritici, G. graminis var. graminis, G. graminis var. avenae, and Fusarium culmorum.

The ability of phytopathogenic fungi to overcome the chemical defense barriers of their host plants is of great importance for fungal pathogenicity. We studied the role of cyclic hydroxamic acids and their related benzoxazolinones in plant interactions with pathogenic fungi. We identified species-dependent differences in the abilities of Gaeumannomyces graminis var. tritici, Gaeumannomyces graminis var. graminis, Gaeumannomyces graminis var. avenae, and Fusarium culmorum to detoxify these allelochemicals of gramineous plants. The G. graminis var. graminis isolate degraded benzoxazolin-2(3H)-one (BOA) and 6-methoxy-benzoxazolin-2(3H)-one (MBOA) more efficiently than did G. graminis var. tritici and G. graminis var. avenae. F. culmorum degraded BOA but not MBOA. N-(2-Hydroxyphenyl)-malonamic acid and N-(2-hydroxy-4-methoxyphenyl)-malonamic acid were the primary G. graminis var. graminis and G. graminis var. tritici metabolites of BOA and MBOA, respectively, as well as of the related cyclic hydroxamic acids. 2-Amino-3H-phenoxazin-3-one was identified as an additional G. graminis var. tritici metabolite of BOA. No metabolite accumulation was detected for G. graminis var. avenae and F. culmorum by high-pressure liquid chromatography. The mycelial growth of the pathogenic fungi was inhibited more by BOA and MBOA than by their related fungal metabolites. The tolerance of Gaeumannomyces spp. for benzoxazolinone compounds is correlated with their detoxification ability. The ability of Gaeumannomyces isolates to cause root rot symptoms in wheat (cultivars Rektor and Astron) parallels their potential to degrade wheat allelochemicals to nontoxic compounds.

Journal Article↗