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Sheila Okoth* and Elizabeth Siameto
Abstract: Fusarium root rot of maize and beans is a common problem in Taita District, Kenya causing reduction in yields to the small scale farmers. The pathogen attacks maize and beans at all growth stages and causing rot at the seedling stage, yellowing of the leaves, stunted growth and death if severe. Potentially effective crop rotations to maintain the pathogen at low levels are not currently acceptable in this region due to the small size of farms and prices of fungicides which are out of reach to the small scale farmer. This study is aimed at assessing alternatives to the use of fungicides in controlling root infection by Fusarium spp in maize and beans. Field trials were done in Taita District where agriculture contributes to 95% of household income with very little or no fertility inputs in farms. The following were tested in the trial: three kinds of fertilizers, cow manure and Trichoderma seed coating. Planting was done during the long and short rains. Soil and roots were collected from the rhizosphere during harvesting and assessed for inoculum density, while the roots were evaluated for incidence of infection by Fusarium spp. The most common species in both soil and roots were Fusarium oxysporum (Schlecht) Snyd. et Hans. and Fusarium sporotrichoides Sherb. Addition of soil amendments had a positive effect of reducing root infection and in some cases lowering inoculum density in the soil. Of the four fertilizers tested, Mavuno had the highest yield and was the most effective in suppressing root colonisation by Fusarium spp.[...] Read More.
Keywords: Fusarium spp, root infection, fertilizers, Trichoderma, soil amendments.
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E. I. Eziashi*, I. B. Omamor, C. E. Airede, C. V. Udozen and N. Chidi
Abstract: Bottled raphia palm wine was cultured in a laboratory medium amended with 0.5% acetic acid (pH 4.8). Two cultures of identified heat resistant yeast (HRY) and one unidentified yeast species were isolated. Cultures of the isolates grown on potato dextrose agar for 10 days at 26°C, survived pasteurization temperature at 80°C for 20 min and 85°C for 15 min. Of these HRY identified were Byssochlamys nivea, Byssochlamys zollerniae and one unidentified yeast species. To determine the source of contamination, fresh un-pasteurized Raphia palm wine was cultured. Result revealed that, colonies of the three HRY were higher compared with the pasteurized Raphia palm wine. Frequencies of occurrence at 80°C, 85°C and in un-pasterurized raphia palm wine were B. nivea 15.2, 6.1 and 24.2%; B. zollerniae 6.1, 3.0 and 12% and yeast species 9.1, 6.1 and 18.2% respectively. The thermal destruction time were B. nivea 90°C for 15 min, B. zollerniae 90°C for 5 min and yeast species 90°C for 10 min. The result indicates they are acid tolerant and thermophilic yeasts with B. nivea having the highest frequency of occurrence.[...] Read More.
Keywords: Culture, pasteurization, spoilage, identification, thermophilic.
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文章
G. Sharma and R. R. Pandey*
Abstract: The mycelial growth rate, colony character and sporulation pattern of ten fungal isolates, grown on three different culture media viz., Potato Dextrose Agar (PDA), Czapek’s Dox + Yeast Extract Agar (CYA) and Lignocellulose Agar (LCA) were observed after seven days of incubation at 25±1°C. The colony diameter, culture characteristics (texture, surface and reverse colouration, zonation) and sporulation of selected test fungi were greatly influenced by the type of growth medium used. LCA exhibited comparatively higher mycelial growth in six test fungi, whereas all the ten isolates revealed heavy sporulation on this culture medium. Penicillium sp. and Acremonium kiliense exhibited maximum colony growth on PDA, while Chaetomium funicola and Fusarium oxysporum showed highest growth on CYA medium. These results will be useful for fungal taxonomic studies.[...] Read More.
Keywords: Mycelial growth, colony character, sporulation, culture media.
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文章
João Vicente Braga de Souza*, Carolina Talhari, Dieter Reinel and Sinésio Talhari
Abstract: The aim of this work was to evaluate the influence of glucose and ammonium sulphate in the chlamydosporulation of Candida albicans FMT123-05. Different media were produced and inoculated with C. albicans FMT123- 05. The glucose and ammonium sulphate content were defined using an experimental design (22 + star). Glucose content inhibits C. albicans chlamydosporulation two times more than ammonium sulphate. The mathematical model and the surface response demonstrated that the total absence of carbon and nitrogen sources was the best condition for chlamydosporulation of C. albicans 123-05 in the experimental conditions.[...] Read More.
Keywords: Chlamydosporulation, glucose, ammonium sulphate, experimental design.
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文章
Krishnamoorthy, R. Narayanan*, K. Vijila and K. Kumutha
Abstract: In this study, Intergeneric protoplast fusion of the yeast cultures Viz., Saccharomyces cerevisiae and Kluyveromyces marxianus was carried out for enhancing production to ethanol temperature tolerance and lactose utilizing characters in a single stain. S. cerevisiae (Parent 1) has ethanol tolerance, whereas, K. marxianus (Parent 2) is temperature tolerant and also has lactose utilizing capacity. Twelve fused cultures were obtained by protoplast fusion. Fused cultures recorded higher DNA content than the parent strains, which showed complementary banding pattern of two parental Strains. SDS-PAGE confirms the presence of HSP 70 in the fused culture, which is responsible for temperature tolerance. Fermentation of cheese whey was carried out with two parental and fused cultures. The results revealed that the ethanol production was higher with fused culture (12.5%, with 18.09 g/l of biomass) after 72 h of fermentation. Parent 1 showed poor growth on the cheese whey medium, but growth of the Parent 2 was inhibited when the ethanol production reached 6%.[...] Read More.
Keywords: Marker selection, protoplast fusion, RAPD, SDS-PAGE, whey.
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Varsha Nenwani, Pratima Doshi, Tithi Saha and Shalini Rajkumar*
Abstract: A fungal species namely F1 was isolated from the rhizosphere on the basis of its ability to form halos (zone of solubilization) on Pikovskaya’s agar. F1 was assessed for phosphate solubilization, titratable acidity (TA), gluconate concentration and change in pH over incubation period of 21 days and other plant growth promoting traits. F1 solubilized maximum inorganic phosphorus (662 g P ml-1) from tricalcium phosphate present in the Pikovskaya’s broth on 18th day. The TA followed a similar trend as that of P solubilized, except on day 21 when the value that for TA was highest. A similar pattern was also observed with production of gluconic acid, for which a constant value of 8.96 × 10-4 g% was observed till 18th day of incubation. However, gluconic acid was not the only organic acid produced in the culture broth, because the amount of gluconic acid produced did not relate to the high values observed for P solubilized and TA. Efficiency of the F1 to solubilize phosphate from organic reserves was determined by performing assays of phosphatases and phytases. The culture F1 produced 1.86 and 1.90 EU of enzymes alkaline and acid phosphatase, respectively and phytase activity was 28 mU. The concentration of catechol and hydroxymate type siderophores produced by F1 was 4.50 and 4.55 µgml-1 respectively and it also produced 11.45 µgml-1 of IAA which is significantly high. Some fungi may possess traits associated with biocontrol of plant pathogens such as production of enzyme chitinase which was 0.037 EU for F1. On the basis of cultural and microscopic features, the isolate F1 could be Absidia spp. and has potential of being a competent bioinoculant.[...] Read More.
Keywords: Phosphate solubilization, bioinoculant, plant growth promoting fungus (PGPF).
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文章
M. A. Abdel-Rahman Tahany*, A. K. Hegazy, A. Mohsen Sayed, H. F. Kabiel, T. El-Alfy and S. M. El-Komy
Abstract: Three plants were used in this study: Moringa pregrina, Achillea fragrantissima and Coleome droserifolia. Six active constituents were separated from n-hexane and ethyl acetate fractions of Moringa pregrina. These active constituents were lupeol acetate, -amyrin, -amyrin, -sitosterol, - sitosterol-3-O- -D-glucoside and apignin were assayed individually and in combination against pathogenic bacteria and fungi. All constituents were proved to be more antibacterial than antifungal agents. Aspergillus flavus and Fusarium solani were completely resistant to all constituents. -amyrin was the most effective antibacterial compound. The least relative activity was achieved by -sitosterol against Bacillus subtilis compared to ampicillin. Reasonable antifungal activity was recorded in case of lupeol acetate, -amyrin and -amyrin, while -sitosterol and -sitosterol-3-O- -D-glucoside, revealed no antifungal activity. Apignin missed both antifungal and antibacterial activities. Low MICs were detected by -amyrin, -amyrin and -sitosterol-3-O- -D-glucoside against all tested bacteria. Concerning fungi, -sitosterol and - sitosterol- 3-O- -D-glucoside showed no antimycotic activity. Lupeol acetate, -amyrin and -amyrin, however, have slightly high MICs for all tested dermatophytic fungi compared to that of fluconazole. Among ninety nine assayed combination mixtures, thirty seven synergistic combination mixtures were detected which exerts 37 synergisms against different pathogens with FICI less than 0.5, which indicates high efficacy of combination mixtures over monotherapy treatments.[...] Read More.
Keywords: Combined antimicrobial therapy, active constituents, Moringa peregrina, Achillea fragrantissima, Coleome droserifolia.
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文章
Juan Carlos González-Hernández
Abstract: Debaryomyces hansenii is often found in salty environments. This yeast species is not only halotolerant, but also halophilic. Its genome sequence is known completely, but the mechanisms behind its halotolerance are poorly understood. It was compared to the STL1 protein sequence of Saccharomyces cerevisiae against the translated sequence from the D. hansenii genome sequence database released by Génolevure. An ORF (DEHA0E01122g) was found with 54% homology and 39% identity with Stl1p from S. cerevisiae. DhSTL1 was heterologously expressed successfully in a S. cerevisiae (BY4741) wild type and in another strain lacking its own system for the glycerol transport (STL1) gene. The DhSTL1 gene in transformed S. cerevisiae strains showed a slight but significant difference in the doubling times in growth curves obtained in liquid YNB-ura medium, with glycerol as carbon source. DhSTL1 gene in transformed stl1 yeast strain showed phenotype growth at pH 7.5 under salt stress conditions (glucose as carbon source). The kinetic parameters of transport and glycerol accumulation conferred by DhSTL1 in the S. cerevisiae transformant strains did not show significant differences. An increase in the transcript level of DhSTL1 gene in the presence of saline stress at pH 5.6; whereas, at 7.5 pH, it was expressed in all evaluated conditions.[...] Read More.
Keywords: Debaryomyces hansenii, glycerol, transport, salt tolerance.
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E. N. Siameto, S. Okoth*, N. O. Amugune, and N. C. Chege
Abstract: Species in the genus Trichoderma are important as commercial source of several enzymes and as biofungicides/growth promoters. The most common biological control agents of the genus are strains of T. harzianum, T. viride and T. viriens. In this study, sixteen selected isolates of T. harzianum from different land use types in Embu, Kenya were tested for anatognism against five soil borne phytopathogenic fungi (Rhizoctonia solani, Pythium sp, Fusarium graminearum, F. oxysporum f. sp phaseoli and F. oxysporum f. sp Lycopersici) using dual culture assay and through production of non-volatile inhibitors. Seven isolates were further characterized using RAPD-PCR procedure to determine genetic variability. All T. harzianum isolates had considerable antagonistic effect on mycelial growth of the pathogens in dual cultures compared to the controls. Maximum inhibitions occurred in Pythium sp-055E interactions (73%).The culture filtrates obtained from Czapek’s liquid medium reduced the dry weight (mg) of the mycelia significantly while those from the potato dextrose broth showed minimum inhibition growth. Pythium sp was inhibited the most compared to other pathogens. Genetic similarities generated using Jacquard’s coefficient of similarity ranged from 0.231 between isolates 055E and 011E to 0.857 between isolates 010E and 015E. The technique of RAPD was efficient in demonstrating the DNA polymorphism in the isolates of T. harzianum tested showing intraspecific genetic variability. Since all T. harzianum isolates evaluated were effective in controlling colony growth of the soil borne pathogens both in dual cultures and in culture filtrates they could be tried as a broad spectrum biological control agent in the green house and under field conditions.[...] Read More.
Keywords: Trichoderma harzianum, growth antagonism, genetic similarity, RAPDs.
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文章
Amany H. Aboellil* and Majdah M. Y. Al-Tuwaijri
Abstract: Yeast of the genus Candida has been recognized as important microorganisms responsible for Nosocomial fungemia. Six isolates of clinical Candida albicans isolated from patients and studied by electrophoretic karyotyping of chromosomal DNA by pulsed field gel electrophoresis. Six chromosal DNA profiles were more or less identical. Natural fungicide nystatin is more effective on C. albicans growth than the other synthesitic miconazole nitrate and clotrimazole. The minimum inhibitory concentration for 90% growth of C. albicans (MIC90) of nystatin is1500 unit/ml. The antimicrobial activities of alternative and traditional medicine in Saudi Arabia were evaluated against C. albicans growth. Natural acetic acid, plant extract, charcoal and Elshab are used as natural drug for Candidiasis. The percent of 36% Concentration of acetic acid in media causes maximum inhibition of C. albicans growth. There are direct relation between acetic acid concentrations and inhibition zones. Increase or decrease of pH inhibits the growth of C. albicans. The ideal pH for inhibiting C. albicans growth is pH 10.  The combination of Salvadora persica extract (Meswak) and Elshab (KAl(SO4)2) in concentration of (28.5 + 12.75 mg/ml, respectively), have an antimicrobial effect on C. albicans growth (0.01 g/10ml of media). Charcoal in 20 mg/ml concentration or Lawsonia alba extract (Henna) in 250 mg/ml is the ideal concentration used for stop growth of C. albicans. The susceptibility of yeast to the previous alternative medicine shows that, it could be used in treating candidiasis resulting from different strains of C. albicans instead of commercial antibiotics used, without any adverse side effects. Also, it is an attempt to stop development of multidrug resistance organism. Aspergillus fumigatus performed a good tool as biocontrol for C. albicans which caused infections mainly candidiasis. Both are isolated as clinical isolates of nosocomial of infected patients.[...] Read More.
Keywords: Candida albicans, chromosomal DNA, Lawsonia alba, Salvadora persica, antibiotics, biocontrol.
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