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Cabbage plants showing symptoms of leaf spot were detected from various fields in the Almaty region of Kazakhstan in the winter seasons of 2015 and 2016. The disease incidences of approximately 50% were recorded in various fields visited in the Almaty region. The pathogen was aseptically isolated from the symptomatic leaves and maintained in an in vitro culture media. Morphological characteristics and sporulation of the fungus was determined under both light and electron microscopy. The extracted genomic DNA of the fungi was subjected to Polymerase Chain Reaction (PCR) using ABCsens/ABCrev and ITS1/ITS4 primers amplifying ABC transporter (Atr1) gene and the internal transcribed spacer regions, respectively. The amplified products of PCR were sequenced, aligned, blasted and compared for similarity with other species in the NCBI GenBank. The cluster analysis result showed 99% homology with related fungi retrieved from the NCBI GenBank for the ITS region. The fungal isolate was pathogenic towards twenty-two-day-old plants, namely, Brassica oleracea, Lycopersicon esculentum, Solanum melongena, and was established as the causal agent of leaf spot on these plants. This is the first record implicating A. brassicae for black leaf spot disease of cabbage in Kazakhstan.
Severe leaf spot disease was observed on Aloe vera plants in the winters of 2011 and 2012 during a survey of various nurseries of Gwalior, India. Irregular, sunken, dark creamish brown spots having reddish brown margin were noticed on both surfaces of the leaves. The causal organism was consistently isolated from symptomatic leaves on potato dextrose agar media (PDA). A total 59 isolates of fungi were recovered from diseased A. vera leaves, and 37 isolates were identified as belonging to the genus Fusarium. On the basis of morphological characteristics and internal transcribed spacer (ITS) region of rDNA amplified using the primers ITS4/ITS5 the pathogen was identified as Fusarium proliferatum (Matsushima) Nirenberg and pathogenicity of the isolate was confirmed by using Koch’s postulates. To the best of our knowledge, this is the first report of leaf spot disease caused by Fusarium proliferatum on A. vera plants in India.
The effect of cercospora leaf spot caused by Cercospora arachidicola i Phaeoisariopsis personata on quality of groundnut haulm was assessed using official methods of analysis. The respective field experiments were conducted in 2004 and 2005 cropping seasons, while the laboratory analyses were carried out at the end of the seasons. The scale of 1-9 was used to determine severity of infection on randomly selected groundnut plants. The results showed that the year effect was not significant as related to haulm composition. However, severity of the disease was found to affect haulm composition either negatively or positively. Crude fibre, crude protein, fat and dry matter content of haulm were significantly lower in severely infected haulm samples compared to uninfected or less severely infected samples. While ash, moisture content and nitrogen free extracts (NFE) increased with increasing disease severity. The regression analysis showed that crude fibre, crude protein, fat and dry matter content were negatively related to cercospora leaf spot severity, while ash, moisture content and nitrogen free extracts showed positive relationship with increasing disease severity. Since infection by cercospora leaf spot pathogen lowers the quality of groundnut haulm, controlling the disease is necessary to ensure good quality of haulm at the end of the season.
In the present study, the antagonistic capability of bacterial agents inhabiting the rhizosphere of sugarbeet plants were evaluated against Cercospora beticola Sacc. under laboratory and greenhouse conditions. After preliminary screening using the dual culture method, 14 strains with higher antagonistic capability were selected for further inhibitory assays against C. beticola. Bacterial strains were identified based on the sequence data of the small subunit-rDNA (SSU-rDNA) gene. Based on the SSU sequence data, the identity of bacterial strains were determined as Bacillus (10 strains: RB1, RB2, RB3, RB4, RB5, RB6, RB7, RB8, RB9, RB10), Paenibacillus (two strains: RP1, RP2), Enterobacter (one strain: RE), and Pseudomonas (one strain: RPs). The results obtained in this study showed that in all of the assays (dual culture, volatile and non-volatile metabolites) bacterial antagonists significantly inhibited the growth of C. beticola compared to the control. Bacillus (RB2) showed the highest inhibition rate on C. beticola in all of the assays. Based on the results of the laboratory assays, three bacterial strains RB2 (Bacillus), RPs (Pseudomonas), and RE (Paenibacillus) were selected for greenhouse assays. The experiment was designed based on a completely randomised design (CRD) with the application of antagonists prior to, simultaneously, and after inoculation with C. beticola on sugarbeet leaves. The reduction in disease severity was evaluated seven days after inoculation. The results of greenhouse assays were consistent with the results of laboratory studies. The obtained results showed that bacterial antagonists significantly reduced the disease severity when compared to the control.
Field trails were conducted to evaluate the economics of controlling cercospora leaf spot of groundnut using different fungicides. The experiments were laid out in a strip plot design with three replications at the Teaching and Research farm of the Department of Crop Protection, University of Maiduguri, Sudan savanna of Nigeria during the 2002 and 2003 cropping seasons. Four fungicides namely: Benlate 50 WP, Trimangol 80 WP, Bentex T, and Ridomil 72 WP were applied as foliar sprays at three spray regimes while the control was left untreated. The application of the fungicides led to 20-50% reduction in the disease incidence and 15-22% reduction in disease severity and gave higher yield of seed and haulm than the control. The cost-benefit analysis revealed positive returns per hectare from the use of the fungicides for the control of disease in the study area. Application of Bentex T, for instance, gave 78.13% seed yield increase over the control which translated into a mean (two years) net profit of N52,267.50, N90,905.00 and N138,755.00 Nigerian Naira for one, two and three sprays, respectively, equivalent to $522.675, $909.05 and $1,387.55 per hectare. Even the least effective of the fungicides (Trimangol 80 WP) gave seed yield increase of 62.74% over the control which translated into a mean (two years) net profit of N41,287.50, N68,082.50 and N93,995.00 equivalent to $412.88, $680.83 and $939.95 per hectare for one, two and three sprays, respectively. Three sprays gave 115. 76% increase of yield over one spray and 39.35% yield increase over two sprays. These returns are attractive particularly to the farmers in the study area who grow the high yielding Ex-Dakar groundnut variety which is susceptible to cercospora leaf spot.
Several species of Solanum produce secondary metabolites with antimicrobial activity. In the present study, the inhibitory activity of Solanum chrysotrichum, S. erianthum, S. torvum and S. rostratum against phytopathogenic Curvularia lunata was determined. Methanol extracts from roots, stems, leaves and fruits were evaluated by the method of mycelial inhibition on agar and the minimum inhibitory concentration (MIC) was determined on a liquid medium. To increase the antimicrobial activity, the combined activity of the most active extracts for each phytopathogen was also determined (a combination of intra and interspecies extracts). The results showed that 12 of the 16 methanolic extracts of Solanum species had antifungal effects against C. lunata. The extracts of S. rostratum and S. erianthum developed the highest activity (~80% inhibition and 28.4 MIC μg . ml–1), even, equal to or greater than, the reference fungicide. The mixture of the active extracts of S. chrysotrichum and S. torvum increased their activity. Various extracts affected the macro and microscopic morphology and most of them reduced the number of conidia of the fungus. This resulted in the capacity to control the vegetative growth and reproduction of C. lunata, the causal fungus of corn leaf spot disease.
The aim of this studies was characteristic of the sources of primary infection for tan spot. During the period 1998 - 1991 the development of ascomata and conidimata of Pyrenophora tritici-repentis on naturally infected wheat and triticale straws was monitored. The process of pseudothecia formation was extending over the time. It started immediately after harvest and protothecia of the fungus was commonly occurred each year already in the fall. The first fruit bodies with maturated typical!y pigmented ascospores were observed in January 2001 and in February 1998 and 1999. The percentage of pseudothecia with maturate ascospores successively increased richening maximum in April when the massive liberation of spores from asci occurred. After the total ascospore release on surface of empty ascomata aroused conidiophores with conidia which mayaIso act as inoculum source. Moreover this type of sporulation was observed directly on over wintered cereals stems especially after prolonged period of rains.The present studies indicated also on infected by P. tritici-repentis wheat and triticale seeds as a source of inoculum for tan spot.
Odporność wiechliny łąkowej (Poa pratensis L.) na brunatną plamistość powodowaną przez Drechslera poae (Baudys) Shoemaker jest jednym z głównych celów hodowlanych nowych odmian tego gatunku. W pracy przedstawiono przegląd literatury dotyczącej ochrony wiechliny łąkowej przed D. poae. Główny akcent położono na rolę hodowli odpornościowej. Scharakteryzowano rolę ekotypów jako ewentualnych źródeł odporności do dalszej hodowli oraz opisano metody wstępnej selekcji. Omówiono ponadto ochronę chemiczną oraz prawidłową agrotechnikę, jako ewentualne metody wspomagające.
Antimycotic activity of three fern extracts from Hemionitis arifolia (Burm.f.) Moore., Pteridium aquilinum (Linn.) Kuhn. and Christella parasitica (Linn.) H. Lev. were evaluated against groundnut early leaf spot and rust disease causative agents viz., Puccinia arachidis Speg. and Phaeoisariopsis personata (Berk & M.A. Cuortis) Vanarx., espectively by mycelial dry weight method. Both the fungi were sensitive to all the three fern extracts tested. Among the extracts, chloroform extract of H. arifolia was found to have maximum antifungal activity against both fungi. Between these two fungi, P. personata was found to be more sensitive to the tested plant extracts than P. arachidis. From this study it is concluded that chloroform extract from H. arifolia can be utilized for managing rust and leaf spots diseases on groundnut.
The efficacy of Benlate 50 WP (benomyl), Bentex T (benomyl +thiram), Ridomil 72 WP (metalaxyl) and Trimangol 80 WP (maneb) applied as foliar spray in the control of cercospora leaf spot of groundnut in the Sudan savanna of Nigeria was evaluated during the 2002 and 2003 cropping seasons. Three spray regimes (once, twice and thrice per season) were evaluated. Strip plot design with three replications was used in setting up the experiments. Ex-Dakar, a cercospora leaf spot susceptible groundnut variety was used as planting material. All the four fungicides significantly reduced the incidence and severity of cercospora leaf spot in both seasons. However, the application of Bentex T significantly better reduced the incidence and severity of the disease than the other fungicides. This was followed by application of Benlate 50 WP. Ridomil 72 WP and Trimangol 80 WP which gave moderate control of the disease. Three sprays with fungicides gave better control of the disease than one or two sprays in the season. The highest seed yield of 1716kg/ha and 2263kg/ha in 2002 and 2003, respectively, were obtained following treatment with Bentex T. The lowest yield of 962kg/ha and 1270kg/ha in 2002 and 2003, respectively, were recorded from the control plots. Also the highest seed yield of 2028kg/ha and 2672kg/ha in 2002 and 2003, were obtained following three sprays compared to 939kg/ha and 1239kg/ha in 2002 and 2003, respectively, for one spray in the season. The highest haulm yield of 6131 kg/ha and 6722 kg/ha in 2002 and 2003 was recorded from plots treated with Bentex T compared to 4752 kg/ha and 5166 kg/ha in 2002 and 2003, respectively, obtained from the control. Haulm yield of 6355 kg/ha and 7027 kg/ha in 2002 and 2003 were obtained following three sprays compared to 5088 kg/ha and 5593 kg/ha in 2002 and 2003, respectively, recorded for the control. Bentex T or Benlate 50 WP could be used to reduce the effect of cercospora leaf spot and improve groundnut production in the Sudan savanna of Nigeria.
Leaf diseases' influence the relationship between the yield and yield components of winter wheat (Triticum aestivum L.). Field experiments were conducted during 2003-2006 on a light loamy gleyic cambisoil in the central part of Lithuania to determine how leaf disease severity level affects grain yield and yield components. The area under disease progress curves (AUDPC), grain yield and yield components were analysed using the analysis of variance and correlations. Infected wheat straw was applied to initiate epidemics in all treatments. Three winter wheat cultivars: Hereward, Aron and Tauras differing in the level of resistance to leaf diseases were used in the experiments. In total, six treatments were established: (i) untreated control, (ii) powdery mildew control (pmc) + leaf diseases severity level 0%, (iii) pmc + leaf diseases severity level 1.0-5.0%, (iv) pmc + leaf diseases severity level 5.1-10.0%, (v) pmc + leaf diseases severity level 10.1-25.0%, (vi) pmc + leaf diseases severity level > 25.1%. Wheat in all treatments, except for the untreated control, was protected by morpholine and triazole fungicides. Yield and yield components were affected by leaf diseases in all the treated cultivars during all experimental years. Significant (p ≶ 0.01) medium and strong correlation coefficients were found between AUDPC and yield in all the treated cultivars under high pressure of leaf diseases in 2004.
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