Suppression of Fusarium Wilt of Watermelon by NonpathogenicFusarium oxysporumand Other Microorganisms Recovered from a Disease-Suppressive Soil

Larkin, Robert P.; Hopkins, D. L.; Martin, Frank N.

doi:10.1094/phyto-86-812

Cited by 185 publications

(85 citation statements)

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“…Among the bacterial and fungal genera proposed to contribute to Fusarium wilt suppressiveness are Alcaligenes (Yuen and Schroth, 1986), Trichoderma (Sivan and Chet, 1989), Actinomycetes (Amir and Amir, 1989), Pseudomonas (Kloepper et al, 1980;Scher and Baker, 1982; and non-pathogenic F. oxysporum (Alabouvette, 1986;Larkin et al, 1996). Detailed studies on Fusarium-wilt suppressive soils from Châteaurenard (France) and Salinas Valley showed that the suppressiveness was attributed, in particular, to the activity of non-pathogenic F. oxysporum and fluorescent pseudomonads (Scher and Baker, 1982;Alabouvette, 1990;Lemanceau and Alabouvette, 1991;Duijff et al, 1999).…”

Section: Introductionmentioning

confidence: 99%

Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt

et al. 2009

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Natural disease-suppressive soils provide an untapped resource for the discovery of novel beneficial microorganisms and traits. For most suppressive soils, however, the consortia of microorganisms and mechanisms involved in pathogen control are unknown. To date, soil suppressiveness to Fusarium wilt disease has been ascribed to carbon and iron competition between pathogenic Fusarium oxysporum and resident non-pathogenic F. oxysporum and fluorescent pseudomonads. In this study, the role of bacterial antibiosis in Fusarium wilt suppressiveness was assessed by comparing the densities, diversity and activity of fluorescent Pseudomonas species producing 2,4-diacetylphloroglucinol (DAPG) (phlD+) or phenazine (phzC+) antibiotics. The frequencies of phlD+ populations were similar in the suppressive and conducive soils but their genotypic diversity differed significantly. However, phlD genotypes from the two soils were equally effective in suppressing Fusarium wilt, either alone or in combination with non-pathogenic F. oxysporum strain Fo47. A mutant deficient in DAPG production provided a similar level of control as its parental strain, suggesting that this antibiotic does not play a major role. In contrast, phzC+ pseudomonads were only detected in the suppressive soil. Representative phzC+ isolates of five distinct genotypes did not suppress Fusarium wilt on their own, but acted synergistically in combination with strain Fo47. This increased level of disease suppression was ascribed to phenazine production as the phenazine-deficient mutant was not effective. These results suggest, for the first time, that redox-active phenazines produced by fluorescent pseudomonads contribute to the natural soil suppressiveness to Fusarium wilt disease and may act in synergy with carbon competition by resident non-pathogenic F. oxysporum.

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Section: Introductionmentioning

confidence: 99%

Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt

et al. 2009

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“…Their association with host plants are known to improve plant growth and vigour (Ting et al, 2008), enhance plant nutrient absorption (Chanway, 1996) and to potentially confer disease resistance in plants against pathogen infection (Ting et al, 2007). Similar to other soil-borne biocontrol agents, endophytes also produce the following biocontrol activity-production of antimicrobial compounds, competition for colonizing sites and nutrients and stimulation of host defenses; as their mechanisms of inhibition towards various pathogens (Benhamou et al, 2000;Larkin et al, 1996;Pleban et al, 1995).…”

Section: Introductionmentioning

confidence: 99%

Identification of Volatile Metabolites from Fungal Endophytes with Biocontrol Potential towards Fusarium oxysporum F. sp. cubense Race 4

Ting¹,

Mah

Tee

2010

American Journal of Agricultural and Biological Sciences

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Problem statement: Fungal endophytes are widely studied for their potential as biocontrol agents towards fungal pathogens. In vitro assessments usually reveal their antibiosis and mycoparasitism nature, but little is understood regarding their production of volatile metabolites as mechanisms of antagonism. Approach: This study explored the potential of fungal endophytes in controlling the pathogen responsible for Fusarium wilt disease. Nine fungal endophytes were tested for their ability to inhibit the growth of the pathogenic Fusarium oxysporum F. sp. cubense race 4 (FocR4) via production of volatile inhibitory metabolites. The type of volatile metabolites produced were subsequently characterized and identified using the Gas-Chromatography Mass-Spectrophotometry (GCMS). Results: Eight of the isolates (BTF05, BTF07, BTF08, BTF15, BTF21, WAA03, WAA02, MIF01) showed positive results with percentages of inhibition varying from 1.43-31.43% while one isolate (ALF01), showed negative result (0% inhibition). Volatile profiles showed that these fungal endophytes produced between 15-47 volatile metabolites per isolate. However, the more volatile metabolites produced by a single endophyte does not indicate better biocontrol potential. Isolate BTF05 produced 47 different volatile metabolites, but has only 8.57% inhibition, compared to isolate BTF21 with 15 metabolites but a percentage of 11.43% inhibition. The potency of the volatile metabolites produced may also influenced the biocontrol potential of the fungal endophytes as some isolates such as BTF08 and MIF01 have only two to three known inhibitory metabolites but have higher PIDG values at 31.43 and 11.43%, respectively. Contrary, isolates WAA02 and WAA03 which has five to six metabolites but PIDG values of less than 3%. Conclusion: Fungal endophytes have the ability to produce several types of volatile metabolites to inhibit the growth of FocR4. These volatile inhibitory metabolites can be further extracted and the amount produced ascertained for future manipulation in biological control of FocR4.

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“…The persistence of nonpathogenic variants of plant and animal pathogens in the environment has been a springboard for the development of biological control for plant pathogens (van Alfen, 1982;Kerr, 1987;Larkin et al, 1996) and of diseases of human and animal intestinal and urinary tracts (Kruis et al, 2004;Schneitz, 2005). The diversity, abundance and ubiquity of nonpathogenic strains of P. syringae suggest that competitive exclusion of pathogen strains by nonpathogenic conspecifics as a means to control disease might be worth exploring.…”

Section: Discussionmentioning

confidence: 99%

Pseudomonas syringae naturally lacking the canonical type III secretion system are ubiquitous in nonagricultural habitats, are phylogenetically diverse and can be pathogenic

et al. 2012

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The type III secretion system (T3SS) is an important virulence factor of pathogenic bacteria, but the natural occurrence of variants of bacterial plant pathogens with deficiencies in their T3SS raises questions about the significance of the T3SS for fitness. Previous work on T3SS-deficient plant pathogenic bacteria has focused on strains from plants or plant debris. Here we have characterized T3SS-deficient strains of Pseudomonas syringae from plant and nonplant substrates in pristine nonagricultural contexts, many of which represent recently described clades not yet found associated with crop plants. Strains incapable of inducing a hypersensitive reaction (HR À ) in tobacco were detected in 65% of 126 samples from headwaters of rivers (mountain creeks and lakes), snowpack, epilithic biofilms, wild plants and leaf litter and constituted 2 to 100% of the P. syringae population associated with each sample. All HR À strains lacked at least one gene in the canonical hrp/hrc locus or the associated conserved effector locus, but most lacked all six of the genes tested (hrcC, hrpL, hrpK1, avrE1 and hrpW1) and represented several disparate phylogenetic clades. Although most HR À strains were incapable of causing symptoms on cantaloupe seedlings as expected, strains in the recently described TA-002 clade caused severe symptoms in spite of the absence of any of the six conserved genes of the canonical T3SS according to PCR and Southern blot assays. The phylogenetic context of the T3SS variants we observed provides insight into the evolutionary history of P. syringae as a pathogen and as an environmental saprophyte.

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Suppression of Fusarium Wilt of Watermelon by NonpathogenicFusarium oxysporumand Other Microorganisms Recovered from a Disease-Suppressive Soil

Cited by 185 publications

References 0 publications

Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt

Phenazine antibiotics produced by fluorescent pseudomonads contribute to natural soil suppressiveness to Fusarium wilt

Identification of Volatile Metabolites from Fungal Endophytes with Biocontrol Potential towards <i>Fusarium oxysporum</i> F. sp. <i>cubense</i> Race 4

Pseudomonas syringae naturally lacking the canonical type III secretion system are ubiquitous in nonagricultural habitats, are phylogenetically diverse and can be pathogenic

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