尖角突脐孢菌在温室环境下侵染稗草的致病体系研究

稗属（Echinochloa）杂草是全世界水稻等作物生产中的一类恶性杂草。人工除稗安全但费时费力，化学除稗高效但伴随农产品安全和环境相融友好方面的潜在风险。因此，寻求安全高效的除稗活性成分和施药技术成为国际上除稗剂发展的重要方向之一。在研究和开发生物除稗剂的技术体系中，满足高通量筛选安全、高效的除稗生防因子的温室检测体系是极为重要的支持平台，同样，生物除稗剂的田间科学施药技术亦应依据生防因子在稗草上致病和致害所需的最佳条件来制定。基于此，亟需探明生防因子侵染稗草致病的相关条件并建立快速有效的生防因子除稗效果温室检测体系和田间施药技术。本文系统研究了影响尖角突脐孢菌侵染稗草的相关因子，建立了稳定的温室环境下尖角突脐孢菌侵染稗草的致病体系。     

杀葱蝇高毒力真菌菌株的筛选

从实验室保存的真菌菌株初步筛选获得6株对葱蝇有一定致病力的白僵菌菌株,通过室内生测进一步测定不同菌株对葱蝇幼虫的毒力。测试结果表明,在相同浓度的孢子悬浮液处理下(1×10⁷孢子/mL),菌株CQBb119的致死率最强,第14 d对葱蝇幼虫的致死率达到77.78%,僵虫率达到58.52%,致死中时(LT₅₀)为6.10 d。使用不同浓度孢子悬浮液处理葱蝇的各个虫态,结果显示,在不同浓度孢子悬浮液处理下,随着孢子悬浮液浓度的增加,葱蝇的死亡率逐渐升高,致死中时降低。在1×10⁸和1×10⁹孢子/mL浓度的菌液处理下,第14 d对葱蝇幼虫的LT₅₀分别为5.48和4.94 d;LC₅₀为1.35×10⁶孢子/mL。菌株CQBb119对葱蝇成虫和蛹也有一定致死作用,但成虫和蛹的死亡率均未能达到50%。结果表明,球孢白僵菌菌株CQBb119对葱蝇幼虫具有良好杀虫活性,可以用于防控葱蝇的潜在生防制剂开发。     

拮抗细菌A2菌株的鉴定及其对小麦白粉病的防治效果

为适应现代无公害农业的发展,针对小麦白粉病的防治,从保护地土壤中分离得到一株生防细菌A2。通过形态学特征、生理生化特性的观察和测定,结合16S rDNA序列分析并构建系统发育树,对菌株A2进行了初步鉴定。同时,以清水为对照,测定了菌株A2对3432品种小麦白粉病的防治效果。结果显示该菌株主要特征是菌体杆状,内生芽孢、芽孢卵圆形,革兰氏染色阳性,好氧,接触酶反应、乙酰甲基甲醇实验为阳性,能利用柠檬酸盐;该菌株与亲缘关系较近菌株B.subtilis isolate G8的同源性达99%。结合以上两点,将菌株A2初步鉴定为枯草芽孢杆菌（B. subtilis）。防效实验显示菌株A2发酵液处理最好防治效果为72.22%;无菌滤液处理最好防治效果为29.24%,与对照相比均具有显著性差异（α=0.05）。表明,拮抗菌株A2菌体与代谢产物对小麦白粉病都具有较强的防治作用,为研制型、无毒、无公害生物农药提供了依据。     

腐霉对甲霜灵抗性测定及其生物防治

测定了腐霉属的8个种209个菌株对甲霜灵在浓度为0.5和50ug/ml时的抗性，从实验中观察到不同菌株对甲霜灵抗性变化的范围非常大，有95株在0.5ug/ml时，菌丝即停止生长，在20株在50ug/ml时，菌丝生长速度与对照几乎一样。经鉴定，这209株菌中，优势种为终极腐霉(Pythium ultimum）和刺腐霉(P.spinosum)。20株高抗菌中,P.ultimum占16株，P.irregulare占2株，P.spinosum和P.graminicola各占1株。盆栽试验表明：假单胞菌株Pseudomonas sp.CR56对高抗菌株P.ultimum ONCUR01引起黄瓜苗期猝倒病具有显著的防效，防效与甲霜灵和五氯硝基苯相比，达到极显著差异。     

布氏白僵菌的研究与应用

对７０年代以来布氏白僵菌的生物学、致病性、生理生化特性等基因研究以及该菌的规模征税和田间防治应用地综述。目前已发现该菌能寄生７个目的７０种昆虫,特别对鞘翅目害虫具有独特寄生效果,已在林区、农田、草地、果园中用于防治各种金龟子和天牛。在法国、瑞士等地,用布氏白僵菌连续多年防治林区的西方五月鳃金龟,取得了令人瞩目的防治效果和生态效果,日本用该菌防治杉树天牛、我国用该菌防治农田及苗圃蛴螬都取得明显成效。     

Combining competition from Lolium perenne and an insect–fungus combination to control Rumex obtusifolius seedlings

Although adult Rumex obtusifolius are problematic weeds, their seedlings are poor competitors against Lolium perenne, particularly in established swards. We investigated the possibility of using this weakness to augment control of R. obtusifolius seedlings with combinations of Gastrophysa viridula (Coleoptera: Chrysomelidae) and the rust fungus Uromyces rumicis. Rumex obtusifolius seedlings were grown in competition with L. perenne sown at different rates and times after R. obtusifolius: they competed successfully with L. perenne when sown 21 days before the grass. Sowing both species at the same time resulted in a dominant grass sward, with R. obtusifolius becoming dominant when sown 42 days prior to L. perenne. Grass sowing rate had no effect on R. obtusifolius growth or biomass. A second experiment investigated how competition from L. perenne sown 21 days after R. obtusifolius combined with damage from G. viridula and/or U. rumicis (applied at either the 3–4‐ or 10–13‐leaf stage, or at both stages) affected the growth and final biomass of R. obtusifolius. Beetle grazing at the latter leaf stage was the only treatment that reduced R. obtusifolius biomass, although rust infection at the earlier application led to an increase in shoot and root weight. The results are discussed in terms of the potential for use of these agents in the field.     

禾谷镰刀菌拮抗菌株的筛选及鉴定

禾谷镰刀菌引起的小麦赤霉病能够导致小麦产量的大幅降低和品质的严重损失。为探索赤霉病生物防治方法,本试验从扬花期被禾谷镰刀菌侵染的麦穗上分离得到28株芽孢杆菌,利用平板对峙法对其进行筛选,其中20株菌对禾谷镰刀菌表现出明显的拮抗作用。根据生理生化特性和16S rDNA序列分析,这20株拮抗菌分别被鉴定为甲基营养型芽孢杆菌(11株)、解淀粉芽孢杆菌(2株)、枯草芽孢杆菌(2株)、暹罗芽孢杆菌(3株)和特基拉芽孢杆菌(2株)。这些菌株能够有效降低小麦赤霉病的发病率、发病程度和病情指数,其中菌株JS62N、JS15E和JS29I能够将赤霉病发病率降低80%以上;菌株JS29I、JS62N、JS39C和JS39D能够将赤霉病发病程度降低80%以上。16株菌能将病情指数降低80%以上;所有菌株均能极显著增加小麦的百粒重,JS12Q效果最好(+101.4%)。本研究结果为小麦赤霉病的防治提供了生物防治材料。     

柑橘砂皮病菌生防菌的筛选及其发酵条件优化

以柑橘砂皮病菌为靶标菌株,采用平板对峙法从土壤中分离到的227株细菌中获得4株对柑橘砂皮病菌有明显抑制活性的菌株,其中Y2菌株发酵液稀释5倍和10倍后,对柑橘砂皮病菌菌丝生长的抑制率分别为69.85%、61.76%。生理生化测定与16S r RNA基因序列分析结合,确定Y2菌株为短小芽孢杆菌(Bacillus pumilus)。Y2菌株培养的最佳氮源和最佳碳源分别为蛋白胨和可溶性淀粉,最佳发酵温度28℃,转速180 r/min。Y2菌株产生的抑菌活性物质经80℃高温处理和强酸、强碱处理,活性明显下降。     

Partial Characterization of Chitinolytic Extract from Endophytic Streptomyces sp. and Its Effects on the Boll Weevil

The present study achieves the biochemistry partial characterization of the chitinolytic extract produced by an endophytic Streptomyces sp. strain （A8）. This extract was also tested against Anthonomus grandis, the cotton boll weevil aiming its control. The chitinase crude extract from the A8 strain was cultured for five days in a minimum liquid media supplemented with chitin. The extract was partially characterized by standard methods. The chitinolytic extract had an optimum temperature of 66 ＂C and an optimum pH between 4 to 9 （around 80% of relative activity）. We also characterized the temperature and pH stability and measured the effects of enzyme inhibitors. The filtered chitinolytic extract was added to an artificial boll weevil diet. Boll weevil development from the egg stage to the adult stage was prolonged, and the percentage of adults that emerged was approximately 66% less than on control diet. This study showed that the.larval development of A. grandis was inhibited by the presence of characterized chitinolytic extract in artificial diet. This work provides an experimental basis for using the chitinase from an endophytic bacterium Streptomyces sp. as a biocontrol alternativeto controlling the plant pest A. grandis.     

Commercial development of Trichoderma species for control of soil-borne vegetable diseases and their integration into standard crop management practices

A 10 year research programme at Lincoln University, investigating the use of Trichoderma species for biological control of soil-borne diseases of vegetable crops, has resulted in the development of two commercial products. Trichodry TM. 6S and Trichoflow TM. 6S based upon Trichoderma hamatum isolate 6SR4, are used to control Sclerotinia lettuce drop disease. The Trichodry 6S product is formulated as a dry flake, which is incorporated into nursery seedling mix and the Trichoflow 6…