The Infection Court of Faba Bean Seedlings for Oospores of Peronospora viciae f.sp. fabae in Soil

The infection court of Faba bean seedlings for oospores of Peronospora viciae f.sp. fabae in soil was determined. Soil naturally infested with oospores was placed as 3-cm thick layers at four different depths relative to Faba bean seeds. Seedlings with downy mildew were obtained only from seeds sown in the middle of a 3-cm layer of oosporeinfested soil. No infection was obtained from oosporeinfested soil placed more than 1.5 cm above or below seeds. Histological observations showed that the hypocotyl and first part of the main root were the most probable sites of infection.     

Development of Sporangiophores of Peronospora parasitica (Pers. ex Fr.) Fr.

The morphology of developing sporangiophores of Peronosporaparasitica from wallflower is described, and morphogenesis maybe divided into the following five stages: the sporangiophoreprimordium, unbranched sporangiophore, branched sporangiophore,spore formation and maturation, and formation of the cross wall.The growth of individual sporangiophores in a humidity chamberwas followed under the microscope, and increase in height andincrease in volume measured. The greatest increase in volumewas during spore formation, when the sporangiophore volume mightquadruple within an hour.     

Laboratory tests of fungicides against Peronospora parasitica (Pers. ex Fr.) Fr

Methods were investigated of culturing Peronospora parasitica on detached cotyledons in plastic box moist chambers in constant-temperature cabinets. Light was essential and a temperature of 15 °C was most suitable for infection and survival of cotyledons. Using such cotyledons the protectant and eradicant actions of various fungicides against P. parasitica were compared with those of zineb. Captafol, Daconil 2787, dichlofluanid and propineb were markedly superior to zineb as protectants, being highly effective at 0·025 % a.i. None of these compounds (at 0·2 % a.i.) checked fungal development when applied 5 h after inoculation, during which time the fungus had penetrated the cotyledons, and it was concluded that the fungicides had thus no internal effect. Internal fungistasis was shown, however, by a maneb-nickel sulphate fungicide and also by nickel sulphate. The latter (at 0·4% NiSO₄.6H₂O) gave some disease control when applied up to 72 h after inoculation and appeared to be translocated within the tissue of the cotyledon.     

Methods for Integrated Air Sampling and DNA Analysis for Detection of Airborne Fungal Spores

Integrated air sampling and PCR-based methods for detecting airborne fungal spores, using Penicillium roqueforti as a model fungus, are described. P. roqueforti spores were collected directly into Eppendorf tubes using a miniature cyclone-type air sampler. They were then suspended in 0.1% Nonidet P-40, and counted using microscopy. Serial dilutions of the spores were made. Three methods were used to produce DNA for PCR tests: adding untreated spores to PCRs, disrupting spores (fracturing of spore walls to release the contents) using Ballotini beads, and disrupting spores followed by DNA purification. Three P. roqueforti-specific assays were tested: single-step PCR, nested PCR, and PCR followed by Southern blotting and probing. Disrupting the spores was found to be essential for achieving maximum sensitivity of the assay. Adding untreated spores to the PCR did allow the detection of P. roqueforti, but this was never achieved when fewer than 1,000 spores were added to the PCR. By disrupting the spores, with or without subsequent DNA purification, it was possible to detect DNA from a single spore. When known quantities of P. roqueforti spores were added to air samples consisting of high concentrations of unidentified fungal spores, pollen, and dust, detection sensitivity was reduced. P. roqueforti DNA could not be detected using untreated or disrupted spore suspensions added to the PCRs. However, using purified DNA, it was possible to detect 10 P. roqueforti spores in a background of 4,500 other spores. For all DNA extraction methods, nested PCR was more sensitive than single-step PCR or PCR followed by Southern blotting.     

The Distribution of Substances in the Sporangiophores of Peronospora parasitica (Pers. ex Fr.) Fr.

The distribution of nuclei, RNA, mitochondria, lipid material,protein, and insoluble carbohydrates in the developing sporangiophoresof Peronospora parasitica was demonstrated by cytochemical staining.Nuclei, mitochondria, and protein showed a more or less uniformdistribution throughout the young sporangiophores, but werelocated almost entirely within the mature spores when sporedispersal commenced. Lipid material had a similar distribution,but was absent from the sporangiophore apex and sporangiophorebranch tips during the early stages of development. RNA wasabundant in the sporangiophore apices during early development,but occurred only within the spores, in small quantities, atmaturation. Although insoluble carbohydrates were sparse, theyhad a similar distribution to the nuclei, mitochondria, andprotein. Glycogen was not detected. The major soluble carbohydrates, present in the mature sporesin about equal proportions, were identified by thin-layer chromatographyas trehalose and an aldo-hexose, either glucose or mannose.These sugars were present in about equal quantities in the immaturesporangiophores and spores, while in the mature sporangiophoresfrom which the spores had been removed, trehalose was the majorsugar present. Sugar alcohols were not detected.     

Cytochemistry and Ultrastructure of Hyphae and Haustoria of Peronospora parasitica (Pers. ex Fr.) Fr.

The uniform distribution of nuclei, mitochondria, lipid material,protein, and RNA in the hyphae and haustoria of Peronosporaparasitica was demonstrated by staining techniques. Glycogenwas not detected, the only insoluble carbohydrate material detectedby the periodic acid-Schiff reaction being in the fungal wall.The host cell walls reacted more intensely to this stain thanthe hyphal walls. The reaction of haustorial walls varied betweenthe slight staining reaction characteristic of the fungal walls,and the strong reaction of the host cell wall. Callose sheathswere occasionally seen. Fine structure was found to be similar to that of other Oomycetes.Welldeveloped sheaths of a vesicular nature, possibly synonymouswith callose sheaths, were occasionally seen partly surroundinghaustoria.     

芒果胶孢炭疽病菌应答菌丝机械损伤产生无性孢子的分子机制

胶孢炭疽菌(Colletotrichum gloeosporioides)是引发芒果(Mangifera indica)炭疽病的主要病原体。室内平板培养胶孢炭疽菌不产生或产生很少分生孢子的情况时有发生, 但菌丝在机械损伤后24-48小时会产生大量分生孢子。胶孢炭疽菌应答机械损伤诱导产孢的核心基因及关键代谢通路尚未见报道。基于转录组测序(RNA-seq)技术检测了芒果胶孢炭疽菌菌丝在机械损伤处理后2小时内5个时间点的基因表达变化, 对差异表达基因进行GO富集和KEGG代谢通路富集分析, 并对菌丝响应胁迫的基因动态表达数据进行分析。基于常微分方程ODE模型结合变量选择技术, 构建了动态基因调控网络。结果表明, 有417个差异表达基因参与应答胶孢炭疽菌菌丝机械损伤, 分属12个聚类模块, 有4条通路存在显著富集, 分别是丙酮酸代谢、硫代谢、黄曲霉素合成途径和二萜合成途径。结合功能注释筛选出12个应答菌丝损伤胁迫的核心基因。研究结果为后续深入开展芒果胶孢炭疽菌产孢和致病机理研究奠定了重要基础。     

Spores of Serpocaulon (Polypodiaceae): morphometric and phylogenetic analyses

The morphometry and sculpture pattern of Serpocaulon spores was studied in a phylogenetic context. The species studied were those used in a published phylogenetic analysis based on chloroplast DNA regions. Four additional Polypodiaceae species were examined for comparative purposes. We used scanning electron microscopy to image 580 specimens of spores from 29 species of the 48 recognised taxa. Four discrete and ten continuous characters were scored for each species and optimised on to the previously published molecular tree. Canonical correspondence analysis (CCA) showed that verrucae width/verrucae length and verrucae width/spore length index and outline were the most important morphological characters. The first two axes explain, respectively, 56.3% and 20.5% of the total variance. Regular depressed and irregular prominent verrucae were present in derived species. However, the morphology does not support any molecular clades. According to our analyses, the evolutionary pathway of the ornamentation of the spores is represented by depressed irregularly verrucae to folded perispore to depressed regular verrucae to irregularly prominent verrucae.     

Improved Device for the Administration of Fungal Spores to Small Animals via the Respiratory Route

An improved device has been designed and constructed for the administration of fungal spores or other air-suspended particles to mice via inhalation. Fabricated from Lucite [0.25 inch (0.63 cm)], the device was built in the shape of a 6-inch (15.2-cm) cube with two 1-inch (2.5-cm) holes drilled in each side. Mice are restrained in plastic conical centrifuge tubes which fit into the holes by friction. The device is safe, easily cleaned and sterilized, and can accommodate up to eight animals at a single exposure.     

Susceptibility of tobacco blue mould (Peronospora hyoscyami) to metalaxyl

The lethal dose (LC₅₀) of metalaxyl for a wild isolate of Peronospora hyoscyami f. sp. tabacina was determined using a bioassay. Infection levels were recorded using 5-wk-old tobacco seedlings that had been treated with foliar sprays of metalaxyl (Ridomil®) 24 h prior to inoculation. Plants were maintained in a controlled environment cabinet. LC₅₀ estimates determined by probit analysis of the data from three independent experiments ranged between 0–46 and 0–58 μg/ml. Pooling the results for all three experiments, probit analysis gave a slope of 8·733 (S.E. 0·805) with an LC₅₀ of 0·51 μg/ml (95% fiducial limits 0·45, 0·57). This determination will be useful as a guide to future monitoring of P. hyoscyami for resistance to metalaxyl.     

Protein Synthesis During Fungal Spore Germination: Differential Protein Synthesis During Germination of Botryodiplodia theobromae Spores

The preformed messenger ribonucleic acid in Botryodiplodia theobromae spores directs the synthesis of several relatively stable polypeptides     

Electrical Sensing Zone Particle Analyzer for Measuring Germination of Fungal Spores in the Presence of Other Particles

Microscopic, respirometric, and electronic sizing methods for measuring germination of fungal spores were compared. With the electronic sizing method, early stages of germination (i.e., spore swelling) were detected long before germ tube emergence or significant changes in respiratory rates were observed. This method, which is rapid, easy, sensitive, and reproducible, also permits measuring the germination of spores when similar-size particles are present in concentrations considerably in excess of the number of spores.