Binucleate Rhizoctonia sp. AG G causing root rot in yacon (Smallanthus sonchifolius) in Brazil

A new rot caused by a binucleate Rhizoctonia sp. affecting the tuberous root cortex of the domesticated yacon ( Smallanthus sonchifolius ) has been observed in Brazil. Isolates of a binucleate Rhizoctonia sp. were collected from roots with rot symptoms and characterized by the number of nuclei per cell, hyphal anastomosis, RAPD molecular markers, ITS-5·8S rDNA sequence and pathogenicity tests. All isolates had a mean of 1·9–2·2 nuclei per cell and anastomosed with the binucleate Rhizoctonia sp. AG G-tester strain. RAPD analysis was carried out between 11 isolates recovered from yacon and 11 AG (A, Ba, Bb, Bo, C, D, F, G, O, P, Q) standard testers of binucleate Rhizoctonia sp. Genetic similarities of 94·8–100% were observed among isolates of the binucleate Rhizoctonia sp. from yacon and all isolates were genetically more closely related to the AG G tester than other strains according to upgma analysis using RAPD markers. Homologies of complete ITS nucleotide sequences were 100% between binucleate isolates of Rhizoctonia sp. from yacon and the AG G tester. According to pathogenicity tests, the isolates caused typical rot symptoms of yacon tubers 90 days after inoculation     

Pathogenicity of the root-knot nematode Meloidogyne javanica on potato

Host–parasite relationships and pathogenicity of Meloidogyne javanica on potatoes (newly recorded from Malta) were studied under glasshouse and natural conditions. Potato cvs Cara and Spunta showed a typical susceptible reaction to M. javanica under natural and artificial infections, respectively. In potato tubers, M. javanica induced feeding sites that consisted of three to four hypertrophied giant cells per adult female. Infection of feeder roots by the nematode resulted in mature large galls which usually contained at least one mature female and egg mass. In both tubers and roots, feeding sites were characterized by giant cells containing granular cytoplasm and many hypertrophied nuclei. Cytoplasm in giant cells was aggregated alongside the thickened cell walls. Stelar tissues within galls appeared disorganized. The relationship between initial nematode population density ( P ) [0–64 eggs + second-stage juveniles (J2s) per cm³ soil] and growth of cv. Spunta potato seedlings was tested under glasshouse conditions. A Seinhorst model [ y = m  + (1 −  m ) z ^{( P − T )}] was fitted to fresh shoot weight and shoot height data of nematode-inoculated and control plants. Tolerance limits ( T ) for fresh shoot weight and shoot height of cv. Spunta plants infected with M. javanica were 0·50 and 0·64 eggs + J2s per cm³ soil, respectively. The m parameter in that model (i.e. the minimum possible y -values) for fresh shoot weight and shoot height were 0·60 and 0·20, respectively, at P  = 64 eggs + J2s per cm³ soil. Root galling was proportional to the initial nematode population density. Maximum nematode reproduction rate was 51·2 at a moderate initial population density ( P  = 4 eggs + J2s per cm³ soil).     

Direct examination of soil for sporangia of Synchytrium endobioticum using chloroform, calcium chloride and zinc sulphate as extraction reagents

Fields infested with Synchytrium endobioticum can be descheduled when the soil is found free from sporangia of S. endobioticum . For direct examination, EPPO Standard PM 3/59 describes a soil extraction technique based on the use of a sieve shaker with six sieves. We compared recovery of sporangia between this (modified) method and an extraction method employed by the Dutch Plant Protection Service (PPS method). Recovery was determined using an inoculum dilution series: 125, 25, 5, 1, 0.2 or 0.04 sporangia per g soil. Extraction reagents used were chloroform and calcium chloride in the method described by EPPO, calcium chloride and zinc sulphate in the PPS method. At 125 sporangia per g soil, the mean density determined for the modified EPPO method was 228 sporangia per g soil when chloroform was used. Using calcium chloride, recovery percentage was higher for the modified EPPO method than for the PPS method (286, 136%, n.s. P  < 0.05). The advantage of the modified EPPO method was the larger soil volume to be processed; its disadvantages were use of complex equipment and noxious reagents (chloroform). Both extraction methods showed high variation in recovery between samples, making accurate estimation of sporangial densities in soil awkward.     

CABI/EPPO distribution maps of plant pests and plant diseases and their important role in plant quarantine

Never before has the need for accurate distribution data for plant pests been so important. CAB International (CABI) and EPPO are international organizations with a long history and strong involvement in collating and disseminating information on the global distribution of plant pests. Distribution Maps of Plant Pests and Distribution Maps of Plant Diseases, first published in 1951 and 1942, respectively, are respected, referenced sources of such data, expertly compiled and validated and used by plant health organizations around the world. They have been joint CABI/EPPO publications since 1997, and provide an essential complement to expanding knowledge on plant pest distribution. The Distribution Maps continue to be the most authoritative sources of information on the presence and extent of specific plant pests, sourced from the 4.5 million records in CAB Abstracts as a basis and numerous other sources. They also feed directly into CABI's Crop Protection Compendium (CPC) and EPPO's Plant Quarantine Data Retrieval System (PQR) databases. Their history, compilation and value are discussed.     

Detection and characterization of two strains of Grapevine fanleaf nepovirus in Tunisia

The nematode-borne Grapevine fanleaf nepovirus (GFLV) causes severe degeneration of grapevines in vineyards worldwide. In a recent survey of the sanitary status of grapevine plants in north Tunisian vineyards, we were interested to study the polymorphism of GFLV. Purified virus, from mechanically inoculated Chenopodium quinoa , was used to produce anti-GFLV antiserum, which specifically recognized GFLV in different Tunisian grapevine samples using the DAS-ELISA technique. Positive samples were subjected to oligoprobe-RT-PCR to amplify a 606 bp region of the viral coat protein sequence. PCR products used for RFLP analysis after digestion with endonuclease Alu I produced 3 restriction profiles. RFLP data allowed clear distinction of two GFLV strains in Tunisia. The nucleotide sequence of the PCR-generated amplicons from each strain was determined showing 93.4% identity at the nucleic acid level and 97.5% similarity at the aminoacid sequence level compared to the previously characterized GFLV-F13 French isolate. This paper is the first report on molecular variability of GFLV in Tunisia.     

草坪常用化学药剂对昆虫病原线虫存活和侵染率的影响

测定了草坪上常用的14种化学药剂对蝼蛄斯氏线、长尾斯氏线虫X-7品系和小卷蛾斯氏线虫All品系存活和侵染率的影响。杀虫剂乙酰甲胺磷在高浓度和推荐浓度下对蝼蛄斯氏线虫、长尾斯氏线虫和小卷蛾斯氏线虫的致死率分别为21％和9．5％，13％和5．5％，5．5％和2％；敌百虫在高浓度和推荐浓度下对蝼蛄斯氏线虫的致死率分别高达94．5％和92．5％，在高浓度下对长尾斯氏线虫的致死率为8％，对小卷蛾斯氏线虫没有明显致死作用；克蛾宝对3种线虫的致死作用均比乙酰甲胺磷和敌百虫低。杀菌剂对3种线虫的存活均无影响。除草剂2，4-D丁酯对3种线虫低浓度和高浓度下致死率分别为2％、6％、3．5％和5％、85．5％、6％。经化学药剂处理24h后的线虫侵染黄粉虫9-11龄幼虫，对线虫存活没有影响或者影响较小的化学药剂对线虫的侵染率都没有明显的影响，但剂型为10％可湿性粉剂的吡虫啉对长尾斯氏线虫，以及高浓度的2，4-D丁酯对小卷蛾斯氏线虫的侵染率有明显抑制作用。     

昆虫病原线虫的贮存和剂型研究进展

阐述了昆虫病原线虫的贮存原理,介绍业已建立的昆虫病原线虫贮存方法及其优缺点,影响昆虫病原线虫贮存效果的主要因素,并讨论了昆虫病原线虫剂型制备方法。     

二化螟对杀虫剂抗药性的研究进展

综述了国内外关于二化螟抗药性的研究成果,包括:二化螟的分布、危害、防治,抗药性产生和发展,抗药性机理,抗药性测定方法以及抗药性治理措施。     

大豆疫霉菌对大豆下胚轴侵染过程的细胞学研究

 接种后1.5~24h,用光镜和电镜研究了2个大豆品种与大豆疫霉菌Ps411的亲和性和非亲和性互作。观察结果表明,大豆疫霉菌对大豆下胚轴的侵染过程可分为侵入前、侵入、皮层组织中的扩展和进入维管束组织4个连续阶段。大豆下胚轴接种后在25℃保湿培养,1.5h后游动孢子即形成休止孢并萌发产生附着孢,3h后侵入表皮细胞,6h后进入皮层组织,24h后进入维管束组织。病原菌主要以侵染菌丝直接侵入表皮,表皮细胞间隙是主要侵入部位。皮层细胞是病原菌定殖和发展的主要场所,胞间菌丝侵入皮层细胞并形成吸器。在菌丝与寄主细胞接触部位的寄主细胞壁与质膜之间常有胞壁沉积物的形成。在抗病品种上病菌的侵染事件与感病品种基本一致,但不能形成正常的吸器,胞壁沉积物明显多于感病品种,菌丝在寄主组织内的扩展明显受到抑制。利用β-1,3-葡聚糖免疫金标记单克隆抗体进行的免疫细胞化学的研究表明,胞壁沉积物内含有大量的β-1,3-葡聚糖,在大豆疫霉菌菌丝壁中也存在β-1,3-葡聚糖。以上结果表明,病原菌的侵染可诱导抗病寄主细胞内β-1,3-葡聚糖迅速的合成与积累、并形成胞壁沉积物,以抵御病菌的侵染与扩展。     

影响波尔山羊超排效果的因素

对204只(次)波尔山羊采用C IDR+FSH+PG法超数排卵(以下简称超排),发情配种后第6天采用手术法从子宫角采胚,采胚成功率为92.16%(188/204),头均获胚(16.68±7.89)枚,其中头均获可用胚(14.11±8.37)枚,可用胚率84.66%(2 654/3 135)。对不同国家产FSH、不同剂量FSH、注射LRH+P4、不同季节、重复超排、左右侧卵巢等因素对波尔山羊超排效果的影响进行了研究。结果表明,以日本和国产(动物所)FSH超排效果为佳,头均获可用胚分别为(15.66±8.26)枚(n=89)和(15.39±6.91)枚(n=23);日本产FSH 14~16 mL组效果最佳,头均获可用胚(19.63±8.96)枚(n=19);注射LRH+P4组头均获可用胚(16.04±8.84)枚(n=80),极显著高于对照组(12.16±7.68)枚(n=62);春季、秋季、冬季超排头均获可用胚分别为(10.86±5.10)枚(n=7)、(11.30±8.29)枚(n=23)、(11.00±6.17)枚(n=10),差异不显著;重复超排(间隔12月)第1次头均获可用胚(15.08±5.12)枚(n=26),第2次头均获可且胚(16.92±8.32)枚(n=26)。