Root rot in crocus

In the root rot complex in crocus, three different causes have been identified. Under conditions prevailing in The Netherlands, free-living nematodes (Pratylenchus penetrans andP. pratensis) seem to be of minor importance. The present study has shown that roots are incidentally invaded byStromatinia gladioli; the corms and leaf-sheaths appear to be less susceptible to this pathogen. Crocus is often planted in soil known to be contaminated by this fungus. It is not clear why root rot can only occasionally be ascribed to this cause. Further results indicate thatPythium spp. play a major part in the development of root rot.Samenvatting Minstens drie pathogenen kunnen aanleiding geven tot de vorming van wortelrot in krokussen. Slootweg noemt in dit verbandPratylenchus penetrans enP. pratensis; onder de cultuuromstandigheden in Nederland, waar veel gronden gebruikt voor de krokuscultuur regelmatig worden ontsmet met nematiciden (dichloorpropaan/dichloorpropeen of metam-natrium), speelt deze oorzaak een ondergeschikte rol.Door middel van inoculatieproeven werd aangetoond datStromatinia gladioli, de verwekker van het droogrot in gladiolen, de wortels van krokussen ernstig kan aantasten (Fig. 1). De knollen en bladscheden blijken veel minder vatbaar te zijn dan de wortels. In de praktijk worden krokussen dikwijls geplant op grond, die door intensieve teelt van galdiolen ernstig besmet is geraakt door deze schimmel. Het is nog niet duidelijk waarom slechts in enkele gevallen van wortelrot een verband metS. gladioli kon worden aangetoond. Mogelijk wordt in een later stadium (wanneer bovengronds symptomen worden waargenomen) de aantasting in de wortels gemakkelijk gemaskeerd door opvallender beelden veroorzaakt doorPythium.Nader onderzoek wees uit, dat nog niet nader gedetermineerde schimmels uit het geslachtPythium ook wortelrot tot stand kunnen brengen (Fig. 2). Ernstige schade in de praktijk komt meestal door deze oorzaak tot stand.     

2009年甘肃省玉米穗腐病、茎基腐病的发生危害

2009年对甘肃省9个市的21个县、区玉米穗腐病、茎基腐病的发生危害情况进行了全面调查,并采集病害标样,进行病原分离。调查结果表明,玉米穗腐病、茎基腐病在全省各玉米种植区均普遍严重发生,病田率100%,病穗率和病株率平均为63.57%和34.47%。初步分离结果表明,全省玉米穗腐病、茎基腐病的主要致病菌为禾谷镰刀菌、黄色镰刀菌和轮枝镰孢菌,但在地区间的分布有明显差异。     

Causes of incipient rot and rot in regrowth Eucalyptus diversicolor (karri) trees

Eucalyptus diversicolor (karri) is the second most important commercial timber tree in Western Australia. Sawlogs from regrowth trees often have a discoloration in the heartwood that is more abundant than in sawlogs from mature trees. Other symptoms in regrowth logs include white rot, white pocket rot and brown rot. Fungal isolations and pathogenicity tests were conducted to determine whether this discoloration was incipient rot, and if so, what caused it and which rot(s) would eventually develop. A combined sample of 329 discs from recently felled trees and freshly cut scantling had discoloration in 48%, white rot in 14%, white pocket rot in 12% and brown rot in 4% of pieces of wood. Hymenochaete semistupposa was isolated from 22% of discoloured wood and 39% of white pocket rot samples. Stereum hirsutum was isolated from 4% of discoloured wood and 13% of white rot samples. Koch's postulates in regrowth karri trees showed that H. semistupposa caused extensive discoloration, with white pocket rot developing in the heartwood within 4 years, while S. hirsutum caused extensive discoloration, with white rot developing in both the heartwood and sapwood within 2 years. It was concluded that the discoloration was incipient rot, which would eventually develop into either white rot or white pocket rot.     

大豆疫病的种子处理技术研究

本试验用不同浓度的瑞毒锰锌、杀毒矾和克露进行大豆种子处理试验，结果表明，５００ｐｐｍ瑞毒锰锌对大豆疫病具有很好的治疗作用，而用杀毒矾以种子重量０．４—０．５％的剂量闷种，能显著地抑制大豆疫霉菌的侵入     

Phytophthora oleae sp. nov. causing fruit rot of olive in southern Italy

A homothallic Phytophthora species was found to be consistently associated with a rot of mature fruits of two local cultivars of olive (Olea europaea) in Calabria, southern Italy. The phylogenetic analysis of sequences of the ITS1‐5.8S‐ITS2 region and cox1 gene enabled its identification as a new species of clade 2, with a basal position compared to previously described subclades. The new species is described formally with the epithet Phytophthora oleae, referring to the natural matrix from which it was isolated. A unique combination of molecular and morphological characters clearly separates P. oleae from other already described Phytophthora species. This new species produced semipapillate, occasionally bipapillate, persistent sporangia on simple sympodially branching sporangiophores as well as globose and smooth‐walled oogonia, paragynous antheridia and spherical, plerotic oospores. The pathogenicity of P. oleae was confirmed in inoculation trials on fruits of three olive cultivars, including the two local cultivars from which the pathogen had been isolated.     

香龙血树茎腐病的调查与鉴定

对从哥斯达黎加进境的香龙血树上的茎腐病进行了调查和鉴定，确定其病原菌为根串珠霉Ｔｈｉｅｌａｖｉｏｐｓｉｓｐａｒａｄｏｘａ。迄今为止，该病尚未见报道     

豌豆根腐病研究进展

根腐病是豌豆根部的重要病害之一,在世界各地豌豆产区均有发生,是制约豌豆产业持续健康发展的因素之一。世界上尚未发现对根腐病完全免疫的豌豆品种,防治方法主要以农业防治和化学防治为主。本文从豌豆根腐病的发生与分布、病原菌的分类及特点、抗性鉴定及评价标准、种质资源、分子标记及防治策略等方面对国内外豌豆根腐病研究现状进行综述。并提出抗病育种和未来豌豆根腐病综合防治的研究方向。     

Storage rot of swede caused by Phytophthora sp.

During long-term storage trials of swedes ( Brassica napus ) carried out during five seasons between 1982 and 1987, storage rots caused by a Phytophthora sp. were observed, the first report of the disease in the UK.     

桃褐腐病菌抗药性分子机理研究进展

桃褐腐病是严重危害桃生产的重要病害之一。在实际生产中,该病害的控制主要以化学防治为主。由于杀菌剂的大量使用,桃褐腐病菌已对几类常用的杀菌剂产生了不同程度的抗药性。本文就桃褐腐病菌(Moniliniaspp.)对生产上使用的几大类杀菌剂的抗药性情况及抗药性分子机制研究进展进行简单概述和分析,以供国内同行借鉴与参考。     

Bioassay to assess root rot in pea and effect of root rot on yield

Infection of pea roots by soil-borne pathogens causes foot and root rot. In 1985 research was started to develop a method to predict the root rot likely to occur in prospective pea fields. In a bioassay the pea cultivar Finale was sown in a composite soil sample from each field in pots under standardized conditions in the greenhouse. The plants were removed at the green bud stage and the severity of root rot recorded. Between 1985 and 1988 approximately 200 field pea crops were monitored for root rot development. Forty-eight fields were bioassayed in 1986, 51 in 1987 and 30 in 1988. Each year, root rot readings in the bioassay and disease severity readings at field sampled plants at flowering and green pod were linearly correlated (P<0.001). As the degree of root rot in the field crop increased, there was a proportional lower yield. In heavily infested fields, up to a 50% yield reduction occurred.The bioassay in pots proved to be a reliable method for predicting root rot severity in sampled pea fields.     

北京地区柴胡根腐病的病原菌鉴定

 Root rot disease is one of the most important diseases of Bupleurum chinense DC..Pure isolates from host tissues were obtained.The results of pathogenicity test,morphology observation and ITS sequence analysis indicated that the disease was caused by Fusarium oxysporum.     

玉米镰孢菌穗、茎腐病侵染循环的相互关系

玉米穗腐病和茎腐病是玉米主要病害。茎腐病多数病株明显发生根腐,茎基节间产生不规则状褐斑,随后很快变软,内部空松,导致果穗下垂、籽粒干瘪、整株青枯或黄枯,明显减产。玉米穗腐病的主要致病菌为串珠镰孢菌Fusarium moniliforme和禾谷镰孢菌Fusarium graminearum,茎腐病的主要致病菌除腐霉菌外,也有与穗腐病相同的禾谷镰孢菌     

Control of fruit rot in muskmelon

Most of the fruits formed on muskmelon go to waste due to premature shedding, insect punctures and rotting. An experiment was conducted to test the value of controlling insect damage, eliminating contact of fruits with the soil, avoiding continuous contact of the same part of fruits with the soil, and prophylactic application of fungicides on and around fruits, in saving the fruits from rotting. Placing of fruits on polyethylene sheets was best in reducing the incidence of fruit rot, increasing the yield, and providing high net income. Spraying Bordeaux mixture (6:3:100) on and around the fruits was next best.     

Bacterial inflorescence rot of grapevine caused by Pseudomonas syringae pv. syringae

Molecular sequencing (rpoB) and standard pathological and microbiological methods identified Pseudomonas syringae pv. syringae (Pss) as the causal agent of bacterial inflorescence rot of grapevines (Vitis vinifera) in three vineyards in Tumbarumba, NSW, Australia in 2006 and 2007. Pss strains from shrivelled berries and necrotic inflorescences of diseased grapevines were used to inoculate leaves and inflorescences of potted cv. Semillon grapevines. Pss caused disease symptoms similar to those experienced in the field, including angular leaf lesions, longitudinal lesions in shoot tissues and rotting of inflorescences from before flowering until shortly after fruit set. High humidity promoted symptom severity. The necrotic bunch stem and leaf lesions were susceptible to the development of Botrytis cinerea infections. Cryo‐scanning electron microscopy (cryoSEM) indicated that Pss entered leaves and inflorescence tissues via distorted, open, raised stomata surrounded by folds of tissue that appeared as ‘star‐shaped’ callose‐rich complexes when viewed by UV light microscopy. In necrotic tissues, cryoSEM revealed Pss within petiole parenchyma cells and air‐filled rachis xylem vessels. This is the first report of inflorescence and hence fruit loss caused by Pss in grapevines. The disease is described as ‘bacterial inflorescence rot’ and regarded as one that expands the previously reported pathology of grapevines caused by P. syringae. This study also indicated that infection by Pss might promote destructive B. cinerea infections when the fungus is already present but latent, although further experimentation is needed to prove such an interaction.     

马铃薯细菌性软腐病研究进展

细菌性软腐病是一种可引起果蔬严重危害的世界性植物病害,其频发已成为制约马铃薯种植业发展的瓶颈。本文基于国内外细菌性软腐病最新的研究报道,对马铃薯细菌性软腐病的病原鉴定、发病症状、致病机理、致病因子及防治措施等进行综述,并提出了进一步的研究方向,以期为马铃薯细菌性软腐病的相关研究提供科学参考。     

Pectobacterium spp. associated with bacterial stem rot syndrome of potato in Canada

Pectobacterium atrosepticum, P. carotovorum subsp. brasiliensis, P. carotovorum subsp. carotovorum, and P. wasabiae were detected in potato stems with blackleg symptoms using species- and subspecies-specific polymerase chain reaction (PCR). The tests included a new assay for P. wasabiae based on the phytase gene sequence. Identification of isolates from diseased stems by biochemical or physiological characterization, PCR, and multi-locus sequence typing (MLST) largely confirmed the PCR detection of Pectobacterium spp. in stem samples. P. atrosepticum was most commonly present but was the sole Pectobacterium sp. detected in only 52% of the diseased stems. P. wasabiae was most frequently present in combination with P. atrosepticum and was the sole Pectobacterium sp. detected in 13% of diseased stems. Pathogenicity of P. wasabiae on potato and its capacity to cause blackleg disease were demonstrated by stem inoculation and its isolation as the sole Pectobacterium sp. from field-grown diseased plants produced from inoculated seed tubers. Incidence of P. carotovorum subsp. brasiliensis was low in diseased stems, and the ability of Canadian strains to cause blackleg in plants grown from inoculated tubers was not confirmed. Canadian isolates of P. carotovorum subsp. brasiliensis differed from Brazilian isolates in diagnostic biochemical tests but conformed to the subspecies in PCR specificity and typing by MLST.     

灰枣红点软腐病病原菌的鉴定

 The damage and symptoms of jujube fruit soft rot in Xinzheng, Henan Province, were investigated from 2006 to 2008, and the pathogen was identified based on the morphological characteristics and the ITS se-quence of ribosome DNA. The results showed that the aerial mycelium of colony was white in color in the first four days, then turned gray after incubation on PDA for 5-6 d at 25℃ and became black two weeks later. The mycelia grew luxuriantly with velvet character. The pycnidium was flask-shaped with a height of 196.9μm and a width of 213.3μm on the avereage. The conidium was colorless with single cell and had the shape of spindle, its size was (15.0-20.0)μm× (4.5-6.5)μm. The conidiophore was fastigiate. The homology of ITS sequence of ribosome DNA between the tested strain NXK and Botryosphaeria dothidea (GenBank ac-cession number:AJ938005) reached 99.87%, with a difference of only two base pairs. Based on the results of both morphological characters and molecular identification, the pathogen of jujube fruit soft rot in Xinzheng was identified as B. dothidea (Moug. ex Fr.) Ces. et de Not..     

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).