Effect of water activity and temperature on competing abilities of Penicillium oxalicum against Fusarium oxysporum

The in vitro effect of water activity (0.995, 0.98, 0.95, 0.90 and 0.85) and temperature (25 and 15 degrees C) on competing abilities of the biocontrol agent Penicillium oxalicum against Fusarium oxysporum fsp. lycopersici, a tomato pathogen, and Fusarium oxysporum fsp. gladioli, a gladiolus pathogen, was evaluated. The aim of this study was to assess the suitability of P. oxalicum to be applied as a biocontrol agent against these phytopathogenic fungi. Plates were inoculated in two points with P. oxalicum and one of the Fusarium species. Two different approaches were taken into account: the growth rate of each isolate and the Dominance Index (ID). P. oxalicum showed higher growth rates under most of the conditions tested except for 0.995 aw at both temperatures and at 0.98 and 15 degrees C. Similarly, P. oxalicum was dominating at 25 degrees C and < or = 0.95 aw, and at 15 degrees C and < or = 0.90 aw, while under the other conditions studied, mutual inhibition situations were found. This indicates a high ability of this species to successfully compete over a wide range of conditions and consequently the potential of P. oxalicum as a biocontrol agent against these Fusarium species.     

Effects of culture media, temperature, pH, and light on growth, sporulation, germination, and bioherbicidal efficacy of Phoma exigua, a potential biological control agent for salal (Gaultheria shallon)

In order to evaluate the potential use of Phoma exigua isolate PFC 2705 (PFC2705) as a biological control agent for salal (Gaultheria shallon), effect of cultural and environmental parameters on growth, conidia production, and pathogenicity of P. exigua were characterized in studies conducted under laboratory and greenhouse conditions. Within a range of 5-30°C, the optimum growth and germination temperature range was 20-25°C. The effect of pH on mycelial growth and conidial germination was not significant from pH 5 to 10. Fluorescent light significantly enhanced sporulation of the fungus on most agar media tested, yet was not necessary for growth. The type of culture media significantly affected mycelium growth, sporulation, and conidia germination. Age of mycelia used as inoculum affected the disease severity on salal. PFC2705 suppressed the growth of mature salal plant by inciting lesions on leaves, branch tips, and axillary buds and caused 56% death of the total biomass above ground. Characteristics such as easy inoculum production, wide range of growth environments, and high infectivity on salal increased the potential of P. exigua as a biocontrol agent for management of salal.     

Effect of Nutrition and Environmental Factors on the Endoparasitic Fungus Esteya vermicola, a Biocontrol Agent Against Pine Wilt Disease

The nematophagous fungus Esteya vermicola has tremendous potential for biological control. This species exhibits strong infectious activity against pinewood nematodes, whereas the study on the effect of nutrition and environmental factors is still of paucity. Carbon (C), nitrogen (N), pH value, temperature, and water activity have great impact on the fungal growth, sporulation, and germination. In nutrition study, the greatest number of conidia (2.36 × 10⁹ per colony) was obtained at the C:N ratio of 100:1 with a carbon concentration 32 g l^?1. In addition, the germination rate and radial growth of E. vermicola were used to evaluate the effects of environmental conditions and they were optimized as following: pH 5.5, 26 °C and water activity of 0.98. Our results also confirmed that variation of environmental factors has a detrimental influence on the efficacy of active conidia and growth of fungus. Moreover, under above optimal condition, the biocontrol efficacy was significantly improved in regard to the increase of adhesive and mortality rate, which highlight the study on the application of E. vermicola as pine wilt disease biocontrol agent.     

Reaction of <Emphasis Type="Italic">Bipolaris euphorbiae</Emphasis> to environmental factors and its tolerance to solar and ultraviolet radiation

The determination of the ideal cultivation conditions and the knowledge of solar radiation tolerance are important aspects that must be investigated for the use of Bipolaris euphorbiae Muchovej and Carvalho as a biocontrol agent. The present study was done to assess the growth rate, sporulation and viability of the fungus cultivated under different conditions of the initial pH value of the growth medium, temperature and photoperiod. The tolerance of this fungus’ conidia to light from a source simulating solar and ultraviolet radiation was also assessed. B. euphorbiae was affected by different pH values of the growth medium being 6.0 the adequate pH for fungus cultivation. Incubation of the fungus under temperatures of 22, 25 and 28°C enhanced mycelium growth, while sporulation and viability of conidia were better at 22 and 16°C. Different regimens of exposure to light of fungal cultures only affect sporulation. Conidia exposed to solar and ultraviolet radiation for 8 h and 90 min, respectively, presented viabilities higher than 92%, indicating high tolerance levels to radiation exposure.     

Surface hydrophobicity, viability and efficacy in biological control of Penicillium oxalicum spores produced in aerial and submerged culture

The surface hydrophobicity, viability and biocontrol ability of Penicillium oxalicum spores, produced either in aerial or submerged culture, were characterized. A phase distribution test showed that spores produced in both methods of culture were highly hydrophobic, but those produced in aerial culture were more hydrophobic. Spores stored fresh at either 4 or 25 degrees C retained a high viability (80%) after 27 weeks of storage, although aerial spores survived better. Freeze-drying severely affected viability, especially of submerged spores. Biocontrol ability against Fusarium oxysporum f. sp. lycopersici was studied in the growth chamber. Aerially- produced spores were more effective than submerged ones. Aerially-produced P. oxalicum spores appeared to have more advantages than those produced by submerged culture, in relation to both viability and efficacy. These results demonstrate that physiological changes occur depending on production conditions which significantly influences quality of the biocontrol agent.     

蚊幼虫病原真菌贵阳腐霉的生物学研究

为了开发灭蚊真菌贵阳腐霉Pythiumguiyangense用于蚊虫防治,对贵阳腐霉生物学特性进行了研究。采用菌丝生长率、真菌产孢情况以及对致倦库蚊Culexquinquefaciatus1龄幼虫的毒力作为评价的指标。测试了7种人工培养基、7种单糖、7种氮源、真菌生长所需的pH范围和温度范围、以及4种光-暗比的光照程序对真菌的影响。结果证明该真菌生长的适合温度为5℃～35℃,最佳温度为25℃～30℃;适合pH范围是5～12;在pH9～11范围内菌丝和游动孢子生长最好;测试的人工培养基中,按照菌丝生长速度从高到低排列,依次为Czapek’SFE、PYG、KPYG2、SDAY、CMA和PDA。其中从真菌的游动孢子形成量和对蚊幼虫的毒力来看,最佳培养基为SFE;葡萄糖、果糖、乳糖、蔗糖、麦芽糖、甘露糖和可溶性淀粉都是本真菌的合适碳氢营养源;含有机氮的培养基比含无机氮的培养基好;不同的光照程序没有表现明显的影响,但是观察到紫外光对本真菌有明显的抑制作用。     

Antagonistic activity of Penicillium oxalicum Corrie and Thom,Penicillium decumbens Thom and Trichoderma harzianum Rifai isolates against fungi,bacteria and insects in vitro

The antibiotic activity of 70 isolates belonging to the genera Aspergillus, Penicillium, Fusarium, Alternaria and Trichoderma was tested as preliminary screening. The highest activity was obtained with three Penicillium oxalicum isolates, one Penicillium decumbens isolate and the Trichoderma harzianum isolate. After that, we chose these five isolates in order to carry out other studies with bacteria, fungi and insects. Extracts from these isolates were obtained. The extracts were tested for antibiotic activity with positive results, which implies that metabolite production is involved in this antagonistic effect. The highest activity was shown by T. harzianum and P. oxalicum extracts, but there was high variability among P. oxalicum isolates.     

Effects of carbon and nitrogen sources,carbon-to-nitrogen ratio,and initial pH on the growth of nematophagous fungus <Emphasis Type="Italic">Pochonia chlamydosporia</Emphasis> in liquid culture

The effects of carbon and nitrogen sources, carbon-to-nitrogen ratio (C:N) and initial pH value on the growth and sporulation of the nematophagous fungus Pochonia chlamydosporia in liquid culture were examined. Among the 21 carbon sources and 15 nitrogen compounds tested, the optimal carbon and nitrogen sources for mycelial growth were sweet potato and L-tyrosine, and for sporulation were sweet potato and casein peptone. A C:N ratio of 10:1 at pH 3.7 gave the maximum yield of conidia and a C:N ratio of 40:1 at pH 6.8 gave the maximum biomass. The initial pH value had a significant effect on mycelial growth and conidial production, with the optimal ranges being 3.5–4.5 for sporulation and 5–6 for growth. Maximum conidial production was obtained at an initial pH of 4.0 and the maximum biomass at pH 6.0. The results also showed that the final pH after 7 days cultivation was always higher than the initial value. The variability in growth and sporulation of seven strains of P. chlamydosporia in liquid culture was also compared and discussed.     

Pectic enzyme production and morphogenesis inHelminthosporium atypicum

The production of pectic enzymes byHelminthosporium atypicum and its morphogenesis on different media were studied. It was observed that the fungus produces pectic enzyme (macerating enzyme) adaptively. Increasing concentrations of glucose had an inhibitory effect on enzyme production. Glucose promotes profuse growth and early sporulation whereas presence of pectin slows down the growth and delays sporulation. Delay in sporulation is the effect of presence of pectin and not of the low pH of the medium. It is also suggested that in the case ofH. atypicum low pH of the medium does not allow the fungus to utilize a carbon source as efficiently as at higher pH.     

Effect of culture conditions on spore shelf life of the biocontrol agent Trichoderma harzianum

The influence of pH, carbon:nitrogen (C:N) ratio, carbon content and harvesting time on spore attributes of the biocontrol agent Trichoderma harzianum was evaluated. The effect of these culture parameters on viability, shelf-life and ultrastucture was also assessed. pH was a key parameter to manipulate for both growth and sporulation, while carbon concentration and C:N ratio strongly affected spore production time. At fixed pH, the C:N ratio had a limited influence on production yield, but was critical for spore shelf-life. The highest spore longevity was found in a medium with a C:N ratio of 14 and a pH of 7.0, when most resulting spores were still alive after 45 d storage. These spores also remained viable during storage under a broad range of relative humidities, indicating that they would be more sustainable in the field.     

Effect of beta-glucanases on Penicillium oxalicum cell wall fractions

The polysaccharidic effect of a purified 1,3-beta-glucanase, a purified beta-glucosidase, and of partially purified endo-1,3-beta-glucanase from autolysed Penicillium oxalicum cultures on cell wall isolate fractions from the same fungus were studied. Fractionation of 5-day-old cell wall gave rise to a series of fractions that were identified using infrared spectrophotometry. The fractions used were: F1, an alpha-glucan; F3, a beta-glucan; F4, a chitin-glucan; and F4b, a beta-glucan. The fractions were incubated with each of the enzymes and with a mixture of equal parts of the three enzymes and the products of the enzymatic hydrolysis were analyzed after 96 h incubation. The enzymes were found to degrade fraction F4b (beta-glucan); the greatest degree of hydrolysis was reached when the three enzymes were used together, suggesting the need for synergic action by these enzymes in the cell wall degradation process.     

Selection of Verticillium lecanii Isolates with High Potential for Biocontrol of Cucumber Powdery Mildew by Means of Components Analysis at Different Humidity Regimes

To identify characteristics for the selection of Verticillium lecanii isolates with high potential for biocontrol of Sphaerotheca fuliginea under glasshouse conditions, an exploratory study was performed on the effect of water limitation on the development of 14 isolates. The conidial germination, growth and sporulation of isolates of V. lecanii were studied in a tritrophic system on cucumber leaves and in a ditrophic system in Petri dishes. Their mycoparasitic ability was studied in S. fuliginea and Cladosporium cladosporioides . All characteristics were clearly affected by humidity. Four isolates showed good biocontrol potential. The performance of isolates on agar had less predictive value than on powdery mildew. The germination of isolates of V. lecanii was lower and the mycelial growth faster on agar than on mildewed leaves under corresponding humidity conditions. The results suggest that conditions in the phyllosphere differed from the set humidity in the surrounding air. A correlation was found between the lysis of C. cladosporioides growing in dual culture on agar with isolates of V. lecanii and the parasitism of powdery mildew on detached, rooted leaves. C. cladosporioides might offer a suitable substrate for testing isolates of V. lecanii for mycoparasitic potential under various environmental conditions. Conidial germination, growth and sporulation had limited predictive value.     

草酸青霉对含钾矿物风化及钾溶出的影响

【目的】探讨含钾硅酸盐矿物在草酸青霉(Penicillium oxalicum)作用下的风化及钾溶出情况。【方法】利用等离子体发射光谱、X-射线能谱、X-射线光电子能谱分析了3种常见含钾硅酸盐矿物(钾长石、白云母和黑云母)在草酸青霉作用后浸出液和矿物表面元素含量的变化;通过X-射线衍射分析矿物晶相结构的变化;采用共聚焦激光扫描显微镜表征了草酸青霉在矿物表面形成的生物膜;测量了培养液中不同碳源与氮源组分对草酸青霉解钾的影响。【结果】草酸青霉对结构稳定的钾长石和白云母风化速率较低,相比而言黑云母容易被风化并释放可溶性钾元素;草酸青霉在矿物表面形成了网状结构的生物膜,有利于微环境的生成及有机酸在其内的富集,促进微环境内钾的释放,强化微生物对矿物的风化作用;草酸青霉对多种碳源及氮源都表现出较好的适用性。【结论】草酸青霉是一种能够促进多种含钾矿物风化和钾溶出的真菌,在堆肥和生物肥料领域具有广泛的应用前景。     

Comparative mycelial and spore yield by Trichoderma viride in batch and fed-batch cultures

The effects of cultural parameters such as carbon and nitrogen source and environmental factors including temperature and pH were investigated on spore and mycelial yield of Trichoderma viride, which has potential as a biocontrol agent against species of Fusarium in batch culture and fed-batch culture where there was limiting nutrient. The results obtained indicated that growth and sporulation of T. viride were greatly influenced by various carbon and nitrogen sources, and by environmental factors such as pH and temperature. Mannitol, wheat bran and rice bran as sole carbon sources appear to stimulate high mycelial growth and spore yield in fed-batch culture. Growth and sporulation were also favoured by NaNO₃, peptone and NH₄SO₄ as the nitrogen sources in fed-batch and batch cultures_. Maximum growth and sporulation was between pH 4.5 and 6.0. Temperatures between 30 and 37 °C were good for mycelium growth of T. viride while temperatures between 30 to 45 °C were good for sporulation. The amount of spore and mycelium produced and the time required for attainment of maximum spore yield increased with increasing carbon and nitrogen source in batch culture. The final spore yield obtained in fed-batch culture was two times higher than the apparent spore-carrying capacity of batch culture. These results show that T. viride is capable of growing and sporulating with varied nutritional and environmental conditions, and, therefore, this strain of T. viride may be useful as a biocontrol agent under diverse physiological and environmental conditions.     

Fungal egg-parasites of plant-parasitic nematodes from Spanish soils

We have investigated the presence of fungal egg-parasites in Spanish soils with plant endoparasitic nematodes. Nine out of 68 samples (13%) yielded fungal parasites. The most common (seven strains) was Pochonia chlamydosporia var. chlamydosporia (= Verticillium chlamydosporium var. chlamydosporium), but Lecanicillium lecanii (= Verticillium lecanii) and Paecilomyces lilacinus were also found. Most strains were from cyst nematodes (Heterodera avenae or Heterodera schachtii). Biological factors related with the development and performance of these fungi as biocontrol agents were assessed in laboratory tetsts. Germination for most strains was around 90-100%. Higher biomass values were obtained, for most fungal strains, with complete or yeast extract peptone-glucose liquid media. P. lilacinus and L. lecanii showed the highest sporulation rates (1.0 x 10(9); and 1.5 x 10(10); conidia/g mycelium). All strains had optimum growth at 25 degrees C. High temperature (40 degrees C) was lethal to all fungi but low temperature (5 degrees C) allowed growth of L. lecanii. Most strains showed best growth close to pH 7. Several P. chlamydosporia strains produced diffusible pigments close to pH 3. Lack of moisture (aw = 0.887) in growth medium reduced but never arrested fungus growth. Proteolytic activity was, for all strains, the earliest and highest enzymatic activity. Amylolytic and pectinolytic activities showed the lowest values and the latter was undetectable for most strains. Pathogenicity (70-100percnt; egg infection) and severity (35-40 penetrating hyphae/egg) on Meloidogyne javanica were high for most strains tested. Our results show that agricultural soils in Spain contain fungal parasites susceptible to be biocontrol agents for plant-parasitic nematodes.     

Effect of yeast extract and succinic acid on growth and sporulation of alternaria species

Summary Alternaria solani andA. nyctanthi, these pathogens causing leafspot disease were able to metabolize a variety of nitrogen compounds when grown on different culture media. The amount of growth varied with the nitrogen source. Peptone produced the best zonation when added in definite proportion to the yeast extract medium. Ammonium compounds were found to be moderately effective for growth but poor for sporulation. The effect of adding succinic acid in media containing ammonium sources and the role of pH in the utilization of nitrite nitrogen was investigated.The fungus gave more vegetative growth on a mixture of aminoacids than in culture media in which the same amino acids were supplied singly to study the effect produced on growth and sporulation.     

一株具有拮抗作用的解淀粉芽孢杆菌的筛选、鉴定及生物学特性研究

本研究以樱桃番茄成熟红果为样本,以极细链格孢菌为指示菌筛选得到一株对番茄采后病原菌有抑制作用的菌株KL-1。通过平板拮抗试验研究了菌株KL-1对番茄采后常见病原真菌极细链格孢菌、黑曲霉、青霉菌、尖侧多隔孢霉、拟康宁木霉、盐生枝孢霉、子囊菌、胶孢炭疽菌等八种病原菌的抑制作用,同时通过形态学、生理生化及16S rDNA分子生物学特征对菌株进行了鉴定,并对其基本生物学特性进行了研究。结果表明:菌株KL-1对于七种病原菌极细链格孢菌、黑曲霉、青霉菌、拟康宁木霉、盐生枝孢霉、子囊菌和胶孢炭疽菌均有明显的抑制作用,其中对黑曲霉的抑制率最大为81%,对其他六种病原菌抑制率也均高于70%,对尖侧多隔孢霉的抑制率为0,说明菌株KL-1可以抑制番茄多种常见病原真菌,具有开发为生防制剂的潜力。经鉴定KL-1为解淀粉芽孢杆菌(Bacillus amyloliquefaciens);该菌培养9 h内生长最旺盛,最适生长pH为7.0,最适生长温度为37℃。     

Sulphur and phosphorus requirements of Curvularia pallescens Boed

The effect of different sulphur and phosphorus compounds on the growth and sporulation ofCurvularia pallescens Boed. has been studied. Nine different sulphur sources were tried but among them only magnesium sulphate yielded the best dry weight of the fungus. Zinc sulphate, sodium sulphate, sodium thiosulphate, potassium sulphate and calcium sulphate supported good growth. Poor growth was recorded on sodium bisulphite, ammonium sulphate, sodium sulphide and control. Sporulation was excellent on magnesium sulphate. It was good on zinc sulphate, sodium sulphate and potassium sulphate. On sodium thiosulphate, calcium sulphate, sodium bisulphite and control it was fair. Sodium sulphide and ammonium sulphate had inhibitory effect as sporulation was poor and nil on these two compounds respectively.Six phosphorus compounds were studied. Tripotassium phosphate gave best growth and excellent sporulation. Good growth and excellent sporulation was recorded on monobasic potassium phosphate and magnesium phosphate. Growth and sporulation were good on dibasic potassium phosphate and sodium dihydrogen phosphate. Ammonium phosphate was poorly utilized.     

一株低温玉米秸秆降解真菌的筛选、鉴定及降解特性

【背景】在我国北方地区玉米秸秆还田时期地温低、秸秆降解慢,如何加速玉米秸秆低温腐解成为研究热点。【目的】从冷凉地区土壤中筛选具有高效降解纤维素能力的低温菌株,为秸秆的有效利用奠定基础。【方法】在低温培养条件下,采用稀释涂布平板法、羧甲基纤维素钠(sodium carboxymethyl cellulose,CMC-Na)水解圈测定法、胞外酶活测定法、秸秆失重法进行低温秸秆降解菌株的初筛、复筛和秸秆降解性能的测定;根据菌株形态学特征及ITSrDNA序列分析对筛选菌株进行鉴定;利用3,5-二硝基水杨酸(3,5-dinitrosalicylic acid,DNS)法和秸秆失重法对菌株在不同接种量、培养基初始pH、温度情况下的纤维素酶活力和玉米秸秆降解能力进行研究。【结果】以16°C为筛选温度,获得一株在刚果红-羧甲基纤维素钠平板上D/d值为2.17、CMC酶活力为703 U/mL的高产纤维素酶低温真菌SDF-25;该菌株在4°C可以生长,10-16°C为最适生长温度,37°C条件下仍能生长;综合菌株的形态学和分子生物学测定结果,菌株SDF-25为草酸青霉菌(Penicillium oxalicum);该菌株最佳产纤维素酶的培养条件为接种量2%、初始pH为7.0、培养温度为10°C,在该培养条件下菌株SDF-25的CMC酶活为993.3 U/mL。失重法测定接种SDF-25于10°C培养15 d时秸秆降解率为39.5%,16°C时为44.9%。【结论】草酸青霉菌SDF-25可在低温条件下生长并具有较强的纤维素酶生产能力,在秸秆还田方面具有良好的应用前景。     

草酸青霉液体发酵产果胶酶条件的优化及其产物的酶学性质

采用响应面分析法对草酸青霉（Penicillium oxalicum）L5菌株液体发酵产果胶酶条件进行了优化。结果表明：桔皮粉、米糠及硫酸铵的添加量分别为4.85%、5.89%、0.97%,摇瓶初始pH为6.0~8.0,接种量为9%时,优化后的果胶酶活达54 391.70 U,是初始酶活18 148.00 U的3倍。另外,对其果胶酶性质进行了初步探讨,结果表明：该酶较适反应温度和pH分别为50℃和5.0;30~50℃时有较好的热稳定性,pH值为5.0时稳定性最佳。