Effects of tillage systems on soil characteristics, glomalin and mycorrhizal propagules in a Chilean Ultisol

Tillage affects the soil physical and chemical environment in which soil microorganisms live, thereby affecting their number, diversity and activity. However, soil disturbance generally has the greatest impact on biological properties, including both free and symbiotic fungal populations. Interest in more ecologically sustainable agricultural systems is rising with increasing recognition that agricultural intensification can adversely affect environmental quality. This paper discusses the effect of tillage system on some soil characteristics, such as pH, C, N and S levels, total and Olsen-P contents including some P forms associated with organic matter, glomalin contents and arbuscular mycorrhizae (AM) parameters, such as root colonization, spore number and total and active hyphal length. Measurements were in the sixth year of an on-going tillage-rotation experiment conducted on an Ultisol under no-till (NT), reduced tillage (RT) and conventional tillage with stubble mixed into the soil (CTS) or stubble burnt (CTB). Soil was sampled at two dates; after wheat (Triticum aestivum) harvest (autumn) and 6 months after subsequent grassland seeding (spring). Higher C, N, S, total P and fulvic acid-P concentrations and pH occurred under NT and RT than under CTS and CTB after wheat harvest. However, results at the second sampling were not consistent. AM spore number and active hyphal length were highest under NT having the greatest incidence on AM root colonization and P concentration in shoots of the pasture. Glomalin concentration was higher under NT and RT than under CTS and CTB but no differences in calculated glomalin to total C (ca. 5%) were found. It is concluded that a less disruptive effect of NT influences positively all soil characteristics and also increases P acquisition by the following crop in the rotation system.     

杜鹃花属植物内生真菌对毛棉杜鹃幼苗生长的影响

对来自粤北3种野生杜鹃花属植物根样中的聚多曲霉（Aspergillus sydowii）（菌株号：YJ1,YS2）、杂色曲霉A. versicolor（菌株号：GD1）3个内生真菌菌株及其混合菌剂进行瓶内接种试验,比较其对毛棉杜鹃（Rhododendron moulmainense）幼苗的菌根侵染率、苗高和生物量的影响。结果表明,3个菌株及其混合菌剂均可与毛棉杜鹃幼苗根系形成菌根共生体,但不同菌剂在不同培养基上对毛棉杜鹃幼苗根系的侵染力、苗高增长和生物量增重效果存在显著差异（P<0.05）。多数菌剂（YS2、M3、M1、M2）在MMN培养基上对幼苗根系侵染力显著高于WPM培养基和混合基质培养基（P<0.05）,而多数接菌苗（YJ1、GD1、M2、M3）在WPM培养基上生长显著优于MMN培养基（P<0.05）,YS2、GD1和混合菌剂M2（YS2+GD1）对毛棉杜鹃幼苗的增高和增重具有明显的促生作用。     

蝗虫微孢子虫病在蝗虫和群间的流行规律研究

在同德县北巴滩进行了不同浓度蝗虫微孢子虫（N.L)小区试验和大面积推广试验，并在1997和1999年对防治效果作了调查，结果表明N.L不仅当年虫口减退率和感病率可达60％和50％以上（30天），而且在1997年、1999年防区内平均感病率仍保持在30％和40％。说明N.L具有较强的水平扩散能力和垂直感染能力，可持续、有效地控制蝗灾的发生。     

Fluorescence detection of aluminum in arbuscular mycorrhizal fungal structures and glomalin using confocal laser scanning microscopy

Arbuscular mycorrhizal spores and glomalin-related soil protein (GRSP) isolated from acid soils were analyzed using confocal laser scanning microscopy (CLSM) for Al detection. Mycorrhizal structures of Glomus intraradices produced under in vitro conditions as well as spores and GRSP from neutral and Cu-polluted soils were used as contrasting criteria. Spores and GRSP from soils with 7 and 70% Al saturation showed autofluorescence which increased especially at the highest soil Al level and when Al³⁺ solution was added. G.intraradices spores showed fluorescence only when exogenous Al³⁺ was added. On the contrary, spores and GRSP from neutral and Cu-polluted soils showed little or no significant fluorescence. This fluorescence shown by fungal structures and GRSP when subjected to high Al (of endogenous or exogenous origin) suggest a high capacity for Al immobilization, which could be an effective way to reduce Al activity and phytotoxicity in acid soils.     

新药物对奶牛感染性蹄病动物模型临床疗效试验

为探索治疗奶牛感染性蹄病的新药物,以患蹄病的绵羊为奶牛感染性蹄病的动物模型进行临床治疗试验。试验药物是针对奶牛感染性蹄病痛原特点研制的5种配方,即配方Ⅰ～配方Ⅴ。选择自然感染蹄病的绵羊50只,随机分为7个组,各组羊只分别为配方Ⅰ组6只、配方Ⅱ组7只、配方Ⅲ组10只、配方Ⅳ组9只、配方Ⅴ组8只、药物对照组5只、空白对照组5只。结果表明,在本试验药物组中,临床疗效依次为配方Ⅴ〉配方Ⅲ〉配方Ⅱ〉配方Ⅳ〉配方Ⅰ,配方Ⅴ的效果最佳,有效率和治愈率分别达100％、88．9％。综合比较,本试验药物的治疗效果要优于传统药物。     

Development and survival of Haemonchus contortus infective larvae derived from sheep faeces under sub-tropical conditions in the Potohar region of Pakistan

Assessment on the development and survival of Haemonchus contortus larvae was made to evaluate the influence of microclimatic variables viz., relative humidity (%), temperature (°C), rainfall (mm) and intensity of sunlight (hrs). Pasture plots in a sub-tropical area, Pakistan were contaminated with H. contortus eggs at the start of every month. The plots were sampled on fortnightly basis after contamination for three consecutive months. The overall pattern indicated the most favorable conditions for survival, development and translation to herbage was during the wet season from July to October and the least favorable was during the dry season from April to June. Peak infective larvae (L₃) recovery was during the 15–45 day interval for each plot and the lowest number was during the 75–90 day interval. Herbage was collected in the morning, afternoon and evening and greatest recovery of L₃ was in the morning time and least in the afternoon. The number of L₃ on pasture was directly related to the pattern of rainfall and relative humidity with a significant (P < 0.05) positive correlation and temperature and intensity of sunshine were negatively correlated (P < 0.05). The results suggest that pastures can remain infective for up to 2 months and become relatively clean by 90 days after contamination. Thus, long pasture rest periods, especially during the high risk wet season, may be a helpful strategy to reduce the infection levels.     

Chemically and genetically immunocompromised mice are not more susceptible than immunocompetent mice to infection with Cryptosporidium muris

The prevailing paradigm is that immunosuppressed individuals are more susceptible to infection and are at higher risk of infection from Cryptosporidium oocysts if present in drinking water. To test this hypothesis, three immune conditions were examined: genetically immunocompromised T cell deficient CD-1 nude mice, B and T cell deficient Fox Chase CB-17/IcrClB SCID mice, and chemically immunosuppressed C57Bl/6 mice. Chemical immunosuppression was induced with a single subcutaneous injection of methylprednisolone acetate (MPA) at 600 mg/kg. The MPA immunosuppressed C57Bl/6 mice were characterized by a sustained decrease in circulating CD3, CD4 and CD8 T-lymphocytes of greater than 80% and a similar decrease in B-lymphocytes. A sharp rise in circulating mature segmented neutrophils followed MPA injection, dropping sharply after 10-14 days, mirroring the decrease in lymphocytes. The cessation of oocyst production after MPA was not accompanied by a radical rise in circulating CD3 or CD4 T-lymphocytes, but rather a rise in CD8 T-lymphocytes. The ID50 for the MPA immunosuppressed C57Bl/6 mice was 122 oocysts, whereas the ID50 for the C57Bl/6 immunocompetent group was 44. The genetically immunocompromised mice showed similar differences. The ID50 for CD-1 nude mice was 166 oocysts compared to 64 in CD-1 immunocompetent mice. For Fox Chase CB-17/IcrClB SCID and the immunocompetent CB-17 mice, the ID50's were 83 and 60 oocysts, respectively. These results suggest that the lack of an immune response does not increase the ability of C. muris to establish a productive infection and produce oocysts.     

紫茎泽兰不同繁殖材料繁殖比较

在室内进行紫茎泽兰根、茎、种子等繁殖材料的发芽试验,结果表明:紫茎泽兰根不能长成新的植株,即不可进行无性繁殖。紫茎泽兰的繁殖体主要是种子、茎,且茎的不同部位成株率不同,以上部一年生茎成株率较高,平均为51%;下部茎成株次之,为46%;中部茎成株率仅为29%。种子出苗率为26.5%。紫茎泽兰茎的生根原理为皮部生根。     

微生物群体感应及其在感染性疾病治疗新策略中的潜在应用

微生物抗药性突变株的出现,导致抗生素的治疗效果大幅降低,寻找新的感染性疾病防治策略迫在眉睫。病原菌的致病毒性受群体感应系统调控,因此,以群体感应为靶标,调控群体感应过程中的关键步骤可以达到治疗感染性疾病的目的。这种以阻断群体感应过程而非细胞生长为治疗策略的方式,不会引起抗药性突变株的出现,所开发的药物是抗病原性的,是继抗生素之后最具发展前景的新型抗感染药物之一。主要论述了有关群体感应作为新型药物靶标的可能性及相关研究的最新进展。     

南黄海绿潮暴发早期与末期显微繁殖体分布及种类组成研究

调查了2012年4月、8月和2013年4月、8月两年4个时期的南黄海绿潮藻显微繁殖体分布与种类组成。研究绿潮暴发早期(4月份),南黄海已有显微繁殖体广泛分布,高值区主要分布于如东、大丰近岸海域,2012年4月大丰海域密度最高可达1 312ind/L,2013年4月如东海域密度达到884 ind/L;黄海绿潮暴发末期(8月份),高值区随大面积绿潮藻向北转移,随着如东和大丰海区漂浮绿潮藻消失,显微繁殖体的数量降低至较低水平,2012年和2013年8月密度范围分别为0~38 ind/L和0~28 ind/L。2012年和2013年4月显微繁殖体由曲浒苔(Ulva flexuosa)、浒苔(Ulva prolifera)和缘管浒苔(Ulva linza)组成,8月由曲浒苔(Ulva flexuosa)和浒苔(Ulva prolifera)组成。4月份显微繁殖体在如东、大丰海区高密度分布表明绿潮发生前期南黄海绿潮藻种质库的存在,大量显微繁殖体可以在春末海区温度回升时期迅速萌发,成为早期绿潮形成的贡献者之一。