Relative abundance and activity of melanized hyphae in different soil ecosystems

Here we report on the frequency of melanized fungal hyphae in 323 soils, covering different land use types. The proportion of total hyphae that was melanized averaged 61%. Arable fields with loamy sand, heathlands and city parks on sandy soils had the highest percentage of melanized hyphae. In addition to the frequency determinations, a microcosm study was performed on the role of melanized hyphae in two different ecosystems: an ex-arable field and a forest. Melanized hyphae appeared to be part of the active hyphae in the forest soil but not in the ex-arable soil. In conclusion, our results indicate that (1) melanized hyphae represent a large proportion of the total fungal biomass in soils and that (2) their function might differ between ecosystems.     

不同林型红松林土壤真菌群落组成和多样性

采用基于ITS(Internal Transcribed Spacer)序列的Illumina MiSeq高通量测序技术,分析凉水国家级自然保护区的云冷杉红松林、椴树红松林、红松人工林和红松天然次生林四种林型的土壤真菌群落组成和多样性。共获得1 316个OTUs,四种林型的土壤含有大量未知真菌,在已知真菌类群中,子囊菌门(Ascomycota)和担子菌门(Basidiomycota)为优势菌门,其中后者在四种林型土壤中的分布差异显著(P0.05)。α多样性分析结果表明:原始红松林(云冷杉红松林和椴树红松林)真菌群落丰富度指数(Ace和Chao1指数)显著高于红松天然次生林(P0.05)。β多样性分析显示:四种林型土壤真菌群落组成差异显著(R=0.537,P=0.001),但两种原始红松林之间、人工林和天然次生林之间组成无显著差异。土壤全氮、总有机碳、pH、水分含量和总孔隙度是显著影响四种林型土壤真菌群落组成的环境因子(P0.05)。研究结果为原始红松林的保护、人工植被恢复和真菌资源的开发利用提供依据。     

Specific Responses of Soil Microbial Residue Carbon to Long-Term Mineral Fertilizer Applications to Reddish Paddy Soils

Mineral nutrient inputs to soil may alter microbial activity and consequently influence the accumulation of microbial residues. In this study, we investigated the effects of application rates and ratios of mineral fertilizers on the microbial residue carbon(MRC) of reddish paddy soils after long-term(15-year) fertilizer applications in southern China. Contents of three soil amino sugars as microbial residue contents were determined and MRC were calculated based on amino sugars. Results showed that three individual amino sugar contents increased as fertilizer application rates increased until maximum values were reached at a rate of 450-59-187 kg ha~(-1) year~(-1)(N-P-K). The three amino sugar contents then declined significantly under the highest mineral fertilizer application rate of 675-88-280 kg ha~(-1) year~(-1)(N-P-K). In addition, to enhance the microbial residue contents, it was more beneficial to double P(N:P:K= 1:0.26:0.41) in fertilizers applied to the P-deficient reddish paddy soils than to double either N(N:P:K = 2:0.13:0.41) or K(N:P:K= 1:0.13:0.82). The contents of the three individual amino sugars and microbial residues under different fertilizer application rates and ratios were significantly and positively correlated with soil organic carbon(SOC), total N, total P, and p H. Increases in values of the fungal C to bacterial C ratios showed that soil organic matter(SOM) stability increased because of the fertilizer applications over the past 15 years. The contents and ratios of amino sugars can be used as indicators to evaluate the impact of mineral fertilizer applications on SOM dynamics in subtropical paddy soils. The results indicated that fertilizer applications at a rate of 450-59-187 kg ha~(-1) year~(-1)(N-P-K) may improve crop yields, SOC contents, and SOC stability in subtropical paddy soils.     

影响粉碎机工作性能因素的分析

锤片式粉碎机是一种利用高速旋转的锤片来击碎饲料的机器。它具有通用性广,对饲料的温度敏感性小,调节粉碎方便,粉碎质量好,使用维修方便和生产率高等优点。但是,由于用户对影响饲料粉碎机的工作性能的主要因素分析掌握不够,致使生产率不高、消耗的动力较大,产品质量等指标无法保证。为此,列举了影响粉碎机工作性能的诸因素,为广大用户高效、优质、低耗、安全地使用粉碎机提供了理论基础。     

Naturally occurring bacteraemia in American lobsters, Homarus americanus Milne-Edwards, in Long Island Sound

The health status of the American lobster, Homarus americanus Milne-Edwards, in Long Island Sound (LIS) has been in decline, with seasonal mortality events occurring since 1998. In order to assess the potential effects of environmental conditions on lobster health via haemolymph analysis, lobsters collected from various sites in LIS were examined and sampled while concurrent environmental data (water temperature, salinity and dissolved oxygen) were recorded. The pH of the haemolymph of each lobster was tested, followed by a collection of haemolymph for serum biochemistry analysis and bacterial culture. This report focuses on the results of the bacterial sampling. The majority of bacteria cultured were opportunistic pathogens commonly found in the environment, including some that are associated with sewage and pollution. The prevalence of bacteraemia was correlated with the site of collection, the month in which the lobsters were sampled, and water temperature.     

Effect of eye fluke infection on the growth of whitefish (Coregonus lavaretus) —An experimental approach

Effect of the eye fluke Diplostomum spathaceum on fish growth has remained somewhat unclear because 1) the question has not been subjected to experimental examination with treatment-control setup and 2) growth has not been related to the coverage of parasite-induced cataracts in a quantitative manner. We examined effects of the parasite on growth and competitive ability of whitefish (Coregonus lavaretus) in experimental conditions resembling those at fish farms by maintaining groups of exposed and control fish, as well as mixed groups from both treatments, under optimal conditions for 8 weeks. Contrary to our expectations, we did not observe differences in fish growth between the treatments. However, at the level of individual fish, parasite-induced cataracts had a negative effect on weight of the exposed fish but this took place only when the cataract coverage reached 100% in both eyes. No effect of the infection on competitive ability of fish was observed in mixed treatments which may be related to patterns of food distribution in the tanks or cues received by the fish from less infected conspecifics. Overall, the results suggest that effects of D. spathaceum on fish growth become apparent only in cases of very high cataract coverage, and that feeding regimes and the shape of the cataract coverage distribution in a fish group are important determinants of the magnitude of these effects.     

Identification of resistance to Aspergillus flavus infection in cotton germplasm

Natural resistance in cottonseed to Aspergillus flavus infection has not been explored to date. A green fluorescent protein (GFP) expressing A. flavus strain was used to assess the resistance of seed from 35 cotton varieties from Gossypium arboreum, G. barbadense, and G. hirsutum. Mature cotyledons devoid of seed coat were wounded, inoculated, and assessed for innate resistance to A. flavus infection. Of the initial 35 varieties tested, we observed a range of resistance to infection in representatives of all three species. A subset of 15 representatives was further analyzed. Within this group, G. arboreum cultivar A2 186 and G. hirsutum cultivar SA 1582 were most resistant to fungal infection. The most susceptible cultivar in this group was G. hirsutum SA 1595. The remaining 12 representatives tested in the secondary screen (3 G. arboreum, 3 G. barbadense, and 6 G. hirsutum lines) exhibited intermediate resistance. We did not observe any relationship between species and resistance. Within each species, there was a range of responses to fungal infection. Future studies using this methodology to screen additional diploid and tetraploid cotton lines may enable us to identify naturally resistant germplasm that can be used to develop cotton with enhanced resistance to fungal infection.     

A faster inoculation assay for Armillaria using herbaceous plants

Armillaria (honey fungus) is a virulent necrotrophic pathogen that causes Armillaria root disease. Conventional Armillaria inoculation assays use young saplings as hosts and consequently are cumbersome, frequently conducted outdoors, and take many years from establishment to analysis of infection. We have developed and evaluated a faster inoculation assay for Armillaria that uses herbaceous plants as hosts, is carried out in controlled conditions, and reduces experimental durations to 3 months. Plant species of known susceptibility to Armillaria and comparisons between virulent A. mellea and opportunistic A. gallica were used to validate the assay. Mortality and diagnostic symptoms of Armillaria root disease such as epiphytic rhizomorphs and mycelial fans were used to assess levels of infection. We also attempted to reduce assay preparation time by substituting woody inocula with agar inocula, but typical symptoms of Armillaria root disease were only observed on plants infected with woody inocula. Through our assay, we identified five new potential herbaceous hosts of Armillaria: Kniphofia hirsuta, Hordeum vulgare, Lobelia cardinalis, Nicotiana tabacum and Helenium hoopesii – further expanding the extensive list of plants with susceptibility to Armillaria and suggesting infection of herbaceous species may be more widespread than currently acknowledged.     

葡萄霜霉病菌侵染抗病和感病品种过程的组织学观察

用苯胺蓝染色结合扫描电镜的方法,观察葡萄霜霉病菌(Plasmopara viticola)在葡萄感病品种‘红提’和抗病品种‘北玫’中的侵染过程,发现两品种从接菌到显症的过程基本一致,但孢子囊伸出气孔的时间、伸出孢囊梗气孔比例、孢囊梗数量及孢囊梗分支,‘红提’比‘北玫’多;菌丝在‘北玫’上生长速度慢,后期生长量也较少。‘红提’的潜育期为4 d,而‘北玫’的为5 d,‘红提’和‘北玫’的长菌丝、分支的长菌丝、疏松菌丝体出现的时间也不同。菌丝生长一段时间后,在‘北玫’上停留在疏松菌丝体阶段,而‘红提’96 h时叶片组织内长满致密的菌丝体。两品种在初生菌丝和长菌丝阶段产生吸器的频率差异显著。     

我国玉米茎腐病研究进展

玉米茎腐病是一种世界性土传真菌病害,该病害在我国玉米产区均有发生。近年来,受耕作制度（如保护性耕作、秸秆还田等）的改变和气候变化的影响,生产中使用的高抗茎腐病的玉米品种不多等因素,致使田间病原菌数量增加,我国玉米茎腐病有逐渐加重的趋势。针对玉米茎腐病危害逐年加重的现状,本文系统综述了玉米茎腐病致病菌、发病症状表现、病情分级标准、病害侵染规律、抗性鉴定评价方法等方面的研究进展情况,并提出了玉米茎腐病的防治策略。