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BIOLOGICAL CONTROL IN GREENHOUSE SYSTEMS (2001)

Paulitz, Timothy C. ; Belanger, Richard R.

Palo Alto, Calif. : Annual Reviews

Annual Review of Phytopathology 39 (2001), S. 103-133

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ISSN: 0066-4286

Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Biology

Notes: Abstract The controlled environment of greenhouses, the high value of the crops, and the limited number of registered fungicides offer a unique niche for the biological control of plant diseases. During the past ten years, over 80 biocontrol products have been marketed worldwide. A large percentage of these have been developed for greenhouse crops. Products to control soilborne pathogens such as Sclerotinia, Pythium, Rhizoctonia and Fusarium include Coniothyrium minitans, species of Gliocladium, Trichoderma, Streptomyces, and Bacillus, and nonpathogenic Fusarium. Products containing Trichoderma, Ampelomyces quisqualis, Bacillus, and Ulocladium are being developed to control the primary foliar diseases, Botrytis and powdery mildew. The development of Pseudomonas for the control of Pythium diseases in hydroponics and Pseudozyma flocculosa for the control of powdery mildew by two Canadian research programs is presented. In the future, biological control of diseases in greenhouses could predominate over chemical pesticides, in the same way that biological control of greenhouse insects predominates in the United Kingdom. The limitations in formulation, registration, and commercialization are discussed, along with suggested future research priorities.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1146/annurev.phyto.39.1.103

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Pre-inoculation of Ri T-DNA-transformed pea roots with Pseudomonas fluorescens inhibits colonization by Pythium ultimum Trow: an ultrastructural and cytochemical study (1996)

Benhamou, Nicole ; Bélanger, Richard R. ; Paulitz, Timothy C.

Springer

Planta 199 (1996), S. 105-117

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ISSN: 1432-2048

Keywords: Biological control ; Gold cytochemistry ; Induced resistance ; Plant growth-promoting rhizobacteria ; Pythium (root infection)

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract The influence exerted by Pseudomonas fluorescens, strain 63-28R, in stimulating plant defense reactions was investigated using an in-vitro system in which Ri T-DNA-transformed pea (Pisum sativum L.) roots were subsequently infected with Pythium ultimum. Cytological investigations of samples from P. fluorescens-inoculated roots revealed that the bacteria multiplied abundantly at the root surface and colonized a small number of epidermal and cortical cells. Penetration of the epidermis occurred through the openings made by the disruption of the fibrillar network at the junction of adjacent epidermal cell walls. Direct cell wall penetration was never observed and bacterial ingress into the root tissues proceeded via an intercellular route. Striking differences in the extent of fungal colonization were observed between bacterized and non-bacterized pea roots following inoculation with P. ultimum. In non-bacterized roots, the pathogen multiplied abundantly through most of the tissues while in bacterized roots, pathogen growth was restricted to the epidermis and the outer cortex. At the root surface, the bacteria interacted with the pathogen, in a way similar to that observed in dual culture tests. Most Pythium cells were severely damaged but fungal penetration by the bacteria was never observed. Droplets of the amorphous material formed upon interaction between the bacteria and the host root were frequently found at the fungal cell surface. Incubation of sections with a β-1,4-exoglucanase-gold complex revealed that the cell wall of markedly altered Pythium hyphae was structurally preserved. Successful penetration of the root epidermis was achieved by the few hyphae of P. ultimum that could escape the first defensive line in the rhizosphere. Most hyphae of the pathogen that penetrated the epidermis exhibited considerable changes. The unusual occurrence of polymorphic wall appositions along the host epidermal cells was an indication that the host plant was signalled to defend itself through the elaboration of physical barriers.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00196887

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A Novel Antifungal Furanone from Pseudomonas aureofaciens, a Biocontrol Agent of Fungal Plant Pathogens (2000)

Paulitz, Timothy ; Nowak-Thompson, Brian ; Gamard, Pascale ; [et al.]

Springer

Journal of chemical ecology 26 (2000), S. 1515-1524

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ISSN: 1573-1561

Keywords: 2(5H)-Furanone ; butenolide ; lactone ; butyrolactone ; antibiotic ; biological control ; Pseudomonas chlororaphis ; Pythium ultimum ; Rhizoctonia solani ; Fusarium solani ; Fusarium oxysporum ; Thielaviopsis basicola

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Chemistry and Pharmacology

Notes: Abstract Pseudomonas aureofaciens (= P. chlororaphis) strain 63-28 is a biocontrol agent active against many soil-borne fungal plant pathogens and shows antifungal activity in culture assays. 3-(1-Hexenyl)-5-methyl-2-(5H)furanone was isolated from culture filtrates of this bacterium. The purified furanone showed antifungal activity against Pythium ultimum, Fusarium solani, Fusarium oxysporum, and Thielaviopsis basicola. The ED50S for spore germination of these fungi were 45, 54, 56, and 25 μg/ml, respectively. The compound also inhibited the germ tube growth of Rhizoctonia solani growing from microsclerotia, with an ED50 of 61 μg/ml. The compound is the reduced form of furanones previously described from this bacterium: 3-(1-hexenyl)-5-hydroxy-5-methyl-2-(5H)-furanone and 3-(1-hexenyl)-5-hydroxymethyl-2-(5H)-furanone. This volatile antifungal furanone has structural similarity to other antifungal furanones produced by actinomycetes (Streptomyces spp.), fungi (Trichoderma harzianum), and higher plants (Pulsatilla and Ranuculus spp.). This is the first report of 3-(1-hexenyl)-5-methyl-2-(5H)-furanone produced by a bacterium.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1005595927521

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Role of Salicylic Acid in Systemic Resistance Induced by Pseudomonas spp. Against Pythium aphanidermatum in Cucumber Roots (1999)

Chen, Chunquan ; Bélanger, Richard R. ; Benhamou, Nicole ; [et al.]

Springer

European journal of plant pathology 105 (1999), S. 477-486

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ISSN: 1573-8469

Keywords: cucumber root rot ; high performance liquid chromatography ; induced systemic resistance ; plant growth-promoting rhizobacteria ; Pseudomonas aureofaciens ; Pseudomonas corrugata

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Pseudomonas corrugata strain 13 and P. aureofaciens strain 63-28, applied to roots, induced systemic resistance against Pythium aphanidermatum in cucumber roots. Salicylic acid (SA) from bacterial culture or plant tissues was quantified by high performance liquid chromatography. Both strains produced SA in King's B broth and also induced cucumber root to accumulate endogenous SA one day after bacterial inoculation. Using a split root system, more SA accumulated in roots treated with bacteria than in distant roots on the opposite side of the root system in the first two days, but this difference disappeared after 3–4 days. SA levels were significantly higher in plants treated with bacteria compared to the split control, from one to five days after bacterization. SA did not inhibit mycelial growth of Pythium aphanidermatum at 100–200 µg ml−1 in vitro, but higher levels inhibited mycelial growth. Zoospore germination increased at concentrations of 10–500 µg ml−1, but decreased at 1000 µg ml−1 compared to lower concentrations. Exogenously applied SA failed to induce local or systemic resistance against a challenge infection by the pathogen in planta. The results of this study show that exogenous applied SA does not induce systemic resistance to cucumber root rot caused by P. aphanidermatum, but endogenous SA accumulation in cucumber roots may be involved in induced systemic resistance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008743502784

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In vitro evaluation of fungal isolates for their ability to influence leaf rheology, production of pseudothecia, and ascospores of Venturia inaequalis (1997)

Philion, Vincent ; Carisse, Odile ; Paulitz, Timothy

Springer

European journal of plant pathology 103 (1997), S. 441-452

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ISSN: 1573-8469

Keywords: antagonism ; apple scab ; biological control

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract As part of an ongoing research project on biological control of apple scab, this study presents a novel approach for the in vitro selection of potential antagonists of the saprophytic phase of Venturia inaequalis. A collection of forty-two fungal isolates were tested for their in vitro ability to degrade apple leaf tissue, inhibit pseudothecia, and ascospore production. The inhibition of ascospore production cannot always be linked reliably with leaf degradation or the evaluation of pseudothecia production. Consequently, ascospore production was retained as the most useful screening parameter. Six isolates proved to significantly reduce the ascospore production of Venturia inaequalis. Two were as effective as Athelia bombacina, a previously reported antagonist of pseudothecia formation and inhibited over 98% of the ascospore production. These new organisms are now available for future field tests. Future selections from a large collection of fungal and bacterial saprophytes can now be based on a reliable and simple in vitro screening method.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008637430975

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Induced Systemic Resistance (ISR) by Pseudomonas spp. Impairs Pre- and Post-Infection Development of Pythium aphanidermatum on Cucumber Roots (1998)

Chen, Chunquan ; Bélanger, Richard R. ; Benhamou, Nicole ; [et al.]

Springer

European journal of plant pathology 104 (1998), S. 877-886

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ISSN: 1573-8469

Keywords: biological control ; Pythium root rot of cucumber ; Pythium aphanidermatum ; rhizobacteria ; induced resistance ; Pseudomonas aureofaciens ; Pseudomonas corrugata

Source: Springer Online Journal Archives 1860-2000

Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract The effect of induced systemic resistance (ISR) by Pseudomonas rhizobacteria on the pre- and post-infection development of Pythium aphanidermatum on cucumber roots was investigated. Cucumber plants (cv. Corona) were grown in vermiculite, roots were split with one side bacterized with Pseudomonas corrugata strain 13 or P. aureofaciens strain 63-28 (bacterized roots) and the other distant side was treated with water (distant, induced roots). For the non-induced control, roots on the bacterized side were treated with buffer instead of the bacterial treatment. Intact, non-split roots were also treated with the bacteria or buffer as a control. Cucumber root tissue from these treatments were harvested and incubated with a zoospore suspension of P. aphanidermatum for three hours. Most of the zoospores in the suspension were stimulated to encyst or germinate. The numbers of germinated zoospores were significantly decreased on distant induced cucumber roots in comparison to non-induced controls. Germination was also reduced on intact bacterized roots, compared to controls. There was less attachment, germ tube production and penetration on roots bacterized or induced by the rhizobacteria compared to non-induced roots. Effects were significantly greater on bacterized roots (roots colonized by bacteria) compared to distant induced roots (roots with the opposite side bacterized). Systemic resistance induced by the two Pseudomonas spp. also reduced pathogen spread on split cucumber roots in planta. Crown infection from induced or bacterized roots was delayed for four to six days in comparison to the non-induced control. Results indicated that Pseudomonas spp. can exert both an indirect influence on P. aphanidermatum zoospore behaviour and infection via induced systemic resistance (ISR) and a local influence via antibiosis or local induced resistance.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008613003951

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