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The wilt-inducing strains of Fusarium oxysporum are responsible for severe damage to many economically important plant species. The most cost-effective and environmentally safe method for the management of Fusarium wilt is the use of resistant cultivars when they are available. In the present study, the Arabidopsis genotype with disruptions in the β-amylase 3 (BAM3) gene, which encodes the major hydrolytic enzyme that degrades starch to maltose, had significantly lower susceptibility to Fusarium oxysporum f. sp. raphani (For) compared to wild-type (wt) plants. It showed the lowest disease severity and contained reduced quantities of fungal DNA in the plant vascular tissues when analyzed with real-time PCR. Through metabolomic analysis using gas chromatography (GC)–mass spectrometry (MS) and gene-expression analysis by reverse-transcription quantitative PCR (RT-qPCR), we observed that defense responses of Arabidopsis bam3 mutants are associated with starch-degradation enzymes, the corresponding modification of the carbohydrate balance, and alterations in sugar (glucose, sucrose, trehalose, and myo-inositol) and auxin metabolism. [ABSTRACT FROM AUTHOR]

Vascular wilt fungal pathogens cause heavy economic losses to a wide range of crops; amongst them are Fusarium oxysporum f. sp. melonis (FOM) and Verticillium dahliae Kleb. Several strategies for controlling these pathogens have been introduced, such as soil solarization, resistant rootstocks and biological control. In this study, the suppressive ability of seven different compost amendments and the plant growth-promoting rhizobacterium Paenibacillus alvei K165 (with proven activity against V. dahliae) were tested against FOM in melon and V. dahliae in eggplant. It was shown that K165 had a suppressive effect against the pathogens in all experiments. On the contrary, the composts exhibited a narrow spectrum of effectiveness against the pathogens. Two composts were effective against V. dahliae and one against FOM. Moreover, we investigated the potential of the various compost samples and K165 to induce resistance in an Arabidopsis thaliana– V. dahliae or FOM model system. It was demonstrated that three composts and K165 were effective against V. dahliae; whereas, one compost and K165 were effective against FOM. In a naturally V.dahliae infested field, the ability of K165 to enhance the suppressive effect of one of the compost amendments, was evaluated. It was demonstrated that fortification of the compost with strain K165 significantly reduced disease severity, whereas the single application of the compost was not sufficient to significantly protect the plants. [ABSTRACT FROM AUTHOR]

Phytopathogenic strains of Fusarium oxysporum cause destructive vascular wilt disease limiting the yield of many economically important crops. Because of the pathogen's vascular lifestyle, the use of resistant cultivars is an effective, environmentally friendly and sustainable strategy for disease management. Our study showed that the disruption of β-amylase 3 gene (BAM3) led to increased resistance to F. oxysporum f. sp. raphani, since the Arabidopsis thaliana bam3 mutant exhibited significantly reduced susceptibility to the pathogen. Additionally, cell wall pectin modification by methylesterification is important for bam3 defense responses against F. oxysporum. • Arabidopsis bam3 mutant showed lower disease severity and contained smaller amount of fungal DNA in its vascular tissues compared to the wild type plants. • The resistant phenotype of A. thaliana bam3 plants is related to hormone mediated pathways. • The cell walls of bam3 plants were enriched in pectin with induced degree of methylation after F. oxysporum inoculation. • The level and pattern of pectin in bam3 plants was consistent with the activity of pectin methylesterases and their inhibitors, contributing to defense responses against F. oxysporum. [ABSTRACT FROM AUTHOR]

Abstract: Verticillium wilt is a devastating disease of a wide range of herbaceous and woody plant hosts. It is incited by the soilborne fungus Verticillium dahliae. Management strategies are mainly focused on preventive measures. In a previous study, the efficacy of a non-pathogenic Fusarium oxysporum strain, designated as F2, isolated from a suppressive compost amendment, has been reported to reduce Verticillium wilt symptom development in eggplants under greenhouse and field conditions; in addition, antibiosis or parasitism were ruled out by using a dual culture test. In the present study, we investigated the mode of action of F2 against V. dahliae. For this purpose, the F2 and V. dahliae strains were transformed with the EGFP and DsRed2 reporter genes respectively, so as to visualize their presence on the root surface of eggplants. In addition, the ramification of both fungi into the plant vascular system was monitored by Real Time QPCR analysis. It was shown that F2 colonizes the root surface along the intercellular junctions excluding V. dahliae from the same ecological niche. In parallel, QPCR analysis showed that application of F2 reduces the levels of V. dahliae vascular colonization along with the disease severity. In a split root experiment it was demonstrated that F2 does not trigger the defense mechanisms of eggplants against V. dahliae. Therefore, it seems that competition for space or nutrients on the root surface are the main mechanism of action of F2 against V. dahliae. [Copyright &y& Elsevier]