3种圭亚那柱花草根系分泌物对杂草幼苗生长的影响

为明确3种圭亚那柱花草(Stylosanthes guianensis Sw.)(‘热研2号’、‘热研5号’和热研21号)的根系分泌物对杂草生长的化感效应,采用营养液培法分别收集其根系分泌物,研究其对5种外来入侵杂草幼苗形态特征及生物量分配的影响。结果表明,除对含羞草(Mimosa pudica L.)幼苗无显著影响外,3种圭亚那柱花草对其余4种杂草的总化感综合效应均为抑制作用。‘热研5号’柱花草对杂草幼苗生长的化感抑制效应强于其他二者,对蒺藜草(Cenchrus echinatus L.)幼苗的根长、株高、地下生物量、地上生物量、总生物量和根冠比均有显著抑制效应(P<0.05),对羽芒菊(Tridax procumbens L.)幼苗的侧根数、地下生物量和根冠比有显著抑制效应(P<0.05),也显著抑制假臭草(Eupatorium catarium V.)幼苗的生物量向地下分配(P<0.05),仅对鬼针草(Bidens pilosa L.)幼苗的抑制效应相对较弱。灰色关联分析表明,进行圭亚那柱花草的化感效应研究中应重点关注总生物量、地上生物量和株高。由此推测,3种圭...     

石楠拟盘多毛孢致病毒素除草作用的初步研究

石楠拟盘多毛孢(Pestalotiopsis photiniae)是草莓根腐病的优势致病菌,主要通过毒素引发病害。为明确该病菌毒素对常见几种杂草的影响,本试验利用离体叶片和种子根芽伸长法研究了该病菌粗毒素对几种杂草的致病作用。结果表明:该粗毒素对供试的13种杂草叶片均有不同程度的致病作用,致病强度与杂草种类及粗毒素浓度有关,其中车前、马齿苋、马唐、反枝苋和灰菜5种杂草受害最重,经较低浓度(0.036mg/mL)毒素处理后1d即开始出现褐色斑点,第3天病斑面积达到最大(50%以上);该粗毒素(0.036mg/mL)对车前等5种杂草种子萌发、幼根和幼芽伸长也均有显著的抑制作用,且随毒素浓度升高抑制作用增强,抑制率均在53%以上,但对小麦和大豆种子萌发及根芽伸长均无明显的抑制作用;粗毒素经紫外线照射后,对车前和蒲公英的除草活性在自然光照下比黑暗下明显增强。这些结果揭示石楠拟盘多毛孢粗毒素有一定的除草潜力。     

Alley cropping and mulching withErythrina poeppigiana (Walp.) O. F. Cook andGliricidia sepium (Jacq.) Walp.: effects on maize/weed competition

The potential of allye cropping systems to sustain a high productivity with low external inputs and the reduction of maize/weed competition through weed suppression in different alley cropping and sole-cropped mulched systems was studied in Costa Rica at CATIE. Data were recorded eight years after establishment of the experiment. Plant residues ofErythrina poeppigiana trees (10 t/ha dry matter) planted at 6 by 3 m reduced weed biomass by 52%, whileGliricidia sepium trees (12 t/ha dry matter) planted at 6 by 0.5 m reduced weed biomass by 28%, in comparison to controls.Erythrina had a considerable impact on grass weeds, whileGliricidia reduced the incidence of some dicot weeds. Weed competition significantly reduced maize yield in all systems. Nevertheless weed suppression contributed to the higher maize grain yield underErythrina andGliricidia alley cropping of 3.8 t per hectare as opposed to the unmulched control yield of 2.0 t per hectare.     

紫红短须螨生物学特性初步观察

利用紫红短须螨（Brevipalpus phoenicis)控制薇甘菊，是生物控制杂草的一种新方法，文章着重介绍了紫红短须螨的生物学特性及形态特征。卵椭圆形。卵椭圆形，长约0.10mm，宽约0.07mm。红色，多单产在植物茎叶的裂缝或凹陷处，或叶片背面的主脉两边，成块成串堆聚在一起，幼螨桔红色，长约0.17mm，宽约0.11mm。若螨2龄，背上有黑色斑纹，雌成螨长约0.30mm，宽约0.16mm，身体椭圆形，扁平，多桔红色。背上有一个“H”形标记，紫红短须螨1年6-8代，世代重迭，从孵发育到成虫，恒温30℃为18.6d,20℃为48.8d。当湿度低于30%，平均温度高于30℃或者低于20℃时，紫红短须螨不能完成生活史，室内11.0-28.5℃的自然变温，湿度58%-97%条件下，紫红短须螨发育完成一个世代为28-55d。     

关中地区麦田杂草危害状况及防除对策

为摸清目前关中地区麦田杂草种类、分布、感染危害情况,历时3个月对关中地区4市25个县(区)麦田杂草感染危害状况进行全面调查。结果发现,关中地区麦田杂草不仅种类繁多,分布广泛,而且危害普遍严重,其中以播娘篙、猪殃殃、荠菜和节节麦分布最广,危害最严重,平均每平方米分别是93株、84株、21株和19.5株,最多样方分别是1 0421、246、352和256株/m2。因此,麦田杂草防除,应在一定的轮作与土壤耕作的基础上,把各项除草措施综合在一起,以求高效、低投入。     

Molecular Identification of a New Member of the Clover Proliferation Phytoplasma Group (16SrVI) Associated with Centaurea Solstitialis Virescence in Italy

In the United States, yellow starthistle (Centaurea solstitialis) is an annual invasive weed with Mediterranean origins. Malformed plants displaying witches' broom, fasciations, abortion of buds and flower virescence symptoms were observed in central Italy. Attempts to transmit the causal agent from the natural yellow starthistle host to periwinkle by grafting, resulted in typical symptoms of a phytoplasma, i.e. yellowing and shortening of internodes. The detection of phytoplasmas was obtained from both symptomatic yellow starthistle and periwinkle by the specific amplification of their 16S-23S rRNA genes. PCR amplification of extracted DNA from symptomatic plant samples gave a product of expected size. Asymptomatic plants did not give positive results. An amplicon obtained by direct PCR with universal primers P1/P7 was cloned and sequenced. The homology search using CLUSTALW program showed more than 99% similarity with Illinois elm yellows (ILEY) phytoplasma from Illinois (United States) and 97% with Brinjal little leaf (BLL) phytoplasma from India. Digestion of the nested-PCR products with restriction enzymes led to restriction fragment length polymorphism patterns referable to those described for phytoplasmas belonging to the clover proliferation (16S-VI) group. Since this is a previously undescribed disease, the name Centaurea solstitialis virescence has been tentatively assigned to it. This is a new phytoplasma with closest relationships to ILEY and BLL, but distinguishable from them on the basis of 16S rDNA homology, the different associated plant hosts and their geographical origin.     

间种白三叶草和稻草覆盖控制丘陵茶园杂草效果

开展丘陵茶园杂草生态控制,可减少对茶园土壤水分和养分的消耗,避免使用化学除草剂。连续2年的田间试验,野外应用小样方多点采样调查茶园杂草种群数量、生物量、平均株高和茶芽密度等指标,结合实验室的茶叶内含成分分析和感官评审。结果表明:茶园共有杂草16科31属31种,春季(4月)以生长速度较慢、生物量小、株高在30cm以下的杂草为主,夏季(7月)以生长快、植株高和生物量大恶性杂草为主,秋季(9月)恶性杂草开始减少,酢浆草、白花蛇舌草等生物量小、株高矮的杂草逐渐增多;稻草覆盖处理茶园春、夏和秋季3个观测时期杂草物种丰富度(S)、多样性(H)、均匀度(J)等指数均高于清耕对照,优势集中性指数(C)低于清耕对照;间种白三叶草处理春、夏和秋季3个观测时期杂草总数量和生物量均显著低于清耕对照,夏、秋季杂草平均株高显著低于清耕对照;稻草覆盖和间种白三叶草处理春季茶芽重和产量显著高于清耕对照,鲜叶中游离氨基酸含量高于清耕对照,茶叶感官评审得分高于清耕对照处理。这表明稻草覆盖和间种白三叶草能改变茶园杂草群落结构,有效控制杂草生长,增加茶叶产量和改善茶叶品质。