莲子草假隔链格孢SF 193菌株的复壮对其产孢量和致病性的影响

【背景】莲子草假隔链格孢是空心莲子草的重要生防菌,但长时间保存或继代培养会导致该菌株产孢量和致病性显著下降。【方法】通过对初始菌株回接、分离、纯化和鉴定相继获得复壮一代和二代菌株,分别在3、6、9d后对初始菌株、复壮一代和二代菌株进行产孢培养,比较其产孢量;同时比较分析了这3代菌株的液体发酵原液和1:10稀释液对空心莲子草的防除效果。【结果】获得了10株复壮一代和10株复壮二代菌株,20株菌对空心莲子草均有致病作用,且产生的分生孢子形态特征与初始菌株一致。与初始菌株相比,复壮菌株的产孢量显著提高且达到最大产孢量的时间显著短于初始菌株。其中,复壮二代菌株的孢子量是初始菌株的4.8倍,其次为复壮一代菌株,产孢量是初始菌株的4.1倍;复壮菌株达到最大产孢量的时间为3d,初始菌株为6d。复壮菌株一代和二代的原液对空心莲子草的致病性分别比初始菌株提高了4.65%和9.82%,1:10稀释液的致病性分别提高了25.79%和16.55%。【结论与意义】对长期保存或继代培养的空心莲子草生防菌复壮可显著提高其产孢量和致病性,对维持生防菌遗传性状的稳定性和提高对空心莲子草的防效具有重要意义。     

Optimised fermentation conditions and improved collection efficiency using dual cyclone equipment to enhance fungal conidia production

Methods for enhancing conidial yield and for harvesting pure fungal conidia of entomopathogenic fungi were investigated. Fermentation conditions (liquid-to-solid ratio, MgSO₄·7H₂O, incubation temperature, inoculum sizes, KNO₃ and relative humidity) of Beauveria bassiana s.l. and Metarhizium anisopliae s.l. were optimised to increase the conidial yields that reached 11.2 mg/g and 24.5 mg/g, increases of 72% and 52% compared to the unoptimised yields of 6.5 mg/g and 16.1 mg/g, respectively. Three methods were compared for harvesting pure conidia of B. bassiana: dual cyclone equipment (DCE), sieving 200 and elution with 0.02% Tween-80 suspension. DCE performed the best, giving a conidial yield of 12.6 mg/g and 1.8 × 10¹⁰ conidia·g^–1. To further enhance the harvest efficiency, response surface methodology combined with a Box–Behnken design was employed, and the conidial yield of B. bassiana reached 20.9 mg/g, a total increase of 221% compared to the original conditions. Under these optimised harvest parameters, the conidial yield of M. anisopliae rose to 42.2 mg/g, an increase of 162%. The conidia of B. bassiana and M. anisopliae harvested in this way were pure, with no mycelial fragments or substrate visible in microscopic images.     

Germination and Survival of Fusarium graminearum Macroconidia as Affected by Environmental Factors

The effects of temperature (4–20°C), relative humidity (RH, 0–100%), pH (3–7), availability of nutrients (0–5 g/l sucrose) and artificial light (0–494 μmol/m²/s) on macroconidial germination of Fusarium graminearum were studied. Germ tubes emerged between 2 and 6 h after inoculation at 100% RH and 20°C. Incubation in light (205 ± 14 μmol/m/s) retarded the germination for approximately 0.5 h in comparison with incubation in darkness. The times required for 50% of the macroconidia to germinate were 3.5 h at 20°C, 5.4 h at 14°C and 26.3 h at 4°C. No germination was observed after an incubation period of 18 h at 20°C in darkness at RH less than 80%. At RH greater than 80%, germination increased with humidity. Germination was observed when macroconidia were incubated in glucose (5 g/l) or sucrose (concentration range from 2.5 × 10^?4 to 5 g/l) whereas no germination was observed when macroconidia were incubated in sterile deionized water up to 22 h. Macroconidia germinated quantitatively within 18 h at pH 3–7. Repeated freezing (?15°C) and thawing (20°C) water agar plates with either germinated or non‐germinated macroconidia for up to five times did not prevent fungal growth after thawing. However, the fungal growth rate of mycelium was negatively related to the number of freezing events the non‐germinated macroconidia experienced. The fungal growth rate of mycelium was not significantly affected by the number of freezing events the germinated spores experienced. Incubation of macroconidia at low humidity (0–53% RH) suppressed germination and decreased the viability of the spores.     

Species separation in <Emphasis Type="Italic">Curvularia</Emphasis> “geniculata” group inferred from <Emphasis Type="Italic">Brn1</Emphasis> gene sequences

 Brn1, a reductase gene involved in the melanin biosynthetic pathway, was adopted for species delimitation among members in the “geniculata” group of Curvularia species and proved to be useful for this purpose. Phylogenetic trees of these fungal members were constructed from nucleotide sequences of this region. The so-called geniculata group of Curvularia was separated into several clusters. The conidial morphology of the members in each cluster is closely similar but clearly different among discrete clusters. The phylogenetic groups almost concurred with the morphological grouping. Thus, the synonymous treatment of Curvularia affinis, C. fallax, and C. senegalensis to C. geniculata in a previous study was supported. The isolates with warping hilum conidia were clearly different from C. geniculata and separated into two clusters. C. geniculata ATCC 6671 made an independent cluster situated near these clusters. The protuberant hilum species were located separately in the phylogenetic trees. For sound taxonomic treatment of these isolates, we should accumulate more information and retain our species determination for them. Received: September 26, 2002 / Accepted: March 12, 2003     

Alanine: Glyoxylate aminotransferase 1 is required for mobilization and utilization of triglycerides during infection process of the rice blast pathogen,Magnaporthe oryzae

The rice blast pathogen, Magnaporthe oryzae has been widely used as a model pathogen to study plant infection-related fungal morphogenesis, such as penetration via appressorium and plant-microbe interactions at the molecular level. Previously, we identified a gene encoding peroxisomal alanine: glyoxylate aminotransferase 1 (AGT1) in M. oryzae and demonstrated that the AGT1 was indispensable for pathogenicity. The AGT1 knockout mutants were unable to penetrate the host plants, such as rice and barley, and therefore were non-pathogenic. The inability of ∆Moagt1 mutants to penetrate the susceptible plants was likely due to the disruption in coordination of the β-oxidation and the glyoxylate cycle resulted from a blockage in lipid droplet mobilization and eventually utilization during conidial germination and appressorium morphogenesis, respectively. Here, we further demonstrate the role of AGT1 in lipid mobilization by in vitro germination assays and confocal microscopy.     

The effects of some storage conditions on viability of Lecanicillium lecanii conidia to whitefly (Homoptera: Trialeurodes vaporariorum)

A study on the survival of Lecanicillium lecanii conidia in storage at room temperature was carried out. Firstly, drying methods of conidia powder were compared. Vacuum-freeze drying (VFD) was more suitable for drying conidia as compared to vacuum drying (VD) at room temperature. Vacuum-freeze drying for 24-h resulted in a water content of 5.4%, and a viability, determined as germination of conidia in 2% glucose solution after16 h, was 90.3% and the infection in greenhouse whitefly, Trialeurodes vaporariorum was about 94.7% at a dose of 1×10⁸ conidia/mL. Secondly, the factors influencing viability of conidia stored at room temperature were evaluated in the laboratory. Temperature was the most critical factor influencing conidial storage stability, among the tested factors affecting survival of conidia stored at room temperature for 6 months. Both conidial germination and infection of hosts decreased with storage temperature increasing from 15 to 35°C, and at 35°C the survival of stored conidia for 6 months was near zero. The moisture content of the conidial powder was another major factor influencing viability of stored conidia at room temperature. Conidial powder dried to about 5% moisture content showed higher viability than non-dried conidial powder. For the carriers, clay and charcoal were more suitable for storage of L. lecanii conidia at room temperature. At a room temperature of 25°C, L. lecanii conidia which were dried to 5% water content and mixed with clay or charcoal could retain about 50% survival after 6 months' storage.     

茶树轮斑病的发生及病原菌分生孢子萌发特性

对豫南茶园茶树轮斑病的发生与病原菌分生孢子萌发特性进行了调查和研究。茶树轮斑病在豫南茶区发生较普遍,一般夏秋发病较重,冬春发病较轻;轮斑病的病叶率和病情指数与温度、湿度、光照等生态因子关系密切;病原菌孢子在离体25℃条件下,4 h开始萌发。在茶树叶面上,病原菌分生孢子萌发明显比非叶面条件下好,病原菌菌丝生长较快,说明此病原菌与茶树叶片有高度的亲和力和较强的适应茶树叶面微环境的能力;茶树轮斑病病原菌分生孢子在pH5~7范围内萌发及芽管伸长较好,pH过小或过大均不利于病原菌的分生孢子萌发和菌丝生长。     

球孢白僵菌在红火蚁体表侵染的扫描电镜观察

利用扫描电镜观察了球孢白僵菌Beauveria bassiana Bb04菌株分生孢子对红火蚁Beauveria bassiana 工蚁体壁的侵染过程。结果表明: 分生孢子多分布在红火蚁工蚁节间膜、胸部的褶皱、气门、体壁的凹陷部位、刚毛窝附近, 以及着生较密刚毛的足上。萌发的分生孢子在节间膜以及体表缝隙、刚毛窝及刚毛稀少的凹陷部位、胸部褶皱和足胫节处入侵。分生孢子在附着12 h后开始萌发, 接种后18 h附着在节间膜处的孢子首先侵入成功, 接种后24 h刚毛窝附近孢子萌发入侵, 接种后60 h胸、腹和足等部位的孢子均成功穿透侵入表皮。分生孢子可以直接以芽管侵入表皮, 也可以产生附着胞再侵入。     

Relations entre production et localisation de mycosporine et morphogenèses reproductrices chez le Pyrénomycète Gnomonia leptostyla

Relations between production and localisation of mycosporin and reproductive morphogenesis in the Pyrenomycete Gnomonia leptostyla.
The production of mycosporin (P310) has been analysed in Gnomonia leptostyla (FT.) Ces. et de Not. during mycelial growth and reproductive morphogenesis (macroconidiogenesis, microconidiogenesis and differentiation of perithecia). Conidiogenesis is induced in illuminated cultures while darkness promotes perithecial development. At 20°C, the cultures produce either macroconidia or perithecia with abortive sporophyte. Microconidia differentiation and perithecia maturation require low temperature (10°C). Mycosporin is, at all times, present in the thallus. However, the concentration of mycosporin in highest in the conidiogenous thallus, intermediate in the perithecial thallus. and lowest in the vegetative mycelium. In the conidiogenous thallus, macroconidia and microconidia are both sites of mycosporin accumulation. On the contrary, in the perithecial thallus, mycosporin levels are not higher in perithecia than in mycelia, even during their maturation period. The quantitative variations of mycosporin during the thallus development and its accumulation inside conidia suggest translocation from sites of synthesis towards reproductive cells.     

Mass production of Beauveria bassiana for regulation of Leptinotarsa decemlineata populations

A simple liquid medium which enhanced the production of conidiospores by an isolate of the entomophagous fungus Beauveria bassiana is described. Spore production was attained using cultures floating in inflated sections of plastic tubing (“polyethylene cushions”) and glass bottles. A method is described for determining lethal doses and lethal times for second- and third-instar Leptinotarsa decemlineata larvae.