室内对柑橘酸腐病防治药剂的筛选研究

在室内采用活体测定的方法对几个柑橘常用杀菌剂进行防治酸腐病的筛选研究,测定结果表明,40%双胍三辛烷基苯磺酸盐可湿性粉剂是防治酸腐病较好的药剂。     

13种杀菌剂对百合枯萎病菌的室内毒力测定

采用生长速率测定法和分生孢子萌发抑制率法测定了13种杀菌剂对百合枯萎病尖孢镰刀菌的毒力作用.结果表明烯唑醇、多菌灵、福美双、己唑醇、苯醚甲环唑、(噁)霉灵对菌丝生长具有明显的抑制作用,其中多菌灵、烯唑醇、(噁)霉灵3种药剂对菌丝生长抑制作用最强.对孢子萌发的抑制作用测定结果表明:多菌灵、(噁)霉灵、福美双、己唑醇、烯唑醇等药剂对百合枯萎病菌孢子萌发具有明显的抑制作用,其中多菌灵、福美双、(噁)霉灵、己唑醇对百合枯萎病菌的分生孢子萌发抑制作用明显强于其他药剂.     

几种杀菌剂对香蕉枯萎病菌的室内毒力测定

香蕉枯萎病是世界香蕉产区的重要病害之一，为了更有效的防治此病，我们选用11种药剂对香蕉枯萎病菌进行室内毒力测定，结果表明：18％保冶达乳油抑菌效果最好，EC50为0.13mg／L；15％三唑酮可湿性粉剂的抑菌效果最差，EC50为201．40mg/L。     

22种杀菌剂对芒果蒂腐病菌的毒力测定

采用牛长速率法进行了22种杀菌剂对2株芒果蒂腐病菌的室内毒力测定.研究结果表明:同一杀菌剂对供试2株菌株的毒力无明显差异.通过EC50值和EC75值综合分析,对芒果蒂腐病菌毒力最强的是多菌灵,其EC50、EC75值分别为0.03、0.05 mg/L,其他依次为甲基硫菌灵、咪鲜胺、丙环唑、咪鲜胺锰盐、苯醚甲环唑、氟硅唑、烯唑醇、异菌脲、吡唑醚菌酯、戊唑醇和腈菌唑,这1 2种杀菌剂均可作为防治芒果蒂腐病的首选杀菌剂;另外,百菌清、醚菌酯和代森锰锌的EC50、EC75值均相对较低,也可作为防治芒果蒂腐病的杀菌剂.     

内吸性杀菌剂对橡胶白根病菌的室内毒力测定

由木硬孔菌[Rigidoporus lignosus (Klotzsch) Imaz.]引起的白根病是橡胶树(尤其是幼龄期胶树)的重要病害。在室内采用菌丝生长速率法测定了几种内吸性杀菌剂对木硬孔菌的抑菌能力。结果表明,三唑类杀菌剂的EC50值普遍小,且病菌对它们的敏感性也较高,抑菌效果最好,其中以5%烯效唑WP最优;75%十三吗啉EC的EC50值较小,病菌对它的敏感性也较好,抑菌效果较好;80%乙蒜素EC、50%代森锰锌·乙膦铝·烯酰吗啉WP、50%多菌灵WP和70%甲基硫菌灵WP的抑菌效果最差。     

8种杀菌剂对大豆南北方茎溃疡病菌和拟茎点种腐病菌的室内毒力测定

试验选用8种低毒杀菌剂,采用菌丝生长抑制法对大豆北方茎溃疡病菌、大豆南方茎溃疡病菌和大豆拟茎点种腐病菌进行了室内毒力测定.结果表明,50%多菌灵SC对供试3种病菌毒力最强,EC50值分别为0.118、0.112、0.152 mg/L.25%噁醚唑EC对南方茎溃疡病菌和拟茎点种腐病菌的毒力仅次于多菌灵,5%己唑醇EC对北方茎溃疡病菌抑菌效果也仅次于多菌灵,这3种药剂都可作为防治3种病害的有效杀菌剂.     

几种杀菌剂及其混配剂对香蕉枯萎病菌的毒力测定

采用菌丝生长速率法测定了8种杀菌剂对香蕉枯萎病菌的毒力,并在此基础上用Horsfall的毒力试验设计和共毒系数法进行了混配剂的筛选. 结果表明:450 g/L咪鲜胺EW的EC50值最小,为0.038 4 mg/L,毒力最强;450 g/L戊唑醇SC、25%吡唑醚菌酯EC、30%丙环唑·苯醚甲环唑EC、50%多菌灵WP、25%丙环唑EC、10%苯醚甲环唑WG、15%霉灵AS的毒力依次减弱,EC50 值分别为:0.245 8、0.385 7、0.943 5、1.379 8、2.438 4、10.981 4、33.333 0 mg/L. 多菌灵与霉灵按EC50值剂量9∶1比例混配后共毒系数为131.63,具有一定的增效作用,多菌灵与丙环唑按EC50值剂量3∶7的比例混配后共毒系数为691.87,具有显著的增效作用. 咪鲜胺与霉灵、咪鲜胺与丙环唑、咪鲜胺与多菌灵3组混配药剂均无显著增效作用.     

12种农药对油茶炭疽菌的室内毒力测定

[目的]通过室内试验筛选出可有效防治油茶炭疽病的药剂。[方法]采用菌丝生长速率法测定了12种杀菌剂对油茶炭疽病的抑菌作用,并得到了12个毒力回归方程及抑制有效中浓度(EC50)。[结果]12种杀菌剂对油茶炭疽病病原菌的毒力最强的为10%苯醚甲环唑WG,EC50值为47.8630 mg/L;21%硅唑多菌灵SC、25%咪酰胺EC次之,EC50值分别为97.7232、125.8925 mg/L;100%硫酸铜结晶和70%代森锰锌WP的毒力最差。[结论]10%苯醚甲环唑WG、21%硅唑多菌灵SC以及25%咪酰胺EC均可有效抑制油茶炭疽病菌的生长,可进一步用于田间试验。     

7种药剂对白菜黑斑病菌的毒力及增效配方筛选

为了有效防治白菜黑斑病,本研究采用生长速率法测定7种药剂及不同药剂的复配对白菜黑斑病菌的毒力及增效作用。试验结果表明,在7种供试药剂中95%氟环唑原药、98%吡唑醚菌酯原药和98%戊唑醇原药对白菜黑斑病菌的毒力较强,EC50分别为0.37、0.60 mg/L和0.60 mg/L。95%氟环唑原药与98%戊唑醇原药以4∶1、1∶1和1∶4的质量浓度比复配时,EC50分别为0.29、0.34 mg/L和0.35 mg/L,共毒系数分别为139.29、135.35和151.59,表现为增效作用,而95%氟环唑原药与98%吡唑醚菌酯原药以4∶1、1∶1和1∶4的质量浓度比复配时,EC50分别为0.40、0.46 mg/L和0.53 mg/L,共毒系数分别为117.54、108.02和118.37,具有相加作用。该研究结果可为白菜黑斑病的化学防控提供科学用药指导。     

不同杀菌剂对祁山药炭疽病菌室内毒力及田间药效

[目的]筛选出防治祁山药炭疽病菌的有效化学药剂。[方法]采用菌丝生长速率法测定11种杀菌剂对祁山药炭疽病菌的抑制作用,并进行了5种药剂对祁山药炭疽病的田间药效试验。[结果]室内毒力测定结果表明:咪鲜胺、氟硅唑、吡唑醚菌酯、丙环唑和苯醚甲环唑这5种杀菌剂对炭疽病菌的抑菌效果好,其EC50值分别为0.0249、0.0378、0.0406、0.3941、1.2812 mg/L。田间试验结果表明咪鲜胺的防治效果最好,防效高达85.13%。[结论]为药剂混配和防治炭疽病提供药剂筛选的理论依据。     

10种杀菌剂对甘薯黑斑病的毒力及联合毒力

[方法]通过菌丝生长速率法测定了10种杀菌剂对引起甘薯黑斑病的甘薯长喙壳菌(Ceratocystis fimbriataEllis and Halsted)的毒力及部分药剂混配的联合毒力。[结果]粉唑醇毒力较高,其EC50值为0.0654 mg/L;其次为氟硅唑,EC50值为0.1508 mg/L;异菌脲、三唑酮、霉灵的EC50值在1~10 mg/L之间,抑菌活性高于甲基硫菌灵。联合毒力的测定结果表明:甲基硫菌灵与百菌清质量比2∶1的配比、甲基硫菌灵与粉唑醇质量比2∶1的配比、百菌清与粉唑醇质量比5∶1的配比增效作用最强。[结论]为筛选防治甘薯黑斑病的杀菌剂提供了毒力测定依据。     

Comparison of lipase production by Geotrichum candidum in stirring and airlift fermenters

The production of lipase by Geotrichum candidum in both, stirred tank and airlift bioreactors were compared. G candidum an imperfect filamentous fungus, grows well in liquid medium, and produces a lipase with specific affinity for long‐chain fatty acids with cis‐9 double bonds but, lipase production is generally not efficient because the optimum medium composition and fermentation conditions are not known. Response surface methodology was used to optimize the agitation speed (100–500 rpm) and aeration (0.2–1.8 vvm) for production of lipase by G candidum in a bench‐scale stirred fermenter. A Central Composite Rotatable Design (CCRD) was used to optimize lipase activity and productivity. Lipase production in an airlift fermenter was also studied with aeration ranging from 1 to 3 vvm. A previously optimized culture medium containing 3.58% of peptone, 0.64% of soy oil and an initial pH of 7.0, was used in the experiments, incubating at 30°C. In the stirred reactor the optimum conditions of agitation and aeration for lipase production and productivity were 300 rpm and 1 vvm, leading to an activity of 20 U cm^?3 in 54 h of fermentation and 0.3900 (U cm^?3 h^?1) of productivity. The best aeration condition in the airlift fermenter was 2.5 vvm, which yielded similar lipase activity after 30 h of fermentation, resulting in a productivity of 0.6423 (U cm^?3 h^?1). In the absence of mechanical agitation similar lipase yields were achieved but in less time, resulting in productivity, about 60% greater than in a stirred fermenter; the lower energy demand for the same lipase yield offers economic advantages. Copyright © 2004 Society of Chemical Industry     

Production of Lipase from Geotrichum candidum Using Corn Steep Liquor in Different Bioreactors

The production of an extracellular lipase using corn steep liquor (CSL) as the nitrogen source in the cultivation of Geotrichum candidum NRRLY‐552 was evaluated. The optimized conditions in shake flasks were CSL, 8.0 % w/v, soybean oil, 0.6 % w/v, pH 7.0, 30 °C, 250 rpm, and 48 h, resulting in a maximum lipase productivity of 0.438 U mL^?1 h^?1(U = the amount of enzyme required to liberate 1 μmol of fatty acid per minute). Scale‐up was evaluated with airlift and stirred tank reactors; the best conditions, respectively, were 1 vvm(volume of gas per volume of medium per minute) of aeration which resulted in 0.535 U mL^?1 h^?1 (32 h) and 1 vvm and 300 rpm resulting in 0.563 U mL^?1 h^?1 (16 h). To facilitate downstream processes, lipase production was also evaluated using CSL previously clarified with activated charcoal resulting in 0.275 U mL^?1 h^?1 (24 h) using 12 % (w/v) of clarified CSL in shake flasks. The obtained results showed that CSL leads to similar productivity compared to peptone using the same microorganism under similar conditions. In addition the cost of fermentation medium using CSL is much lower because it is a very inexpensive by‐product from corn processing.     

Analysis of batch submerged cultivations of Geotrichum candidum growing in lactate with either glutamate or lysine

Amino acid and lactate assimilation by Geotrichum candidum were examined in submerged culture. G candidum growth on lysine and lactate clearly showed that lactate can be assimilated as a carbon source, in addition to an energy source. Lysine was chosen since G candidum did not grow on lysine as the sole carbon and nitrogen source. On the contrary, when a convenient carbon source amino acid (glutamate) was used, lactate appeared to have no effect on G candidum growth; it was only assimilated at a low rate during the stationary state for energy supply, in agreement with previous observations recorded during growth on peptones. The assimilation of glutamate, the more convenient substrate for G candidum growth, required less energy than lysine assimilation, indicated by the lower level of CO₂ released. Copyright © 2004 Society of Chemical Industry     

Carbon assimilation and dissimilation during growth of Geotrichum candidum on amino acids and glucose

BACKGROUND: This work examines the metabolic behaviour of amino acids during Geotrichum candidum growth, in the presence of a primary carbon source like glucose. Amino acids were characterized based on their carbon assimilation and dissimilation by G. candidum, in the presence of glucose as the limiting substrate. RESULTS: The first group (Cys, His, Phe, Thr and Trp) was only used as nitrogen sources by G. candidum, with glucose being the carbon and energy source. Glucose repression was shown for the rest of the amino acids, since only after glucose depletion amino acids from the second group (Gly, Lys, Met, Val) were dissimilated for energy supply by oxidation into CO₂, while those from the third group (Ala, Arg, Asp, Glu, Leu, Pro and Ser) were assimilated as carbon sources (and additionally used as nitrogen sources), leading to a diauxic growth. CONCLUSION: This energy‐saving response was not previously shown for the second fungus involved in ripening of soft white cheese—P. camembertii—leading to simultaneous use of some amino acids and glucose as carbon and energy sources, and hence lower growth rates than those recorded during G. candidum growth. Copyright © 2007 Society of Chemical Industry     

不同杀菌剂对人参黑斑病菌的毒力测定及田间药效

[方法]采用菌丝生长速率法测定了24种杀菌剂对人参黑斑病菌的室内毒力作用,并进行了5种药剂对人参黑斑病的田间药效试验.[结果]室内毒力测定结果表明:25％丙环唑EC和50％嘧菌环胺WG对人参黑斑病菌毒力最强,其EC90值分别为0.05、0.65 mg/L,2％戊唑醇WS等7种药剂对人参黑斑病菌也具有较好的抑制效果,其EC90值在1.59～19.94 mg/L之间.田间试验结果表明:3％中生菌素WP、50％嘧菌环胺WG和76％丙森霜脲氰WP在田间对人参黑斑病表现较高的防效.[结论]筛选出了对人参黑斑病具有较好防效的药剂,对人参黑斑病的药剂防治具有重要指导意义.     

Characterization of Crude and Partially Purified Lipase from Geotrichum candidum Obtained with Different Nitrogen Sources

Lipases from Geotrichum candidum were produced in two different medium: A = 12 % (w/v) clarified corn steep liquor (CCSL) + 0.6 % (w/v) soybean oil (SO) and B = 3.5 % (w/v) yeast hydrolysate (YH) + 0.7 % (w/v) SO. Lipases were partially purified from both media by hydrophobic interaction chromatography using 3.0 mol L^?1 of NaCl as mobile phase, and they were characterized in the crude and partially purified forms. The recovery of lipase activity from CCSL and YH via HIC were 96 and 94.3 %, and the purification factors were 44.3 and 86.7‐fold, respectively. All evaluated lipases had similar optimum pH (7.0–7.7), but, for the CCSL crude lipase, optimum temperature (47 °C) was 10 °C higher than others lipases evaluated. CCSL crude lipase possessed a higher thermo stability than YH crude lipase, e.g., at 37 °C (pH 7.0) the half‐life of CCSL crude lipase was 19.25 h and at pH 8.0 (30 °C) the half‐life was 48 h, which are five and ten times higher than with YH crude lipase, respectively. On the other hand, the YH crude lipase possessed a higher catalytic constant (k_cat = 2.3 min^?1) but with almost the same catalytic efficiency (K_m/k_cat = 32.12 mg mL min^?1) in relation to CCSL crude lipase. The lipases differ in biocatalytic properties between substrates, suggesting that the two lipases can be employed for different applications.     

Enrichment of Erucic and Gondoic Fatty Acids from Crambe and Camelina Oils Catalyzed by Geotrichum candidum Lipases I and II

Erucic (22:1, cisΔ13) and gondoic acids (20:1, cisΔ11) are building blocks obtained from renewable sources for the oleochemical industry. Different biocatalytic strategies for the enrichment of these compounds with high recovery yields were developed in our group. Geotrichum candidum lipases (GCL) strongly discriminate against fatty acids longer than 18 carbon atoms. Thus, GCL-I and -II were investigated using hydrolysis or ethanolysis reactions with Crambe and Camelina oils. Hydrolysis was also studied using fatty acid ethyl esters (FAEE) derived from the corresponding oil. Both isoforms were highly selective; however, interesting differences were observed. Although it has been reported that GCL-I displays a higher preference toward 18 cisΔ9, which is present in the studied oils at high levels, GCL-II showed higher enrichment values during hydrolysis independent of the substrate used. Hence, enrichments of 87% (Crambe oil) and 82% (Crambe FAEE) for erucic acid and 50% (Camelina oil) and 45% (Camelina FAEE) for gondoic acid, with recovery values between 89% and 99%, were achieved. On the contrary, the best enzyme for ethanolysis was GCL-I (82% and 41% for erucic and gondoic acid, respectively). In this case, although GCL-II also displayed good enrichment and recovery levels (77% and 28%, respectively), they were lower compared to the former reactions. In both ethanolysis reactions, the FAEE fraction contained between 92% and 97% of 18 unsaturated fatty acids.     

Diffusion of glutamic acid in relation to growth of Geotrichum candidum and Penicillium camembertii at the surface of a solid medium

Growth of pure cultures of Geotrichum candidum or Penicillium camembertii at the surface of a solid medium was studied. Consumption of nutrients by the microorganisms growing at the surface of the gel induced their diffusion from the core to the rind. Particular attention was paid to the diffusion of glutamic acid, the nitrogen source, in relation to the growth of the microorganism at the surface. The growth kinetic has been described using the Verlhust model. The diffusion coefficient of glutamic acid in sterile culture medium was measured and found to be 0.55 cm² day^?1. With this coefficient and assuming that the glutamic acid consumption was partially linked to growth, the experimental diffusion gradients have been fitted. Good agreement was found between experimental data and the diffusion/reaction model. The glutamic acid diffusion cannot be assumed to limit growth, since noticeable amounts of this substrate always remained at the upper surface of the gel. Copyright © 2004 Society of Chemical Industry