田间黄顶菊种子成熟进度研究

河北地区8月中旬黄顶菊可产生具有萌发力的种子.9月上、中旬黄顶菊开花3～5 d即可产生具萌发力的种子.此时产生的种子成熟进度最快、所需日度最少.9月中旬至10月初,黄顶菊种子成熟度最高,萌发率达94％以上.10月黄顶菊进入末花期,开花20 d内完成种子成熟过程,但种子萌发率低于20％.9月25日前开花的黄顶菊,种子达到50％发芽率所需有效积温随开花始期递减.黄顶菊植株初花期是对其防治的最晚时期,7月底至8月初为河北地区黄顶菊最晚防治适期.     

动物过腹对黄顶菊种子活力的影响

为了明确黄顶菊种子动物传播的可能性,利用添加黄顶菊种子的饲料饲喂牛、羊、驴、兔和鸡等动物,研究了黄顶菊种子过腹后的种子活力和田间出苗能力。结果表明,黄顶菊种子经上述5种动物取食后,粪便中均有完整种子存在,5种动物取食种子后排空时间分别为4d、6d、5d2、d和1d,且粪便中种子量随时间延长呈减少趋势;黄顶菊种子经5种动物过腹后(第1天收集)的发芽率分别为25.3%、31.3%、19.3%、10%和11.7%。说明5种动物均具有传播黄顶菊种子的可能性,黄顶菊发生区动物的长途贩运是黄顶菊人为传播的重要途径。     

光对入侵性植物黄顶菊种子萌发及植株生长的影响

入侵性杂草黄顶菊原产南美,2003年在我国河北省衡水湖首次报道。采用室内控制试验,对光与黄顶菊种子发芽及植株生长的关系进行了研究。结果表明：黄顶菊种子属光敏型,种子需要光刺激才能发芽。但其萌发对光强要求不严,1 000 lx光照强度30 ℃培养6、12 h和24 h转入暗培养,5 d后黄顶菊种子发芽率分别为67.0%、88.0%和95.8%。黄顶菊种子出苗与光照关系密切,播种在土壤表面、0.5 cm和1 cm深土层的种子出苗率分别为96.0%、8.0%和0。随光照强度减弱,植株的生物量及繁殖力显著降低。黄顶菊在35%自然光强下生长时其生物量、结实数比自然光强下分别降低55.0%和55.6%。上述结果为预测黄顶菊的适生区域及制订有效的防除策略提供了科学依据。     

温度对黄顶菊生长发育影响的研究

在梯度恒温条件下,研究温度对黄顶菊各生育期生长发育影响的试验结果表明,黄顶菊在12～42℃时均能萌发和出苗。温度高于16℃时,种子发芽率与出苗率随温度上升而显著增高;24～40℃时种子发芽率与出苗率均高于50%,28～36℃时均高于90%;温度达36℃以上时出苗率开始随温度上升而下降,温度达40℃时发芽率也逐渐降低。以叶片净光合速率(Pn)为代谢活力指标进行测定,结果表明,不同发育阶段黄顶菊的代谢活力从8℃到40℃逐渐增大,超过40℃后迅速减小。28～48℃现蕾开花期植株代谢活力明显高于苗期植株。     

外来植物黄顶菊根、茎、叶的化感作用初探

对黄顶菊［Flaveria bidentis (L.) Kuntze］营养器官进行了解剖学观察,发现其根、茎、叶均存在分泌结构或分泌物。以白菜（Brassica pekinensis Rupr.）作为受试植物,从白菜种子发芽率、幼苗的简化活力指数、幼苗下胚轴及胚根伸长、幼苗中叶绿素、丙二醛（MDA）及可溶性糖（WSS）含量等指标对黄顶菊根、茎和叶水浸提液的化感作用进行了探讨。研究发现,根、茎、叶的浸提液降低了白菜种子发芽率和幼苗胚根长度;幼苗中叶绿素a及总叶绿素随浸提液浓度的升高最终呈下降趋势;MDA和WSS含量随叶片和茎的浸提液浓度升高相应增加。白菜种子萌发及幼苗生长对黄顶菊不同器官浸提液反应有差异,其对叶片浸提液的浓度响应最明显。     

外来入侵植物黄顶菊与白三叶草异株克生研究

以白三叶草和外来植物黄顶菊成熟植株为材料,用蒸馏水做活性物质浸提,得到0.1g/ml、0.075g/ml、0.05g/ml共3个不同浓度的植株地上部分水浸提液,以蒸馏水作对照,用培养皿法对二者的异株克生,即化感作用进行了初步研究。结果表明:①不同浓度黄顶菊水浸提液对白三叶草种子发芽率、根长、根茎比有显著抑制作用,其抑制强度随浓度加大而上升;②不同浓度的白三叶草水浸提液对黄顶菊种子发芽率无显著影响,但抑制了黄顶菊幼苗的根长、根茎比;③化感综合效应指数(SE)表明,0.1g/ml黄顶菊水浸提液化感抑制最大,0.05g/ml、0.075g/ml白三叶草浸提液化感抑制最弱。     

黄顶菊种子休眠与种子寿命研究

黄顶菊是一种新近传入我国的入侵植物。初步研究黄顶菊种子休眠和种子寿命特性发现,黄顶菊种子不具有原生休眠,但需要一定的时间完成其后熟阶段。室温储藏下4年后,黄顶菊种子仍保持很高的萌发率,说明黄顶菊种子的寿命较长,但长时间的冷冻(-18℃)和自然条件下深埋(10 cm土层)会显著缩短黄顶菊种子的寿命。     

不同环境因素对苘麻种子萌发及出苗的影响

苘麻Abutilon theophrasti Medikus具有生长旺盛、结籽量大和适应性强等特点,已成为多种农田中的恶性杂草,研究环境条件对苘麻萌发的影响对进一步探究其生物学特性与综合防治技术具有重要意义。通过室内试验研究温度、光照、酸碱度、水分胁迫、盐胁迫与苘麻种子萌发及埋土深度与其出苗的关系。结果表明,在10～35℃下苘麻种子均可萌发,20～30℃为其最适萌发温度范围;种子萌发对光照不敏感;适应pH范围广,在pH 4～9条件下种子发芽率均在70%以上;水势在-0.2～0 MPa范围内种子发芽率最高,当水势小于-0.7 MPa时,种子萌发受到完全抑制;有较强的耐盐性,NaCl浓度为160 mmol/L时发芽率超过40%;种子对播种深度适应性较强,覆盖不超过8 cm的土层均可出苗。     

黄顶菊竞争植物的替代控制效果评价

为寻找安全、高效的防控黄顶菊措施,采用室内试验筛选出的效果较好的12种替代植物进行田间试验。在田间干旱条件下,按数量比1∶1分别设置12种植物与黄顶菊的种植组合,调查供试植物与黄顶菊之间的相对竞争表现。结果表明,高丹草、墨西哥玉米、甜高粱、油葵出苗快,生长速度快,能够迅速实现地面覆盖,对同处理种植的黄顶菊抑制率达95%以上,表现出较强的替代优势;而紫花苜蓿等植物在试验生境下很少出苗。     

黄顶菊化学防除技术研究

通过对黄顶菊植株生长速度的调查和除草剂防除的试验,结果表明,在5月17日,黄顶菊为4对叶之前用药的防除效果最好.20%百草枯AS 200、300 ml/667m2,41%草甘膦AS 200、300、400 ml/667m2喷施后15 d和30 d的校正防效差异不显著,均达96%以上.     

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.     

福寿螺配偶个体大小选择性初步观察

通过野外观察与实验研究,掌握了福寿螺的婚配体制及其配偶选择性规律。福寿螺与多数低等动物一样,其婚配属于乱交制,无固定配偶;雌螺对与其交配的雄螺个体大小没有选择性,而雄螺对雌螺的个体大小有选择性,倾向于与较大个的雌螺交配。     

青稞种子带菌检测及杀菌剂消毒处理效果

为了研究青稞种子外部和内部携带真菌情况,比较不同杀菌剂对青稞种子的带菌消毒效果和对幼苗生长的影响,为青稞种子播前包衣处理和种传真菌病害防控提供依据,采用离体平皿法对云南迪庆‘云青1号’、‘云青2号’和‘短白青稞’3个主栽品种进行带菌检测,并对种子进行拌种或浸种处理测定6种杀菌剂对种子消毒效果,分析杀菌剂对种子发芽和幼苗生长的影响。结果表明:供试青稞种子表面携带的优势菌群为青霉(Penicilliumspp.)、镰刀菌(Fusariumspp.);种子内部寄藏的真菌主要为镰刀菌、核腔菌(Pyrenophoraspp.)、附球菌(Epicoccumspp.)、丝核菌(Rhizoctoniaspp.)、链格孢(Alternariaspp.)和木霉(Trichoderma spp.)。青稞不同品种的种子表面及内部携带的真菌种类差异较大。致病性测定表明,镰刀菌对种子萌发和幼苗生长影响最大,后期出现幼苗坏死现象。45%咪鲜胺EW、75%百菌清WP、50%福美双WP对青稞种子携带真菌均有显著抑制作用和消毒效果,50%福美双WP消毒效果最优,达100%;45%咪鲜胺EW、75%百菌清WP、50%福美双WP处理对青稞种子发芽和幼苗生长均无显著影响。     

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。     

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.     

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.     

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.     

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。     

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.