青花菜根肿病苗期抗性鉴定技术的建立

为建立快速、有效的青花菜根肿病苗期抗性鉴定技术,将芸薹根肿菌Plamodiophora brassicae Woron.人工接种于高感根肿病青花菜自交系90196,研究了接种菌液浓度、接种寄主苗龄、接种基质p H和接种方法等对人工接种鉴定效果的影响。结果表明,在一定范围内,根肿病发病率及病情指数随着接种菌液浓度的升高而增大,接种菌液浓度为3×108CFU/m L时,发病率及病情指数分别为97.22%和86.11,可以反映寄主真实的抗性水平;接种寄主苗龄为2~6叶期均能使植株发病,但2~3叶期发病效果最佳;接种基质偏酸性(p H 5~6)有利于根肿病的发生;使用伤根灌菌法进行鉴定,青花菜根肿病发病率和病情指数均最高,分别为100.00%和88.10,优于蘸根法和浸芽法。用已知抗性水平的12个自交系和8个杂交种进行验证,鉴定结果表明该苗期抗性鉴定技术可客观反映供试材料的实际抗性水平。     

土壤pH对芸薹根肿菌侵染及病害发生的影响

通过设置不同pH梯度,研究土壤pH对根肿菌侵染及病害发生的影响。结果表明:土壤酸性时病菌侵染速度快,碱性时慢,而强酸性和碱性土壤条件则抑制孢子萌发;pH为6.0时最有利于根肿菌休眠孢子萌发,萌发率最高,为53.96%;碱性条件可使初级原生质团变形凝结成球状,不能正常分裂或延迟形成游动孢子囊,从而不利于根肿菌侵染。白菜发病率与病情指数随pH升高,呈先上升后下降趋势。其中,pH为5.0时,发病率和病情指数最高,pH 7.0~8.0时发病轻。因此,适宜的偏酸性环境条件下,通过作用于病菌休眠孢子萌发和侵染,提高病害危害程度,而中性或碱性条件干扰该过程并降低病害发生。     

植保抗生素阿扎霉素对白菜根肿病的防治效果

采用盆栽试验和田间试验相结合的方法,测定了12.5%阿扎霉素水剂不同质量浓度对白菜根肿病的防治效果。试验结果表明:采用12.5%阿扎霉素水剂500~1 000倍,在大白菜播种后5d第一次用药,之后每间隔7d施药1次,共施药3次,温室盆栽试验最高防治效果为87.58%,田间试验最高防治效果为80.62%,其与对照药剂500g/L氟啶胺悬浮剂的防治效果间差异显著。植保抗生素12.5%阿扎霉素水剂对白菜根肿病具有较好的防治效果,具备开发成防治根肿病新型杀菌剂的潜力。     

江西油菜根肿菌生理小种鉴定及品种抗病性鉴定

油菜根肿病在江西省多市均有分布, 尤以上饶婺源、吉安永新、九江瑞昌等地发生严重。为明确江西省油菜主产区根肿菌的生理小种, 采用SCD鉴定系统对江西油菜主产区根肿菌进行了生理小种鉴定, 结果共鉴定出3个生理小种类型:Pb1、Pb5和Pb12。为筛选出适于江西根肿病发病地区种植的油菜材料, 开展了油菜材料对根肿菌的抗性测定。室内盆栽抗性测定表明, 育种中间材料‘P360429001’‘2018362481’‘P360924009’‘P360281040’‘中油杂12’‘华油杂62R’和‘华双5R’的病情指数均低于或等于30.00, 其中‘华油杂62R’和‘华双5R’表现为中抗水平。田间抗性测定结果表明, ‘华油杂62R’‘秦优DK4’‘阳光50’和育种中间材料‘P360429001’‘ZS115R’的根肿病病情指数均低于30.00, 但只有‘华油杂62R’对Pb1生理小种表现出中抗水平。本研究针对性地筛选出适于江西油菜根肿病发病地区种植的油菜材料, 对江西油菜根肿病的防控和创制抗病性油菜资源提供了科学依据。     

防治白菜根肿病的药剂筛选

分别采用拌药法和灌药法,比较了10种供试药剂对白菜根肿病的温室防治效果,并对盆栽试验防效较好的3种药剂进行了田间药效试验。结果表明,在温室条件下,50%氟啶胺悬浮剂(1 g/m3)、50%甲基硫菌灵可湿性粉剂(25 g/m3)、70%代森锰锌可湿性粉剂(35 g/m3)和40%五氯硝基苯粉剂(20 g/m3)的拌药处理,对白菜根肿病的防效均在50%以上,显著优于灌药处理的防效。田间药效试验结果表明,50%氟啶胺悬浮剂(2 g/m3)拌药处理的防效在80%以上,与盆栽药效试验结果一致,并显著优于其他药剂处理。     

陆川县白菜根肿病发生原因分析及其防治

农业产业结构调整后,陆川县蔬菜种植面积不断扩大,尤其是无公害蔬菜生产得到认证后,蔬菜种植面积发展迅猛,导致重茬,造成病害严重发生。目前白菜根肿病在该县已上升为主要病害,给广大菜农造成了重大的经济损失,严重影响了农民种植白菜的积极性。     

一株多黏类芽胞杆菌 Paenibacillus polymyxa 菌株P1防治广东菜心根肿病的研究

芸薹根肿病是一种危害极大的世界性病害。对此病害的防治多采用化学药剂,但过多地使用化学农药,不仅会导致病原菌的抗药性和药剂防效的不稳定,还会造成环境污染和食品安全等问题。筛选生防菌株并将其开发成有效的生物农药,是防治根肿病并保持绿色农业可持续发展的新途径。本研究选用了多种生防菌对芸薹根肿菌Plasmodiophora brassicae Woron.的休眠孢子进行拮抗测试,筛选出一株能抑制P.brassicae休眠孢子萌发的多黏类芽胞杆菌Paenibacillus polymyxa菌株P1。通过液体发酵和剂型处理,将P1制成悬浮剂(P1-SC),用于室内生测和大田试验,测定其对广东菜心根肿病的防治效果。盆栽试验结果表明,对菜心根肿病的防治效果与所使用的P1-SC浓度呈正相关,当施用P1-SC中P1的浓度≥1×10~6 cfu/mL时,对菜心根肿病的防治效果(83.0%)与化学农药氟啶胺(500 mg/L)的防治效果(100.0%)没有显著性差异,但显著高于(P≤0.05)一种商品枯草芽孢杆菌(2×10~7 cfu/mL)的防治效果(29.8%)。2018年的大田试验结果表明,P1-SC处...     

芸薹根肿菌次生游动孢子侵染致病分析

为明确芸薹根肿菌Plasmodiophora brassicae Woron.在其它寄主中是否广泛存在无性短循环及次生游动孢子的侵染致病性,以不结球白菜为寄主培养3批幼苗(G1、G2和G3),用休眠孢子悬浮液接种G1,被侵染的G1接种G2,被侵染的G2接种G3,采用离心管水培法研究其侵染致病性。结果显示,无性短循环研究中,G1、G2和G3根毛均被侵染,除G3并株接种侵染率为33.33%外,其它处理侵染率均在50.00%以上,根毛里有明显的游动孢子囊;次生游动孢子能侵染不结球白菜的皮层组织,致使不结球白菜发病形成明显的肿根;G1、G2和G3水培发病率为20.00%、15.00%和6.00%,砂培发病率为22.50%、18.75%和7.50%;G3肿根病理切片中可观察到休眠孢子。表明芸薹根肿菌侵染不结球白菜时,其生活史中存在无性短循环,次生游动孢子具有侵染致病作用。     

土壤中芸薹根肿菌qPCR检测与风险预警体系的建立与应用

 建立了土壤中芸薹根肿菌荧光定量PCR(qPCR)快速检测及风险预警体系。确定了芸薹根肿菌qPCR检测的特异性引物PbF/PbR,对根肿菌质粒DNA的检测灵敏度为1.612×10^-6 ng·μL^-1,比普通PCR高出1 000倍;对土壤和基质中芸薹根肿菌孢子的最低检测下限均为10 个·g^-1,而土壤和基质带菌的发病阈值分别为100和1 000 个·g^-1,高于该浓度时根肿病发生风险大。本研究建立的芸薹根肿菌qPCR技术体系检测下限远低于发病阈值,可以快速、准确、定量地检测出采自四川绵阳、湖北恩施、江苏无锡、山东青岛、辽宁沈阳、山西运城、内蒙古巴彦淖尔和宁夏固原等8个地区的27份田间土壤中芸薹根肿菌的数量,实现对十字花科根肿病的监测预警,为制定产前病害防控方案提供依据。     

不同杀菌剂对油菜根肿病的防效及对油菜产量损失的影响

本研究使用5种杀菌剂和1种微肥于油菜苗期2~3片真叶期进行灌根处理,以传统的石灰处理方法比较,评价不同处理对油菜根肿病的防治效果和对油菜产量损失的影响。5种杀菌剂处理、微肥以及石灰处理均对油菜根肿病有较好的防效,其中50%多菌灵可湿性粉剂防效达90.82%;从产量损失方面比较,10%氰霜唑悬浮剂、50%多菌灵可湿性粉剂,75%百菌清可湿性粉剂和60%硫磺·敌磺钠可湿性粉剂处理可显著减少根肿病引起的产量损失;50%氟啶胺悬浮剂处理较对照增产不显著,而且对油菜生长有抑制作用;油菜根肿病的病情指数与油菜产量呈显著的负相关性,相关系数r=-0.796 2,油菜产量(y)与病情指数(x)的回归方程为y=-32.65x+2 372。     

Effects of cyazofamid against Plasmodiophora brassicae Woronin on Chinese cabbage

Cyazofamid (4-chloro-2-cyano-N,N-dimethyl-5-p-tolylimidazole-1-sulfonamide) is a novel fungicide with high levels of activity against Oomycetes fungi and Plasmodiophora brassicae Woronin. The effects of cyazofamid were investigated against P. brassicae, the causal agent of clubroot disease in Chinese cabbage. Cyazofamid at 0.3 mg litre(-1) inhibited resting spore germination of this pathogen by about 80%. Cyazofamid at 3-10 mg litre(-1) exhibited fungicidal activity to resting spores of P. brassicae 1-10 days after treatment. When cyazofamid was applied to infested soil, both root-hair infections and club formation caused by P. brassicae were strongly inhibited at 1-3 mg kg(-1) dry soil. These results suggest that cyazofamid directly inhibits resting spore germination, thereby leading to the inhibition of root-hair infection and club formation. Cyazofamid at 3 mg kg(-1) dry soil also exhibited complete control of clubroot disease. The effect of broadcast soil application using a dust formulation at 2 kg AI ha(-1) (equivalent to 1.3 mg AI kg(-1) dry soil), and plug seedling tray application by a suspension concentrate formulation at 200 and 400 mg AI tray(-1) (30 x 60 x 4 cm3) against P. brassicae was also evaluated. Cyazofamid exhibited good efficacy against the pathogen. The sequential treatment including plug seedling tray application with cyazofamid and pre-plant broadcast soil application with the fungicide fluazinam also exhibited excellent levels of control. These results indicate that cyazofamid has a high potential to be an effective fungicide for the control of clubroot disease.     

Growth and movement of secondary plasmodia of Plasmodiophora brassicae in turnip suspension-culture cells

Growth of secondary plasmodia of the clubroot pathogen Plasmodiophora brassicae was studied in dual culture of P. brassicae and turnip suspension cells. Suspension culture of P. brassicae -infected turnip cells was achieved by using P. brassicae -infected callus in Murashige and Skoog medium supplemented with 0·1 mg 2,4-D L⁻¹ and 0·02 mg kinetin L⁻¹. The shape of secondary plasmodia in suspension cells was spherical-to-subspherical. A few young plasmodia divided and became numerous spherical, small plasmodia which eventually formed a plasmodial cluster. The plasmodia fused and became vegetative plasmodia. Infected cells were significantly larger than noninfected cells. Secondary plasmodia moved within transformed turnip suspension host cells by cytoplasmic streaming of the host cells. Secondary plasmodia divided in synchrony with the transformed turnip cells.     

百菌清防治大白菜根肿病应用技术研究

直播大白菜于播种后即用百菌清1000倍液每穴300mL药液淋施．移栽大白菜于移栽时即用百菌清1000倍液每株300mL药液灌根1次．2种防治技术均对根肿病有显著的控病保产效果，对大白菜根肿病根瘤的抑制率分别达86．2％和71．7％。     

Plasmodiophora brassicae resting spore dynamics in clubroot resistant canola (Brassica napus) cropping systems

The soilborne pathogen Plasmodiophora brassicae, causal agent of clubroot of canola (Brassica napus), is difficult to manage due to the longevity of its resting spores, ability to produce large amounts of inoculum, and the lack of effective fungicides. The cropping of clubroot resistant (CR) canola cultivars is one of the few effective strategies for clubroot management. This study evaluated the impact of the cultivation of CR canola on P. brassicae resting spore concentrations in commercial cropping systems in Alberta, Canada. Soil was sampled pre-seeding and post-harvest at multiple georeferenced locations within 17 P. brassicae-infested fields over periods of up to 4 years in length. Resting spore concentrations were measured by quantitative PCR analysis, with a subset of samples also evaluated in greenhouse bioassays with a susceptible host. The cultivation of CR canola in soil with quantifiable levels of P. brassicae DNA resulted in increased inoculum loads. There was a notable lag in the release of inoculum after harvest, and quantifiable P. brassicae inoculum peaked in the year following cultivation of CR canola. Rotations that included a ≥2-year break from P. brassicae hosts resulted in significant declines in soil resting spore concentrations. A strong positive relationship was found between the bioassays and qPCR-based estimates of soil infestation. Results suggest that CR canola should not be used to reduce soil inoculum loads, and crop rotations in P. brassicae infested fields should include breaks of at least 2 years away from B. napus, otherwise the risk of selecting for virulent pathotypes may increase.     

Reduction of Spore Density of Plasmodiophora brassicae in Soil by Decoy Plants

The severity of clubroot (Plasmodiophora brassicae) on Chinese cabbage was reduced by growing plants such as oats, spinach and leafy daikon prior to Chinese cabbage in pot experiments. Resting spore densities of P. brassicae in the soil were 29–62%, depending on the pervious crop, as compared to unplanted control plot after ploughing under the previously cultivated plants. Root hairs of the preceding plants were infected with P. brassicae, but clubbed roots were not formed on these plants. The results indicate that these plants functioned as decoy plants reducing the resting-spore density in soil and thereby suppressing disease severity. Received 21 February 2000/ Accepted in revised form 5 September 2000     

Influence of cultivar resistance and inoculum density on root hair infection of canola (Brassica napus) by Plasmodiophora brassicae

The impact of cultivar resistance and inoculum density on the incidence of primary infection of canola root hairs by Plasmodiophora brassicae, the causal agent of clubroot, was assessed by microscopy. The incidence of root hair infection in both a resistant and a susceptible cultivar increased with increasing inoculum density, but was two‐ to threefold higher in the susceptible cultivar; the relationship between root hair infection and inoculum density was also substantially stronger and more consistent in the susceptible cultivar. In the susceptible cultivar, the root hair infection rate peaked between 6 and 8 days after sowing and then declined. In the resistant cultivar, it increased over the 14‐day duration of each study. It appears that examination of root hair infection by microscopy in a bait crop of susceptible canola could serve as a useful tool for estimating P. brassicae inoculum levels in soil. In a separate trial, the relationship between inoculum density and clubroot severity, plant growth parameters, and seed yield was assessed under greenhouse conditions. Inoculum density in the susceptible genotype was strongly and positively correlated with clubroot severity and negatively correlated with plant height and seed yield. In addition, a single cropping cycle of the susceptible cultivar contributed significantly higher levels of resting spores to the soil in a greenhouse test than did a cycle of the resistant cultivar, as assessed by quantitative PCR and microscope analysis.