小麦矮化腥黑穗病菌侵染能力的研究

中美专家合作在美国犹他州对小麦矮化腥黑穗病菌的侵染能力进行了研究。试验采用不含抗病基因的小麦品种Cheyanne,播种前用溴甲烷对试验小区进行了熏蒸。接种物为含有多种致病型的冬孢子悬浮液,采用土壤表面喷洒冬孢子悬浮液的方法进行接种,接种密度为每cm20、0.88、8.84、88.45、884.49、8844.89、88449个孢子。结果表明,接种密度为每cm20.88个孢子时即可产生0.21％的穗发病率。对试验数据进行分析后表明,小麦矮化腥黑穗病菌的侵染规律符合侵染概率理论,在本试验条件下,单个孢子的侵染概率为0.0002。     

稻曲病种子传病的研究

据前人报道,稻曲病粒上附有大量厚垣孢子但不能作为初侵染源,并证明该病既不是种子引起的病害,也不是种子侵染而发生的病害,认为目前推广种子处理缺乏科学根据。本研究结果表明:从种子带菌量、越冬厚垣孢子萌发力、人工接种、直接播种试验,初步认为病穗种子是可以传病的,种子消毒仍有必要。     

玉米穗粒腐病接种技术研究

用带菌牙签插入果穗、孢子悬浮液注射和喷雾３种接种方法和不同接种时期的比较试验，明确３种接种方法部能使玉米穗期发生穗粒腐病，但发病率和病指以牙签法适中，品种和年度间差异不明显，操作简便；注射法发病率和病指较高，但操作复杂，费时费工；喷雾法发病不完全，病指低，费工并要保湿。接种越早，发病率和病指越高，以吐丝期和灌浆初期更为适宜。     

葡萄白粉病抗性鉴定方法优化及品种抗性评价

本研究通过对叶盘保湿方法的改进,不同菌源接种后发病严重度的分析,抗、感病对照品种的确定,建立了一种更为便捷、可靠、稳定的葡萄白粉病室内抗性鉴定方法:取葡萄藤自上而下第2～4片幼嫩叶片,打取直径15 mm的叶盘置于1.5％水琼脂平板进行保湿,采集田间菌源直接制备孢子浓度为2×105个/mL的孢子悬浮液接种,选定抗、感病葡...     

向日葵菌核病接种方法及品种抗病性鉴定

为建立有效的向日葵菌核病田间接种鉴定方法,以核盘菌菌丝体悬浮液和孢子悬浮液作为接种物,分别对抗、感向日葵品种在现蕾期、始花期和盛花期进行人工接种,并对接种后保湿材料和保湿时间进行比较。试验结果表明:两种接种物均可使向日葵抗、感品种产生盘腐症状。用菌丝体悬浮液和孢子悬浮液接种时,浓度分别为10.0~15.0g/L和200~500个/mL,始花期接种,牛皮纸袋保湿2~4d,即可区分出向日葵品种间抗感性差异。用此方法鉴定出13个对盘腐型菌核病表现抗病的向日葵品种。     

禾谷多粘菌分离、培养、接种及用于大麦抗黄花叶病的鉴定

 通过禾谷多粘菌Polymyxa graminis L.休眠孢子分离接种感病大麦品种,并进行砂培养,获得13个纯化了的禾谷多粘菌分离物,且其中3个带有大麦黄花叶病毒(BaYMV)。用分别带有BaYMV和大麦温和花叶病毒(BMMV)的英国禾谷多粘菌分离物的游动孢子接种13个中国大麦品种,以及用BaMMV摩擦接种36个中外大麦品种,抗性鉴定结果游动孢子接种与摩擦接种一样,均与田间鉴定结果一致,且大麦对BaYMV的抗性与对BaMMV的抗性一致,从而这2种接种方法可用于大麦品种(系)和育种中间体对BaYMV抗性的快速鉴定和筛选。游动孢子或休眠孢子接种方法还可有效地鉴定大麦对禾谷多粘菌的抗性。     

小麦条锈孢子悬浮液保存时间与接种效果

小麦锈菌人工接种是育种家培育抗锈品种的手段之一。多采用夏孢子悬浮液注射或喷雾的方法。为提高接种效果一般在下午进行。这就要求在约3—4小时内接种大量试验,为合理使用孢子悬浮液作者于1988年1—2月在温室对条锈孢子悬浮液不同保存时间的接种效果进行了试验分析。     

玉米丝黑穗病菌侵染条件与栽培防病措施的研究

玉米丝黑穗病菌侵染寄主的适宜土壤温度范围为20～30℃,最高限点为35℃,最低为10℃左右。播种期与发病关系决定于种子发芽、幼苗生长速度与病菌侵染机会的多少。在吉林省的气象条件下,适期播种发病率高,早播和晚播的病株率较低。催芽播种和育苗移栽能减轻为害。种子带菌虽可传病,但侵染率不高。土壤带菌是主要传病途径。厚垣孢子在土壤中可存活三年。土壤微生物的拮抗作用是病菌丧失致病力的原因之一。此外,植物幼芽与幼根的渗出物促进厚垣孢子萌发,如遇不到寄主则丧失生命力。实行三年以上轮作及连续拔除病株是有效的栽培防病措施。     

拟粗壮螺旋线虫对棉花的致病力及其与棉枯萎病的复合症

 温室测定结果:拟粗壮螺旋线虫(Helicotylenchus pseudorobusius)接种量在每100cm³土壤100~1000条的条件下,接种30天后棉苗生长量比无线虫对照苗显著降低(P<0.05)。抗枯萎品种86-1在单接枯萎菌无线虫处理中不发生枯萎病,在枯萎菌(Fusarium oxysporum f. sp. vasinfectum)接种量为每克土7.5×10⁵孢子和线虫(每100cm³±500~1000条)组合处理中发病,棉苗枯萎病情指数与线虫接种量之间呈正相关(γ=0.97)。田间试验结果表明:防治线虫和枯萎病复合症用薰蒸剂棉隆每m²8~14g处理土壤比用非薰蒸性杀线虫剂克百威(呋哺丹),丙线磷(益收宝)和克线磷的效果更好。     

玉米穗粒腐病接种技术及品种抗病性鉴定

以玉米穗粒腐病的优势病原菌串珠镰刀菌Fusarium moniliforme为接种菌源,采用4种接种方法进行比较,以针刺果穗较深处(籽粒与穗轴间)发病最重,花丝喷雾法发病最轻;接种时期以玉米乳熟期接种为好;接种浓度10×40倍下每视野60个分生孢子;接种量以每果穗接种2.5ml孢子悬浮液发病最重。同时规范了病情分级标准及品种抗、感程度划分标准。采用规范程序,对63份玉米自交系及杂交种进行了抗病性鉴定。     

Dendrobiumorchids contain an inducer ofAgrobacteriumvirulence genes

SuccessfulAgrobacterium-mediated transformation of monocots such as orchids hinges on the induction of virulence(vir)genes in the bacterium, an event that is required for the activation of the T-DNA processing and transfer pathway. In dicots, several plant phenolic compounds, for example acetosyringone, coumaryl alcohol and sinapyl alcohol, are knownvirgene inducers, but in monocots their presence and characteristics are not well established. We report herein the presence and identification of coniferyl alcohol as thevirgene inducer in the monocotDendrobium.At an early stage of development as protocorm-like bodies (PLBs), this orchid contains an aryl β-glycoside, similar to coniferin, whose aglycone moiety is coniferyl alcohol. Coniferyl alcohol is elaborated in high amounts from PLBs and its production or stability is enhanced almost six-fold higher when the PLBs were exposed to light than when maintained in the dark. PLBs produced 11-fold more inducer than leaves. These studies show for the first time that orchids, i.e.Dendrobium,exude coniferyl alcohol as avirgene inducer.     

Identification and in planta detection of Pseudomonas syringae pv. tomato using PCR amplification of hrpZPst

A rapid detection method based on PCR amplification of Pseudomonas syringae pv. tomato chromosomal sequences was developed. Primer design was based on the P. syringae DC3000 hrpZ_Pst gene, which maps on a pathogenicity-associated operon of the hrp/hrc pathogenicity island.A 532 bp product corresponding to an internal fragment of hrpZ_Pst was amplified from 50 isolates of P. syringae pv. tomato belonging to a geographically representative collection. The amplification product was also obtained from three coronatine-deficient strains of P. syringae pv. tomato.On the other hand, PCR did not produce any such products from 100 pathogenic and symbiotic bacterial strains of the genera Pseudomonas, Xanthomonas, Erwinia, and Rhizobium and 75 unidentified bacterial saprophytes isolated from tomato plants. The method was tested using leaf and fruit spots from naturally-infected tomato plants and asymptomatic nursery plants and artificially contaminated tomato seeds. The results confirmed the high specificity observed using pure cultures.     

Plant amphipathic proteins delay the hypersensitive response caused by harpinPssandPseudomonas syringaepv.syringae

Harpin_Pssfrom the plant pathogenPseudomonas syringaepv.syringaeis a proteinaceous elicitor that induces a hypersensitive response (HR) in non-host plants. The plant products which recognize harpin_Pssin the triggering of the HR are not yet known. According to the elicitor-receptor model, we hypothesize that an exogenous cell membrane receptor infiltrated into the intercellular space will interfere with the interaction between harpin_Pssand the putative receptor. We demonstrate a plant amphipathic protein (AP1) which can postpone the HR induced by harpin_Pssas well asP. syringaepv.syringae.AP1 was extracted by solubilizing proteins from healthy leaves in the non-polar n-octanol buffer followed by a polar Tris buffer. The amphipathic extracts were then further separated by gel filtration and anion exchange chromatography to obtain highly purified AP1. Similar proteins can be extracted from cotton, tomato, and sweet pepper. The N-terminal amino acid sequence of AP1 is conserved among cotton, tomato, and sweet pepper. The postponement of the harpin_Pss-mediated HR was characterized as a competitive dosage-dependent pattern of AP1. An analysis of the bacterial population development indicates that the effect of AP1 on the postponement of bacteria-mediated HR was attributed to the suppression of bacterial growth during the early stages of the HR. The time course analysis of the infiltration indicates that the postponement of HR resulted from the co-interaction between AP1 and the bacteria. Based on these results, we suggest that the postponement of bacteria-mediated HR is due to the interference of the interaction between harpin_Pssand the putative receptor in the plant. Our research provides a new approach to elucidating the role that plants may play in the nonhost response caused by pathogens.     

Movement of fluometuron, simazine, 36Cl− and 144Ce3+ in soil under field conditions: qualitative aspects

The distributions of two herbicides and two radioactive ions in field plots at two sites were determined at periods up to 187 days following surface applications in the spring. The results demonstrated the variability characteristic of field situations. At one site some fluometuron moved a short distance down the profile but after 187 days most remained above 6 cm whereas at the other site there was essentially no movement below 3 cm. At both sites simazine was almost entirely confined to the top 3 cm. The adsorption characteristics of the two compounds are similar so the greater mobility of fluometuron is probably a consequence of its greater solubility, Measurements of ³⁶Cl^? indicated a significant movement of water through the 30 cm depth studied. ¹⁴⁴Ce³⁺ used as a tracer of soil particles was of similar mobility to simazine. In general the movement of chloride and the two herbicides can be interpreted in terms of the concept of mobile and immobile fractions of soil water in which a proportion of the mobile water does not reach equilibrium with solutes in the bulk of the soil. Soil structural effects may therefore be more important than adsorption in controlling the movement of solutes and redistribution in association with soil particles can be significant. A parallel laboratory experiment showed that the results from a standard leaching column procedure did not necessarily indicate field performance.     

Antagonismusin vitro vonBacillus spp. gegenüberRhizoctonia solani undPythium spp.

Es konnten 132Bacillus-Stämme isoliert und gegenüber7 Rhizoctonia-solani- und 6Pythium-Stämmen auf Antagonismusin vitro untersucht werden. Die gefundenen Antagonisten hemmten die Pilzisolate unterschiedlich stark, so daß Gemische von Antagonisten für die Praxis zu empfehlen sind.There were 132Bacillus-strains isolated and tested for antagonism against 7 strains ofRhizoctonia solani and 6 strains ofPythium spp. The isolated antagonists didn't show a uniform effect against the tested strains ofRhizoctonia solani andPythium spp. For an application in practice it will be better to use a mixture of antagonists.

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