一个与稻瘟病菌无毒基因AVR-Pik~m连锁的SCAR标记的分离

 本研究将以前在稻瘟病菌菌株S1522获得的与决定对水稻品种梅雨明无毒性的基因(AVR-Pik^m)相连锁的1个RAPD标记OPO12₁₀₀₀进行了克隆和鉴定。核苷酸序列测定与分析结果表明:OPO12₁₀₀₀的大小为946个碱基,不含有与已报道的稻瘟病菌Mg-SINE、Fosburry、Magyy、Grasshopper、Pot2以及Pot3等同源的重复序列。根据OPO12₁₀₀₀的核苷酸序列,设计了1对24个核苷酸的特异引物,对无毒表型亲本S1522和毒性表型亲本S159、无毒表型群体基因池、毒性表型基因池以及有性杂交后代108个菌株进行了PCR扩增,所有无毒表型的菌株均能特异性地扩增出1条与OPO12₁₀₀₀大小相同的DNA条带,而毒性表型的菌株除5个重组个体外,均不能扩增出这条特异带。此结果表明,与稻瘟病菌无毒基因AVR-Pik^m连锁的RAPD标记OPO12₁₀₀₀被成功地转化为SCAR标记,为进一步通过染色体步移克隆该无毒基因奠定了基础。     

树木细根主要研究领域及展望

细根是树木根系的重要组成部分,具有重要的生理和生态作用。论文根据国内外近几十年来树木细根研究现状,对细根的几个主要研究领域即细根分解、细根寿命、细根周转和细根衰老的研究进展进行综合概述,并指出寻找适宜的研究方法、明确细根的定义、认识细根的异质性及探究影响细根周转的因子和机理是树木细根各研究领域未来需深入探讨的基本问题。论文的概述皆在帮助研究者全面认识国内外细根各领域的研究概况,同时也为细根研究的深入开展提供了良好的借鉴,从而加快中国根系生态学研究的步伐。     

6种梨果实对轮纹病的抗性差异及4种杀菌剂对轮纹病菌的抑菌作用

由葡萄座腔菌Botryosphaeria dothidea引起的梨轮纹病是梨生产中重要的真菌性病害,主要造成树势早衰和果实腐烂,严重影响梨的产量和品质。本研究选取市售的6个品种的梨果实,用分离自梨枝干的轮纹病菌进行了离体果实接种,测定不同品种果实对梨轮纹病的抗性差异。接种后6 d,按照病斑直径从大到小的顺序,品种排序依次为‘丰水梨’>‘南果梨’>‘库尔勒香梨’>‘皇冠梨’>‘雪花梨’>‘砀山酥梨’,随病斑减小抗性依次增强。测定了4种杀菌剂对梨轮纹病菌菌丝生长的抑制作用,结果表明,咯菌腈、氟啶胺和咪鲜胺对梨轮纹病菌的菌丝生长有很强的抑制作用,EC 50分别为0.010 3、0.022 4μg/mL和0.034 3μg/mL;代森锰锌的EC 50为3.860 7μg/mL,也有较好的抑菌效果。本试验结果为了解不同梨品种对轮纹病的抗性及杀菌剂的选用提供了依据,具有一定的指导意义。     

草莓丝核菌根腐病病原菌鉴定及7种杀菌剂的抑菌作用测定

为了解草莓丝核菌根腐病的病原种类及筛选防治丝核菌根腐病的有效杀菌剂,本研究基于形态学特征、细胞核荧光染色、菌丝融合群测定以及rDNA-ITS的序列分析,对北京和河北承德地区的草莓丝核菌根腐病的病原菌进行了鉴定,并利用菌丝生长速率法测定了7种杀菌剂对丝核菌的抑菌作用。结果发现,北京地区的丝核菌为双核丝核菌(binucleate Rhizoctonia,BNR),属于融合群AG-A;河北的丝核菌为立枯丝核菌Rhizoctonia solani,属于融合群AG-4。氟啶胺、吡唑醚菌酯、噻呋酰胺、戊唑醇、咯菌腈、氟硅唑对2种丝核菌均有很强的抑制作用,EC_(50)值为0.063 9～2.485 7μg/mL,抑霉唑的抑制作用较差,EC_(50)值为9.966 8～11.236 8μg/mL。同一种杀菌剂对不同丝核菌的抑制作用存在差异,噻呋酰胺、戊唑醇、氟硅唑、咯菌腈和抑霉唑对立枯丝核菌的抑制作用强于对双核丝核菌。试验结果为生产上合理选用杀菌剂防治草莓丝核菌根腐病提供了科学依据。     

土壤处理对西洋参根际线虫数量动态的影响及对防治茎线虫根腐病的效果

 Root rot of American ginseng (Panax quinquefolium) caused by Ditylenchus destructor is a novel disease found recently in Beijing area. The effects of three soil treatments (fumigating with chloropicrin, chloropicrin + lvfeng organic manure and nematicide fosthiazate) on the number of rhizospheric nematodes, survived plants, root yield and root rot of 3-year ginseng plant were compared. The effects were also investigated at the second year after treatment. The results indicated that the number of parasitic nematodes in rhizosphere of treated soil reached the peak value in late June to early July as the soil temperature raised in the growing season. Compared with the regular treatment, the number of plant parasitic nematodes was reduced while non-plant parasitic nematodes increased. The number of non-plant parasitic nematodes in the soil treated with chloropicrin + lvfeng organic manure was 2 times than that treated with chloropicrin only. The ratio of non-parasitic to parasitic nematodes of three treatments was higher than the control. Percent of survived plants was 94.8%-96.4% and diseased root was decreased obviously. The control efficacy was more than 89% at the first year after treatment. The survived plants and plot yield of ginseng increased significantly and the control efficacy was around 40% at the second year. The best of the three treatments was by chloropicrin + organic manure.     

西藏辣椒疫病菌及其对新型杀菌剂的敏感性测定

经分离鉴定,引起西藏辣椒疫病的病原菌为辣椒疫霉,菌丝生长温度为10~37℃,最适生长温度25~30℃,致死温度40℃。交配型为A2自育型。烯酰吗啉和腈嘧菌脂均对辣椒疫霉的菌丝生长具有很强的抑制作用,分别抑制菌丝的生长速度和菌丝的生长量,EC50分别为0.241 mg/L和0.302 8 mg/L,比常规杀菌剂甲霜灵EC50分别低32.6和25.9倍。     

苜蓿黄萎病菌在我国的适生性分析研究

本文以适生性评判指标分析为基础,采用生物学建模与GIS分析相结合的方法,依据我国677个气象站点的逐月气温数据以及全国土壤pH等值线图,对苜蓿黄萎病菌在我国的适生性作了分析研究。结果表明,苜蓿黄萎病菌在我国的适生性强,适生范围较广,每年4~9月份,该病菌在我国西北、东北以及华北地区的适生程度处于较高水平。鉴于此,我国应加强苜蓿黄萎病菌的植物检疫措施力度,严防该病的传入或扩散。     

塔式起重机倾倒事故原因分析

塔式起重机由于具有起升高度高、起重力矩大、工作幅度大等特点,在工业与民用建筑施工中被广泛应用。由于塔式起重机作业环境复杂,加上人为因素的影响,整机倾倒事故时有发生,现将塔式起重机整机倾倒的原因作一简单分析。