Variation in Efficacy of Isolates of the Fungus ARF Against the Soybean Cyst Nematode Heterodera glycines

An unnamed fungus, designated ARF, that parasitizes eggs and sedentary stages of cyst nematodes is a potential biological control agent of Heterodera glycines. The objectives of this study were to determine whether ARF isolates differ in their ability to suppress nematode numbers in soil and to compare the efficacy of ARF in heat-treated and native soil. The effectiveness of 11 ARF isolates was compared by introducing homogenized mycelium into heat-treated soil. Soybean seedlings were transplanted into pots containing fungus-infested soil and inoculated with H. glycines. After 30 or 60 days, the number of nematodes and the percentage of parasitized eggs were determined. Three isolates (907, 908, and TN14), which were previously reported to be weak egg parasites in vitro, consistently suppressed nematode numbers by 50% to 100%. Of the isolates previously reported to be aggressive egg parasites, four (903, BG2, MS3, and TN12) reduced nematode numbers by 56% to 69% in at least one experimental trial, but the other four had no effect on nematode numbers. When the efficacy of isolate TN14 was tested in heat-treated and native soil, nematode suppression was greater in the heat-treated soil in only one of two trials. In both soil treatments, nematode numbers were reduced by more than 60%. We conclude that virulence toward nematode eggs in vitro is a poor indicator of effectiveness of an ARF isolate in soil, and that the presence of soil microbes may reduce, but does not completely inhibit, activity of isolate TN14.     

Purification and characterization of thermostable β-amylase and pullulanase from high-yielding Clostridium thermosulfurogenes SV2

Thermostable -amylase and pullulanase, secreted by the thermophilic anaerobic bacterium Clostridium thermosulfurogenes strain SV2, were purified by salting out with ammonium sulphate, DEAE-cellulose column chromatography, and gel filtration using Sephadex G-200. Maltose was identified as a major hydrolysis product of starch by -amylase, and maltotriose was identified as a major hydrolysis product of pullulan by pullulanase. The molecular masses of native -amylase and pullulanase were determined to be 180 and 100 kDa by gel filtration, and 210 and 80 kDa by SDS–PAGE, respectively. The temperature optima of purified -amylase and pullulanase were 70 and 75°C, respectively, and both enzymes were completely stable at 70°C for 2h. The presence of starch further increased the stability of both the enzymes to 80°C and both displayed a pH activity optimum of 6.0. The starch hydrolysis products formed by -amylase action had -anomeric form.     

Channelling of glucose by methanol for citric acid production from Aspergillus niger

Citric acid produced by Aspergillus niger was increased from 4.6g l^-1 to 7.8gl^-1 by supplementing basal medium with methanol (30mll^-1). While stimulating citric acid production, methanol did not improve membrane permeability of the fungus for citric acid. Methanol inhibited the germination of Aspergillus spores. An increase in glucose concentration from 50gl^-1 to 100gl^-1 in the presence of methanol (30mll^-1) improved citric acid production (1.6-fold) while at higher levels of glucose concentration methanol had no effect on citic acid production.     

稻瘟病菌致病突变体的REMI诱变与鉴定

以水稻“爱知旭”(Aichi—aShahi)为寄主,将带选择标记的质粒pCSN43和pBF101为外源DNA,利用限制酶诱导整合(REMI)这种新方法转化稻瘟病菌原生质体,从筛选到的数百个转化体中分离出3个与致病能力密切相关的突变体R2H65、R2H69和R281565。其中,R2H65和R2H69只产生畸形分生孢子,分生孢子的发育和附着胞的形成以及黑色素的合成均受到极大影响,致病性测试证明完全丧失致病能力;R281565的许多表型与野生型的相似,但致病能力却大大降低。     

A Device for Infecting Adult Tsetse Flies,Glossinaspp., with an Entomopathogenic Fungus in the Field

Various chamber designs for infecting natural populations ofGlossina pallidipes, G. longipennis,andG. fuscipes fuscipeswith the entomopathogenic fungusMetarhizium anisopliaewere tested in the field. All three species of tsetse flies entered the chambers and became infected with the fungus. Mortality attributed to infection byM. anisopliaeranged from 0 to 76% forG. pallidipes/G. longipennisand from 0 to 80% forG. fuscipes.One design proved to be more efficient than the others in permitting the passage of flies and contaminating them with fungal conidia. Dry conidia ofM. anisopliaein the infection chamber retained their infectivity for more than 21 days in the field.     

Emericella appendiculata, a new species from Chinese soil

Emericella appendiculata, a new species isolated from soil of the Pamire Plateau, is described and illustrated. It is characterized by grayish green non-ostiolate ascomata surrounded by a thick layer of hülle cells, membranaceous peridium, prototunicate asci, violet-brown, lenticular ascospores which are ornamented by two stellate equatorial crests, capitate convex surfaces, and long filiform appendages, and anAspergillus anamorph with biseriate conidiogenous cells.     

Reduced toxicity and broad spectrum resistance to viral and fungal infection in transgenic plants expressing pokeweed antiviral protein II

Pokeweed antiviral protein II (PAPII), a 30 kDa protein isolated from leaves of Phytolacca americana, inhibits translation by catalytically removing a specific adenine residue from the large rRNA of the 60S subunit of eukaryotic ribosomes. The protein sequence of PAPII shows only 41% identity to PAP and PAP-S, two other antiviral proteins isolated from pokeweed. We isolated a cDNA corresponding to PAPII and introduced it into tobacco plants. PAPII expressed in transgenic tobacco was correctly processed to the mature form as in pokeweed and accumulated to at least 10-fold higher levels than wild-type PAP. We had previously observed a significant decrease in transformation frequency with PAP and recovered only two transgenic lines expressing 1–2 ng per mg protein. In contrast, eight different transgenic lines expressing up to 250 ng/mg PAPII were recovered, indicating that PAPII is less toxic than PAP. Two symptomless transgenic lines expressing PAPII were resistant to tobacco mosaic virus, potato virus X and the fungal pathogen Rhizoctonia solani. The level of viral and fungal resistance observed correlated well with the amount of PAPII protein accumulated. Pathogenesis-related protein PR1 was constitutively expressed in transgenic lines expressing PAPII. Although PR1 was constitutively expressed, no increase in salicylic acid levels was detected, indicating that PAPII may elicit a salicylic acid-independent signal transduction pathway.