具有除草活性的小麦根腐病菌发酵条件优化

通过单因子试验和正交试验对小麦根腐病菌菌株进行了发酵条件优化,以提高其活性物质的产量。结果表明:最适合小麦根腐病菌产毒的培养基是察氏培养基;该培养基的最佳碳源为葡萄糖,氮源为氯化铵,无机盐为氯化钾、磷酸氢二钾、硫酸镁和硫酸亚铁;发酵培养基各组分的最佳配比为:葡萄糖2.0%,氯化铵0.25%,氯化钾0.05%,磷酸氢二钾0.025%,硫酸镁0.025%,硫酸亚铁0.000 5%;有利于提高菌株活性物质产量的培养条件为初始pH7.0,转速为130r/min,温度为28℃,培养时间为5d,装液量为120mL/250mL,接种量为6%。小麦根腐病菌菌株发酵产物具有良好的热稳定性和光稳定性,在弱酸性及中性条件下较稳定。发酵条件优化后提高了小麦根腐病菌的除草活性。     

Integration of soil, crop and weed management in low-external-input farming systems

Greater adoption and refinement of low-external-input (LEI) farming systems have been proposed as ways to ameliorate economic, environmental and health problems associated with conventional farming systems. Organic soil amendments and crop diversification are basic components of LEI systems. Weed scientists can improve the use of these practices for weed management by improving knowledge of four relevant ecological mechanisms. First, multispecies crop rotations, intercrops and cover crops may reduce opportunities for weed growth and regeneration through resource competition and niche disruption. Secondly, weed species appear to be more susceptible to phytotoxic effects of crop residues and other organic soil amendments than crop species, possibly because of differences in seed mass. Thirdly, delayed patterns of N availability in LEI systems may favour large-seeded crops over small-seeded weeds. Finally, additions of organic materials can change the incidence and severity of soil-borne diseases affecting weeds and crops. Our research on LEI sweetcorn and potato production systems in central and northern Maine (USA) suggests that these mechanisms can reduce weed density and growth while maintaining crop yields. Low-external-input farming systems will advance most quickly through the application of interdisciplinary research focused on these and other ecological mechanisms.     

柠条枝条覆盖对宁夏荒漠草原土壤水热及补播牧草生物量的影响

干旱是影响宁夏东部沙化区荒漠草地退化的主要自然因素,也是天然草地补播成功率低的主要原因,该地区大面积种植的柠条是土壤覆盖保水的丰富资源,但是缺乏相关研究.选择平坦的、未生长柠条的退化天然补播草地作为研究对象,在临近有柠条生长的草地平茬其柠条枝条用于试验覆盖,研究不同柠条覆盖厚度(TSM0,覆盖0 cm;TSM1,覆盖1...     

南疆果园套种食用菌对土壤理化性状及微生物量的影响

为探明林下套种食用菌对土壤的改良效果,分析比较在3种果树下种植鸡腿菇后,菌渣直接还田,对土壤的物理性状、养分含量及微生物数量的影响:(1)土壤物理性状方面,含水量从大到小依次为枣树>梨树>核桃树,孔隙度从大到小依次为枣树>梨树>核桃树,pH为核桃树>梨树>枣树,电导率为枣树>核桃树>梨树;(2)土壤养分方面,碱解氮含量从大到小依次为梨树>核桃树>枣树,速效磷含量为核桃数>枣树>梨树,速效钾含量为枣树>核桃树>梨树,有机质含量为枣树>梨树>核桃树;(3)土壤微生物方面,含细菌数量从大到小依次为梨树>枣树>核桃树,含放线菌数量为枣树>核桃树>梨树。得出在南疆果园套种鸡腿菇,对果园土壤改良作用从大到小依次为枣树>梨树>核桃树的结论。     

Human and climatic drivers of land and water use from 1997 to 2019 in Tarim River basin,China

Climate and human activities change spatial and temporal distribution of water and land use. The Tarim River, the largest inland river in China, faced a long-term exploitation of land and water over a rapid economic development. We analyzed land and water use from 1997 to 2019 in Tarim River Basin by Landsat images, and data on hydrology, climate, population, economy and PM_2.5 (air particulate matter ≤2.5 μm). Agricultural land expanded the fastest (4–11%), followed by natural vegetation (15–16%) and water area (4–5%) with population and economic increase. Air quality (PM_2.5 μg m⁻³) improved in upper (62–27) and middle (48–17) reaches. The water area in lower increase 5% because of ecological water delivery since 2000. Land use in the lower reach was dominated by agriculture, where the downstream runoff consumption increased by 6.8 times. The average annual air temperature and precipitation gradually increased by 0.5 °C and 51 mm in source and 0.9 °C and 30 mm in main reaches. The average annual water consumption in upper and middle reaches was 4 × 10⁹ m³, accounting for 87% of input runoff in the main reach. Water consumption in middle reach increased by 33 times in 2009–2017. The industry structure was changing from primary to secondary and tertiary industry. To sum up, implementation of water saving strategies and ecological water delivery restored local ecology. Sustainable strategies should be applied facing industrialization. Furthermore, changing the industry structure and restoring the degraded farmlands to grasslands or forests would keep sustainability of Tarim River Basin.     

坏死梭杆菌白细胞毒素研究进展

坏死梭杆菌白细胞毒素(Lkt)是一组对反刍动物白细胞特别是多形性白细胞(PMNs)有特异性毒性作用的细胞外毒素,被认为是坏死梭杆菌感染动物的主要毒力因子。白细胞毒素的物理稳定性较低,高温或极端pH环境中都能使白细胞毒素活性丧失。研究发现,白细胞毒素开放阅读框(ORF)全长9 726bp,由3个基因(lktB、A和C)组成,结构基因是第2个基因(lktA)。白细胞毒素对白细胞的毒性作用有剂量依赖性,并且溶血活性较低,不能在豚鼠猪皮肤上形成皮肤坏死症状。     

中国麇鹿朊蛋白核心片段的原核克隆表达与纯化

从采取的新鲜麋鹿血液中提取麋鹿基因组DNA,通过PCR的方法从麋鹿基因组中扩增麋鹿PrP蛋白核心片段的DNA,并分别在引物的5′和3′端引入EcoRⅠ和HindⅢ两个酶切位点,下游引物将原序列TATTAC突变为TAAT从变成两个终止密码子。通过两个酶切位点将麋鹿PrP蛋白核心片段DNA连接到pET-32a（＋）,转化DH5α,通过酶切鉴定和PCR鉴定,筛选出阳性克隆送菌液测序,从测序结果分析阳性克隆是否符合要求。测序正确后将核心片段基因连接到pET-32a（＋）,阳性质粒命名为MPrP-pET-32a（＋）,阳性质粒转化E.coli BL21（DE3）,进行诱导表达、蛋白质纯化鉴定。     

不同窖藏时间丹溪红曲酒活性成分及抗氧化评价

为探究不同窖藏时间（3、5、8、15和20年）丹溪红曲酒的活性成分及抗氧化能力,参照GB/T 13662—2018《黄酒》的方法对酒精度、总酸、pH、总糖和非糖固形物含量进行测定,采用3,5-二硝基水杨酸比色法对还原糖进行测定,采用福林酚法对总多酚和总黄酮含量进行测定,利用1,1-二苯基-2-苦肼基（DPPH）自由基清除能力和氧自由基吸收能力（ORAC）评价红曲酒的体外抗氧化能力,并且运用高效液相色谱（HPLC）法测定红曲酒中洛伐他汀的含量。结果表明：1）总糖含量随着窖藏时间的增加先降低后升高,窖藏20年的红曲酒总糖和还原糖的质量浓度最高,分别为46.92和22.35g/L;非糖固形物的含量随着窖藏时间的增加先升高后降低,窖藏8年的红曲酒非糖固形物的质量浓度最高,为33.95g/L;2）总多酚及总黄酮含量随着窖藏时间的增加先小幅升高后降低,窖藏5年的红曲酒总多酚及总黄酮质量浓度最高,分别为6.49和4.23mg/mL;3）各窖藏时间红曲酒均具有较强的抗氧化能力,其中窖藏3年的红曲酒对DPPH自由基的清除能力最强,8年红曲酒具有最高的ORAC值;4）各窖藏时间红曲酒中洛伐他汀含量较为稳定...     

猪链球菌2型溶血素基因缺失株构建及其生物学特性分析

猪链球菌溶血素(SLY)是较早确定的猪链球菌毒力因子之一,具有细胞毒性,在猪链球菌致病过程中发挥重要作用。利用同源重组技术成功构建了猪链球菌2型(SS2)sly基因缺失的突变株SS2-Δsly,缺失株的体外溶血活性消失,对小鼠脑血管内皮细胞的细胞毒性显著低于亲本菌株(P<0.01),但不影响猪链球菌2型在巨噬细胞中的存活。该菌株可以用于研究SS2溶血素在感染细胞中的作用机制。     

不同温湿度和培养环境对离体绵羊痒螨生存活力的影响

目的 测不同温度及培养环境对离体绵羊痒螨生存能力的影响,进一步了解痒螨的传播机制,为制定防治瘁螨的有效措施提供理论基础。方法 置室内外自然温度和实验室恒温条件,以及5种相对湿度：50、60、70、80及90％RH,培养观察绵羊痒螨不同虫态（卵、幼虫、幼虫静止期、若虫、若虫静止期、雌虫、雄虫）的生存发育情况;同时观察痒螨在水、痂皮屑、羊毛、羊粪、土壤、皮组织等6种条件下的生存活力。结果 痒螨的最适生长发育温度及繁殖期在21℃-28℃范围内,随着温度的升高,痒螨存活时间缩短,绵羊痒螨对4℃低温有一定耐受力,但对35℃以上的高温耐受力较弱。在同一温度下,相对湿度越高,各虫态存活时间越长。结论 体外观察实验表明痒螨对外界环境有较强的适应能力,在缺乏营养的条件下仍能存活较长一段时间。