Suppression of wheat-seedling diseases caused by Fusarium culmorum and Microdochium nivale using bacterial seed treatment

Snow mould, caused by Microdochium nivale , and seedling blight caused by members of the Fusarium complex, are cereal diseases of great economic importance in many temperate zones. In a glasshouse bioassay designed to enhance disease, about 600 plant-associated bacterial isolates obtained by different methods were screened for suppressive effects in wheat against infection caused by Fusarium culmorum . Although most of the isolates tested had a neutral effect on test plants and disease development, a few were synergistic to the pathogen and about one-fifth showed > 80% disease suppression. During five consecutive growing seasons, 164 bacterial isolates were tested in field experiments against both F. culmorum and M. nivale as causal agents of seedling blight. Tests for effects on yield in experiments with spring and winter wheat, performed in different climatic regions of Sweden, showed that disease-suppressive effects were repeatable. The most efficient isolates, three fluorescent pseudomonads and a species of Pantoea , suppressed disease equal to that of the fungicide guazatine, both with respect to crop stand and yield. Seed treatment with Pantoea sp. (isolate MF 626) increased yield by an average of more than 500 kg ha⁻¹ in six field experiments.     

Approach of allelopathy study with Arabidopsis thaliana (L.) Hevnh. and Neurospora crassa

Allelopathy in Arabidopsis seeds was investigated in the present study because there are few available reports of allelopathy studies regarding the early development stage of the plant life cycle, and because Arabidopsis is widely used as a model plant for molecular biology. When cockscomb ( Celosia cristata ) was incubated together with Arabidopsis seeds, the growth of cockscomb was promoted by Arabidopsis seeds. Exudate of Arabidopsis seeds showed a promotive activity on the growth of cockscomb and Arabidopsis itself. A new method for studying allelopathic mechanisms involving the interaction of the plant Arabidopsis thaliana (L.) Hevnh. and the fungus Neurospora crassa was suggested. Arabidopsis seed exudate and the water-soluble fraction of the exudate promoted Arabidopsis growth and reduced fungal germination, indicating that the seed exudate has a species-selective activity. Conversely, the ethylacetate-soluble fraction inhibited growth of all tested materials in the current study. These results demonstrate that the water-soluble substance(s) released from Arabidopsis seeds have species-selective activity on growth of both plants and microorganisms.     

拮抗细菌菌株Bacillus spp.间的相互作用及其对水稻纹枯病的抑制

测定了6个Bacillus spp.和1个Pseudomonas sp.P-13(G-对照菌株)在PPM培养基上的相互作用。在总共42个组合中，有27个组合是可亲和性的。在以B5423为单剂之一的5个组合中，亲和性的组合有4个。在温室条件下通过分批播种，在水稻分蘖盛期喷以B5423-R(B5423的标记菌株，是利福平抗性的突变体)为单剂之一的4个亲和性组合的菌悬浮液，以检测该组合中B5423-R在水稻茎基部的种群数量。结果发现，与单剂B5423-R相比，在应用1～7天内，组合B5423-R B45中，B5423-R的群体数量显著性降低；组合B5423-R B95、B5423-R B77中，B5423-R的群体数量与单剂无显著差异；组合B5423-R B4313中，B5423-R的群体数量在应用1～4天内与单剂无显著性差异，但在应用第7天显著地高于单剂。离体叶片纹枯病痛斑面积的抑制试验表明，与各自的单剂相比，组合B95 B5423及B95 Er77显著地抑制了纹枯病病斑面积；而组合B45 B80、B45 B5423和B45 B95纹枯病病斑面积显著地高于各自的单剂；其余10个组合与各自的单剂无显著差异。     

疫霉菌对霜脲氰抗性遗传及对霜脲氰和甲霜灵的交互抗性

就疫霉菌对霜脲氰抗性的产生和遗传，以及疫霉菌对霜脲氰和甲霜灵的交互抗性进行了研究。结果表明，苎麻疫霉容易对霜脲氰产生抗药性突变，但抗性在连续３代单游动孢子分离过程中逐渐丧失。大雄疫霉对霜脲氰不易产生抗性突变，恶疫霉、大雄疫霉和苎麻疫霉对甲霜灵和霜脲氰不存在交互抗性     

不同镉水平对白菜生长及抗氧化酶活性的影响

 不同镉(cd)水平对白菜[Brassica campestris L．ssp．chinensis (L．)Makino]两个品种生长及抗氧化酶活性研究结果表明：cd 1 mg·L^-1 对两品种生长(除‘杭州油冬儿’地上部干质量)及叶绿素 含量无显著影响，cd 10 mg·L^-1显著抑制植株生长(除‘沪青1号’根干质量)，减少叶绿素含量。cd可诱导叶片中活性氧0₂^-. 、H₂O₂的产生，引起膜脂过氧化产物丙二醛(MDA)的累积。Cd 1 mg’L 显著增加‘沪青1号’过氧化物酶(POD)、过氧化氢酶(CAT)及‘杭州油冬儿’抗坏血酸过氧化物酶(APx) 活性。cd 10 mg·L 显著降低两品种叶片超氧化物歧化酶( SOD ) 、CAT、APX及‘沪青1号’POD活性， 显著增加脱氢抗坏血酸还原酶(DR)和谷胱甘肽还原酶(GR)活性。     

半自然条件下几种赤眼蜂及品系对亚洲玉米螟卵寄生能力比较

在半自然条件(田间网罩)下,将人工饲养的玉米螟卵按4、8、16块/株3个处理分别固定在网罩内的玉米植株中上部叶片上,然后每网罩分别引入供试赤眼蜂20头,24 h后更换玉米螟卵块,连续3 d。7 d后调查供寄生的玉米螟卵被寄生率及羽化率。结果表明:在半自然条件下广赤眼蜂伊朗1-1品系虽寄生能力高于其他供试品系,但到第2、3天明显降低;玉米螟赤眼蜂北京6-2-2品系每天均维持一个较平稳的寄生能力,产卵量在时间上的分配比较分散,并在第2、3天显示出比其他品系较高的寄生潜能。广赤眼蜂伊朗1-1品系的卵块寄生数量可随卵块密度的增加而增加,而其他品系则在各处理密度下,寄生数量基本没有变化;从卵粒寄生率看,广赤眼蜂伊朗1-1和吉林1-2两个品系的寄生数量随卵块密度的增加而大幅度提高,其他品系增加幅度较小。     

几种牧草对河西走廊盐渍化土壤改土培肥的效应研究

在河西走廊盐渍化土地上种植老芒麦、扁穗冰草、碱茅和紫花苜蓿4种优质牧草,对盐渍化程度均有一定的改良效果.其中碱茅对盐渍化土壤的改土培肥效果最好,建植3年后的碱茅,与对照比较,0～20 cm土层中自然含水量增加125.99 g/kg,总孔度增加16.14%,容重降低0.27 g/cm3,pH值由8.43降到8.10,全盐含量降低52.90 g/kg,脱盐率达到76.12%,有机质增加3.67 g/kg,碱解氮含量增加18.63 mg/kg,速效磷和钾亦随之增加.     

棉铃发育过程中不同组织IAA含量变化特点

为了解IAA与棉纤维品质形成间的关系及棉铃各部位IAA积累转运特点,本研究分析了棉铃各部分在发育过程中IAA含量的变化特点。通过选择陆地棉标准系TM-1、长纤维种质‘母35’和短纤维种质‘208’3个纤维长度差异较大的陆地棉材料,利用酶联免疫法对浙江杭州、海南三亚两地田间试验的各材料不同发育阶段的棉仁、棉籽壳、棉纤维、棉铃壳进行了IAA含量的测定。结果表明,不同参试材料的棉仁IAA含量存在明显差异,棉籽壳、棉纤维与棉铃壳的IAA含量峰值出现时间晚于棉仁,棉铃各个组织IAA含量具有随棉铃组织从内向外逐渐降低的趋势。研究表明,IAA可能是棉纤维发育的正效应因子,且棉铃发育过程中IAA可能呈初期在棉仁富集、随发育进程沿棉铃组织由内向外运输的规律。