芝麻立枯病内生生防细菌的筛选

利用表面消毒涂布平板的方法从大田健康芝麻根内分离芝麻内生细菌399株。平板对峙试验结果显示,176株细菌对立枯丝核菌(Rhizoctonia solani)有不同程度的拮抗能力,其中编号为B16、b10、D31、e23、G10、I10的6个菌株在PDA平板上对于立枯丝核菌具有极强的抑制作用,对西瓜枯萎病菌、西瓜炭疽病菌、小麦全蚀病菌和油菜菌核病菌也表现出广谱的抑菌作用。利用胶体几丁质和胶体壳聚糖作为唯一碳源,测定了上述6株细菌产生几丁质酶和壳聚糖酶的能力,发现b10和G10具有产壳聚糖酶的能力,I10有产几丁质酶的能力。活体盆栽试验测定了上述6株细菌对芝麻立枯病的生防效果,结果显示测定的6株细菌均具有一定的防治效果,其中G10的生防效果最好,可达到52%。利用胶体壳聚糖作为唯一碳源的选择性培养基测定了G10菌株在芝麻根系内部的定殖动态,发现G10在芝麻根部可以长期定殖。     

杀菌剂SYP-4288对几种常见土传病害的防治效果

采用室内盆栽试验测定了杀菌剂SYP-4288对立枯丝核菌引起的棉花立枯病、大豆疫霉根腐病及瓜果腐霉菌引起的黄瓜猝倒病的防效。结果表明,SYP-4288推荐剂量下对3种病害具有较好防效。最高推荐剂量下对棉花立枯病、黄瓜猝倒病和大豆根腐病防效分别为72.67%±10.59%、100%和82.62%±12.48%。SYP-4288对西瓜枯萎病田间药效试验表明,SYP-4288最高推荐剂量下对西瓜枯萎病防效为56.82%~66.51%,好于或相当于对照药剂。基于室内与田间药效试验结果,SYP-4288可以推荐用于防治瓜果蔬菜常见土传病害。     

水稻纹枯病生防细菌筛选及其与病原菌侵染垫形成的关系

为筛选对立枯丝核菌Rhizoctonia solani具有拮抗作用的生防细菌,利用稀释涂布平板法,从吉林省水稻纹枯病样中分离筛选出对立枯丝核菌AG-1A具有高拮抗活性的生防菌株,通过gyrB基因序列分析鉴定其分类地位,并采用离体侵染试验和温室防治试验测定筛选生防菌株对水稻纹枯病的防效,在显微镜下观察生防菌株预处理后接种病原菌的水稻叶片表面的菌丝生长情况,分析其生防机理。结果显示,从水稻纹枯病样中共分离获得35株菌株,其中菌株ND11对立枯丝核菌AG-1A的抑制率和抑菌圈直径最大,分别为74.12%和31.50 mm。基于gyrB基因序列分析最终将菌株ND11鉴定为短小芽胞杆菌Bacillus pumilus;该菌株能够减缓立枯丝核菌AG-1A的侵染速度,抑制其侵染垫的形成,对水稻纹枯病的温室防效达70.69%以上。表明短小芽胞杆菌菌株ND11能够通过抑制立枯丝核菌侵染垫的形成来防治水稻纹枯病,且防效较好,具有开发为生防菌剂的潜力。     

关防风立枯病病原菌根际拮抗细菌筛选与鉴定

为筛选出对立枯丝核菌Rhizoctonia solani Kühn具有优良防效的拮抗菌株。本研究从关防风根际土壤中分离纯化出156株细菌,采用平板对峙法测定菌株SC-32和SC-127对立枯丝核菌均有良好拮抗效果,且兼具广谱抑菌能力;抗生素标记法测定菌株SC-32和SC-127接种35 d后在土壤中含菌量仍能保持2.93×10⁷和7.83×10⁶ CFU/g;通过盆栽试验研究结果表明,菌株SC-32和SC-127对关防风立枯病的防治效果为60.53%和65.89%,高于菌剂和农药处理。通过形态学、生理生化特征、16S rDNA基因序列进行分类学鉴定确定菌株SC-32和SC-127均为贝莱斯芽胞杆菌Bacillus velezensis。     

五种杀菌剂对烟草立枯病菌的生物活性

由立枯病丝核菌引起的烟草立枯病是我国烟草苗床上危害最严重的病害之一。本研究评价了5种杀菌剂 (嘧菌酯、啶酰菌胺、氟啶胺、丙环唑和嘧霉胺) 对立枯丝核菌菌丝生长、菌核形成和萌发的影响,以及其对烟草立枯病的防治效果。结果表明:立枯丝核菌菌丝对氟啶胺和嘧菌酯的敏感性高于丙环唑和啶酰菌胺,而对嘧霉胺的敏感性较低;嘧菌酯对菌核形成的抑制作用强于丙环唑、氟啶胺、啶酰菌胺和嘧霉胺;5种杀菌剂对立枯丝核菌菌核萌发均无抑制作用。在离体烟叶的保护活性方面,12.5和50 mg/L的嘧菌酯和啶酰菌胺对立枯病的保护作用优于氟啶胺、丙环唑和嘧霉胺;在治疗活性方面,50和200 mg/L的嘧菌酯的治疗作用优于其他4种杀菌剂。因此,供试的5种杀菌剂中嘧菌酯最适合用于烟草立枯病的防治。     

内吸杀菌剂拌种灵防治棉苗立枯病、炭疽病的研究

本文是报道内吸杀菌剂拌种灵(2—氨基—4—甲基—5—甲酰苯胺基噻唑)及其复配剂拌种双(拌种灵+福美双)对棉苗立枯病、炭疽病的防治效果的研究。通过室内活性测定及田间试验,证明拌种灵对立枯病具有相当或略高于常用药剂五赛合剂(五氯硝基苯+赛力散)、稻脚青(甲基砷酸锌)的效果,而拌种双除保持了对立枯病与拌种灵相当的效果外,对炭疽病的防效与五赛合剂相近,略低于稻脚青。使用拌种灵或拌种双的棉籽发芽率近于未处理的对照,后期长势良好。拌种灵对立枯病效果优于拌种双,而拌种双对炭疽病效果优于拌种灵。     

哈茨木霉Thga1基因敲除突变株对几种植物病原真菌的离体拮抗作用

Thga1是哈茨木霉Th-33的1种I型G蛋白α亚基基因(GenBank JN874387)。本文针对前期研究获得的2株基因Thga1敲除突变株ΔThga1 1-1和ΔThga1 10-1,通过平皿对峙培养分析其对立枯丝核菌、辣椒疫霉菌和尖孢镰刀菌的拮抗作用,研究了突变株产生的挥发性代谢物和非挥发性代谢物对上述3种病原菌生长的影响和对立枯丝核菌的重寄生作用的光学显微镜观察。结果表明,与野生型Th-33相比,基因敲除突变株ΔThga1 1-1和ΔThga1 10-1对病原菌的拮抗作用显著下降,不能对3种病原菌菌落进行覆盖和寄生;突变株产生的挥发性代谢产物对病原菌生长的抑制率显著低于野生菌Th-33,2株突变株对立枯丝核菌、辣椒疫霉和尖孢镰刀菌生长的抑制率分别降低了50%~57%、43%~58%和58%~63%,且突变株之间差异不显著;突变株产生的非挥发性代谢产物对病原菌生长的抑制作用中,除突变株ΔThga1 1-1对立枯丝核菌的抑制作用与野生菌相比差异不显著外,均显著低于野生菌Th-33,突变株ΔThga1 1-1和ΔThga110-1对3种病原菌的抑制率分别降低了8%~25%、23%~56%和38%~50%。显微观察发现,野生菌Th-33菌丝能够缠绕、附着、穿透和裂解立枯丝核菌菌丝,但突变株菌丝对立枯丝核菌菌丝没有发现类似作用。上述结果表明,Thga1基因影响了哈茨木霉菌的拮抗、次级代谢和重寄生等作用。     

新疆棉花立枯病根际拮抗放线菌的筛选

从采集的新疆棉苗根际土样中经分离、纯化获得优势放线菌菌株95个,采用平板对峙培养法对立枯丝核菌(Rhizoctonia solani)进行根际拮抗放线菌的筛选。结果表明,共获得根际拮抗放线菌菌株22株,其中菌株M-1抑菌谱广,抑菌活性强,热稳定性较好,是一株具有良好应用潜力的防治棉花立枯病的生防菌。     

根际微生物对蔬菜苗期立枯丝核菌的生物防治作用

立枯丝核菌Rhizoctonia solani是一种严重为害农作物的土传病原菌。它在上海地区引起蔬菜,尤其茄果类蔬菜苗期的严重死亡,一般死亡率为15％—20％,严重者达70％以上。近十多年来,国内外学者相继开展该菌的生物防治研究工作。并已筛选到对该菌有生物防治作用的拮抗微生物,诸如:Bacillus subtilis、Trichoderma harzianum、Laetisaria arvalis等。作者初步研究了土壤中根际微生物对蔬菜苗期立枯丝核菌的生物防治作用。     

25%噻虫·咯菌腈·精甲霜灵悬浮种衣剂防治棉花苗期病虫害药效试验

试验表明,试验药剂25%噻虫·咯菌腈·精甲霜灵悬浮种衣剂对棉花立枯、猝倒病及蚜虫的防效较好。在棉籽播前施药拌种基本能控制棉花苗期立枯病、猝倒病及蚜虫的为害,其内吸性较好,持效期较长。供试药剂在试验剂量范围内对作物生长无明显影响,是防治棉花苗期立枯病、猝倒病及蚜虫较理想的药剂。     

Effect of Seed Quality and Combination Fungicide-Trichoderma spp. Seed Treatments on Pre- and Postemergence Damping-Off in Cotton

ABSTRACT Good quality seeds of cotton cultivars often escaped pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae, and they were resistant to postemergence damping-off incited by Rhizoctonia solani. Poor quality seeds, however, were highly susceptible to both phases of seedling disease and required seed treatment in order to survive. Pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae could be controlled by seed treatment with biocontrol preparations of a number of Trichoderma spp., but these treatments were much less effective in controlling postemergence disease incited by Rhizoctonia solani. Postemergence seedling disease can be controlled by fungicides, but they were much less effective in controlling the pre-emergence phase of the disease. Combination seed treatments of poor quality cotton seeds with fungicides and Trichoderma spp. preparations, followed by planting in pathogen-infested soil, indicated that this technique will control both phases of seedling disease. Seed treatment with either the fungicides or the biocontrol agents alone did not achieve this goal. The optimum combination treatment for disease control was that of chloroneb plus Trichoderma spp., followed by chloroneb plus metalaxyl (Deltacoat AD) plus T. virens strain G-6.     

Cotton Seedling Preemergence Damping-Off Incited by Rhizopus oryzae and Pythium spp. and Its Biological Control with Trichoderma spp

ABSTRACT Planting the cotton cv. Sure-Grow 747 in cotton seedling disease plots during the 2001 growing season resulted in high levels of preemergence damping-off among the seedlings. Four cotton pathogens, Pythium aphanidermatum, P. ultimum, an unidentified Pythium sp., and Rhizopus oryzae, were isolated from diseased seed embryos and seedlings. Disease incited by the Pythium spp. could be controlled by seed treatment with Metalaxyl, but disease incited by R. oryzae could not. Seed treatment with Metalaxyl in naturally infested field soil was only partially effective; therefore, symptoms in 47% of the diseased seedlings could be attributed to R. oryzae. Susceptibility to disease appeared to be related to release in the spermosphere, by the germinating seeds, of compounds that stimulate pathogen propagule germination, because exudates from seed of the suscept Sure-Grow 747 and extracts from wheat bran induced pathogen germination and growth, whereas exudates from resistant cv. Stoneville 213 did not. However, even Stoneville 213 became susceptible when infested soil was amended with wheat bran. Seed treatment with preparations of Trichoderma virens parent, mutant, and hybrid strains gave effective biological control of preemergence damping-off. Disease control was attributable to metabolism by the biocontrol agent of pathogen germination stimulants released by the seed, because amendment of pathogen-infested soil with the propagule germination stimulants in wheat bran negated the protective effect of the seed treatment.     

Selection of bacterial antagonists for the biological control of Rhizoctonia solani in oilseed rape (Brassica napus)

Spore-forming bacteria isolated from oilseed rape (OSR) roots were tested for biological control activity against Rhizoctonia solani damping-off of OSR, using a simple slurry coat formulation. From a total of 239 strains which were tested, Bacillus subtilis 205 was selected as the most promising biocontrol agent (BCA). A known isolate of B. subtilis (NCIMB 12376), which had previously shown activity against R. solani in cotton, was used as a standard comparison throughout. In an in vivo screening, pre-emergence damping-off disease control by B. subtilis 205 was excellent, with plant stands being almost as high as non-diseased controls. However, post-emergence survival was less good, although the surviving plants exhibited significantly reduced hypocotyl rot. Growth-room trials which assessed the effect of ambient temperature on the biological control efficacy of B. subtilis strains 12376 and 205 showed that isolate 205 was more effective at lower temperatures. Disease control by isolate 205 at 15°C/10°C (day/night) suggests that this bacterium could operate under autumn sowing field conditions. Further investigations also indicated that the addition of iron (III) to the BCA formulation may enhance disease control by both bacilli. The potential of bacterial BCAs for the control of seedling diseases is discussed.     

Induction of Terpenoid Synthesis in Cotton Roots and Control of Rhizoctonia solani by Seed Treatment with Trichoderma virens

ABSTRACT Research on the mechanisms employed by the biocontrol agent Trichoderma virens to suppress cotton (Gossypium hirsutum) seedling disease incited by Rhizoctonia solani has shown that mycoparasitism and antibiotic production are not major contributors to successful biological control. In this study, we examined the possibility that seed treatment with T. virens stimulates defense responses, as indicated by the synthesis of terpenoids in cotton roots. We also examined the role of these terpenoid compounds in disease control. Analysis of extracts of cotton roots and hypocotyls grown from T. virens-treated seed showed that terpenoid synthesis and peroxidase activity were increased in the roots of treated plants, but not in the hypocotyls of these plants or in the untreated controls. Bioassay of the terpenoids for toxicity to R. solani showed that the pathway intermediates desoxyhemigossypol (dHG) and hemigossypol (HG) were strongly inhibitory to the pathogen, while the final product gossypol (G) was toxic only at a much higher concentration. Strains of T. virens and T. koningii were much more resistant to HG than was R. solani, and they thoroughly colonized the cotton roots. A comparison of biocontrol efficacy and induction of terpenoid synthesis in cotton roots by strains of T. virens, T. koningii, T. harzianum, and protoplast fusants indicated that there was a strong correlation (+0.89) between these two phenomena. It, therefore, appears that induction of defense response, particularly terpenoid synthesis, in cotton roots by T. virens may be an important mechanism in the biological control by this fungus of R. solani-incited cotton seedling disease.     

Suppression of Seedling Damping-Off Caused by Pythium ultimum, P. irregulare, and Rhizoctonia solani in Container Media Amended with a Diverse Range of Pacific Northwest Compost Sources

ABSTRACT Suppression of seedling damping-off disease caused by Pythium spp. and Rhizoctonia solani is a potential benefit of formulating soilless container media with compost. Thirty-six compost samples from Pacific Northwest commercial composting facilities were analyzed for a number of physical, chemical, and biological properties, including suppression of damping-off caused by Pythium ultimum, P. irregulare, and R. solani. The samples were produced from diverse feedstocks and composting technol ogies; this was reflected in a large degree of variability in the measured properties. When mixed with sphagnum peat moss and inorganic aggregates, 67% of the compost samples significantly suppressed P. irregulare damping-off of cucumber, 64% suppressed P. ultimum damping-off of cucumber, and 17% suppressed damping-off of cabbage caused by R. solani. Suppression of Pythium damping-off was related to the potential of compost to support microbial activity and a qualitative index of ammonia volatilization. Suppression of Rhizoctonia damping-off was not related to any one compost factor. Currently available compost products potentially could provide commercially acceptable control of damping-off caused by Pythium spp., but it is necessary to fortify composts with microbial antagonists for the control of R. solani.     

拌种防治玉米二点委夜蛾的药剂筛选及其安全性研究

为了筛选拌种防治二点委夜蛾的有效药剂,并明确其对玉米种子萌发的安全性。本文通过培养皿法和室内盆栽试验比较了9种不同类型杀虫剂拌种对玉米种子萌发的影响以及保苗效果。结果表明,60%溴氰虫酰胺SC和20%氯虫苯甲酰胺SC拌种处理效果较好,保苗效果分别达到90.02%和70.07%,可将死苗率控制在10%以内,被害指数控制在20%以内,且对玉米出苗安全。因此,60%溴氰虫酰胺SC和20%氯虫苯甲酰胺SC可作为拌种防止玉米二点委夜蛾为害的有效药剂。     

Biological control of Pythium ultimum–induced damping-off by treating cress seed with the mycoparasite Pythium oligandrum

Incorporation of the aggressive mycoparasite Pythium oligandrum into a carboxymethyl cellulose-based seed coating decreased damping-off of cress seedlings by Pythium ultimum in both naturally infested soil and artificially infested sand. This effect is attributed to the germination of P. oligandrum oospores on the seed surface with subsequent generation of a protectant mycelium around the seedling.
P. oligandrum oospores survived storage periods of 10—20 weeks at zero relative humidity both on glass slides and within seed coatings. The mycoparasite also survived an 18–month burial in natural soil, probably in the form of oospores.
The implications of these observations for biocontrol of seedling diseases by P. oligandrum are discussed.     

微生物菌剂拌种对花生土传病害的防治效果及产量影响

为探索微生物菌剂拌种防治花生根部病害的防治效果及对产量的影响,以鲁花8号为试验材料,选择3个微生物菌制剂和1个化学药剂,设置1000亿CFU/mL解淀粉芽胞杆菌、200亿CFU/mL多粘类芽胞杆菌、1亿CFU/g真菌生防菌（TB）、1000亿CFU/mL解淀粉芽胞杆菌+1亿CFU/g真菌生防菌（TB）、200亿CFU/mL多粘类芽胞杆菌+1亿CFU/g真菌生防菌（TB）和25%咯菌腈拌种处理进行田间药效试验。结果表明： 6种供试药剂拌种处理均对花生有一定的增产作用,且对根腐病和白绢病均有一定的控制效果,其中1000亿CFU/mL解淀粉芽胞杆菌+1亿CFU/g真菌生防菌（TB）种子处理的出苗率、增产率和综合防效最高,其出苗率和增产率分别为94.35%和23.15%;出苗30 d后根腐病防效为76.95%,出苗60 d后根腐病和白绢病防效分别为83.54%和83.88%,在绿色防控技术推广应用中具有良好的应用前景。     

邻烯丙基苯酚处理黄瓜种子控制土传腐霉菌和丝核菌侵染危害秧苗的效果

采用ISTA滤纸法检测得出:20%邻烯丙基苯酚悬浮种衣剂按1∶ 30~1∶ 90药种比(质量比)包衣处理"中农8号"和"长春密刺"黄瓜品种的种子,对黄瓜种子安全,种子发芽率分别达到95.75%~97.75%和80.00%~84.25%;PDA平板上检测药剂包衣处理对黄瓜种子带菌消毒效果显示,消毒处理效果达到66.67%~100%。菌丝生长速率法和染色处理结合显微技术实验证实,邻烯丙基苯酚对危害黄瓜秧苗的土传病原菌腐霉病菌Pythium aphanidermatum和立枯丝核菌Rhizoctonia solani具有较强的抑制作用,EC50值分别为27.59和34.16 μg/mL;药剂处理使供试病菌的菌丝发生中空、解体断裂等异常现象。20%邻烯丙基苯酚悬浮种衣剂1∶ 30~1∶ 90包衣处理黄瓜种子后接种供试病菌,对腐霉病菌和立枯丝核菌的防病效果分别达到73.31%~100%和85.16％~100%;随着药剂包衣处理浓度的增大,邻烯丙基苯酚防治两种病原菌侵染危害黄瓜秧苗的效果提高,等效或者优于常规药剂福美双种子处理。