施药治疗板栗黄化皱缩病效果调查

在确定了板栗黄化皱缩病为植原体病害,并在怀柔板栗产区连续多年调查的基础上,采用树干打孔注药的方式,针对不同树龄的板栗黄化皱缩病病株,进行药剂治疗试验。结果表明,盐酸四环素和祛疯1号对板栗黄化皱缩病具有一定治疗效果。盐酸四环素治疗效果最好,施药当年对幼龄树、中龄树和成龄树的治疗效果分别为70.70%、64.47%和53.49%,治愈率分别为33.33%、26.67%和13.33%;连续两年施药的治疗效果分别是89.40%、75.79%和66.88%,治愈率分别是66.67%、40.00%和26.67%。施药的治疗效果随树龄增大而降低,连续两年施药的治疗效果较当年有所提高。硫酸亚铁对板栗黄化皱缩病有一定缓解作用,但效果有限。青霉素钠对板栗黄化皱缩病无疗效。     

甘薯病毒病检测技术研究

湖北省甘薯病毒病主要有皱缩花叶型、卷叶型、叶片斑点型(含黄斑型和紫环斑型)等三种症状类型。对三种类型的病株样本进行了电镜观察,结果表明,卷叶型、黄斑型和紫环斑型的病株叶片中均有长线形病毒粒子,长度为1 050m~1 650m,形态和大小无明显差异,皱缩花叶型病株叶片中有时也可观察到长线形病毒。用三种症状类型病株与巴西牵牛靠接,巴西牵牛和甘薯植株成活率达90%以上,巴西牵牛染病率可达80%以上。嫁接后的巴西牵牛叶片表现皱缩而且褪绿症状者,电镜检测均有病毒,因此,巴西牵牛可以用作甘薯病毒病诊断的指示植物。     

南城县淮山炭疽病发生情况及防治措施

南城淮山是一种著名的山药品种，已成为该县的一种特色作物，迄今种植面积已达１０００ｈｍ２。当地淮山管理较粗放，农民对病虫害少有防治。２０００年１０月中旬，笔者到南城调查发现，不少乡镇种植的淮山普遍发生了炭疽病，病株率１０％左右，严重的病株率达１００％，病叶率为８０％～９０％，并出现了大量落叶或死藤现象。根据调查，现将该病的发生情况与防治措施简报如下。１症状淮山炭疽病主要为害叶和藤茎，叶柄也可受害。下部叶片先发病，初始病斑为暗绿色水渍状凹陷的小斑点，扩展后呈黑褐色、病健明显的圆形或不规则形病斑。常在…     

小麦条纹叶枯病发生特点及重发原因初步分析

小麦条纹叶枯病是苏北洪泽县等地近年来新发展起来的一种病毒病,发生有逐年加重的趋势。为了解和掌握该病发生的基本规律,我们对其发生、发展情况进行了初步调查。1为害症状开始时病株矮化不显著,分蘖减少,心叶或是剑叶基部出现黄白色斑纹,然后沿中脉或叶缘向叶尖发展成宽、窄不一的黄白色条纹。到孕穗末、抽穗初期症状最为典型,剑叶和部分倒二叶出现黄、绿相间的条纹,或叶片大部分呈黄白色,抽出的穗全呈黄白色,穗部扭曲皱缩较为明显,穗短,粒少或不结实,大部分田块出现“金镶边”现象。2发生主要特点2.1发生时期小麦返青、拔节前未发现有症…     

草莓丛枝病的发现及初步研究

在沈阳,从表现丛枝症的草莓、春香和宝交早生品种上,分离到新发生的类菌原体(MLO)。用小叶嫁接法测定指示植物草莓EMC和UC—10均能表现出典型的丛枝症(witchetbroom),病叶变小,颜色变浅。将病叶经固定和包埋后,制成超薄切片,于电镜下观察,可见到在韧皮部组织内有大量球形、椭圆形及哑铃形,并具有单位膜结构的类菌原体。用四环素处理病株可减轻症状。     

草莓丛枝病的发现及初步研究

 在沈阳,从表现丛枝症的草莓、春香和宝交早生品种上,分离到新发生的类菌原体(MLO)。用小叶嫁接法测定指示植物草莓EMC和UC-10均能表现出典型的丛枝症(witchetbroom),病叶变小,颜色变浅。将病叶经固定和包埋后,制成超薄切片,于电镜下观察,可见到在韧皮部组织内有大量球形、椭圆形及哑铃形,并具有单位膜结构的类菌原体。用四环素处理病株可减轻症状。     

玉米丝黑穗病早期特异症状

玉米丝黑穗病Sphace-lotheca reiliana var.zeae是系统侵染性病害。典型症状在雌、雄穗抽出后呈现。拔除病株是防治丝黑穗病的一项有效措施。但后期拔除却不能挽回当年损失,拔除过程中有遗漏病株、病穗,仍难达到预期效果。因此,探索早期症状表现规律及识别方法,争取对病苗、病株早认、早拔,在防治上有一定意义。我们于1976—1978年进行了初步观察。试验在人工     

水稻干尖线虫引起"小粒翘穗"症状的观察

水稻干尖线虫(AphelenchoidesbesseyiChristie)为害水稻引起的典型症状,是在水稻孕穗期上部叶片的尖端2～4cm处形成扭曲状干尖,这是作为病害田间诊断的主要依据。对高秆散穗型品种,这种症状表现十分明显。近年来淮安市水稻品种更换为矮秆密穗型品种后,干尖线虫病仍有发生,但干尖现象不明显,田间大量出现“小粒翘穗”现象。对这一现象我们进行了田间观察及对病稻粒进行了分离检测,结果从病稻粒中分离出了水稻干尖线虫。据此,我们初步认为“小粒翘穗”为水稻干尖线虫病所致。1“小粒翘穗”发生情况水稻干尖线虫病是江苏省水稻一种常见的种传…     

江西大豆新病害──根结线虫病

大豆根结线虫病是江西大豆上的一种新病害,笔者于1987年在邓家埠水稻原种场首见,1989、1992年在兴国园艺场、永修县郊及南昌市郊区蚊桥镇上罗村又发现此病,病株率一般为5～10％,重的100％,产量损失一般为5％,重的50％以上,少数重病株不结荚或全部为瘪荚,给大豆的产量和品质带来严重影响。1症状病株矮缩,叶片变小,叶色黄化,无光泽,结荚减少,瘪荚增多,豆荚中多数只有一个籽粒（健荚中含2～3个）,豆荚形似老鹰嘴,群众称之为鹰嘴豆。病株根系上市有许多高粱粒至大豆粒状的肿胀根结,后期报结相互连接形成须根团;重病株根系后期…     

玉米镰刀菌秆腐病的初步研究

玉米镰刀菌秆腐病是世界性大病害,在各主要玉米产区均有发生。七十年代以来,该病在陕西夏玉米地区渐趋严重,已成为争取夏玉米稳产、高产的重要限制因子,应予以高度重视。 症状和病原菌:病株通常在果穗抽丝后逐渐出现明显症状,病秆基部节间表面有褐色病斑,纵向扩展,形状不规则,用手指挤     

柑桔裂皮病发生情况鉴定

 柑桔裂皮病(exocortis)是以枳、枳橙和檫檬作砧木的柑桔树的严重病害,它的病原是一种类病毒^[4]。有的毒系引起砧木部树皮纵向开裂或翘裂,植株矮化,树势衰退;有的毒系仅引起植株矮化。此病除了嫁接传播外,亦通过修枝剪等与韧皮部接触传播。病害的鉴定,以利用指示植物为主。敏感的指示植物是Etrog香橼的USDCS 60-13选系和亚利桑那861选系^[1、2]。此外,亚利桑那861-S-1选系更为敏感^[3]。它不仅适用于鉴定一般毒系,亦适用于鉴定弱毒系。防治措施以通过茎尖嫁接脱毒或鉴定选择无病母树繁殖无毒苗木为主,亦要注意防止通过工具等的田间传播。     

Resistance to plum pox potyvirus in apricots1

The susceptibility of 115 apricot cultivars to plum pox potyvirus (PPV) has been examined, since 1981, in the experimental plots of the Pomology Institute at Naoussa and Skydra, Makedonia (GR). Inoculation was assured by aphids, transmitting strain PPV-M (Marcus) from naturally infected trees in adjacent peach orchards. For each cultivar, four to six trees were examined for at least 4 years. Observations on symptoms were made on leaves early in May and on fruits at maturity. Most cultivars expressed severe disease symptoms. Those without symptoms were inoculated by grafting onto heavily infected old apricot trees. The grafted shoots were tested for PPV in the following year by ELISA and on the woody indicator GF305. The cultivars which were rated as resistant after artificial inoculation and ELISA came from North America: Early Orange, Stella, NJA2, Sunglo, Veecot, Harlayne, Goldrich and Henderson. Most of these have been crossed with quality cultivars for the creation of resistant hybrids. The PPV resistance of large numbers of these apricot hybrids is now under investigation.     

Field effectiveness of fosetyl-AI against citrus foot rot and brown rot1

The effectiveness of fosetyl-A1 against citrus foot rot caused by Phytophthora citrophthora has been evaluated in a 25-year-old orchard of sweet orange cv. Tarocco, showing severe symptoms of the disease and in a 10-year-old orchard of the clementine-type mandarin cv. Monreal, apparently healthy. All the trees were grafted on sour orange. In both orchards, three sprays at 200 g a.i. per 100 1 were applied in May, July and September for 3 years. The results were evaluated on the basis of yield and fruit quality. Trees of cv. Tarocco had yield increased by 25–44% whereas cv. Monreal yielded 3–16% higher than the unsprayed trees. Fruits of orange cv. Tarocco were collected from trees sprayed with fosetyl-A1 and plunged in a water suspension of P. citrophthora. Fruits treated 11 days before inoculation showed an infection rate of 8.7%) whereas those unsprayed were 77% infected. Fruits inoculated 21 days after the treatment with fosetyl-A1 were 32% infected whereas those unsprayed were 91%, infected. In other trials, trees of volkamer lemon were sprayed with a conidial and mycelial suspension of P. citrophthora at different times after application of fosetyl-A1. The number of infected fruits and leaves in the unsprayed trees was very high (up to total leaf drop) and decreased sharply with the number of sprays (1 to 3).     

Detection of Citrus Leaf Blotch Virus Using Digoxigenin-Labeled cDNA Probes and RT–PCR

Citrus leaf blotch virus (CLBV) was detected by dot-blot hybridization (DBH), and tissue print hybridization (TPH) and by one-step RT–PCR in citrus plants growing both in the greenhouse and in the field. DBH with digoxigenin-labeled cDNA probes allowed CLBV detection in dsRNA-rich and total RNA preparations equivalent to 5 and 0.1mg of infected tissue, respectively. DBH gave intense signals with RNA extracts from young bark, tender shoots and young leaves, whereas the best hybridization signals with TPH were obtained using tender shoots and young leaf petioles. One-step RT–PCR was 10-fold more sensitive than DBH and amplification was obtained with all infected tissues. CLBV was readily detected in young leaves of infected Eureka lemon, Marsh grapefruit, Nules clementine, Navelina orange and Nagami kumquat in the greenhouse, using either hybridization or RT–PCR, but not in leaves of Pineapple sweet orange. Detection in field trees was less consistent and was only achieved by RT–PCR and DBH. CLBV was detected by DBH and RT–PCR in different citrus varieties from several geographic areas showing bud union crease on trifoliate rootstocks, but not in neighbor trees with the same symptoms or in other varieties showing bud union crease on those rootstocks. Failure to detect CLBV in trees with bud union crease could be due to low virus titer or uneven distribution within the plant. Alternatively, a different agent could be involved in causing bud union crease.     

茶皱叶病的研究

 茶皱叶病在我省各茶场均有发生,近年来我们采回典型的皱叶病病叶进行电镜观察。经病原鉴定,确定为类细菌(Bacteria Like Organism)。其大小为96.0—312.0nm,壁厚度平均为20.5nm左右。青霉素对茶皱叶病有明显抑制作用。通过菟丝子(Cuscuta campestris Yunck)作媒介,茶皱叶病病原菌能引起长春花(Vin-ca rosea L.)发病。     

桑枝枯菌核病的发病规律研究

桑枝枯菌核病是近年来在江苏发现的一种新的桑树病害,该病主要危害春季一年生枝条上已萌发的桑芽及新梢,常造成桑芽枯萎和病芽上方的枝条干枯死亡。经鉴定,病原菌为子囊菌亚门,核盘菌属真菌[Sclerotina sclerotiorum(Libert)de Bary]。病原菌在桑芽或新梢的寄生部位能形成黑色菌核。菌核随采叶、伐条等田间操作而掉入土中越冬越夏,成为翌年的初侵染源。病害发生与桑树品种关系密切,育2号为易感病品种。桑园间作是造成病害交互感染的重要原因。     

枣疯病的研究

 对枣疯丛枝与花、叶畸变的症状作了比较系统的观察和描述。病树根部的超薄切片和疯枝韧皮匀浆的部分提纯物在电镜下都检查到类菌原体(MLO)。健树的相应对照样品中未见任何病原物。试验表明:四环素族抗菌素对枣疯病有一定的疗效,少数病树经治疗后,外观康复,正常开花结果已维持两年之久。认为枣疯病是由MLO感染所致。     

<Emphasis Type="Italic">In planta</Emphasis> multiplication and graft transmission of ‘<Emphasis Type="Italic">Candidatus</Emphasis> Liberibacter asiaticus’ revealed by Real-Time PCR

The bacterium Candidatus Liberibacter asiaticus (CLas) is associated with huanglongbing (HLB) in citrus in many countries. Despite the fact that many characteristics of the disease are known, the rate of multiplication of the bacterium within an infected tree is still poorly understood. To study this feature, we used the quantitative Real-Time polymerase chain reaction (Q-PCR) assay to follow and to quantify the multiplication of CLas in grafted infected young sweet orange plants. The rate of infection by grafting reached 100% at 120 days post-inoculation (dpi) showing that grafting could easily transmit CLas. A well-adjusted linear regression equation describing the bacterial growth in planta was obtained independently with measurements taken using repeated sampling in the same plant or different plants through the analysed period. The bacterial population, measured as copy number (CN) of the 16S rDNA target gene g⁻¹ of tissue, increased 10,000 times from 10³ at 30 dpi to approximately 10⁸ CN at 240 dpi indicating that CLas multiplication was fastest in young citrus plants. We observed a direct relationship between the concentration of pathogen and the expression of symptoms. Yellowed leaves or shoots, are commonly the first observed symptom of HLB, and were present in trees with a low amount of bacteria (10⁵ CN g⁻¹). Blotchy mottle symptoms were observed in trees with 10⁷ CN g⁻¹ of bacteria after 180 dpi. Buds taken from infected, but non-symptomatic branches were grafted on Rangpur lime and resulted in transmission rates ranging from 10 to 60%.     

Interactions between citrus viroids affect symptom expression and field performance of clementine trees grafted on trifoliate orange

ABSTRACT Citrus exocortis viroid (CEVd), Citrus bent leaf viroid (CBLVd), a noncachexia variant of Hop stunt viroid (HSVd), Citrus viroid III (CVd-III), and Citrus viroid IV (CVd-IV) were co-inoculated as two-, three-, four-, and five-viroid mixtures to Clementine trees grafted on trifoliate orange to evaluate their effect on symptom expression, tree growth, and fruit yield. Most trees infected with CEVd-containing viroid mixtures developed exocortis scaling symptoms, as did CEVd alone, whereas most trees infected with HSVd- or CVd-IV-containing mixtures developed bark-cracking symptoms. Trees infected with mixtures containing both CEVd and CVd-IV revealed the existence of antagonism between these two viroids in terms of the expected bark-scaling and cracking symptoms. Synergistic interactions also were identified in trees infected with certain viroid combinations that, in spite of lacking CEVd, expressed exocortis-like scaling symptoms. Viroid interactions also affected the expected response of trees in terms of vegetative growth and fruit yield. Trees infected with viroid combinations containing CEVd or CVd-III were smaller and produced less fruit than trees infected with mixtures not containing these viroids. Viroid interactions on scion circumference and cumulative fruit yield, in terms of additivity of their effects, were statistically confirmed using a factorial analysis of variance model with two mean estimation approaches. In single-viroid infections, CEVd, CVd-III, and, to a lesser extent, CBLVd consistently and significantly reduced tree size and fruit yield. Conversely, HSVd and CVd-IV slightly increased fruit yield and reduced scion circumference. Rare and not consistent significant interactions were detected with the five-, four-, and three-viroid combinations. Antagonistic interactions between CEVd and CVd-III or CBLVd and CVd-III were revealed over the years with consistent significance. The antagonistic interaction between CEVd and CVd-IV was highly significant over the years when additional viroids were present; however, this antagonism appeared much later in the case of an exclusive interaction. HSVd and CVd-IV showed a consistent and significant synergistic interaction on yield only when both viroids were exclusively present. These results demonstrate antagonistic or synergistic relationships between citrus viroids depending on the viroid mixtures present in the host.     

苹果短粗根病的发生及病原线虫种的鉴定

 本文首次报道了苹果上的新病害——短粗根病:根系团状,侧根丛生,黑褐色,短、粗,尖端钝或稍膨大,无根毛,无吸收功能与活力。地上部生长衰退,枝条生长缓慢,产量低,重者枯死。该病发生在北京市南口农场,经诊断为巴基斯坦毛刺线虫(Trichodorus pakiatanensis Siddiqi,1962)所致。病原线虫主要形态特征是雄虫具3个颈乳突、三个腹乳突和一对尾乳突,交合刺有环纹;雌虫有一对体侧孔。