海南省香蕉果实潜伏炭疽菌生物学特性研究

 从海南13个地区分离获得的17个Colletotrichum musae分离菌系经测定,无论是菌丝生长还是孢子萌发均以30℃为适温,pH值6~7为最佳条件;菌丝生长的最佳碳源是葡萄糖,而孢子萌发最佳碳源则是蔗糖,5种碳源都可提高孢子萌发率;自然光照(12h光暗交替)最有利于菌丝生长,30min紫外照射可使分生孢子致死。17个菌系菌落形态特征、菌丝体生长速率和致病力均有很大差异,其中以屯昌3、文昌4、琼山1和万宁1等菌系的菌丝生长快,而临高1、昌江3和昌江6则最为缓慢。     

海南省番木瓜果实潜伏侵染真菌种类及其分布状况的研究

 1990~1992年,通过对外观无病和无伤口的健康番木瓜果实进行分离和致病性测定及贮藏期发病调查,探明在我国海南省各种植区,番木瓜果实的果皮中均存在多种真菌的潜伏侵染。其中以Colletotrichum gloeoasporioides发生最普遍,致病性最强。其次Trichoderma sp., Alternaria sp.和Fusarium sp.,不同气候类型区,潜伏真菌种类相似,但潜伏菌量有差异,以雨量充沛,温度较高的东部地区潜伏菌量为最高,潜伏真菌集中于果蒂附近。     

川麦冬炭疽病菌的潜伏侵染和越冬研究

从2004年12月至翌年3月,定期从田间麦冬采集有炭疽病症状和无炭疽病症的叶片,进行洗涤收集炭疽菌分生孢子,测定其存活力,并分离测定样本中是否有炭疽菌存在。结果表明,田间病叶上的分生孢子具有一定存活力,病叶病斑中的越冬病菌菌丝仍具有生活力;无症状样本中能分离到炭疽病菌。这表明川麦冬炭疽病菌具有潜伏侵染特性,能以田间病株上的分生孢子和病组织中的菌丝越冬,作为初侵染源。     

甘薯瘟病菌的潜伏侵染与品种抗性反应

在“老瘟地”上进行甘薯品种抗病鉴定，对某些甘薯品种地上部症状不明显，而地下部薯块感染、薯肉变色者进行分离接种，鉴定确认这类病株系由薯瘟Ⅱ群菌系潜伏侵染引起。试验还表明湛７３－１６５．湘杂９号等１５个品种（薯块完好，薯肉正常），具抗潜伏侵染能力。     

甘薯瘟病菌的潜伏侵染与品种抗性反应

在“老瘟地”上进行甘薯品种抗病鉴定，对某些甘薯品种地上部症状不明显，而地下部薯块感染、薯肉变色者进行分离接种，鉴定确认这类病株系由薯瘟Ⅱ群菌系潜伏侵染引起。试验还表明湛73－165．湘杂9号等15个品种（薯块完好，薯肉正常），具抗潜伏侵染能力。     

疏水表面诱导橡胶树炭疽菌侵染结构的发育分化过程

为了解橡胶树2种炭疽病菌的侵染结构发育分化过程,采用平板菌落生长速率法测定了3株胶孢炭疽菌Colletotrichum gloeosporioides和3株尖孢炭疽菌C.acutatum的菌丝生长速率,测量其分生孢子大小,显微观察2种炭疽菌在疏水表面诱导下侵染结构的发育分化过程。结果表明,胶孢炭疽菌菌丝生长速率为0.96~1.36 cm/d,显著高于尖孢炭疽菌的菌丝生长速率0.72~0.89 cm/d,但二者分生孢子大小无显著差异。在疏水表面诱导下,2种炭疽菌分生孢子在接种2~6 h后开始萌发,12 h孢子萌发率为71.70%~88.05%,13~16 h开始分化附着胞,24 h附着胞形成率为48.99%~70.74%,36 h菌丝诱发形成大量附着枝,48 h后分生孢子产生的次生菌丝也可诱发形成附着枝,附着枝呈圆形、姜瓣形、梨形或不规则形。分生孢子极易产生,可在菌丝顶端成簇或菌丝侧面排列产生,也可由分生孢子形成的芽管产生,或在芽管分化附着胞过程分枝形成分生孢子;附着胞多着生于芽管顶端,少数附着胞顶端可继续萌发类似短芽管结构,再次分化形成可黑色化的次级附着胞。表明橡胶树2种炭疽菌不同菌株间分生孢子萌发时间、孢子萌发率、附着胞形成时间和形成率有一定差异,但种间无明显差异;橡胶树炭疽菌分生孢子极易形成,在疏水表面容易分化形成附着胞和附着枝,说明具有极强的适生性。     

13种萜类化合物对胶孢炭疽菌和链格孢的抑制活性

炭疽菌Colletotrichum和链格孢Alternaria是引起植物病害的重要真菌,给农业生产造成巨大的损失。本研究选取13种萜类化合物,采用菌丝生长速率法对胶孢炭疽菌、链格孢进行抑菌活性分析。研究结果表明:香芹酚、丁香酚、异丁香酚、枯茗醛、百里香酚对两种病原菌有较好的抑菌活性,其中香芹酚对胶孢炭疽菌和链格孢的抑菌活性最强,IC50分别为40.89μg/mL和18.19μg/mL。本试验为植物精油和天然杀菌剂的开发利用提供理论依据。     

应用real-time PCR定量检测小麦条锈菌潜伏侵染量方法的建立

 小麦条锈病是我国小麦主要病害之一。快速、及时地诊断与定量监测处于潜育状态下的病叶,对准确估计越冬、越夏后的病情,制定正确的防治方案具有重要的意义。根据小麦条锈菌Puccinia striiformis的β-tubilin基因序列设计对该病原菌的种具有特异性的引物betaf/betar,并分别在普通PCR和real-time PCR扩增时对该引物的特异性和灵敏性进行了测定。结果表明该引物对小麦条锈菌特异性高,可稳定扩增出243 bp的目标条带。Real-time PCR的灵敏度为普通PCR的100倍。应用此特异性引物,建立了real-time PCR测定系统,定量测定了条锈菌在小麦叶片接种后组织内的DNA随时间的变化。结果表明,在接种后12 h,可在小麦叶片内检测到条锈菌,且条锈菌在小麦叶片内潜育期间随时间呈指数增长。接种第6 d后叶片内的菌量有明显的增加。建立的小麦条锈菌的real-time PCR早期定量测定方法,为及时、快速监测小麦条锈病在潜育期间的发病规律以及为该病的预测、防治提供依据。     

8种杀菌剂对核桃炭疽病病原菌胶孢炭疽菌的室内毒力

由胶孢炭疽菌Colletotrichum gloeosporioides引起的核桃炭疽病是目前危害山东省核桃生产的主要病害。为筛选防治该病害的高效药剂,在确定了最适菌丝生长和分生孢子萌发温度的基础上,采用菌丝生长速率法和孢子萌发法,测定了8种常用杀菌剂对胶孢炭疽菌的毒力,评估了温度对咪鲜胺和戊唑醇毒力的影响,检测了17个胶孢炭疽菌菌株对咪鲜胺和戊唑醇的敏感性,同时评价了这2种杀菌剂的预防和治疗作用。结果显示:在胶孢炭疽菌菌丝生长和孢子萌发的最适温度28℃下,供试8种杀菌剂中,咪鲜胺、戊唑醇和三唑酮对供试菌株菌丝生长的抑制作用最强,平均EC50值分别为0.07、1.45和3.04 mg/L;异菌脲、代森锰锌和咪鲜胺对分生孢子萌发的抑制作用最强,平均EC50值分别为21.07、25.14和25.18 mg/L。咪鲜胺对菌丝生长的抑制作用受温度影响较小,而戊唑醇对菌丝生长的抑制作用随温度降低而增强;供试17个菌株对咪鲜胺和戊唑醇均有较高敏感性,平均EC50值分别为0.08 和 1.03 mg/L。建议在核桃炭疽病发病的不同时期,轮换使用咪鲜胺、戊唑醇、三唑酮、异菌脲和代森锰锌等杀菌剂,以有效控制该病害。     

双重real-time PCR定量测定小麦条锈菌潜伏侵染方法的建立与应用

 小麦条锈病是我国小麦生产上的重要病害之一。为高效准确地定量检测处于潜伏侵染阶段的小麦条锈菌,本研究根据已发表的小麦条锈菌和寄主小麦的引物,设计了各自的探针,建立了双重real-time PCR检测方法。为排除多个引物互作造成的干扰,对小麦条锈菌引物探针体系、小麦体系以及二者的双重real-time PCR体系进行了比较。CT值相关线性回归分析证明,引物之间互作很小,对定量检测无影响。已知浓度样品经梯度稀释,进行灵敏度检测,确定了双重real-time PCR对小麦条锈菌DNA和小麦DNA准确定量测定的最小检测限为0.4 pg和0.5 ng。同时建立了小麦条锈菌和小麦各自的标准曲线。用此方法检测来自两个不同地区的田间样本,得到的分子病情指数(MDI)与随后的发病趋势一致。本研究建立的双重real-time PCR分析方法可靠、高效、低误差,是对本实验室已有小麦条锈菌潜伏期分子检测方法的进一步优化。     

Tracing Latent Infection of Colletotrichum acutatum on Strawberry by PCR

Colletotrichum acutatum, a quarantine organism on strawberries in the EU, was found in Finland for the first time in 2000. Concern about rapid, unnoticeable spread of this pathogen has necessitated studies to find methods with which the quiescent fungus infection can be detected in imported, cold-stored strawberry plant material. Successful detection of C. acutatum in strawberry tissues by polymerase chain reaction (PCR) is dependent on the method of DNA extraction used. Good-quality nucleic acid, free of PCR inhibitors, was successfully prepared by slightly modifying the DNA extraction method of a commercially available kit. Species-specific primers, previously described in the literature, were successfully used in the PCR reaction. C. acutatum was detected by PCR both on symptomatic and asymptomatic plant parts and in artificially and naturally infected strawberry tissues. Positive PCR results were obtained from ripe and unripe berries, runners, petioles and different parts of crowns. The data demonstrate that the PCR technique can be used to detect C. acutatum in strawberry tissue even in plant parts that do not show visible symptoms.     

Heat treatment to control Colletotrichum acutatum on corms of Anemone coronaria

Anemone corms may be infected with the fungusColletotrichum acutatum, which under certain conditions causes leaf curl and leaf necrosis.A hot-water treatment (hwt) of infected corms for 1.5 h 47.5 °C or 1 h at 50 °C suppressed the disease almost completely. The period of application of hwt between harvest and planting time of corms did not influence the efficacy of hwt. Germination potential of different lots of untreated anemone corms varied between approximately 65% and 95%. Hot-water treatment for 1.5 h at 47.5 °C or 1 h at 50 °C reduced germination only slightly if corms of lots that germinated well without hwt were used. However, germination after hwt was severely reduced if lots with a poor germinating potential were used. Germination potential of hwt-treated corms was restored when they were stored for 4 days in moist vermiculite at 20 °C between hwt and planting. Drying of hwt-treated corms after storage in moist vermiculite reduced germination.A dry heat treatment of infected corms reduced disease incidence too, but results were inconsistent and germination of corms was considerably reduced when control of the fungus was optimal.     

Grouping of Colletotrichum Species in Japan Based on rDNA Sequences

Internal transcribed spacers (ITS) of the ribosomal RNA gene (rDNA) were sequenced for 236 isolates covering 25 Colletotrichum species collected in Japan. The Japanese isolates could be grouped into 20 ribosomal groups (RGs) based on the sequences of ITS1, correlating the species identified by the morphology. Colletotrichum gloeosporioides sensu lato separated into three RGs that were morphologically different. Colletotrichum destructivum, C. linicola and C. higginsianum were possibly conspecific. Colletotrichum dematium sensu lato including C. capsici and other species that produce falcate conidia except for graminicolous ones were separated into three RGs that were difficult to distinguish morphologically. In the phylogenetic study using ITS2 and the 28S rDNA domain 2 region, topologies compiled by neighbor-joining and maximum-parsimony methods were almost the same, reflecting the conidial morphology. The phylogenetic group 1 (PG1) produced conidia with acute ends, e.g., C. acutatum, C. destructivum and C. graminicola; PG2 produced those with obtuse ends, e.g., C. gloeosporioides, and C. orbiculare. Colletotrichum theae-sinensis, which produced the smallest conidia, was grouped as PG3, far from other species, indicating it should not belong to Colletotrichum. Grouping and phylogenetic analysis using ribosomal DNA was an effective tool to classify and identify Colletotrichum species without using morphology. Received 15 July 2002/ Accepted in revised form 12 November 2002     

Morphological and molecular characterization of Colletotrichum spp. from citrus orchards affected by postbloom fruit drop in Brazil

Brazilian isolates of Colletotrichum spp. from citrus orchards affected by postbloom fruit drop were examined for colony colour, mycelial growth, benomyl-resistance, pathogenicity, and genetic variability by random amplified polymorphic DNA (RAPD) analysis. All isolates were obtained from flowers and persistent calyxes from different citrus hosts from Sao Paulo, Brazil. DNA polymorphisms detected after amplification with random 10-mer primers were used to classify the isolates into two groups. Group I isolates grew rapidly on potato-dextrose agar (PDA) and were sensitive to benomyl, and group II isolates grew slowly on PDA and were benomyl-resistant. Colletotrichum acutatum was analyzed by RAPD and had high genetic similarity with group II isolates of Colletotrichum from citrus. Probably, the group I is C. gloeosporioides and group II is C. acutatum.     

Attenuation of Virulence in Sclerotinia homoeocarpa during Storage is Associated with Latent Infection by Ophiostoma mitovirus 3a

The hypovirulence-associated mitovirus, Ophiostoma mitovirus 3a (OMV3a), has been shown to be widespread in eastern Canadian populations of Sclerotinia homoeocarpa in the form of latent infection. Latent infection by OMV3a was not associated with an apparent phenotype and did not significantly reduce the growth and virulence of the pathogen. In the present study, we found that isolates of S. homoeocarpa latently infected by OMV3a can change to hypovirulent isolates after storage at 4 °C, and that this attenuation of virulence was associated with increased concentration of the OMV3a virus. Recurrent observations revealed that up to 29.8% of latently infected isolates changed to hypovirulent isolates after 21 months of storage. Transmission of OMV3a dsRNA from latently infected isolates to virus-free isolates resulted in latent infection of the recipient isolates, indicating that latent infection by OMV3a was not associated with genetic differences in the fungal host. The RNA genomes of the OMV3a virus in an isogenic pair of latently infected and hypovirulent isolates were sequenced and compared. Each of the two RNAs contained an open reading frame of 726 amino acids with conserved motifs typical of RNA-dependent RNA polymerase (RdRp). The OMV3a RNA sequences in these two isolates share 95.1% nucleotide and 94.6% amino acid sequence identities. The development of hypovirulence from latent infection by OMV3a virus may provide new strategies to improve the biological control efficacy of hypovirulence in dollar spot management.     

Effects of Latent Infection of Stock Plants and Abundance of Thrips on the Occurrence of <Emphasis Type="Italic">Tomato spotted wilt virus </Emphasis>in Chrysanthemum Fields

DAS-ELISA proved to be reliable enough to detect a latent infection by Tomato spotted wilt virus (TSWV) in asymptomatic stock plants of chrysanthemum. A high density of Frankliniella occidentalis, the predominant vector, in the presence of latently infected stock plants resulted in a high incidence of disease in the chrysanthemum production field. The incidence of disease was low when the vector thrips were not abundant in spite of the presence of latently infected stock plants. These results suggest that an infestation of the vector thrips causes severe secondary spread of TSWV originating from latently infected stock plants in chrysanthemum production fields. Received 27 July 2001/ Accepted in revised form 27 November 2001     

枯草芽胞杆菌262XY2x固体发酵条件优化及对马铃薯炭疽病的防治效果

本试验以枯草芽胞杆菌262XY2x为目标菌,通过单因素分析与正交组合试验,筛选其固体发酵基质,优化发酵条件,并对其进行防病促生作用测定。结果表明,枯草芽胞杆菌262XY2x固体发酵最佳培养基配方为：麸皮36.4%、稻壳粉31.8%、玉米面18.2%、豆粕13.6%、乳糖1.0%、尿素1.1%和ZnSO₄ 0.11%;最优发酵条件为：接种量10%,固料添加量44 g/L,料水比1:1.4,发酵温度28℃,发酵初始pH 7.0,发酵时间40～44 h,活菌数可达7.13×10¹⁴ CFU/g。该菌剂用量为1.0%时,马铃薯株高和根长显著高于对照（P<0.05）,增长率分别为45.25%和28.43%,体内PAL活性较对照显著增加（P<0.05）,增长率为16.57%,且对马铃薯炭疽病的预防效果为63.45%,治疗效果为46.70%。     

Effects of wounding, fruit age and wetness duration on the development of cherry brown rot in the UK

This research investigated the effects of wounding, fruit age and wetness duration on the development of cherry brown rot. Both Monilinia laxa and M. fructigena infected wounded detached cherry fruits, but M. laxa caused more infections than M. fructigena and only M. laxa efficiently infected intact detached fruits. Results from field monitoring and controlled inoculation in a polyethylene tunnel showed that the susceptibility of fruits to infection by M. laxa increased with fruit maturity. Infection of attached intact fruits by M. laxa was not affected by the length (3–24 h) of the wet period tested.     

剑麻提取液对芒果炭疽病菌的抑制作用及苗期防治效果

本文利用剑麻提取液对芒果炭疽病的防治进行了研究,结果表明,剑麻叶片水提液对芒果炭疽病菌的菌丝扩展速度以及菌丝生长量均有明显的抑制作用,且随着处理浓度的增高,抑制效果增强,当每100mL培养基中加0．2mL提取液处理时,抑制率达到50％以上;对孢子产孢能力以及孢子萌发率也有明显抑制作用,当100mL培养基中加5mL提取液处理时,产孢抑制率为98．18％,孢子萌发抑制率为97．43％;用提取液处理菌丝后电导率升高,表明该提取物对芒果炭疽病菌菌丝体细胞结构有影响,导致菌丝体电解质外渗;芒果苗期盆栽试验表明,处理后21d,对照发病率达到92．22％以上,而处理仅为44．44％,表明该提取物对芒果炭疽病有明显的防治效果。     

城市公园绿地水热通量的小波特征

在北京海淀公园架设涡度相关仪,连续观测下垫面和大气之间的显热和潜热通量,定量研究城市公园绿地影响下的水热通量变化趋势,并利用连续小波变换研究其时间尺度结构及变化特征.结果表明:城市小气候环境显热和潜热呈现多尺度结构,其变化包含不同时间尺度准周期分量,存在不同的显热和潜热相干结构;时间尺度准周期分量在春夏初秋较小,而在深秋和冬季较大.显热和潜热变化越剧烈,对应越小时间尺度的准周期分量.在均匀下垫面,利用该方法可进一步研究显热和潜热的空间尺度结构.