Epidemiology and population ecology of kiwifruit blossom blight

A study of the ecology and epidemiology of kiwifruit blossom blight, believed to be caused by the bacterium Pseudomonas viridiflava , was made at the Horticulture and Food Research Institute's Kumeu Research Orchard during spring 1991. Populations of Pseudomonas species, progression of disease symptoms, and micrometeorological conditions were monitored during flowering. No correlations were found between disease progress and the climate variables measured. The rate of increase in disease incidence changed with the transition of buds to flowers. Changes in the rate of increase, logit transformed, were compared with climate variables using cross-correlation. Populations of P. viridiflava were related to the number of diseased blossoms remaining on the vine. The population of a saprophytic bacterium, P. fluorescens , increased as flowering progressed and as dead flower parts became available for colonization. Other Pseudomonas species were only present in low numbers. The population of P. viridiflava and the rate of disease progress decreased at fruit set. A comparison of simulated disease progress curves (calculated using disease model formulae) with disease progress curves from real data suggested that the epidemic was polycyclic, and observations suggested that disease was spreading to unopened buds.     

Adaptation of the New Zealand Psa risk model for forecasting kiwifruit bacterial canker in Korea

Bacterial canker of kiwifruit, caused by Pseudomonas syringae pv. actinidiae (Psa), is a severe threat to kiwifruit production in Korea. An existing infection risk model from New Zealand was adopted to respond to this epidemic. Disease incidence (proportion of diseased leaves on each vine) and weather (hourly temperature, rainfall and relative humidity) data required to develop the model were collected and analysed in the study. Disease incidence data were used to modify and validate the existing model. Because the Psa risk model was originally developed in a region where the characteristic climatic conditions are completely different from those in Korea, the temperature and rainfall functions of the existing model were modified. Analyses using statistical correlation and prediction–realization tables revealed that the modified model is valid with high agreement (a correlation coefficient of 0.85 and an accuracy of 85.7%, respectively) between the observed disease incidence and simulated disease risk from the model. The model was also found to be more highly sensitive to the presence or absence of rainfall than any other weather variable inputs. Uncertainty in simulated disease risk was measured based on the level of uncertainty in temperature input from weather forecasts. Overall, these results indicate that the modified Psa risk model can be used to provide practical and applicable information for timely disease control to the kiwifruit growers in Korea.     

Polyphasic phenotypic and genetic analysis reveals clonal nature of Xanthomonas axonopodis pv. punicae causing pomegranate bacterial blight

Yellow-pigmented bacteria isolated from blight-affected pomegranate leaves and fruit across seven Indian states in epidemics during the years 2008–2016 were characterized and identified using phenotypic and genotypic tools. All bacterial isolates shared phenotypic traits such as colony morphology, NaCl and pH sensitivity and fuscan production, and caused typical lesions on pomegranate plants upon artificial inoculation. Analysis of 16S ribosomal DNA and 16S–23S rDNA intergenic spacer sequences confirmed their identity as Xanthomonas axonopodis pv. punicae. The new isolates collected after 2000 were compared with an old isolate from the 1950s using polyphasic taxonomic approaches including multilocus sequence analysis (MLSA). Nucleotide polymorphism in 24 isolates for nine genomic loci (dnaK, fyuA, gyrB (Young), gyrB (Almeida), rpoD, fusA, gapA, gltA and lepA) showed minor variations in loci fyuA and gyrB. Isolates were grouped into four nearly identical sequence types, ST1, ST2, ST3 and ST4, based on their allelic profiles, ST3 being widespread in Indian states. Molecular phylogenetic analysis of concatenated 5690 bp with other Xanthomonas pathovars revealed its close genetic similarity with the X. citri group. The blight outbreak in diverse geographical locations is attributed to a re-emerged clonal population of X. axonopodis pv. punicae on a genetically homogenous pomegranate cultivar. The latently infected vegetative planting material of elite pomegranate cultivars contributed to the dissemination of the bacterial inoculum. This study highlights and forewarns of the role played by the clonally propagated elite pomegranate cultivars in disseminating and sustaining clonal populations of this bacterial plant pathogen in many Indian states.     

猕猴桃软腐病的病原菌鉴定

<正>猕猴桃果实软腐病是我国猕猴桃贮藏期的主要病害,在四川、陕西、江西等猕猴桃主产区发生普遍,平均发病率达20%~50%,造成了严重的经济损失。中国、意大利、智利等国家认为葡萄座腔菌Botryosphaeria dothidea是该病的主要病原菌(Zhou et al.,2015),拟茎点霉菌Phomopsis sp.也可造成危害(Luongo et al.,2011)。我国关于该病病原菌的报     

陕西省猕猴桃黑斑病病原菌鉴定

<正>‘翠香猕猴桃’属美味猕猴桃品系,具有早熟优质、味道香甜等优点,是陕西省周至县、鄠邑区、眉县等猕猴桃主产区特有的主栽品种[1]。2013年起,陕西周至‘翠香猕猴桃’果园连年发生黑斑病,平均病园率达85.8%,病果率达48.5%以上[2]。该病在果实生长后期呈现黑色病斑症状并在低温贮藏期引起果实腐烂,严重制约了猕猴桃产业的发展。‘翠香猕猴桃’黑斑病病原菌种类、形成机理尚不明确。本研究针对该病发生情况进行田间调查和病原菌分离,通过回接试验     

陕西省猕猴桃黑斑病病原菌鉴定

To confirm the causal pathogen and damage degree of a new disease of kiwifruit-black spot in Shaanxi Province, a field investigation was conducted in Zhouzhi County and Huyi District in 2018. The pathogen was isolated from the diseased fruits and identified based on morphological characteristics, pathogenicity testing, sequence alignment and phylogenic tree analysis. The results showed that the average incidence of black spot was 65%, and the early fruiting rate was 33%. Fruits infected with black spot disease were soft-rotted after being stored for two months under low temperature conditions. The pathogenic fungi were isolated from the under skin of Cuixiang kiwifruits and the strains could produce two types of conidia, including oval α-type conidia and curved β-type conidia. Through sequences alignment of 18S rRNA, ITS, reference gene (EF1-α) and phylogenetic tree clustering analysis, it was identified for the first time that the causal pathogen causing black spot disease of Cuixiang kiwifruit in Shaanxi Province was Diaporthe eres.     

楠木枝枯病病原菌鉴定

<正>楠木为我国传统名贵树种,其木质紧密、耐腐蚀性强,能够驱虫美化环境,是建筑、家具、雕刻的首选木料;同时具有净化空气、吸烟滞尘、涵养水源、固土防沙等功能,有着巨大的经济及生态价值。楠木主要包括润楠属(Machilus Nees)以及楠属(Phoebe Nees)植株,均属于濒危树种,在我国境内     

楠木枝枯病病原菌鉴定

Phoebe is a traditional precious tree species in China, which has great economic and ecological value. A new disease twig blight was found in the Phoebe planting area of Zhejiang province. Symptoms usually appear on the base or fork of branches with black swollen epidermis and gradually get worse resulting branch wilting or whole plant death when longitudinal epidermis cracking. The diseased samples were collected in 2017-2018 and the fungal isolate was identified as Lasiodiplodia pseudotheobromae based on morphological characteristics of colony and spore and sequence analysis of ITS region and EF1-α gene. The pathogenicity tests on Phoebe showed that L. pseudotheobromae caused the typical symptoms of twig blight. Koch′s postulates were satisfied following reisolation and identification of the isolate from the infected tissues using the methods described above. This is the first report of Phoebe twig blight caused by L. pseudotheobromae in China.     

岗梅枝枯病病原鉴定

为明确引起岗梅Ilex asprella枝枯病的病原,对从广东梅州采集的岗梅枝枯病病部分离的致病菌株Gangmei 2进行了形态学观察,并运用MEGA-X构建了病原菌株rDNA内转录间隔区(internal transcribed spacer, ITS)的系统发育树。结果显示:病原菌的形态学特征与拟盘多毛孢属Pestalotiopsis真菌相似,在系统发育树中该菌株与小孢拟盘多毛孢菌Pestalotiopsis microspora在同一分支上。因此,初步将岗梅枝枯病病原菌鉴定为小孢拟盘多毛孢菌P.microspora。     

百合疫病病原菌的鉴定及培养基的筛选

从具典型症状的新鲜百合疫病植株茎基部病组织中分离到百合疫霉菌,根据其病原菌菌丝的形态、菌落特征,厚垣孢子、游动孢子囊和卵孢子的形态和大小,以及病原菌致病性测定,该病原菌鉴定为烟草疫霉Phytophthora nicotianae van Brede de Haan.供试的16种培养基中,病原菌在胡萝卜琼脂培养基(CaA)和辣椒琼脂培养基(PeA)上生长最好,生长速率分别为1.771和1.770mm/h.在常规培养条件下,病原菌不易产生厚垣孢子、游动孢子囊和卵孢子,在低温、皮氏溶液和土壤浸出液中分别诱导产生出大量厚垣孢子、游动孢子囊和卵孢子.     

Pseudonectria buxi causing leaf and stem blight on Buxus in Canada

An outbreak of a boxwood disease was observed in nurseries in southern Ontario in 2008, but the disease appears to have been present in Ontario for at least 15 years. From 2008 to 2010, over 300 fungal isolates were obtained from diseased samples, which included cuttings and whole plants. Almost half of the isolates (144) were found to belong to a single cultural morphotype which was confirmed as Pseudonectria buxi by DNA sequencing of several isolates. The remaining isolates were grouped into another seven major morphotypes, the largest of which accounted for 11 % of the isolates. Single representatives of all eight morphotypes were identified to species using morphological and molecular techniques, and were subjected to pathogenicity testing. Among them, only Pseudonectria buxi successfully satisfied Koch’s postulates on detached leaves, small twigs and rooted cuttings, which confirmed it as the causal agent of Volutella blight. Inoculation tests showed that wounds may be the major infection courts for P. buxi, since non-wounded inoculated tissues did not become diseased. Among several commonly grown boxwood cultivars in Ontario, ‘Green Gem’ was the most susceptible compared to ‘Green Velvet’, ‘Green Mound’, ‘Green Mountain’ or ‘Pincushion’, but all were found to be susceptible. Rather than behaving just as a saprophyte or secondary invader, P. buxi is capable of primary invasion after wounding, and causing extensive disease on live boxwood tissues.     

五味子叶枯病病原菌鉴定

 The pathogen causing leaf blight on Schisandra chinensis (Turcz.) Baill. was isolated from diseased leaf. Based on morphological characteristics and pathogenicity test, the pathogen was identified as Alternaria tenuissima (Fr.) Wiltshire. This is the first report of this fungus infecting S. chinensis.     

红掌细菌性疫病的病原菌初步鉴定

 在云南西双版纳的红掌上发现一种由细菌侵染引起的病害,从叶片的病组织上分离到具有致病性的杆状细菌,将分离的病原菌接种于健康的红掌上,表现出与田间一致的症状。感病初期在叶缘或叶脉间出现水渍状小点,后期病斑多呈棕褐色至黑色坏死,病健交界处多呈黄色。从接种发病的病斑与田间标样上分离的病原菌菌落形态完全相同。通过菌株的培养性状、常规生理生化特性及透射电镜下菌体形态观察结果,将病原菌初步鉴定为黄单胞菌属(Xanthomonas)。BIOLOG鉴定和致病性测定结果进一步鉴定病原菌为地毯草黄单胞菌花叶万年青致病变种Xanthomonas axonopodis pv. dieffenbachiae(Xad)(McCulloch & Pirone) Vauterin et al.     

The various means of dissemination of the fire blight bacterium Erwinia amylovora

A brief review is presented of the means of dissemination of Erwinia amylovora. The bacterium exists in the form of ooze, strands, epiphytic populations and endophytic populations. The status of endophytic bacteria in budwood and fruits is discussed. International dissemination of fire blight has taken place by wind, probably by birds, and by movement of budwood. It has been suggested that fruits may be involved, but there is international disagreement whether measures should be taken to protect against this pathway of dissemination.     

辽宁梨树间座壳菌枝枯病的病原鉴定

 在辽宁兴城“锦丰”梨栽植园出现一种新的枝干病害,该病害主要发生在主干及侧枝,主要症状为主干呈现黑斑、枝条枯萎。本研究对该病害进行了系统调查及病原物分离培养;经形态学观察、柯赫氏法则验证,ITS、EF1-α、CAL、TUB和HIS基因联合建树分析,确定引起“锦丰”梨枝枯病的病原菌为间座壳属真菌Diaporthe nobilis。     

烟草赤星病菌嘧菌酯敏感与抗性菌株的代谢表型差异分析

 为了解烟草赤星病菌(Alternaria alternata)嘧菌酯抗性菌株与敏感菌株在代谢表型上的差异,采用Biolog代谢表型技术比较了抗性菌株(6-5和6-11)和敏感菌株(J6)的950种代谢表型。结果表明,抗性菌株和敏感菌株在代谢表型上基本一致,2个抗性菌株均不能代谢糖酵解中的氮源D-甘露糖胺,抗性菌株6-11还不能代谢尿素循环中的氮源L-鸟氨酸。烟草赤星病菌能代谢24.74%、85.26%、97.14%、89.83%的供试碳、氮、硫、磷源;具有广泛渗透压和pH适应能力;具有脱羧酶活性而无脱氨酶活性;能在高达10%氯化钠、6%氯化钾、5%硫酸钠、20%乙二醇、6%甲酸钠、6%尿素、12%乳酸钠、200 mmol·L^-1 磷酸钠、100 mmol·L^-1硫酸铵、100 mmol·L^-1硝酸钠和20 mmol·L^-1亚硝酸钠的渗透液中正常代谢,不能在20~200 mmol·L^-1的苯甲酸钠渗透液中代谢;其pH适应范围为3.5~10.0,最适约为6.0。研究结果有助于了解烟草赤星病菌的营养需求特性、渗透压和pH环境适应力,同时从代谢表型上揭示了赤星病菌对嘧菌酯抗性的潜在机理。     

绿豆立枯丝核菌研究初报

本研究通过形态学、菌丝融合群和致病力测定研究,对从河北省石家庄地区绿豆种植区分离的90个立枯丝核菌进行鉴定。在90个分离物中有71个属于AG4,占供试分离物的78.89%,2个属于AG2-2,占供试分离物的2.22%,另外17个分离物与标准菌株不融合,占供试分离物的18.89%;属于AG4的71个分离物中,55个与AG4完全融合（占77.46%）,16个与AG4不完全融合（占22.54%）。在温室条件下采用人工接菌法对40个代表性分离物的致病力进行测定,发现不同分离物对同一品种的致病力存在差异,其中分离物R3、R6、R9、R35致病力最强,分离物R23、R31-1致病力最弱。属于AG 4的分离物R3、R6、R9、R35与其他供试分离物致病力差异极显著;属于未知群体的分离物R20、R29和R24之间致病力差异极显著;属于AG2-2的分离物R21、R31-1致病力较弱,且差异不显著。