Efficiency of isolates ofConiothyrium minitans as mycoparasites ofSclerotinia sclerotiorum,Sclerotium cepivorum andBotrytis cinerea on tomato stem pieces

Summary Twenty five isolates ofConiothyrium minitans were screened for antagonism toSclerotinia sclerotiorum in a Petri dish bioassay using tomato stem segments placed on sterile sand. The antagonistic activity of 23 isolates was quite uniform and only two less antagonistic isolates were identified. Antagonism, expressed as a reduction in the rate of tissue colonization byS. sclerotiorum, occurred, whetherC. minitans was co-inoculated at the same time, one day before or one day afterS. sclerotiorum, but was slightly restricted whenS. sclerotiorum was given a lead of one day. On average, 50–80% of sclerotia of S.sclerotiorum formed on the stem pieces were infected byC. minitans two weeks after inoculation. Excluding the less antagonistic isolates,Coniothyrium minitans was recovered from over 80% ofS. sclerotiorum-infected stem segments when co-inoculated but from a maximum of only 7% of stem pieces when exposed toC. minitans alone. When the experiments were carried out on non-sterile soil instead of sterile sand, infection of stem pieces byS. sclerotiorum was reduced and recovery ofS. sclerotiorum andC. minitans from stem segments was decreased. SevenC. minitans isolates were also screened againstSclerotium cepivorum andBotrytis cinerea and, whereas the effect ofC. minitans onS. cepivorum-infected tissue and sclerotia was essentially similar to that observed withS. sclerotiorum, B. cinerea infected tissue and sclerotia were not invaded by the antagonist.     

Physiological basis for antagonism induced by mixtures of quizalofop-ethyl and bromoxynil in maize (Zea mays)

In this study, the physiological basis for antagonism induced by mixtures of quizalofop‐ethyl and bromoxynil was investigated in maize seedlings. In sequential applications, antagonism was observed when bromoxynil was applied before quizalofop‐ethyl or in a mixture with quizalofop‐ethyl, but was minimal when bromoxynil was applied afterwards. The degree of antagonism differed with application rates of bromoxynil and with the timing of the treatment. When test herbicides were applied locally to the second leaf, the inhibition of photosystem II (PS‐II) in the herbicide‐treated leaf was higher with the mixture than with bromoxynil or quizalofop‐ethyl alone. Subsequent growth of the untreated third leaf inhibited by quizalofop‐ethyl alone then recovered, depending on the dose of bromoxynil. There was no evidence that bromoxynil affected absorption of quizalofop‐ethyl. In local applications at different positions on the second leaf, antagonism was only observed when quizalofop‐ethyl was applied to the distal part of the leaf and bromoxynil applied to the proximal part. The antagonism of bromoxynil + quizalofop‐ethyl did not occur at the level of acetyl CoA carboxylase and Hill reaction, as revealed by in vitro assays. These results suggest that bromoxynil inhibits the phloem transport of quizalofop‐ethyl and thus antagonises its whole‐plant activity in maize.     

Joint action of amino acid biosynthesis-inhibiting herbicides

The joint action of binary mixtures of the amino acid biosynthesis‐inhibiting herbicides glyphosate, glufosinate‐ammonium, metsulfuron‐methyl and imazapyr was assessed in pot experiments applying the Additive Dose Model (ADM). Plants of Sinapis arvensis or S. alba were sprayed with seven doses of the herbicides alone and binary fixed‐ratio mixtures of the four herbicides. In total, 73 binary mixtures were studied in six separate experiments. Mixtures of glyphosate and glufosinate‐ammonium were less phytotoxic than predicted by ADM whether commercial formulations or technical grade products were applied. In contrast, mixtures of glyphosate and metsulfuron‐methyl, glyphosate and imazapyr, glufosinate‐ammonium and metsulfuron‐methyl, glufosinate‐ammonium and imazapyr, and metsulfuron‐methyl and imazapyr either followed ADM or were synergistic. Synergism was observed most frequently for mixtures of glyphosate or glufosinate‐ammonium with metsulfuron‐methyl. Synergism was also more pronounced for commercial formulations of glyphosate and glufosinate‐ammonium than for the corresponding technical grade formulations, implying that synergism was caused by the presence of the formulation constituents of the commercial glyphosate and glufosinate‐ammonium formulations in the spray solution.     

Compatible Biological and Chemical Control Systems for Rhizoctonia solani in Potato

A series of chemical and biological control agents were tested for compatibility with the Rhizoctonia-specific biocontrol fungus Verticillium biguttatum aimed at designing novel control strategies for black scurf (Rhizoctonia solani) and other tuber diseases in potato. The efficacy of chemicals, alone and in combination with V. biguttatum was tested in in vitro assays on nutrient agar plates, in bio-assays with minitubers and in the field. Generally, there were both antagonistic, neutral and additive interactions with V. biguttatum among the combinations tested; there were no indications for synergistic interactions. Broad-spectrum fungicides (azoxystrobin, chlorothalonil, thiabendazole) were fungitoxic to V. biguttatum as shown in in vitro assays, and hampered black scurf control by V. biguttatum in bio-assays. Oomycete-specific chemicals (cymoxanil and propamocarb) and various biocontrol strains (Gliocladium spp., Pseudomonas spp. and Trichoderma spp.) did not interfere with the growth of V. biguttatum on agar nutrient plates and did not affect black scurf control by V. biguttatum in co-applied treatments in the minituber bio-assay. Rhizoctonia-specific (pencycuron, flutalonil) fungicides co-applied with V. biguttatum showed additive effects on black scurf control. When combinations of V. biguttatum and cymoxanil or propamocarb were applied to immature potato tubers at green crop lifting, a reduction of both black scurf and Pythium- or Phytophthora-incited tuber rot was observed at harvest. In conclusion, the biocontrol fungus V. biguttatum is compatible with selected chemical control systems and may improve control efficacy in combination with Rhizoctonia-specific fungicides or may extend control spectrum in combination with Oomycete-specific fungicides.     

水稻纹枯病菌强拮抗菌B34的分离与鉴定

 从水稻植株上分离到1株对水稻纹枯病菌有强烈拮抗作用编号为B34的菌株,在PDA平板上表现有对水稻纹枯病菌较强作用的抑菌带,其发酵菌液对纹枯病菌丝有强烈的致畸作用,抑菌率达到71.5%,使菌核的菌丝萌发率降低69.0%。离体防效和田间小区防效分别高达81%和48.74%,高于清水和井冈霉素处理。经生理生化检测及细胞壁化学成分分析,确定其为致黄假单胞菌(Pseudomonas aureofaciens)。     

Trichoderma longibrachiatum Rifai 对 Botrytis cinerea 的拮抗机制研究

 从竞争、抗生和重寄生3方面研究Trichoderma longibrachiatum Rifai对Botrytis cinerea的拮抗机制.结果表明:T.longibrachiatum对B.cinerea的拮抗机制主要是竞争作用和抗生作用,没有观察到重寄生现象.     

复合微生物肥对植物土传病原真菌的抑制作用

测定了两株链霉菌R 1、R 2及其分别与有机肥配制的两种复合微生物肥料对几种植物病原真菌菌丝生长和孢子萌发的影响。R 1对草莓灰霉病菌、棉花黄萎病菌、棉花枯萎病菌的抑菌圈直径分别是 2 7、1 4和 2 1cm ,对孢子萌发的抑制率分别是 4 6 %、1 9%和 1 1 % ;R 2对以上 3种病菌的抑菌圈直径分别是 3 1、1 2和 1 7cm ,对孢子萌发的抑制率分别是 4 2 %、1 2 %和 4 %。苗期人工接种试验表明 ,一号复合微生物肥料对棉花黄萎病、油菜菌核病的抑制率分别为 2 8 0 %、4 1 9% ,二号肥分别为 72 0 %、97 2 %。     

黏质沙雷氏菌次生代谢物对TMV的抑制机理

【目的】分离、纯化和鉴定黏质沙雷氏菌2A2次生代谢物中具有抑制TMV侵染力的活性成分,明确其对TMV的抑制机理。【方法】通过病毒生物学测定,确定黏质沙雷氏菌2A2菌株对TMV的抑制效率。为明确黏质沙雷氏菌2A2发酵液次生代谢物中抑制TMV侵染力的活性成分,通过TLC和硅胶柱层析对其发酵液进行了分离纯化,获得主要的次生代谢物,通过局部枯斑法测定各代谢物的生物学活性,筛选可显著抑制TMV侵染活性的物质,经NMR分析,确定其成分结构,进而确定物质组分。为进一步揭示代谢物对TMV的抑制机理,利用透射电子显微镜探索代谢物对TMV粒体形态的影响,TMV粒体与代谢物甲醇溶液混合30 min后,于透射电子显微镜下观察TMV粒体形态。同时,用代谢物甲醇溶液喷施处理寄主下部3片叶,共设5个处理：处理Ⅰ,喷施代谢物24 h后,接种TMV;处理Ⅱ,代谢物与等体积TMV汁液混合30 min后,接种叶片;处理Ⅲ,先接种TMV,24 h后喷施代谢物;处理Ⅳ,宁南霉素（50 μL•mL-1）与等体积TMV汁液混合30 min后,接种下部叶3片做阳性对照;处理Ⅴ,无菌水与等体积TMV汁液混合30 min后,接种下部叶3片做空白对照。分别在次生代谢物诱导和TMV侵染后1、3、5、7、9 d,取未经任何处理的上部叶,TRIZOL法快速提取总RNA并反转录cDNA,利用real-time RT-PCR分析样品PR基因和TMV的RNA相对表达量,进而明确代谢物处理寄主对寄主PR基因表达的影响和对TMV在寄主体内复制增殖的抑制作用。【结果】黏质沙雷氏菌2A2菌株对TMV具有显著的抑制作用。对其发酵液进行分离纯化,获得3种主要代谢物,通过局部枯斑法测定,编号为BJH-2的代谢物可显著抑制TMV的侵染活性,经NMR分析,确定了该代谢物为灵菌红素（prodigiosin）。透射电子显微镜结果显示灵菌红素可显著破坏TMV粒体,使TMV典型的杆状病毒粒体降解断裂成排列紊乱的短杆状。real-time RT-PCR结果表明,灵菌红素处理植株后,处理Ⅰ、处理Ⅱ、处理Ⅲ可诱导寄主体内PR基因表达随着时间逐渐上调,第7 天左右,三者处理的寄主体内PR1、PR2、PR4、PR5表达上调至高峰,显著高于空白对照,亦高于处理Ⅳ的阳性对照,从而提高系统抗性;灵菌红素处理植株后,处理Ⅰ、处理Ⅱ、处理Ⅲ寄主体内TMV RNA的表达量随着时间上调减缓,在接种TMV后的第9天,三者处理的寄主体内的TMV RNA含量分别是空白对照的11.98%、5.23%、15.90%,显著低于空白对照,亦低于处理Ⅳ的阳性对照。【结论】灵菌红素既对TMV在寄主体内的复制增殖具有抑制作用,又可诱导寄主产生系统抗性,整体效果高于宁南霉素,可作为防治植物病毒新的生物制剂。     

基于形态学与ITS序列对冠突散囊菌多样性研究

为研究茯砖茶中冠突散囊菌多样性的问题,以来自中国3个省份的5种茯砖茶为样品,从中分离出优势微生物金花菌4、16、B1、B3、B7,依托形态学与和分子生物学技术对菌株进行鉴定。结果发现,这5株菌株均属冠突散囊菌,并且存在着遗传多样性,其中16号菌株的电镜观察结果与其他4株菌株差异明显,且菌株子囊孢子的“赤道”周围存在较多小孔;在ITS序列构建系统发育树中4、B1、B3、B7聚类为一组,16号聚类成另一组,说明冠突散囊菌可能存在亚种,这与形态学结果一致。     

1株油茶病害拮抗真菌的鉴定、生物学特性及拮抗作用研究

为了给油茶病害的生物防治提供科学依据,从油茶根部土壤分离获得1株能拮抗油茶主要病害的真菌F217-3。依据该菌株的形态特征,并结合全自动微生物鉴定系统及r DNA-ITS序列分析,将其鉴定为草酸青霉(Penicilium oxalicum)。对其生物学特性研究结果表明:该菌株在查氏培养基上生长最佳,碳源和氮源分别以蔗糖和尿素最适宜,生长适温为28℃,致死温度为65℃,在p H值为3~10条件下均生长良好,其中最适p H值是4~7,通气与否对菌丝生长无明显影响,但光照24 h条件下菌丝生长较差。平板对峙试验结果表明,F217-3对油茶炭疽病菌(C.nicotianae)、油茶软腐病菌(A.camellia)、黑斑病菌(A.alternate)和溃疡病菌(B.dothidea)的抑菌率均达到90%以上,可抑制油茶胶孢炭疽病菌、黑斑病菌分生孢子产生,抑制或致畸油茶炭疽病菌、溃疡病菌和叶斑病菌菌丝,是一株具有广谱拮抗作用的生防菌株。