Impact of salinity stress on soil-borne fungi of sugarbeet

The sugarbeet cultivar Kaumera was found to be highly susceptible to infection by the root-rot pathogens Rhizoctonia solani and Sclerotium rolfsii in the absence of salinity stress. Under this environmental condition, R. solani was more efficient than S. rolfsii in producing cell wall-degrading enzymes in infected hypocotyls. Xylanase and galactanase were most effective. The rate of cell wall degradation by R. solani was nearly 2.5 times that of S. rolfsii when cells walls of healthy hypocotyls were used as sole carbon substrate for the in vitro produced crude enzymes.Under salinity stress the pathogenicity and the performance of cell wall-degrading enzymes of R. solani and S. rolfsii varied profoundly. Pathogenicity studies showed that R. solani appeared to be more tolerant than S. rolfsii of the salinity stresses applied, and relatively more virulent to cv Kaumera. The activities of cell wall enzymes of R. solani decreased and those of S. rolfsii increased with increased salt concentration when cell wall material was used as a sole carbon source. The metabolic products produced under salinity stress by R. solani and R. solani in the cell wall amended culture media shifted the initial pH towards neutrality or slight alkalinity for R. solani and to high acidity for S. rolfsii.When model substrates were used, xyland and galactan were the most responsive substrates for degradation by the cell wall enzymes of the two fungi studied. The rate of degradation was higher for S. rolfsii than for R. solani. The excessive acidity in salt stressed S. rolfsii culture media suggested reduced activities of the enzymes involved in cell wall degradation in vivo. This may explain the decreased virulence potentialities.     

Metabolic activities of the sugarbeet pathogens Fusarium solani (Mart.) Sacc. and Sclerotium rolfsii Sacc. under pyramin stress

Effects of different concentrations of active ingredient of the herbicide pyramin on metabolic activities of Fusarium solani and Sclerotium rolfsii were examined. High concentrations of this herbicide (1000 and 2000 g mL^-1 for F. solani and 100 and 200 g mL^-1 for S. rolfsii) had inhibitory effects on the metabolic activities of both fungi. These were demonstrated by significant decreases in growth, and increases in rates of CO₂ evolved, O₂ consumed and keto acids produced. These were accompanied by increased rates of sugar, nitrate and inorganic phosphorus absorption as well as lowered rates of synthesis of carbohydrates and insoluble nitrogenous (including protein) and phosphorus (including RNA-P and DNA-P) compounds. In addition, rates of excretion of both nitrogen and phosphorus fractions by the mycelial mats were increased.A concentration of 25 g mL^-1 exerted little or no effect on the metabolic activities of these fungi, although S. rolfsii was somewhat sensitive to this concentration.     

Drug Resistance of Staphylococci

According to an epidemiological survey of drug resistance in Staphylococcus aureus, it was found that there are three types of cross-resistance to macrolide antibiotics (EM, erythromycin: OM, oleandomycin: LM, leucomycin: SP, spiramycin), i.e., resistance to EM, OM, LM, and SP, to EM and OM, and inducible resistance to “EM, OM”. In the inducible strains of S. aureus, EM and OM are active inducers, and the optimal concentrations of the inducers are 0.1 μg/ml and 1.0 μg/ml, respectively. The induction of high resistance (800 μg/ml or more) to both EM and OM occurred within 10 min exposure to 0.1 μg/ml of EM, and the resistance of induced cells was lost after overnight growth in the absence of inducer. After 1 to 3 hr exposure to 1.0 μg/ml of OM, the inducible strains acquired high resistance (100 μg/ml or more) to EM and to a lesser extent, resistance to OM, and the acquired resistance was lost when grown in antibiotic free media. When a known concentration of EM was mixed with the induced cells or with a crude extract from induced cells which had acquired high resistance to EM and OM, the antibiotic activity of EM was still retained in the mixture, indicating that the induced mixture or the extract from the induced cells was incapable of antibiotic (EM) inactivation under the test conditions.     

Hydrogen peroxide is involved in the sclerotial differentiation of filamentous phytopathogenic fungi

Aims: The purpose of this study was to investigate the role of H₂O₂ and the related oxidative stress markers catalase (CAT) and lipid peroxidation in the sclerotial differentiation of the phytopathogenic filamentous fungi Sclerotium rolfsii, Sclerotinia minor, Sclerotinia sclerotiorum and Rhizoctonia solani. Methods and Results: Using the H₂O₂‐specific scopoletin fluorometric assay and the CAT‐dependent H₂O₂ consumption assays, it was found that the production rate of intra/extracellular H₂O₂ and CAT levels in the sclerotiogenic fungi were significantly higher and lower, respectively, than those of their nondifferentiating counterpart strains. They peaked in the transition between the undifferentiated and the differentiated state of the sclerotiogenic strains, suggesting both a cell proliferative and differentiative role. In addition, the indirect indicator of oxidative stress, lipid peroxidation, was substantially decreased in the nondifferentiating strains. Conclusions: These findings suggest that the differentiative role of H₂O₂ is expressed via induction of higher oxidative stress in the sclerotiogenic filamentous phytopathogenic fungi. Significance and Impact of the Study: This study shows that the direct marker of oxidative stress H₂O₂ is involved in the sclerotial differentiation of the phytopathogenic filamentous fungi S. rolfsii, S. minor, S. sclerotiorum and R. solani, which could have potential biotechnological implications in terms of developing antifungal strategies by regulating intracellular H₂O₂ levels.     

Double resistance by citrus green mould Penicillium digitatum to the fungicides guazatine and benomyl

In vitro dosage response data with different isolates of Penicillium digitatum and the fungicide guazatine indicated an approximate 10-fold shift in tolerance when compared with wild type strains. ED₅₀ values for resistant strains were approximately 0.5 μg/ml compared to approximately 0.05, μg/ml for the wild type strains. Colony growth of guazatine resistant isolates on selective media containing carbendazim showed that they were also resistant to the benzimidazole group of fungicides. In vivo tests in inoculated oranges with strains previously characterised by in vitro tests confirmed resistance to guazatine and benomyl. A combined treatment of these fungicides at 400 /μ/ml and 500 μg/ml respectively, which normally gives protection against decay, also failed to provide adequate mould control. Growth and pathogenicity of the resistant strains in these tests in oranges were indistinguishable from that of wild type strains.     

Anti-fungal activity of essential oils of Ceylon Eucalyptus species for the control of Fusarium solani and Sclerotium rolfsii

The essential oils were extracted from the leaves of Eucalyptus microcorys, Eucalyptus grandis and Eucalyptus robusta which were grown in Sri Lanka and their major chemical compounds were determined. 1,8-Cineole and α-pinene were identified as major aroma compounds in these oils. In this study, the anti-fungal activity of essential oils of E. microcorys, E. grandis and E. robusta, ethanol extract of E. microcorys and 1,8-cineole were evaluated against Sclerotium rolfsii, a fungi responsible for leaf spot disease of indoor plants and Fusarium solani, a fungi responsible for dry rot diseases of potato by poisoned food technique, and minimum inhibitory concentrations (MICs) were determined. The essential oils from three Eucalyptus species showed significant inhibitory effect against S. rolfsii and F. solani than the ethanol extract of E. microcorys. Of treatments, the essential oil of E. grandis showed the best anti-fungal activity with the MIC values of less than 0.1% for S. rolfsii and 0.5% for F. solani. The MICs of the oils of E. microcorys and E. robusta were between 0.3–0.5% against S. rolfsii and 0.5–0.75% for F. solani. The 1,8-cineole did not exhibit inhibition activity as much of Eucalyptus essential oils and hence, it can be assumed that minor chemical components of the oils contribute to the growth inhibition of the tested fungi. This is the first report of anti-fungal activity of Sri Lankan oils of E. microcorys, E. grandis and E. robusta and ethanol extract of E. microcorys against S. rolfsii and F. solani. These findings would be useful for the designing of natural fungicide for agriculture- and food-based industries.     

Antifungal and antibacterial potential of methanol and chloroform extracts of Marchantia polymorpha L.

The methanol and chloroform extracts of Marchantia polymorpha were tested against three Gram-negative bacterial strains, viz. Xanthomonas oryzae pv. oryzae, Salmonella enterica and Pasturella multocida and four fungal strains, viz. Tilletia indica Mitra, Fusarium oxysporum f. sp. lini, Sclerotium rolfsii Sacc. and Rhizoctonia solani Kuhn. by using disc diffusion and micro broth dilution techniques. Both the extracts showed unique activity against X. oryzae and P.multocida [per cent inhibition (PI) 11.58 and 12.55, minimum inhibitory concentration (MIC) 2.50 and 1.25 μg/mL, minimum bactericidal concentration (MBC) 2.75 and 1.25 μg/mL, respectively] but for fungi, it was shown against S.rolfsii and F. oxysporum [PI 32.65 and 33.44, MIC 2.50 and 0.65 μg/mL, minimum fungicidal concentration (MFC) 4.50 and 0.65 μg/mL, respectively].The extracts possessed antimicrobial activity with different potency against variety of micro-organisms pathogenic to plants as well as animals. Some extracts were fungistatic and bacteriostatic (methanol extract against R. solani and chloroform extract against F. oxysporum and methanol extract for bacteria, respectively), while rest showed fungicidal/bactericidal potential. The results suggest the potential of M. polymorpha for developing a broad spectrum antimicrobial formulation in future.     

A Comparative Study of Caffeine Degradation by Four Different Fungi

The objective of the present study is to investigate the caffeine-degrading abilities of different fungi and to apply this knowledge to environmental remediation and industrial decaffeination process. Chrysosporium keratinophilum, Gliocladium roseum, Fusarium solani, and Aspergillus restrictus were isolated from the coffee pulp obtained from a coffee estate. Pure cultures of fungi were isolated on standard conventional potato dextrose broth (PDB) medium and authenticated. Pure cultures were subjected to a caffeine tolerance study at different concentrations of caffeine (1–8 g/L) in potato dextrose agar (PDA) and minimal media. On PDA, Fusarium solani could tolerate caffeine concentration up to 8 g/L, whereas Chrysosporium keratinophilum, Gliocladium roseum, and Aspergillus restrictus could tolerate up to 6 g/L. On minimal agar medium containing different concentrations of caffeine (1–8 g/L), Fusarium solani tolerated up to 8 g/L and the other fungi up to 2 g/L. A time-bound caffeine degradation study was undertaken at 1 g/L concentration of caffeine and glucose in nitrogen-containing and nitrogen-free liquid minimal media by subjecting the four fungi to shake flask culture at 120 rpm and 30°C. Degradation of caffeine up to 7 days at 24-h intervals was analyzed by high-performance liquid chromatography (HPLC). Gliocladium roseum followed by Aspergillus restrictus showed maximum degradation of caffeine at 0.47 and 0.3 mg/ml, respectively, by 96 h in nitrogen-containing minimal medium, whereas Fusarium solani showed maximum degradation of caffeine by 48 h (0.35 mg/ml) and Chrysosporium keratinophilum by 72 h (0.29 g/ml). In nitrogen-free minimal medium, Chrysosporium keratinophilum showed maximum degradation of caffeine at 72 h (0.45 mg/ml), followed by Gliocladium roseum, Fusarium solani (0.3 mg/ml), and Aspergillus restrictus (0.25 mg/ml) at 96 h. Overall, Chrysosporium keratinophilum showed a comparatively higher rate of caffeine degradation in minimal medium with or without a nitrogen source as compared with the other three fungi, indicating that nitrogen affects caffeine metabolism.     

Design,Synthesis, and Antifungal Activities of Novel Carboxamides Derivatives Bearing a Chalcone Scaffold as Potential SDHIs

In search for SDHIs fungicides, twenty-five novel carboxamides containing a chalcone scaffold were designed, synthesized, and evaluated for antifungal activities against five pathogenic fungi. The results showed that compound 5 k exhibited outstanding antifungal activity against R. solani with an EC₅₀ value of 0.20 μg/mL, which was much better than that of commercial SDHIs Boscalid (EC₅₀=0.74 μg/mL). Moreover, compound 5 k also displayed promising antifungal activities against S. sclerotiorum, B. cinerea, and A. alternate (IC₅₀=2.53–4.06 μg/mL), indicating that 5 k had broad-spectrum antifungal activity. Additionally, in vivo antifungal activities results showed that 5 k could significantly inhibit the growth of R. solani in rice leaves with good protective efficacy (57.78 %) and curative efficacy (58.45 %) at 100 μg/mL, both of which were much better than those of Boscalid, indicating a promising application prospect. Moreover, SEM analysis showed that compound 5 k could remarkably disrupt the typical structure and morphology of R. solani hyphae. Further SDH enzyme inhibition assay and molecular docking study revealed that lead compound 5 k had a similar mechanism of action as commercial SDHI Boscalid. These results indicated that compound 5 k showed potential as a SDHIs fungicide and deserved further investigation.     

Mechanisms of biocontrol of soil-borne plant pathogens by Rhizobacteria

Bacterial antagonism, responsible for biological control, may operate by antiobiosis, competition or parasitism. Parasitism relies on lytic enzymes for the degradation of cell walls of pathogenic fungi. Serratia marcescens was found to be an efficient biocontrol agent of Sclerotium rolfsii and Rhizoctonia solani under greenhouse conditions. Populations of 10⁵ or 10⁶ colony forming units g^-1 soil were the most effective. Drench and drip application of S. marcescens suspension were more effective in controlling S. rolfsii than spraying, mixing in soil or seed coating. The highest population density of the bacteria in the rhizosphere was found on the proximal portion of the root, decreasing significantly until the tips, where it increased again. The isolated Serratia, found to possess chitinolytic activity, was able to release N-acetyl D-glucosamine from cell walls of S. rolfsii. The gene coding for chitinase was cloned into Escherichia coli and the enzyme was uniquely excreted from the bacterium into its growth medium. When S. rolfsii was sprayed by partially purified chitinase produced by the cloned gene, rapid and extensive bursting of the hyphal tips was observed. This chitinase preparation was effective in reducing disease incidence caused by S. rolfsii in beans and R. solani in cotton, under greenhouse conditions. A similar effect was obtained when a viable E. coli cell, containing the plasmid with the chitinase gene (pLCHIA), was applied. It appears that genetic engineering of the lytic enzymes, such as chitinase which play an important role in plant disease control, may improve the efficacy of biocontrol agents.     

Antifungal Activities of N-Arylbenzenesulfonamides against Phytopathogens and Control Efficacy on Wheat Leaf Rust and Cabbage Club Root Diseases

A set of N-arylbenzenesulfonamides with various substituents at the arylamine and benzenesulfonyl positions were prepared, and their antifungal properties were measured in vitro against such plant pathogenic fungi as Pythium ultimum, Phytophthora capsici, Rhizoctonia solani, and Botrytis cinerea. Compounds 3, 4, 8, 9, 10, 14, 16, 18, 20, 21, 24 and 27 had antifungal activity over a broad spectrum of the phytopathogenic fungi tested, where 50% of inhibition (ED₅₀) was in the range of 3-15 μg/ml. Based on the in vitro activity, six derivatives (3, 4, 10, 18, 21 and 27) were selected and tested further for their fungicidal efficacy in vivo. The fungicidal efficacy of 10, 21 and 27 had a disease control value of over 85% at 50 μg/ml against wheat leaf rust, while that of 4 was selective against cabbage club root disease.     

Natural Product‐Based Fungicides Discovery: Design,Synthesis and Antifungal Activities of Some Sarisan Analogs Containing 1,3,4‐Oxadiazole Moieties

A series of sarisan analogs containing 1,3,4‐oxadiazole moieties were synthesized by iodine‐mediated oxidative cyclization and screened in vitro for their antifungal activities at 50 μg/mL against five phytopathogenic fungi such as Valsa mali, Curvularia lunata, Alternaria alternate, Fusarium solani and Fusarium graminearum. 1,3,4‐Oxadiazole derivatives 7e , 7p , 7r , 7t and 7u exhibited potent and a broad spectrum of antifungal activities against at least three phytopathogenic fungi at the concentration of 50 μg/mL. Especially, compound 7r displayed more potent antifungal activities against five phytopathogenic fungi than the positive control hymexazol. The EC₅₀ of 7r against V. mali, C. lunata and A. alternate were 12.6, 14.5 and 17.0 μg/mL, respectively. Additionally, some interesting results of structure‐activity relationships (SARs) were also observed.     

Clinical isolates of <Emphasis Type="Italic">Nocardia brasiliensis</Emphasis> from Japan exhibit variable susceptibility to the antibiotic imipenem

Clinical isolates of Nocardia brasiliensis from Japan were classified into two groups based on their susceptibility to the carbapenem antibiotic, imipenem (IPM). Of 33 strains tested, 10 belonged to an IPM susceptible group, with MIC of from 0.25 to 2 εg/ml and a MIC₈₀ value of 1.5 εg/ml for this antibiotic. The remaining 23 strains belonged to an IPMresistant group with MIC and MIC₈₀ values of 8–16 εg/ml and >16 εg/ml, respectively. The type strain of N. brasiliensis belonged to this resistant group. Analysis of 16S rDNA genes sequences showed that the IPM susceptible group had characteristic single nucleotide substitutions at positions 103 (T), 381 (A), and 456 (A), in contrast to the IPM resistant group. This grouping, however, was not associated with their clinical manifestation.     

Enzymes Associated with Defence against Toxic Oxygen Species in PCNB-Tolerant and Sensitive Soil Fungi

The specific activities of enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPOX) and glutathione reductase (GR), which are involved in protection against toxic species of oxygen, were determined in mycelia extracts of pentachloronitrobenzene (PCNB)-tolerant and susceptible soil fungi. The organisms assayed were the highly PCNB-sensitive Rhizoctonia solani and Rhizopus arrhizus; Sclerotium rolfsii and Trichoderma harzianum, which are moderately susceptible to PCNB, and the fungicide-tolerant Fusarium oxysporum f. sp. melonis and Pythium aphanidermatum. No GPOX activity was detected in the six examined fungi. Significant differences in the specific activities of the other enzyme systems among the fungi were evident. Remarkably low levels of CAT activities were measured in R. solani. Except for T. harzianum, no meaningful differences regarding SOD, CAT and GR activities with age of the fungi cultures were observed. The electrophoretic patterns of SOD and CAT displayed dissimilarities among the fungi under study. P. aphanidermatum is more polymorphic with respect to both SOD and CAT enzyme systems as compared to the other fungi. The SOD of F. oxysporum f. sp. melonis, R. arrhizus and T. harzianum is a cuprozinc enzyme, while the mangano-SOD species was detected in S. rolfsii, R. solani and T. harzianum.     

Quinoline Alkaloids from the Roots of Orixa japonica with the Anti-Pathogenic Fungi Activities

A new quinoline alkaloid, 5-hydroxy-6-methoxy-N-methyl-2-phenylquinoline-4-one ( 1 ), and seventeen known quinoline alkaloids ( 2 – 18 ) were isolated from the roots of Orixa japonica. The structure of 1 was determined by analysis of spectroscopic data. Among them, compounds 2 , 3 , and 13 were isolated from this plant for the first time. All isolates were screened for the anti-pathogenic fungi activities, including Rhizoctonia solani, Magnaporthe oryzae, and Phomopsis sp. The results showed that five compounds ( 4 , 8 , 10 , 11 , and 12 ) exhibited significant anti-pathogenic fungi effects at 50.0 μg/mL. In special, compound 10 exhibited the best antifungal activities toward R. solani and M. oryzae with the IC₅₀ values of 37.86 and 44.72 μM, respectively, better than that of the positive control, hymexazol (IC₅₀ 121.21 and 1518.18 μM, respectively). Moreover, eleven new quinoline alkaloids derivatives ( 12a–12k ) were designed and synthesized to investigate the structure−activity relationships (SARs). The SARs analysis indicated that the furo[2,3-b]quinoline skeleton and the methoxy at C-7 (compounds 8 , 11 , and 12 ) played a key role for improving the antifungal activities.     

Plumieride from Allamanda cathartica as an inhibitory compound to plant pathogenic fungi

Allamanda leaf extract (Allamanda cathertica) was made in water at room temperature (25?± 2?°C) as well as in a number of less polar to highly polar solvents like methylene chloride, benzene, chloroform and ethyl acetate at their boiling point, that means, at refluxing temperature (40?± 2?°C). Methylene chloride, benzene, chloroform, ethyl acetate and water extracts were applied to determine their growth inhibition against Phomopsis vexans, Phytophthora capsici, Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii. Results of these extracts showed that refluxing methanol, ethanol and ethyl acetate extracts of Allamanda were statistically similar for inhibition of mycelial growth of all fungi tested. But effect of 50% ethanol extract is different; it inhibited 100% mycelial growth of P. vexans, P. capsici and F. oxysporum; 83.33% of R. solani and 88.63% of S. rolfsii. Effort was also made to find out the compound in Allamanda to be responsible for such antifungal activity. Thin layer chromatography (TLC) of Allamanda extracts showed the presence of a number of compounds having polarity very high to low. The R_f values of compounds in 37–42 fractions were calculated and from these six fractions, crystals were separated. These crystals were more or less white. Melting point of these crystals was determined by ordinary and digital melting point apparatus that ranged from 145.5–162 C. Structural determination of the compound was done by Infra-red (IR) spectral study. The finger print region was 700–1400?cm^?1. The strong band at 1612.4, 1633.6, 1693.4, 1655 and 2850.6?cm^?1 indicated the presence of conjugated double bond (–C=C–C=C–), non-conjugated double-bond (–C=C–C–C–C=C–), carbonyl group attached to carbon–carbon double (–CO–C=C), ester (–COOR) and C–H stretching, respectively. Mass spectra of separated compounds gave molecular weight 470. All these characters are typical to pumieride as described previously. Again, In vitro screening of plumieride against P. vexans, P. capsici, F. oxysporum, R. solani and S. rolfsii were found effective in inhibiting radial mycelial growth of these fungi at 1:2 w/v concentration.     

An Improved Growth Medium to Assess Mycelial Compatibility Groups in Sclerotium rolfsii

Mycelial compatibility is assayed mainly by pairing mycelial plugs of field isolates on Petri dishes with agar media. Although methodologically simple, mycelial compatibility testing requires an artificial growth medium that permits the identification of compatible and incompatible interactions. In this work, several growth media were studied to assess consistently mycelial interactions between Sclerotium rolfsii isolates. A modification of Patterson’s medium with an increment of 25% glucose from the original concentration at a rate of 23.4 g/l and amended with 180 μl/l of red food colouring was the most effective combination for enhancing the size, density and distinctiveness of the aversion zone between incompatible isolates. This medium allowed the unequivocal identification of compatible and incompatible reactions of a set of five S. rolfsii isolates, which could be determined quickly after 5 days of incubation in the dark at 25°C. This new formulation improved significantly and consistently the assessment of the aversion zone reaction that was visible as a red line on the colony reverse as compared to that assessed using previous media formulations, for which the visualization of aversion zones was scarcely discernible. The utility of the improved growth medium was validated by microscopic observations of the contact area of hyphal pairings between isolates of S. rolfsii in microscope slide cultures.     

<Emphasis Type="Italic">Exiguobacterium acetylicum</Emphasis> strain 1P (MTCC 8707) a novel bacterial antagonist from the North Western Indian Himalayas

Exiguobacterium acetylicum strain 1P (MTCC 8707) is a rhizospheric, Gram positive, rod shaped, yellow pigmented bacterium isolated from an apple orchard rhizospheric soil, on nutrient agar plates incubated at 4°C. The species level identification was arrived on the basis of 16S rRNA gene sequencing. The sequence showed 98% similarity with sequences of E. acetylicum available in the public domain. The strain was positive for siderophore and HCN production. In separate invitro assays it was found to inhibit the growth and development of Rhizoctonia solani, Sclerotium rolfsii, Pythium and Fusarium oxysporum. The volatile compound produced by the bacterium was found to be the most potent in inhibiting the hyphal development of R. solani, S. rolfsii, Pythium and F. oxysporum by 45.55, 41.38, 28.92 and 39.74% respectively. Commonly observed deformities caused by the diffusible and volatile compounds produced by the bacterium included hyphal inhibition, constriction and deformation. Under pot culture conditions the bacterium improved the germination and early growth parameters of pea (Pisum sativum) in the presence of R. solani and S. rolfsii.     

Cultivar response against root-infecting fungi and efficacy of Pseudomonas aeruginosa in controlling soybean root rot

Abstract

A study was conducted in the greenhouse to examine the resistance of three soybean cultivars against root-infecting fungi, and to determine the role of five strains of Pseudomonas aeruginosa in protecting the roots from these fungal pathogens. In this study soybean cv RAWAL was found to be less susceptible against charcoal rot fungus Macrophomina phaseolina than cvs PARC and BRAGG. Most of the strains of P. aeruginosa used as seed dressing significantly reduced M. phaseolina and Rhizoctonia solani infection on all three cvs PARC, BRAGG and RAWAL (p < 0.05). Most of the strains of P. aeruginosa were effective on cv PARC against Fusarium solani infection, while on cv BRAGG P. aeruginosa strain Pa₃, and on cv RAWAL strain Pa₅ were effective. Both strains Pa₃ and Pa₂₂ gave maximum plant height and fresh weight of shoots, respectively on cvs PARC and BRAGG than other strains. These characteristics make these P. aeruginosa strains good candidates for use as biocontrol agents against soil-borne plant pathogens.     

Comparative Resistance Patterns of Fludioxonil and Vinclozolin in Botryotinia fuckeliana

Fludioxonil is a new non-systemic phenylpyrrole fungicide. It is a derivative of the antibiotic pyrrolnitrin and is highly active against Ascomycetes. Basidiomycetes and Deuteromycetes. In the present study we determined the baseline sensitivity of B. fuckeliana for fludioxonil in comparison to the dicarboximide vinclozolin. Subsequently these baselines were compared with the sensitivity of dicarboximide-resistant field isolates and with resistant laboratory strains selected on media amendedwith vinclozotin or fludioxonil, respectively. Additionally, sensitivities of genetically homogeneous ascospore progenies of sexual crosses of sensitive isolates with dicarboximide-resistant field isolates or resistant laboratory strains were compared to, the baselines. Baseline ECst, values for the inhibition of germination ranged from 0.07 to 0.20 μg ml^-1 of vinclozolin and for mycelial growth from 0.003 to 0.016 μg ml’ of fludioxonil and from 1.7 to 2.0 μg ml^-1 of vinclozolin and for mycelial growth from 0.003 to 0.016 μg ml^-1 of fludioxonil and from 0.13 to 0.27 μg ml^-1 of vinclozolin. Sensitivity to fludioxonil of all dicarboximide-resistant field isolates did not differ from their baseline. However, resistant laboratory strains that were selected either on media amended with fludioxonil or vinclozolin showed decreased sensitivities to both active ingredients. All sexual progenies of the crosses described above were of the parental phenotypes. We found no independent segregation of the resistance markers.