Revival of saprotrophic and mycorrhizal basidiomycete cultures after 20 years in cold storage in sterile water

Vegetatively colonized agar cores of 69 basidiomycete fungus isolates (48 species in 30 genera and 17 families) were stored at 5 degrees C in tubes of sterile distilled water without manipulation for 20 years. These were represented by 34 isolates of saprotrophic fungi (29 species in 19 genera) and 35 isolates of mycorrhizal fungi (19 species in 11 genera). Viability was evaluated based on revived growth on agar media at room temperature. Fifty-seven of the 69 isolates (82.6%) grew vigorously when revived after storage for 20 years; of the 34 saprotrophic fungus isolates, 30 revived (88.2%); of the 35 mycorrhizal fungus isolates, 27 revived (77.1%). Thirteen isolates of Laccaria were all viable after 20 years, indicating cold storage in sterile water to be a good method for maintaining this important genus of mycorrhizal fungi. In general, however, mycorrhizal fungus species demonstrated lower viability than saprotrophic fungi.     

植物病原真菌的菌核研究进展

真菌菌核是相关真菌在特殊环境下由营养体菌丝交织和聚集形成的具有抵御恶劣环境能力的休眠结构,在真菌生活史及病原真菌的病害循环中具有重要的生物学和生态学意义。许多引起严重植物病害的病原真菌能够形成菌核,这类真菌通过菌核度过逆境。菌核在适宜条件下萌发形成子囊盘和孢子或菌丝,造成植物的侵染。本文从形成菌核的真菌种类、生物学特性、黑色素及分子生物学等方面进行综述,旨在为深入研究真菌菌核及其在真菌学、植物病理学及药用真菌学等领域应用提供研究思路和参考依据。     

Antioxidants and iron chelators inhibit oxygen radical generation in fungal cultures of plant pathogenic fungi

Eutypa dieback and Esca are serious fungal grapevine trunk diseases (GTDs). Eutypa dieback is caused by Eutypa lata (Elata), and is often associated Phaeoacremonium minimum (Pmin), and Phaeomoniella chlamydospora (Pch) which are also important contributors to Esca disease.Understanding the complex pathogenesis mechanisms used by these causative fungi may potentially lead targeted treatments for GTDs in the future. Elata has been reported as a wood decay “soft rot” fungus and understanding of Elata’s pathogenesis chemistries can aid in controlling GTDs. Recent work that suggests that Pmin and Pch may contribute to pathogenesis by stimulating hydroxyl radical generation via secretion of low molecular weight phenolic metabolites. Building on these findings, we tested a hypothesis that antioxidants and chelators, and biocontrol agents that have been reported to secrete antioxidants and low molecular weight chelators, may inhibit the growth and activity of these fungi. Butylated hydroxy anisole (BHA) and butylated hydroxytoluene (BHT) were tested as antioxidant/chelators. BHA was found to be a highly effective control measure for the three pathogenic fungi tested at concentrations >0.5 mM. The biocontrol species Bacillus subtilis and Hypocrea (Trichoderma) atroviride were also tested, with both H. atroviride and B. subtilis effectively inhibiting growth of the three GTD fungi.     

Interaction between embryogenic cultures of Scots pine and ectomycorrhizal fungi

 Embryogenic cell masses of three Scots pine (Pinus sylvestris) cell lines K779, K884 and K1009 were cultivated with the ectomycorrhizal (ECM) fungi Laccaria bicolor, L. proxima, Pisolithus tinctorius, Paxillus involutus and two strains of Suillus variegatus. The average growth ratio of the slowly proliferating cell line K1009 was improved by L. proxima and S. variegatus strain H, while of the rapidly proliferating lines K779 and K884 the non-mycorrhizal controls grew best. The fungi caused two distinct reactions in embryogenic cultures. In the positive reaction, the shape and light yellow colour of the cultures resembled the controls, while in the negative reaction the embryogenic cells became brown and necrotic and the fungi grew aggressively over them. These reactions to the fungi did not correlate completely with effects on the growth ratio. All the cell lines enhanced the radial growth of S. variegatus H and of P. tinctorius, while the Laccaria species and S. variegatus strain 1 thrived better alone. This study shows that early-stage embryogenic cells of Scots pine and ECM fungi are able to interact. As some fungi produced a positive reaction or even increased proliferation, they could be used to enhance somatic embryogenesis of Scots pine. Specific fungi might be used to induce the growth of slowly proliferating cell lines, and knowledge of positive cell line-fungus interactions could be useful in work with later stages of somatic embryogenesis, such as rooting. Accepted: 16 July 1998     

Effects of pH,water stress and temperature on in vitro cultures of ectomycorrhizal fungi from Mediterranean forests

A comparative study of the growth of eight species of ectomycorrhizal fungi [Hebeloma edurum Métrod ex Bon, Lactarius deliciosus (L.: Fr.) S.F. Gray., Rhizopogon roseolus (Corda) Th.M.Fr., Suillus collinitus (Fr.) Kuntze, Suillus granulatus (L.: Fr.) Roussel, Suillus luteus (L.: Fr.) Roussel, Tricholoma focale (Fr.) Ricken, Tricholoma striatum (Schaeff.) Sacc.] in pure culture at different pH values, water potentials and temperatures was carried out. The biomass production and mycelial growth of each strain were assessed and characterised morphologically. H. edurum and L. deliciosus showed a clear affinity for neutral or slightly basic media. Most species had the lowest colony diameters and biomass production at pH 2.5. Only H. edurum, R. roseolus and S. collinitus grew at the highest water stress levels (−13.85 and −15.45 bar). All species grew at the lowest values of temperature whereas only R. roseolus and S. collinitus did at 30 °C.     

Immuno-identification of cultures of fungi pathogenic to man

Because isolates of the fungal pathogensBlastomyces dermatitidis. Coccidioides immitis, Histoplasma capsulatum, andParacoccidioides brasiliensis frequently vary widely in gross and microscopic features and are often difficult or impossible to convert to their tissue forms, a simple diagnostic procedure not dependent upon sporulation is needed to identify them specifically and rapidly. The exoantigen technique has been found to meet this need effectively. On the basis of studies with 166Histoplasma spp. isolates, 128C. immitis isolates, 59B. dermatitidis isolates, 30P. brasiliensis isolates, and 181 saprophytes, we determined that the exoantigen test is valuable for the presumptive identification of the four fungal pathogens studied. All of the positive reactions have correlated with the cultural, histologic, or other available laboratory data, and we are unaware of any false positive or flase negative reactions.     

我国植物病原真菌最新研究进展——植物病原真菌专刊序言

本期《菌物学报》"植物病原真菌专刊"刊登了12篇文章,其中关于病原真菌种类调查、鉴定及形态描述的文章5篇,病原真菌检测与检疫的文章2篇,病原真菌种群结构的文章2篇,基因组学研究进展的文章3篇。本期内容基本体现了我国植物病原真菌研究的最新进展,对今后的植物病原菌形态分类、分子分析和基因组学研究都具有重要的参考价值。     

Myco-heterotroph/epiparasitic plant interactions with ectomycorrhizal and arbuscular mycorrhizal fungi

More than 400 achlorophyllous plant species in 87 genera are parasitic upon fungi, and exploit them as their principle source of carbon. With a few exceptions, most of these myco-heterotrophic plants are now thought to be 'cheats', stealing carbon and nutrients from the mycorrhizal associates of adjacent autotrophic plants. Most myco-heterotrophs are therefore considered to be epiparasitic on green plants. Both the ectomycorrhizal and arbuscular mycorrhizal symbioses have been invaded by myco-heterotrophic epiparasites. DNA analysis is revealing the identities of many of the fungal partners of myco-heterotrophs, and their exceptionally high specificity. Myco-heterotrophs have distinctive stable isotope signatures, which can be used to establish the dependence upon fungal carbon of green plants that are partially myco-heterotrophic.     

Endophytic yeast fungi in plant storage tissues

It was found that plant storage tissues (fleshy sugar-containing fruits, subsurface metamorphically altered plant organs (storage roots, tubers, etc.), and starch-containing seed lobes) nearly always contain yeasts that are able to actively reproduce in these tissues causing no visible damage. Within storage tissues, yeast cells were detected both in the intercellular space and inside plant cells. In the tissues of fleshy fruits, endophytic yeasts are represented by the same species as epiphytic ones; cryptococci of the order Filobasidiales and ascomycetes belonging to the genera Hanseniaspora and Metschnikowia are predominant. In subsurface plant organs, red pigmented basidiomycetous yeasts of the genus Rhodotorula prevail. Selective growth of representatives of one species, Candida railenensis, is typical of starch-containing storage tissues of seeds. The results obtained change the established notion of the distributional patterns of yeast fungi in natural habitats and suggest that internal storage tissues of plants can be considered as a new interesting model for studies of coevolving plant-microbial associations.     

Secondary metabolite toxins and nutrition of plant pathogenic fungi

Fungal pathogens derive nutrition from the plants they invade. Some fungi can subvert plant defence responses such as programmed cell death to provide nutrition for their growth and colonisation. Secondary metabolite toxins produced by fungi often play a role in triggering these responses. Knowledge of the biosynthesis of these toxins, and the availability of fungal genome sequences and gene disruption techniques, allows the development of tools for experiments aimed at discovering the role of such toxins in triggering plant cell death and plant disease.     

Antagonistic activity of Rhizobium spp. against beneficial and plant pathogenic fungi

Six different Rhizobium strains were tested for their antagonistic activities against 10 isolates of fungi. Their abilities to inhibit the growth of fungal isolates varied tremendously. Rhizobium legurninosnrum biovar phaseoli 6-3 showed the highest antagonistic activity which significantly reduced the mycelium dried weights of all the fungal isolates tested. This suggests that care should be taken when Rhizobium and fungal biocontrol agents are to be used together.     

植物病原真菌的自噬

作为真核生物中普遍存在的现象,自噬不但实现了对细胞内物质的降解和回收利用,而且与植物病原真菌早期侵染阶段的附着胞发育、膨压升高、菌丝体形成、完成侵染等一系列过程密切相关,并且发挥了重要的作用。本文归纳了植物病原真菌自噬的相关基因和自噬过程;总结了自噬对病原真菌生长发育、致病力的调控和影响;概括了病原真菌自噬所涉及的信号通路;阐明了自噬影响植物病原真菌侵染过程的主要分子机制。为今后以自噬相关基因或蛋白作为靶点来筛选抑制病原真菌侵染的新型药物提供新的策略和思路。     

链霉菌KIB-H1556次级代谢产物抗植物真菌活性研究

对曼陀罗(Datura stramonium L.)根际链霉菌Streptomyces sp.KIB-H1556的次级代谢产物进行研究,利用硅胶柱色谱、凝胶柱色谱和半制备HPLC等分离手段对其发酵产物进行分离纯化,采用MS和NMR等波谱学手段并结合文献数据鉴定了3个单体化合物的结构,分别为:Bafilomycin D(1)、Bafilomycin B1(2)和Bafilomycin B2(3)。初步抗植物病原真菌活性筛选发现化合物2和3具有广谱抗真菌活性,尤其对玉米病原真菌的抑制活性显著,可作为玉米病原真菌病害的潜在生物防治剂。     

The biotechnological use and potential of plant pathogenic smut fungi

Plant pathogens of the family Ustilaginaceae parasitise mainly on grasses and cause smut disease. Among the best characterised members of this family are the covered smut fungus Ustilago hordei colonising barley and oat as well as the head smut Sporisorium reilianum and the corn smut Ustilago maydis, both infecting maize. Over the past years, U. maydis in particular has matured into a model system for diverse topics like plant–pathogen interaction, cellular transport processes or DNA repair. Consequently, a broad set of genetic, molecular and system biological methods has been established. This set currently serves as a strong foundation to improve existing and establish novel biotechnological applications. Here, we review four promising aspects covering different fields of applied science: (1) synthesis of secondary metabolites produced at fermenter level. (2) Lipases and other hydrolytic enzymes with potential roles in biocatalytic processes. (3) Degradation of ligno-cellulosic plant materials for biomass conversion. (4) Protein expression based on unconventional secretion, a novel approach inspired by basic research on mRNA transport. Thus, plant pathogenic Ustilaginaceae offer a great potential for future biotechnological applications by combining basic research and applied science.     

Antifungal activity of herbal extracts against plant pathogenic fungi

The present study was designed to evaluate in vitro antifungal activity of herbal extracts against three plant pathogenic fungi (viz. Rhizopus stolonifer, Botrytis cinerea and Colletotrichum coccodes). Extracts of leaves and rinds of Garcinia indica, rhizomes of Curcuma aromatica, roots of Glycyrrhiza gahliae, leaves of Nyctanthes arbour-tristis and seeds of Vernonia anthelmintica were used for screening. Screening was done using poisoned food technique. Relatively potent extracts were shortlisted from this study and were further assayed to find out their minimum fungicidal concentration (MFC). From the above studies, it was observed that ethyl acetate extract of rhizomes of C. aromatica and unripe fruit rinds of G. indica have shown the lowest MFC values amongst the other tested plant extracts. This study indicates that the potential of these plant extracts in the management of diseases caused by plant pathogenic fungi.     

Volatiles modulate the development of plant pathogenic rust fungi

Rust fungi are obligate biotrophic pathogens that differentiate a series of specialized cells to establish infection. One of these cells, the haustorium, which serves to absorb nutrients from living host cells, normally develops only in planta. Here, we show that the rust fungus Uromyces fabae (Pers.) Schroet. stimulates volatile emission of its host, broad bean (Vicia faba L.). Volatiles were identified and shown to be perceived by the fungus in in vitro assays that excluded the host. Three of them, nonanal, decanal, and hexenyl acetate promoted the development of haustoria on artificial membranes. In contrast, the terpenoid farnesyl acetate suppressed this differentiation. In assays using whole plants, farnesyl acetate reduced rust disease not only on broad bean but also on several cereals and legumes including soybean. This natural substance was effective against all rusts tested when directly applied to the host. This demonstrated that farnesyl acetate may serve as a powerful novel tool to combat rust fungi including Phakopsora pachyrhizi that currently threatens the production of soybeans world-wide.