烟草黑胫病菌拮抗放线菌LY18的分离筛选与鉴定

为了寻找对烟草黑胫病具有生防潜力的放线菌,笔者采用平板对峙法,从烟草黑胫病发病烟田健株根际土壤中,分离得到1株对烟草黑胫病菌具有显著拮抗效果的放线菌株LY18,其发酵液的无菌滤液对烟草黑胫病菌菌丝的抑制率达70%以上。电镜观察发现,抑菌圈周围的烟草黑胫病菌丝破裂、瘪陷。通过对LY18的形态观察、培养性状观察、生理生化测定结合16S rDNA序列分析,将该菌株鉴定为Streptomyces rajshahiensis。     

Reduction of in vitro growth in Flavobacterium columnare and Saprolegnia parasitica by products containing peracetic acid

Commercial products containing peracetic acid (PAA) are strong disinfectants with a wide spectrum of antimicrobial activity and have been suggested as potential therapeutic agents in aquaculture. The aim of this study was to compare the in vitro reduction of growth on two fish pathogens, Flavobacterium columnare and Saprolegnia parasitica, by seven commercial PAA‐containing products. Flavobacterium columnare was exposed to 1, 2, 4, 6, 8 and 10 mg L^?1 PAA and S. parasitica was exposed to 0.5, 1, 2, 4, 6, 8 and 10 mg L^?1 PAA in petri dishes for 24 h incubation. The reduction of growth was measured in comparison to a PAA‐free control. A reduction of the growth was observed for both pathogens with increasing PAA concentration. Hydrogen peroxide (H₂O₂) possibly has a role in the effectiveness of the products, since products with lower PAA concentrations had a higher concentration of H₂O₂. The commercial products with a low concentration of PAA and a low PAA:H₂O₂‐ratio were generally more effective against pathogens. The practical application of the products with low PAA concentration should be prioritized.     

贵州省烟草黑胫病菌对甲霜灵的抗药性

为了明确贵州地区烟草黑胫病菌对甲霜灵的抗药性水平, 从贵州省12个市、县采集黑胫病病株, 经分离纯化鉴定, 获得98株黑胫病菌株, 采用生长速率法测定其对甲霜灵的敏感性。结果表明, 采自不同地区的菌株对甲霜灵的敏感性差异较大, 各供试菌株的EC50 值分布范围为0.419 2～20.486 1 μg/mL; 各地区平均EC50 在0.551 9～10.986 0 μg/mL之间; 最低抗药性水平为1.00, 最高抗药性水平为48.87, 相差48.87倍, 各地区平均抗药性水平在1.32～26.21之间。遵义、兴仁、贵定、赫章和兴义有抗甲霜灵菌株出现, 除遵义部分菌株的抗性水平表现为高抗外, 其余菌株对甲霜灵产生的抗性均处于中抗水平。     

低毒病毒CHV1-CN280生防潜力的初步研究

前期研究表明,分离自中国的低毒病毒CHV1-CN280与其它多数低毒病毒相比具有更高的水平传播能力。本研究中,我们对CHV1-CN280的田间定殖能力及其它生防性状进行了评估。与其它两个模式低毒病毒相比,CHV1-CN280对栗疫菌Cryphonectria parasitica的毒力显著弱于典型的烈性低毒病毒CHV1-EP713,而更接近于典型的温和低毒病毒CHV1-Euro7。强致病性的栗疫菌感染CHV1-CN280后,成为典型的低毒菌株,不再对板栗植株造成严重危害,但是与感染典型烈性低毒病毒CHV1-EP713的菌株相比,寄主真菌在板栗枝条上仍保持了一定的定殖能力,其菌丝生长速率和分生孢子产量较高。初步的田间试验表明,在人工接种两年后,CHV1-CN280在田间成功定殖,并已扩散到田间自然存在的、与人为释放的低毒菌株不亲和的其它营养体亲合群的栗疫菌菌株中。结果表明,低毒病毒CHV1-CN280对栗疫病具有非常好的生物防治潜力。     

栗疫病菌不同毒力菌株生物学特性的研究

 对不同毒力、含或不含dsRNA的菌株的生物学特性进行了研究。含dsRNA的弱毒力菌株的分生孢子后代,可分化出白色和桔黄色两种菌落类型,菌落白色的单孢菌株,可继续分化出白色和桔黄色两种类型的后代,桔黄色的单孢菌株保持稳定,不再发生分化。不含dsRNA的菌株,未见培养性状发生分化。对含dsRNA的弱毒力菌株的第2代两种类型的单孢菌株进行了毒力测定和dsRNA检测,桔黄色的单孢菌株的毒力水平达到或接近强毒力菌株的水平,不含dsRNA;而白色的单孢菌株的毒力很弱,且都含有dsRNA。对不同毒力菌株分生孢子的萌发率进行了比较,结果表明,孵育12h后,即有部分菌株的分生孢子开始萌发,强毒力菌株孢子的萌发最早,含dsRNA的弱毒力菌株的孢子萌发较迟;孵育24h后,各菌株孢子的萌发率均达到90%以上,差异已不太明显,但芽管的分枝程度有较大差异,强毒力菌株的芽管(菌丝)大量分枝,初步形成菌丝丛,而弱毒力菌株,不论是否含有dsRNA,芽管的分枝程度均较低。     

烟草疫霉的产孢和接种方法研究

烟草疫霉是重要的病原真菌,但在人工培养条件下难以培养、产孢以及释放游动孢子.作者对烟草疫霉培养、产孢、接种方法进行了研究.芝麻培养基、黑麦培养基、燕麦培养基可用来培养烟草疫霉,烟草疫霉在三种培养基上平均每天生长量为1.10、0.78、0.86cm;芝麻培养基、黑麦培养基为烟草疫霉产孢子囊较好的培养基,产孢能力强,分别为2.52×104、2.07×104个孢子囊/cm2.而且孢子囊释放率高,分别为43.0%、32.1%.游动孢子囊悬浮液灌根接种和注射接种都能使烟草发病,但不同的接种方法和接种浓度下,病情指数不同.     

板栗疫病菌脱毒方法的比较研究

 病毒与宿主相互作用中,存在宿主主动或被动摆脱病毒的机制。本研究用光照诱导-单孢分离、原生质体再生和菌丝尖端分离3种方法对携带低毒病毒的板栗疫病菌(Cryphonectria parasitica)的EP721、EP713和Euro7三个菌株的脱毒效率进行了比较。结果表明:经光照诱导-单孢分离后所有菌株均可获得脱毒菌株,而原生质体再生对EP721的脱毒效率最高,是继光照诱导-单孢分离脱毒法之后另一种新的有效的脱毒方法,特别适用于不产孢的真菌脱毒。     

Seedling and adult plant resistance to downy mildew (Peronospora parasitica) in cauliflower (Brassica oleracea convar. botrytis var. botrytis)

Seedlings of six cauliflower cultivars ( Brassica oleracea convar. botrytis var. botrytis ) were assessed for resistance to a Danish isolate of Peronospora parasitica , under controlled conditions. Resistance, characterized by restricted sporulation and necrotic dark flecks at the inoculation site on the cotyledons, was expressed in the hybrids 9306 F1, 9311 F1, and the open pollinated cultivar Perfection. Testing of the parent lines and F2 generations of the two resistant hybrids suggested that resistance was a dominantly inherited trait controlled by a single gene. Inoculation of the cultivars with seven isolates, from different geographical origins, showed that the resistance was isolate specific. The two hybrid cultivars expressing cotyledon resistance and two hybrids expressing susceptibility were assessed for adult plant resistance under field conditions. The AUDPC (Area Under the Disease Progress Curve), based on disease incidence and severity, revealed significant differences between the cultivars. At harvest, the cultivars exhibited significantly different levels of defoliation and curd attack. The cultivars 9306 F1 and 9311 F1 showed high levels of resistance in all assessments, whereas the two cultivars exhibiting susceptibility at the seedling stage, 9304 F1 and 9305 F1, also exhibited susceptibility through the adult plant stage. Thus, the resistance exhibited under field conditions resembled that identified at the seedling stage under controlled conditions. The results suggest that cotyledon resistance similar to that described could provide resistance throughout the adult plant stage, including curds.     

绿针假单胞菌PL9菌株对烟草疫霉的拮抗作用研究

利用离体拮抗试验和烟草幼苗生物测定法研究了棉花根圈细菌绿针假单胞菌（Pseudomonas choloraphis)PL9菌株对烟草黑胫病原菌烟草疫霉（Phytophthora parasitica var.nicotianae)的拮抗作用，该菌株对烟草疫霉菌丝体有很强的抑制作用，并且可以完全抑制烟草疫霉游动孢子对烟草幼苗的侵染，其液体培养物浓缩过滤液也有相同的报制作用，拮抗作用机理研究结果表明，其拮抗作用可能与PL9菌株分泌的抗生素类物质有关。为了解PL9菌株在烟草根圈的定殖情况，采用全套发光酶基因（luxCDABE)标记的菌株PL9L进行跟 踪，结果表明该菌株可以在烟草根圈成功定殖。     

我国烟草黑胫病菌生理小种鉴定

1981—1985年从全国8个主产烤烟省30个地、县共采集和分离到烟草黑胫病菌(Phytophthora parasitica var.nicotianae)57个分离物,用游动孢子悬浮液接种根及茎基部,试验表明这种接种方法效果为好。用此方法将各分离物接种在常用的Burley_(21)、Burley_(37)、N.nesophila、N.stocktonii等4个鉴别寄主上进行了鉴定试验。通过鉴定,采自全国57个分离物中有44个属于生理小种Ⅰ号,占77.2%;有12个属于生理小种0号,占21.1%,还有个别分离物有待进一步鉴定。