Tolerance of chickpea (Cicer arietinum L.) lines to root-knot nematode, Meloidogyne javanica (Treub) Chitwood

The root-knot nematode, Meloidogyne javanica (Treub) Chitwood is an important parasite of chickpea (Cicer arietinum L.). Four chickpea genotypes were evaluated for tolerance to M. javanica in naturally infested fields at three locations. Each genotype was evaluated for number of galls, gall size, root area covered with galls and number of egg masses produced. All the cultivars were susceptible or highly susceptible. Seed yield, weight of 100 undamaged seeds, total dry matter and plant height were compared with checks. Chickpea cultivar Annigeri and a local check were used as nematode susceptible checks in all locations. The four promising nematode tolerant genotypes produced significantly greater yield and total dry matter than the checks in fields naturally infested with M. javanica at three locations. These M. javanica tolerant lines represent new germplasm and they are available in the chickpea genebank at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT) bearing the identification numbers ICC 8932, ICC 11152, ICCV 90043 and ICCC 42.     

Effects of vegetation removal on soil properties and decomposer organisms

The removal of understory vegetation has been a common forest management practice, especially in plantations, but the effects of understory removal on soil physico-chemical properties and decomposer organisms is poorly known. In the present study, the effects of understory vegetation removal and removal of all-plants (i.e. removal of understory vegetation and trees) on soil properties and soil biota were measured in a plantation of mixed native tree species in southern China. During the wet season, understory vegetation removal did not cause significant changes on soil microbial community and major soil faunal groups except for a marked reduction in the density of herbivorous nematodes. However, all-plants removal significantly decreased the fungal biomass, the fungal:bacterial ratio, the density of herbivorous nematodes, the structure of the nematode community, and the density of mites, collembola and total microarthropods. In the dry season, understory vegetation removal resulted in a marked reduction in the density of total and herbivorous nematodes. The effects of plant removal on soil biota were similar to that in dry season. For both seasons, understory removal had no significant effects on soil physico-chemical properties (soil water content, pH, total nitrogen and soil organic carbon) but removal of all-plants significantly decreased soil pH. In general, the effects of understory vegetation removal on soil biota and other soil properties were much less severe than those of all-plants removal. The soil biota did not show significant response to understory removal, suggesting that this part of the vegetation may not be a major governing factor on such biota.     

家畜粪便中捕食线虫性真菌分布情况的研究

分剐采集马属动物(马、骡)、反刍动物(牛、羊)的新鲜粪便，进行捕食线虫性真菌的分离培养，调查了捕食线虫性真菌在家畜粪便中的分布情况；并对分离到的捕食线虫性真菌做了详细的形态学观察，进行种属鉴定。结果表明：从上述家畜新鲜粪便中均分离出捕食线虫性真菌——梨形指环菌(Dactylaria pyriformis)，但该菌株在不同家畜粪便中的分布情况不同，马属动物粪便的分出率为10．0％(骡粪：13．3％。马粪：6．7％)；反刍动物粪便的分出率为26．7％(牛粪：23．3％，羊粪：30．0％)；总分出率为18．3％。     

轮作方式对甘薯根际土壤线虫群落结构及甘薯产量的影响

甘薯茎线虫（Ditylenchus destructor）是国际检疫植物寄生线虫,甘薯茎线虫病是危害我国甘薯生产的严重病害之一。本文通过不同种植方式下甘薯根际土壤线虫群落结构的变化,探索轮作对甘薯茎线虫病防治的作用,明确变性梯度凝胶电泳（DGGE）在土壤线虫群落研究上应用的可行性。试验在河北省卢龙县多年连作的甘薯地上进行,种植方式分别为：A1,休闲→甘薯;A2,玉米-冬闲→甘薯;A3,玉米-黑麦→甘薯;A4,大豆-冬闲→甘薯;A5,大豆-黑麦→甘薯;CK,甘薯连作。提取3个时期甘薯根际土壤线虫,扩增线虫ITS区序列,采用DGGE技术分析土壤线虫群落。结果表明,与连作相比,轮作方式显著提高甘薯根际土壤线虫群落多样性,降低根际土壤甘薯茎线虫数量（P<0.05）,冬季轮作黑麦（A3,A5）使甘薯根际土壤线虫群落结构更加稳定,随时间变化幅度小。甘薯根际土壤中检测到的线虫优势属有：茎线虫属、矛线虫属、滑刃线虫属、头叶线虫属、短体线虫属、小环线虫属、刺线虫属、真滑刃线虫属、双胃线虫属。轮作方式提高甘薯产量42.08%~55.83%,降低病情指数22.72%~30.79%,不同轮作方式之间对甘薯产量和病情的影响差异不显著,收获期的甘薯茎线虫数量与甘薯产量和病情指数显著相关（P<0.05）。因此,轮作方式能够显著提高甘薯根际土壤线虫群落多样性和甘薯产量,DGGE可有效检测土壤线虫群落;大豆-黑麦→甘薯是经济效益和生态效益较好的轮作措施。     

奥氏奥斯特他线虫巨噬细胞转移抑制因子克隆表达与酶功能鉴定

通过原核表达系统表达奥氏奥斯特他线虫（Ostertagiaostertagi）巨噬细胞转移抑制因子（OoMIF）,并对该蛋白的酶功能进行鉴定。通过GenBank和NematodeV3．0数据库发表的序列,利用分子生物学软件设计了1对特异的引物,通过RT—PCR扩增OoMIF全基因,经测序分析后,将OoMIF亚克隆到pET28a（＋）,然后将鉴定为阳性的重组质粒转化到BL21中用IPTG进行诱导表达。利用HPLC对可溶性表达的重组OoMIF蛋白进行纯化,同时通过免疫印迹对线虫自身的MIF及纯化后的OoMIF进行鉴定,最后对OoMIF的互变异构酶和氧化还原酶活性进行鉴定。结果表明OoMIF具有互变异构酶活性,但没有氧化还原酶活性。为进一步探究OoMIF生物学功能及其MIF在宿主免疫调节中的作用提供依据。     

Response of the soil microbial biomass and nematode population to a wetting event in nitrogen-amended Negev desert plots

 Water and N availability are the major limiting factors of primary production in desert ecosystems, and the response of soil biota to these two factors is of great importance. We examined the immediate response of soil nematodes and the microbial biomass to a single pulse of water amendment in N-treated plots in the Israeli Negev desert. Plots were treated with 0, 50 and 100 kg NH₄NO₃ ha^–1 in December 1992, and at the end of the summer period (August 1993) the plots were exposed to a 15 mm water. Soil samples from the 0–10 cm layer were collected daily and analysed soil moisture, total soluble N, nematode populations and microbial biomass. Soil moisture increased to 8.5%, then gradually decreased to 2% during the 11 days of the study. Microbial biomass, soil respiration and metabolic quotient values did not exhibit any significant correlation with soil N levels. Free-living nematode population levels in the different plots were found to increase from a mean level of 45 500 to a mean level of 92 300 individuals m^–2. N treatment was found to affect the patterns of free-living nematode population dynamics. The results of this study demonstrated the importance of moisture availability levels and the ability to mobilize previous N inputs into available N which, occurring in pulses, can affect the microbial ecophysiological status, nematode population dynamics and the interrelationship between these two important components in the desert soil milieu. Received: 5 November 1998     

Solar UV-B influences microfaunal community composition in a Tierra del Fuego peatland

The peatlands of Tierra del Fuego are subject to increased solar ultraviolet-B radiation (UV-B) due to the influence of the Antarctic ‘ozone hole’. Research into the effects of climate change and ozone depletion on peatlands has predominantly focused on the higher plant community and neglected other organisms. In the second 3-year portion of a 6-year experiment, we intensified our investigations of the response of the peatland surface microfaunal community to current and attenuated solar UV-B, and assessed possible links to changes in the microenvironment. Near-ambient UV-B and reduced UV-B treatments were realised by stretching plastic film filters that differentially attenuate UV-B over peatland sample plots. We extracted the microfauna and analysed the dissolved nutrients held within Sphagnum capitula removed from the top 1-cm of the peatland. In line with previous findings in this system, testate amoebae were more abundant under near-ambient UV-B than under reduced UV-B. Populations of the most common genus, Assulina, and other less prominent amoebae species of Heleopera and Euglypha, were consistently increased under near-ambient UV-B. Overall diversity of testate amoebae was also higher under near-ambient UV-B than under reduced UV-B, whereas rotifers, nematodes and mites were less abundant under near-ambient UV-B. Concentrations of DOC and P were generally higher under near-ambient UV-B than under reduced UV-B. These changes, combined with the changes previously reported in the plant and fungal communities, have the potential to influence peatland C storage, and surface nutrient availability. The peatland microfaunal community under near-ambient solar UV-B may be regulated by the plant community through the leaching of nutrients from leaf cells, and changes in Sphagnum morphology that affect the capitulum microenvironment.     

抗松材线虫病马尾松无性系夏季光合作用日变化研究

利用LI6400光合仪测定抗松材线虫病马尾松针叶的净光合速率,研究其夏季变化与生理生态因子的关系。结果表明：（1）抗性马尾松净光合速率日变化趋势呈现“双峰”曲线,峰值出现在10时和15时,有明显的“午休”现象。这种现象不是由于气孔阻力的增大而引起叶肉细胞间CO2亏缺造成的,而是非气孔限制起着主要作用。（2）净光合速率（Pn）与胞间CO2浓度（Ci）、蒸腾速率（Tr）、空气温度（Tair）、叶片温度（Tleaf）、光合有效辐射（PAR）都有极显著的相关关系．但经过通径分析发现,对Pn起作用的最主要因子是PAR。     

Mucin biosynthesis in the bovine goblet cell induced by Cooperia oncophora infection

Mucin hypersecretion is considered to be one of the most common components of the immune response to gastrointestinal nematode infection. However, investigations have not been conducted in the Cattle–Cooperia oncophora system to verify the findings largely derived from murine models. In this study, we examined the expression of seven mucins and seven enzymes in the mucin biosynthesis pathway involved in O-linked glycosylation in the bovine small intestine including goblet cells enriched using laser capture microdissection during a primary C. oncophora infection. At the mRNA level, MUC2 expression was significantly higher in both lamina propria and goblet cells at 28 days post-infection compared to the naïve control. MUC5B expression at the mRNA level was also higher in lamina propria at 28 dpi. Expression of MUC1, MUC4, MUC5AC, and MUC6 was extremely low or not detectable in goblet cells, columnar epithelial cells, and lamina propria from both naïve control and infected animals. Among the seven enzymes involved in post-translational O-linked glycosylation of mucins, GCNT3, which may represent one of the key rate-limiting steps in mucin biosynthesis, was up-regulated in goblet cells, columnar epithelial cells, lamina propria, and gross small intestine tissue during the course of infection. Western blot analysis revealed that MUC2 glycoprotein was strongly induced by infection in both gross small intestine tissue and its mucosal layer. In contrast, the higher MUC5B protein expression was observed only in the mucosal layer. Immunohistochemistry provided further evidence of the mucin glycoprotein production and localization. Our results provided insight into regulation of mucin biosynthesis in various cell types in the bovine small intestine during gastrointestinal nematode infection and will facilitate our understanding of mucins and their role in immune response against parasitic nematodes.     

Nematode succession during composting and the potential of the nematode community as an indicator of compost maturity

One of the key issues in compost research is to assess when the compost has reached a mature stage. The maturity status of the compost determines the quality of the final soil amendment product. The nematode community occurring in a Controlled Microbial Composting (CMC) process was analyzed with the objective of assessing whether the species composition could be used as a bio-indicator of the compost maturity status. The results obtained here describe the major shifts in species composition that occur during the composting process. Compared to terrestrial ecosystems, nematode succession in compost differs mainly in the absence of K-strategists and numerical importance of diplogastrids. At the beginning of the composting process (thermophilic phase), immediately after the heat peak, the nematode population is primarily built by bacterial feeding enrichment opportunists (cp-1) (Rhabditidae, Panagrolaimidae, Diplogastridae) followed by the bacterial-feeding general opportunists (cp-2) (Cephalobidae) and the fungal-feeding general opportunists (Aphelenchoididae). Thereafter, during the cooling and maturation stage, the bacterial-feeding-predator opportunistic nematodes (Mononchoides sp.) became dominant. Finally, at the most mature stage, the fungal-feeding Anguinidae (mainly Ditylenchus filimus) were most present. Both, the Maturity Index (MI) and the fungivorous/bacterivorous ratio (f/b ratio), increase as the compost becomes more mature (ranging, respectively, from 1 to 1.86 and from 0 to 11.90). Based on these results, both indices are suggested as potential suitable tools to assess compost maturity.