Effects of timing and method of application of Penicillium oxalicum on efficacy and duration of control of Fusarium wilt of tomato

The effects of timing and method of application of Penicillium oxalicum on the control of fusarium wilt of tomato were investigated. Application of P. oxalicum to tomato seedlings in seedbeds reduced disease caused by Fusarium oxysporum f.sp. lycopersici in a growth chamber by 45–49% and in glasshouse experiments by 22–69%. Disease suppression was maintained for 60–100 days after inoculation with the pathogen in the glasshouse. No disease reduction was observed in tomato plants where P. oxalicum was applied to seeds. Treatment with P. oxalicum did not affect the population of F. oxysporum f.sp. lycopersici in the rhizosphere.     

Systems of designation of pathotypes of plant pathogens12

A variety of systems of designation has evolved to name pathotypes of plant pathogens. The systems were evaluated to determine those best suited for particular purposes. Virulence and avirulence/virulence formulae of pathotypes have advantage over the use of consecutive numbers or letters given in chronological order of pathotype discovery. As soon as pathotype information exceeds a certain level of complexity, mathematical codes are most advantageous, in particular two codes, octal notation and coded triplets. A more universal adoption of the most appropriate codes is recommended to ease communication and comparisons of results.     

Localization of metabolic sites of action of herbicides

Time- and concentration-course studies were conducted to determine the effect of thirteen herbicides on photosynthesis, respiration, RNA synthesis, protein synthesis, and lipid synthesis using isolated single leaf cells. Each herbicide was from a different chemical class. Appropriate ¹⁴C-substrates and product purification procedures were used for each process prior to liquid scintillation counting. The most sensitive metabolic site of inhibition was photosynthesis for atrazine, bromacil, dichlobenil, monuron, and paraquat; RNA synthesis for dalapon and dinoseb; protein synthesis for chlorpropham; and lipid synthesis for CDAA, chloramben, 2,4-D, EPTC, and trifluralin. However, with several herbicides, one or more process was almost as sensitive as the one mentioned above. All herbicides inhibited more than one process, and the most sensitive site of inhibition may not be the same process that was inhibited the greatest at the maximum concentration and maximum exposure time used. Therefore, a concept of metabolic sites of action, rather than a primary site of action, appears to be more meaningful for herbicides.     

百合地下害虫主要种类调查及生物（源）农药筛选

调查了甘肃省临洮县为害百合的地下害虫种类, 并以主要发生为害种类为供试对象, 采用拌土法测定了几种生物（源）农药对主要害虫的室内毒力和致死中时。调查发现小云斑鳃金龟Polyphylla gracilicornis、棕色鳃金龟Holotrichia titanis为主要发生及为害种类, 不同时间发生种类存在差异, 9月份以小云斑鳃金龟幼虫发生为害为主, 发生量占地下害虫总数的66.16%, 平均种群密度为10.48头/m2, 10月份, 则以棕色鳃金龟幼虫发生为主, 发生量占地下害虫总数的96.86%, 平均种群密度为7.79头/m2, 主要取食百合根系和鳞茎, 造成根系数量减少, 鳞茎出现不规则褐色缺口或凹陷斑。药剂筛选结果表明, 1.8%阿维菌素乳油、200亿孢子/g球孢白僵菌粉剂对两种蛴螬均具有较高的杀虫活性和速效性, 药后7 d时, 校正死亡率在82.22%以上, 对小云斑鳃金龟幼虫和棕色鳃金龟幼虫的LC50分别为0.161、0.060 mg/g和5.558×107、0.362×107孢子/g, LT50分别为2.237 d（2.2 mg/g）、1.393 d（2.2 mg/g）和6.645 d（40.0×107孢子/g）、4.940 d（2.0×107孢子/g）, 这两种生物（源）农药对两种蛴螬的LC50和LT50值均略大于两种化学农药25%二嗪磷乳油、40%辛硫磷乳油处理的, 且对小云斑鳃金龟幼虫的杀虫活性均低于对棕色鳃金龟幼虫的杀虫活性, 致死中时则长于对棕色鳃金龟幼虫的致死中时。     

Investigation of the Mode of Action of Nematode Neuropeptides

The neuropeptide AF2 has a complex set of actions on the dorsal muscle strip of Ascaris suum, including a potentiation of the acetylcholine-stimulated muscle contraction. Caffeine at 100 μm and 5 mm inhibited this potentiation, as did 100 μm theophylline in two out of six studies. The cyclic-AMP-potentiating compounds IBMX, dibutyryl cAMP and forskolin had no effect on the AF2-induced potentiation of the acetylcholine-stimulated muscle contraction. These preliminary data suggest that the potentiating action of AF2 is not mediated by a cAMP pathway.     

厚朴病虫害种类的初步调查

采用标准地法和线路调查法,对湖北恩施市新塘乡双河厚朴基地的厚朴病虫害进行了系统调查,记录主要虫害13种,其中叶部害虫9种,枝干害虫2种,根部害虫2种。厚朴主要病害5种。藤壶蚧、厚朴枝角叶蜂和厚朴新丽斑蚜为湖北省首次报道,小绿叶蝉为厚朴新寄主记录种。同时记录了藤壶蚧的天敌6种,其中寄生小蜂2种,瓢虫4种;厚朴新丽斑蚜的天敌昆虫8种。对藤壶蚧、厚朴枝角叶蜂和厚朴苗木根腐病等重要病虫害的发生规律进行了初步调查,同时提出了防治建议。     

棉花黄萎病菌致病型的AFLP分析

 选用41个棉花黄萎病菌(Verticillium dahliae)代表菌系,在温室条件下,对4个棉花品种鄂荆1号(感)、中棉所12(耐)、文-5(抗)和唐棉2号(抗)进行致病性测定,结果可将供试菌系分为落叶型与非落叶型2类。选取8对AFLP引物PCR扩增的结果中,统计带型稳定、清晰且有多态性的条带,共169条作系统聚类分析,将上述菌系分为2大类,第一类为非落叶型菌系,包括10个非落叶型菌系和1个过渡菌系;第二类为30个落叶型菌系。根据聚类分析建立树状图,发现菌系与地理来源存在一定的相关性,而依据菌系致病力强弱分类则相关关系不大。选用25对EcoRⅠ和MseⅠ引物组合,对供试的41个V.dahliae进行AFLP扩增,筛选到2对引物E64(GACTGCGTACCAATTCGAC)、M53(GATGAGTCCTGAGTAACCG)和E49(GACTGCGTACCAATTCCAG)、M65(GAT-GAGTCCTGAGTAAGAG),能分别扩增出433bp和110bp2条仅为V.dahliae非落叶型菌系独有的特异片段,可将落叶型与非落叶型菌系分开,这2条特异片段被命名为EM₄₃₃和EM₁₁₀。     

油菜素内酯对三个树种苗木抗旱性影响的综合评价

采用盆栽控水模拟土壤干旱环境,根系浸蘸和叶面喷施不同浓度的油菜素内酯(BR)溶液,对黄土丘陵区3个主要造林树种沙棘(Hippophae rhamnoides L.)、山杏(Prunus armeniaca L. var.ansu)、紫穗槐(Amorpha fruticosa L.)苗木20项抗旱性指标进行了测定,应用主成分分析法对3种苗木受油菜素内酯影响的抗旱性变化做了多指标的综合评价.实验结果显示当BR施用浓度在0.1-0.3 mg/L时,对3种苗木抗旱性影响的有效值均高于对照,其中能够有效提高3种苗木抗旱性的BR最佳施用浓度为0.2 mg/L.     

Measures of durability of resistance

ABSTRACT Conventional models for the durability of resistant cultivars focus on the dynamics of the frequency of resistance genes. This leads to a definition of the durability of resistance as the time from introduction of the cultivar to the time when the frequency of the virulence gene reaches a preset threshold. It is questionable whether this is the most appropriate way to measure durability. Here we use a simple epidemiological model to link population dynamics and population genetics to compare three measures of durability: (i) the expected time until invasion of the virulent genotype, by mutation or immigration, and subsequent establishment of a population (T(invasion)); (ii) the virulence frequency related measure of the time for the virulent genotype to take-over the pathogen population ( T(take-over)); and (iii) the additional yield, measured by the additional number of uninfected host growth days (T(additional)). Specifically, we show how the measures of durability are affected by deployment and epidemiological parameters. We use a combination of numerical solution and analytical approximation of a model for the population dynamics of avirulent and virulent genotypes of a pathogen growing in dynamically changing populations of resistant and susceptible cultivars. The three measures of durability are compared. Some consequences of the results for durable resistance in multilines and mixtures and the regional deployment of resistant cultivars are discussed.     

土壤环境因素对棉花黄萎病菌微菌核存活的影响

 试验研究了土壤温度、湿度、pH值和有机质对棉花黄萎病菌微菌核存活的影响。结果表明:40、30和0℃对微菌核土壤存活影响较大,10和20℃影响较小,尤其以10℃影响最小;土壤含水量越高,对微菌核存活影响越大,在含水量低于15%时,对存活影响较小,尤其以5%的含水量影响最小,表明微菌核对土壤干旱逆境具有较强的抵抗能力;pH值低于5.5或高于8.5的土壤条件对微菌核存活影响较大,pH值为6.5~7.5影响较小;土壤有机质含量越高,微菌核存活率越低,含量低,存活率高。本研究结果表明,只要改善和控制棉花黄萎病菌土壤存活的生态条件,就可以有效地减少土壤存活菌量,达到控制病害发生与发展的目的。     

Mode of action of etoxazole

The mode of action of the 2,4-diphenyl-1,3-oxazoline acaricide/insecticide etoxazole has been argued to be moulting inhibition, but experimental results supporting this hypothesis are lacking. This study investigated the effect of etoxazole on chitin biosynthesis in the fall armyworm, Spodoptera frugiperda (Smith) (Lepidoptera: Noctuidae). Etoxazole induced moulting defects in fall armyworm larvae similar, if not identical, to those caused by benzoylphenylureas, a well-known class of insecticidal chitin biosynthesis inhibitors. Furthermore, in contrast to untreated larvae, the chitin content in the integuments of larvae several days after treatment did not differ from that in freshly ecdysed individuals, thus suggesting strong chitin biosynthesis inhibition in vivo. A more detailed investigation of the inhibitory potential by incubating cultured integument pieces from larvae of S. frugiperda with [14C]N-acetyl-D-glucosamine, a radiolabelled chitin precursor, revealed I50 values of 2.95 and 0.071 microM for etoxazole and triflumuron respectively. The incorporation of radiolabel into potassium hydroxide-resistant material was inhibited by etoxazole in a dose-dependent manner. Based on these results, it is concluded that the acaricidal and insecticidal mode of action of etoxazole is chitin biosynthesis inhibition.     

Evaluation of Likelihood of Co-Occurrence of Erwinia amylovora with Mature Fruit of Winter Pear

ABSTRACT Phytosanitary concerns about fire blight prohibit export of U.S.-grown pears to some countries without this disease. To examine these concerns, we evaluated the potential for co-occurrence of Erwinia amylovora with mature, symptomless winter pear fruit by inoculation experiments and by survey of commercial orchards. Immature pear and apple fruit were inoculated in orchards with E. amylovora strain 153N as resuspended lyophilized cells or as ooze from diseased tissues. Regardless of inoculum source, population size of Ea153N on fruit declined by an order of magnitude every 3 to 4 days during the first 2 weeks after inoculation; at 56 days after inoculation, Ea153N was not detected, except on 1 of 450 fruit with 4 colony forming units (CFU). After inoculation of flowers, calyx-end survival of Ea153N on pear and apple fruit declined from high populations at petal fall to a few cells at harvest, with no detection of the pathogen after a 7-week cold storage. Migration of Ea153N into symptomless pear fruit from diseased branches was evaluated by enrichment assay and nested polymerase chain reaction of internal fruit core tissues; these assays failed to detect the pathogen in healthy fruit from diseased trees. At harvest, E. amylovora could not be detected on 5,599 of 5,600 fruit of d'Anjou pear sampled from commercial orchards in major production areas of the Pacific Northwest; one fruit yielded 32 CFU of the pathogen. Postharvest, mature pear fruit contaminated with Ea153N and subsequently wounded required a dose of >10,000 cells at the wound site to allow for persistence of the pathogen through a 7-week-cold storage. We conclude that epiphytic E. amylovora shows similar survival characteristics on both pear and apple fruit, this pathogen is not an endophyte within mature symptomless pear fruit, its presence is exceptionally rare on commercially produced fruit, and that epiphytic survival of E. amylovora through a postharvest chilling period is unlikely given the unrealistically high population size required for persistence.     

莠去津的药害问题及药害防范技术研究概述

本文概述了使用莠去津以来，有关该药的药害情况及药害解除方法的研究状况。     

Mode of action of meturine

The effect of meturine on the light processes of photosynthesis was studied.Meturine is a herbicide for weed control in potato and cotton crops. It is a N-phenyl—N-hydroxy—N′-methylurea.The experiments were carried out on isolated pea and spinach chloroplasts.When examining photosystem I, reduced DPIP was used as an electron donor, whereas methyl-viologen served as an electron acceptor. When examining photosystem II, DPIP represented the electron acceptor.The obtained experimental results have pointed to the absence of the effect of meturine upon the photoreaction I.Unlike N-phenyl—N′, N′-dimethylureas (CMU, DCMU) meturine has been a very weak inhibitor of photoreaction II.The authors explain the photoreaction II inhibition of chloroplasts from plants treated with herbicidal doses of meturine by conversion of N-phenyl—N-hydroxy—N′-methylurea into Hill reaction inhibitor(s). N-Phenyl—N′-methylurea can be one of such meturine metabolites.Meturine herbicidal action is accounted for by meturine transformation into Hill reaction inhibitor(s) in the plant tissues.     

宁夏枸杞炭疽病发生流行的气象条件分析

根据宁夏枸杞主产区中宁县和银川市芦花台园林试验场2000～2004年不同批次的成熟枸杞果实炭疽病病情指数和气象资料,运用主成分分析结合逐步回归方法,分析了宁夏枸杞炭疽病爆发流行的主要气象因子及其影响.结果表明:影响炭疽病发生的气象因子主要是温度和空气相对湿度,其次是风力和降水.在一定温度范围内,温度越高,对炭疽病的发生越不利;空气湿度越大,越有利于枸杞炭疽病的发生.     

甲基硫菌灵标样的制备

本文介绍了用进口甲基硫菌灵样品，采用溶剂萃取，高速离心，重结晶，高效液相色谱，红外光谱等分析方法进行系统分离与鉴定，得到其标样的方法。     

Mode of action of famoxadone

Famoxadone is a preventative and curative fungicide recently developed for plant disease control. The molecule and its oxazolidinone analogs (OADs) are potent inhibitors of mitochondrial electron transport, specifically inhibiting the function of the enzyme ubiquinol:cytochrome c oxidoreductase (cytochrome bc₁). Visible absorbance spectral studies on the purified enzyme suggested that famoxadone bound close to the low potential heme of cytochrome b. This binding mode was confirmed in competitive binding experiments by studying the displacement of a radiolabelled OAD from submitochondria. EPR studies on the binding of famoxadone to submitochondria and purified bc₁ suggested its binding mode was more like that of myxothiazol than that of stigmatellin (ligands known to bind near the low potential heme). Zoospores of Phytophthora infestans, when given low concentrations of famoxadone and other OADs, were observed to cease oxygen consumption and motility within seconds and later the cells disintegrated, releasing the cellular contents. Famoxadone was a potent inhibitor of the growth of Saccharomyces cerevisiae when grown on non-fermentable carbon sources and it was an approximately 50-fold less potent inhibitor of growth when the yeast was grown on a fermentable carbon source, glucose. Such physiological observations are consistent with the loss of mitochondrial function imposed by famoxadone and OADs. Single amino acid changes in the apocytochrome b of baker's yeast cytochrome b located near the low potential heme altered the inhibition constants for the inhibitors famoxadone, myxothiazol, azoxystrobin and kresoxim-methyl differentially, thus strongly suggesting different binding interactions of the protein with the inhibitors. © 1999 Society of Chemical Industry     

Comparison of methods of assessing field populations of Heterodera schachtii

Population assessment methods for Heterodera schachtü were compared in two tests. In the first there were no consistent differences between numbers of H. schachrü extracted by Fenwick cans (at two laboratories), a flotation column and an automatic cyst extraction apparatus, from dried soils from three sites containing no other cyst nematodes. The second, made on 54 commercial sugar beet fields, compared numbers of H. schachtü extracted from dried soil samples by Fenwick cans (at two laboratories) with results of a bioassay of soil samples and a subsequent examination of roots in the field. Most samples were placed into the same broad groups by the cyst extraction and bioassay methods and the two techniques were equally good at predicting field infestations.     

十种藓类植物茎的比较解剖学观察

利用石蜡切片的方法 ,对十种藓类植物 ,钝叶蓑藓 (Macromitriumjaponicum Doz.et.Molk .)、疏齿墙藓〔 Tortulanorvegica(Web .)Wahl.exLindb .〕、岸生连轴藓〔 Schistidiumrivularis(Brid .)Podp .〕、树形疣灯藓〔Trachycystisussuriensis(MaacketRegel )T .Kop .〕、齿边缩叶藓〔 Ptychomitriumdentatum(Mitt.)Jaeg .〕、山羽藓〔 Abietinellaabietina(Hedw .)Fleisch〕、东亚万年藓 ( Climaciumjaponicum Lindb .)鼠尾藓〔 Myurocladamaximowiczii(Borszcz)SteeretSchof.〕、卷叶凤尾藓 (FissidensdubiusP .Beauv .)及二形凤尾藓 (FissidensgeminiflorusDoz .etMolk .)的茎横切面的解剖观察结果表明 :茎的形状、中轴细胞的有无、形状及所占的比例、外皮部厚壁细胞的层数等特征因种类不同而有明显差异 ,可以作为分类依据之一。外皮部厚壁细胞的层数可能与藓类植物的生境有关。     

8个乡土树种抗逆性对比研究

在半干旱地区内蒙古中部3个不同造林立地类型对当地的8个乡土树种进行亚区造林对比试验,调查了被试树种在自然状态条件下的生长特征,应用PV技术测定了其水分生理指标,测定了抗寒及抗春季干旱风的等级,运用综合指标(成活、保存率、抗旱水分生理、耐寒性等)分析各树种的抗逆性和对不同立地条件的适应能力。结果表明:柄扁桃、桃叶卫矛、荆条和山杏(对照)抗逆性强,毛樱桃、山桃抗逆性较强,酸枣(山西种源)、欧李(山西栽培种)为中等,臭椿较差。