Molecular characterization of European and Egyptian isolates of Sclerotium cepivorum,the incitant of onion white rot

Abstract

The tested European and Egyptian isolates of Sclerotium cepivorum were able to infect Giza 6 onion cultivar causing white rot disease with a different degrees of disease severity (ranging from sever to weak). The pattern of esterase isozymes produced by the tested isolates of the pathogen showed two main bands (arrows) which were different in density. Such differences in density of bands were present in every run and therefore appear to be indicators for differences among the tested isolates. Analysis of the protein pattern of the tested isolates of the pathogen indicated that the tested isolates had major proteins of a molecular weight of 52, 36, 23 and 16 kDa. Variation between isolates was detected by presence of bands of low molecular weight. Isolate Nos. 1, 4, 5, 7, 8, 9, 10 and 13 had a band at 17 kDa, whereas isolate Nos. 2, 3, 6, 11, 12, 14, and 15 had a band at 20 kDa. Using RAPD analysis to evaluate the genetic diversity of the tested isolates indicated that the tested field population of the pathogen was genetically heterogeneous but shared a number of common bands with molecular weights ranging from 650 to 2500 bp. Based on the DNA banding pattern the tested isolates can be assigned to seven genetically different groups. All tested isolates produced a band at 2500 bp except isolate No. 7. No correlation was exibited between patterns esterase isozmes, protein and DNA patterns of S. cepivorum isolates and their virulence or geographical origin.     

Biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum with Trichoderma viride under field conditions

Trichoderma viride was selected from three species of Trichoderma and was applied to the soil for biocontrol of yellow disease of Brassica campestris caused by Fusarium oxysporum. The population density of F. oxysporum averaged 10³ to 10⁴ cfu/g of soil in eight greenhouses. Moreover, the results of application of T. viride showed that the yellow disease of the first, second, and third crops in greenhouse A was 33%, 48%, and 35% in control plot, while it was 1.4%, 11.5%, and 3.0% in T. viride plots, respectively. Also in greenhouse B, the yellow disease of the first crop was inhibited by T. viride compared with control. However, the suppressive effect of T. viride declined on the second crop. Therefore, the third crop was not cultured in greenhouse B. The population density of T. viride in greenhouse A, in which yellow disease was successfully controlled, was higher than that in greenhouse B.     

Differentiation of the causal pathogen of onion white rot Sclerotium cepivorum isolates by using the APIZYM system

The APIZYM system of detection of enzymes was proven to be useful in the differentiation of 15 European and Egyptian isolates of S. cepivorum, the incitant of onion white rot. The tested isolates produced alkaline phosphatase, esterase (c4), esterase lipase (c8), leucine arylamidase, valinearylamidase, trypsine, α-chymatrypsin, acid phosphatase, naphthol-AS-B1-phosphohydrolase, ß-galactosidase, ß-glucutronidase, α-glucosidase, ß-glucosidase and N-acetyl-ß-glucosaminidase and did not produced lipase (c14), crystine arylamidase, trypsine, ß-glucutronidase, α-mannosidase and α-fucosidase. According to enzyme activity, isolates can be divided into four groups (G). The differences between groups were in the activity of the enzymes α-chymotrypsin and α-glucosidase. The tested European isolates and the Egyptian isolates No.6 of the pathogen were in G1 and G2; however the rest of the Egyptian isolates were in G3 and G4.     

Revisiting the use of Iprodione and Trichoderma in the integrated management of onion white rot

The biocontrol properties of Trichoderma species are well documented, but their effectiveness in antagonism of the problematic Sclerotium cepivorum, the causal agent of white rot in Allium species, appears limited with reports of significant control only relating to deliberately-mutated strains of Trichoderma. Our previous studies have indicated the possibility of using selected naturally-occurring strains of the antagonist in the suppression of other diseases; now in vitro and controlled environment in vivo studies have indicated that a degree of control of Onion White Rot is possible, and that the selected antagonist strains can be used in integrated treatments with Iprodione to good effect. The possible value of such treatments is considered in light of other approaches to the suppression of this continuing problem.     

Comparison of pyrene biodegradation by white rot fungi

Six strains of white rot fungi, isolated from soil in Korea, were evaluated as to their ability to biodegrade the 4-ring polycyclic aromatic hydrocarbon pyrene. While growing in a complex fungal medium, Irpex lacteus, Trametes versicolor KR11W, and Phanerochaete chrysosporium mineralized 15.6, 12.7 and 7.0% of the added 0.84 nmol of radioactive pyrene, respectively. In these cultures, 33–46% of the added pyrene was converted to water-soluble polar metabolites, and 22–40% was incorporated into fungal biomass. Pleurotus ostreatus mineralized only 2.5% of the added pyrene, while T. versicolor KR65W and Microporus vernicipes failed to evolve ¹⁴CO₂ from pyrene. The information obtained aids in strain selection for clean-up of polycyclic aromatic hydrocarbon contamination.     

Biocontrol of Alternaria triticina by plant growth promoting rhizobacteria on wheat

Abstract

Eighteen isolates of fluorescent pseudomonads and Bacillus spp. were isolated from Alternaria triticina suppressive soils of wheat fields. These isolates were evaluated in the laboratory and greenhouse for the biocontrol of A. triticina. Six isolates were considered to have potential for the biocontrol of A. triticina on the basis of antibiotic sensitivity, fluorescence produced by Pseudomonas, inhibitory effect on A. triticina and root colonization of wheat roots by these isolates. These six isolates (Pa22, Pf27, Pa28, B25, B28, and B30) were further tested for their biocontrol potential against A. triticina on wheat in a pot test. Out of six isolates, isolate B28 was best in improving wheat growth of A. triticina inoculated plants. Isolate B28 also caused higher reduction in percentage infected leaf area caused by A. triticina while isolate Pa22 was found best in improving growth of plants without A. triticina.     

In vitro decomposition of Sphagnum by some microfungi resembles white rot of wood

The abilities of some ascomycetes (Myxotrichaceae) from a Sphagnum bog in Alberta to degrade cellulose, phenolics, and Sphagnum tissue were compared with those of two basidiomycetes. Most Myxotrichaceae degraded cellulose and tannic acid, and removed cell-wall components simultaneously from Sphagnum tissues, whereas the basidiomycetes degraded cellulose and insoluble phenolics, and preferentially removed the polyphenolic matrix from Sphagnum cell walls. Mass losses from Sphagnum varied from up to 50% for some ascomycetes to a maximum of 35% for the basidiomycetes. The decomposition of Sphagnum by the Myxotrichaceae was analogous to the white rot of wood and indicates that these fungi have the potential to cause significant mineralization of carbon in bogs.     

Biodegradation of pentachlorophenol by white rot fungi under ligninolytic and nonligninolytic conditions

The roles of lignin peroxidase, manganese peroxidase, and laccase were investigated in the biodegradation of pentachlorophenol (PCP) by several white rot fungi. The disappearance of pentachlorophenol from cultures of wild type strains,P. chrysosporium, Trametes sp. andPleurotus sp., was observed. The activities of manganese peroxidase and laccase were detected inTiametes sp. andPleurotus sp. cultures. However, the activities of ligninolytic enzymes were not detected inP. chrysosporium cultures. Therefore, our results showed that PCP was degraded under ligninolytic as well as nonligninolytic conditions. Indicating that lignin peroxidase, manganese peroxidase, and laccase are not essential in the biodegradation of PCP by white rot fungi.     

Evaluation of seed dressing and soil application formulations of Trichoderma species for integrated management of dry root rot of chickpea

The efficacy of the newly developed seed dressing and soil application formulations of Trichoderma viride, T. virens and T. harzianum were evaluated individually and in combinations under pot and field experiments for the management of dry root rot (Rhizoctonia bataticola) of chickpea (Cicer arientinum). In pot experiments, T. harzianum based seed dressing formulation, Pusa 5SD, and soil application formulations, Pusa Biogranule 5 (PBG 5) and Pusa Biopellet 10G (PBP 10G), were found to be effective in reducing dry root rot incidence in chickpea and increasing the seed germination, shoot and root lengths of the crop. Under field experiments, a combination of soil application of T. harzianum based PBP 10G and seed treatment with Pusa 5SD+carboxin was found to be the best by providing the highest seed germination, shoot and root lengths and grain yield and the lowest dry root rot incidence in chickpea.     

木霉菌在玉米病害生物防治中的作用机制及应用

目前,世界上共有分属于10个属（Trichoderma,Gliocladium,Chaetomium,Bacillus,Burkhoderia,Streptomyces and Pseudomonas,Pantoea,Enterobacter,Macrobacterium）中的微生物被试验用于玉米病害的生物防治,其中细菌14种,真菌17种,放线菌1种。国际上由木霉菌开发的生物杀菌剂和生物肥料有50余种,其中以哈茨木霉T22菌株开发的产品最为著名。目前在我国也开发出了4种木霉菌剂型（可湿性粉剂、颗粒剂、水分散粒剂和种衣剂）,正式登记的木霉菌杀菌剂有7种,其中6种为可湿粉剂,1种为水分散粒剂,主要登记用于防治番茄、观赏百合、黄瓜的立枯病、猝倒病、根腐病、灰霉病、霜霉病以及小麦的纹枯病,但尚无木霉菌生物农药被登记用于防治玉米病害。以木霉菌为主要成分登记的菌肥产品有11种,其中在玉米上应用的有2种。由课题组研制的木霉菌颗粒剂和种衣剂通过土壤穴施和种子包衣可有效防治玉米茎腐病和纹枯病,其中木霉菌颗粒剂防效达65%-87%。近期研制的木霉菌可湿性粉剂对玉米小斑病的防效达50%-60%。国际上已鉴定出多种可诱导玉米获得系统抗性的木霉菌源激发子,其中包括Sm1、纤维素酶、疏水蛋白和Avr4 /Avr9等效应因子。本课题组近年鉴定出Thc6（锌指蛋白类转录因子）、PAF-AH和Thph1/Thph2的编码产物在系统诱导以JA/ET信号调控的玉米抗弯孢菌叶斑病中具有重要作用,符合植物免疫MAMPs模式,为全面认识木霉菌诱导免疫机理提供了重要理论依据。木霉菌诱导玉米从根至叶片的防御反应系统传导机制还需深入研究。     

Effect of temperature on antagonistic and biocontrol potential of shape Trichoderma sp. on Sclerotium rolfsii

Sclerotium rolfsii is a destructive soil-borne and postharvest plant pathogen. Use of the antagonistic fungus Trichoderma sp. has been earlier reported by us to successfully control this pathogen under postharvest conditions. In the present paper we report on the effects of temperature on the growth and biocontrol potential of Trichoderma sp. on S. rolfsii. Experimental results indicated that S. rolfsii and Trichoderma sp. have different temperature optima for growth: 30–35 °C for the pathogen and 25–30 °C for the antagonist. In dual culture, Trichoderma overgrew S. rolfsii at 25 °C and 30 °C, but at 35 °C and 37 °C, S. rolfsii overgrew the colony of Trichoderma. Trichoderma produced higher concentration of fungitoxic metabolites in broth culture at higher temperatures. In bioassays using ginger slices and whole rhizomes, it has been demonstrated that Trichoderma is not very effective in suppressing S. rolfsii at temperatures above 30 °C. In light of these results, possible mechanisms of biocontrol of S. rolfsii as a postharvest pathogen has been discussed. Storage temperature has been suggested as a critical factor in biocontrol of S. rolfsii. This revised version was published online in June 2006 with corrections to the Cover Date.     

Detection of fungal metabolites of various Trichoderma species by the aphid Schizaphis graminum

The feeding preferences of alate and apterous morphs of the aphid Schizaphis graminum (Rondani) (Homoptera: Aphididae) were evaluated using leaves treated with powdered rice cultures of four fungal isolates belonging to different species of the genus Trichoderma (Deuteromycotina: Hyphomycetes). All of the fungal isolates restrained alate morphs of S. graminum from visiting treated leaves, but only Trichoderma citrinoviride Bisset also influenced the preference of apterous morphs. Trials carried out with supernatants obtained by centrifuging aqueous suspensions of the fungal cultures showed that the feeding preference of aphids was maintained in the absence of fungal spores and mycelia, supporting the hypothesis that at least part of the fungal metabolites responsible for this effect were water‐soluble compounds. Electrophysiological studies showed that the structures involved in the perception of the fungal metabolites are located on the aphid tarsomeres.     

Screening of white‐rot fungi for bioprocessing of wheat straw into ruminant feed

Aim

In this study, the biological variation for improvement of the nutritive value of wheat straw by 12 Ceriporiopsis subvermispora, 10 Pleurotus eryngii and 10 Lentinula edodes strains was assessed. Screening of the best performing strains within each species was made based on the in vitro degradability of fungal‐treated wheat straw.

Methods and Results

Wheat straw was inoculated with each strain for 7 weeks of solid state fermentation. Weekly samples were evaluated for in vitro gas production (IVGP) in buffered rumen fluid for 72 h. Out of the 32 fungal strains studied, 17 strains showed a significantly higher (P < 0·05) IVGP compared to the control after 7 weeks (227·7 ml g^?1 OM). The three best Ceriporiopsis subvermispora strains showed a mean IVGP of 297·0 ml g^?1 OM, while the three best P. eryngii and L. edodes strains showed a mean IVGP of 257·8 and 291·5 ml g^?1 OM, respectively.

Conclusion

Ceriporiopsis subvermispora strains show an overall high potential to improve the ruminal degradability of wheat straw, followed by L. edodes and P. eryngii strains.

Significance and Impact of the Study

Large variation exists within and among different fungal species in the valorization of wheat straw, which offers opportunities to improve the fungal genotype by breeding.     

花青素对神经退行性疾病保护作用的研究进展

对近年来花青素在神经退行性疾病中的研究进展进行综述,并从抑制氧化应激、缓解神经炎症、缓解兴奋性毒性和抑制蛋白异常聚集等方面对花青素的神经保护作用机制进行探讨,为进一步了解和研究花青素类化合物在神经退行性疾病中的预防作用提供科学依据。     

Evaluation of some garlic (Allium sativum L.) mutants resistant to white rot disease by RAPD analysis

Random amplified polymorphic DNA (RAPD) analysis was used to evaluate genetic diversity among eight garlic mutants resistant to white rot disease (Sclerotium cepivorum). Twelve of the 13 synthetic random primers were found to identify polymorphism in amplification products. Mutants characterised with moderate resistance to white rot were closely related to the control using cluster and correlation analyses. On the other hand, highly resistant mutants were quite distant from the control with low correlation coefficients. The banding patterns produced by primer OPB‐15 (GGAGGGTGTT) with highly resistant mutants may by used as genetic markers for early selection of resistant plants.     

Effects of different levels of wheat bran, rice bran and maize powder supplementation with saw dust on the production of shiitake mushroom (Lentinus edodes (Berk.) Singer)

The cultivation of shiitake mushroom (Lentinus edodes) is increasing rapidly in Bangladesh due to its nutritional and medicinal importance with excellent flavor and longer shelf life. With the aim of increased production, we have cultivated L. edodes on saw dust (SD) supplemented with different levels (10%, 15%, 20%, 25%, 30%, 35% and 40%) of wheat bran (WB), rice bran (RB), maize powder (MP) and their combination (WB+RB+MP = 1:1:1) to investigate the growth, yield and quality of this mushroom. Most of the growth, yield and quality parameters varied significantly when mushrooms were cultivated with different levels of supplementation. The yield of mushroom was increased with the level of each supplementation upto a certain level, and then decreased. SD supplemented with 25% WB produced the highest number of fruiting bodies (34.8/500 g packet), highest biological yield (153.3/500 g packet), and biological efficiency (76.6%) of L. edodes. But the yield of the best quality mushroom was observed on SD with 40% WB supplementation; however, the qualities were not always supplementation dose dependent. In this study, we report that 25% WB supplementation with SD may be very effective for higher yield and 40% WB supplementation for better quality of L. edodes.     

混合白腐真菌的固定化及其在治理铅污染废水中的应用

【目的】为缓解重金属废水污染对全球食品安全和人类健康的威胁,降低铅(plumbum, Pb)在土壤及动植物体内的积累,借助固定化技术提高菌株的重金属去除效率。【方法】以白腐真菌(white rot fungi)为实验材料,通过混菌兼容性及铅离子(Pb²⁺)去除能力筛选出吸附效果好且兼容性优的复合菌种,探究最优混菌类型及其比例,优化菌球最佳固定化助剂配方,在此基础上深入探究菌球在实际应用中的最优吸附条件。【结果】黄孢原毛平革菌(Phanerochaete chrysosporium)、云芝(Coriolus versicolor)、凤尾菇(Lentinus sajor-caju)和平菇(Pleurotus ostreatus) 4种菌株兼容效果佳,可进行后续实验;其中云芝和凤尾菇以体积1:1混合后对Pb²⁺去除效果显著优于各单菌作用;固定化条件优化实验中,20.0 g/L海藻酸钠、15.0 g/L生物炭和2.0×10⁶个/mL白腐真菌组成混菌体系,辅以二氧化硅及沸石制得的固定化菌球在96 h Pb²⁺...     

Effect of Burkholderia (Pseudomonas) cepacia and soil type on the control of crown rot in wheat

A rifampicin-resistant isolate of Burkholderia (Pseudomonas) cepacia (A3R) reduced crown rot (Fusarium graminearum Group 1) symptoms significantly (P 0.05) in wheat in glasshouse and field experiments and increased grain yield significantly (P 0.05) in one of two field experiments. In glasshouse experiments, applying the bacteria as a soil drench (2.5 × 109 cfu/g soil) was more effective than coating the bacteria on wheat seed (3.4 × 107cfu/seed). In field experiments, the bacteria were applied as a soil drench at the rate of 1.8 x 10¹⁰ cfu/m row. In both the glasshouse and the field, disease severity in the bacteria-inoculated treatments was significantly less in a silt loam than in a sandy loam. The silt loam had a large proportion of fine clay and silt particles (51.7%), which may have favoured the biocontrol activity and survival of the introduced B. cepacia. In a glasshouse experiment, control by B. cepacia was significantly greater in the silt loam than in the sandy loam, which in turn was greater than in a loamy sand. The loamy sand appeared to favour crown rot development but not the activity or survival of the bacterial antagonist. The latter was reflected by the relative populations of the rifampicin-resistant bacteria re-isolated from the various soils during a 5-week period after application of the bacteria (silt loam > sandy loam > loamy sand). This study further confirms that soil type can influence the populations and the level of biocontrol activity of some bacterial antagonists.     

Biological control of tomato collar rot induced by Sclerotium rolfsii using Trichoderma species isolated in Bangladesh

This study evaluated three Trichoderma strains (T. harzianum TR05, T. virens TR06 and T. asperellum TR08) originating from Bangladesh as potential biological control agents against collar rot of tomato under greenhouse conditions. After seed treatment with TR05, a disease incidence of collar rot (5.36%) was lower than for TR06 (34.2%) and TR08 (20.8%). Germination percentage of tomato was highest for TR05 (90.3%). In soil treatment, inoculation with TR08 resulted in the lowest disease incidence (9.78%), and the disease incidence was statistically no different from that for TR05 (16.4%). Thus, TR05 and TR08 have potential as biological control agents of collar rot in tomato.     

Transformation of 2,4,6-trichlorophenol by the white rot fungi Panus tigrinus and Coriolus versicolor

The toxicity of thirteen isomers of mono-, di-, tri- and pentachlorophenols was tested in potato-dextrose agar cultures of the white rot fungi Panus tigrinus and Coriolus versicolor. 2,4,6-Trichlorophenol (2,4,6-TCP) was chosen for further study of its toxicity and transformation in liquid cultures of these fungi. Two schemes of 2,4,6-TCP addition were tested to minimize its toxic effect to fungal cultures: stepwise addition from the moment of inoculation and single addition after five days of growth. In both cases the ligninolytic enzyme systems of both fungi were found to be responsible for 2,4,6-TCP transformation. 2,6-Dichloro-1,4-hydroquinol and 2,6-dichloro-1,4-benzoquinone were found as products of primary oxidation of 2,4,6-TCP by intact fungal cultures and purified ligninolytic enzymes, Mn-peroxidases and laccases of both fungi. However, primary attack of 2,4,6-TCP in P. tigrinus culture was conducted mainly by Mn-peroxidase, while in C. versicolor it was catalyzed predominantly by laccase, suggesting a different mode of regulation of these enzymes in the two fungi.