辽宁梨树枝枯病病原菌Diplodia seriata的分离与鉴定

在辽宁兴城秋子梨栽培园出现一种新型枝干病害,主要症状为枝枯及木质部坏死。为明确梨树枝枯病病原菌的分类地位,本研究从辽宁兴城地区采样,经过菌株分离培养和致病性测定,以及形态学鉴定结合病原菌的ITS、EF-1α和β-tubulin多基因联合构建系统发育树,确定引起秋子梨枝枯病的病原菌为色二孢Diplodia seriata。研究结果为明确色二孢引起的辽宁梨树枝枯病发生规律和防治措施的制定提供了理论基础。     

Intraspecific variation in Diplodia seriata isolates occurring on grapevines in Spain

Variation of Diplodia seriata, a fungal species associated with botryosphaeria dieback of grapevine, was investigated with respect to its genetic, phenotypic and pathogenic characteristics. The inter‐simple sequence repeat (ISSR) technique was used to investigate the genetic diversity of 83 isolates of D. seriata. Five ISSR primers were able to provide reproducible and polymorphic DNA fingerprint patterns, thus showing a relevant genetic variability in the species. Analyses of ISSR data by different clustering methods grouped the isolates into two distinct clusters through the Bayesian and DAPC analyses. No relationships between either geographic or host origin of isolates and genetic clusters were observed. Several representative isolates from each genetic cluster were chosen for studying their conidial dimensions, in vitro mycelial growth, vegetative and mating compatibility, and pathogenicity on detached grapevine canes and potted vines. No significant differences in conidial dimensions were detected among the groups. Vegetative compatibility reactions were observed among isolates but this was not related with the genetic clustering. Production of sexual fruiting bodies in vegetative compatible crossings was not observed under the experimental conditions used in the study. All 14 isolates tested for pathogenicity were confirmed to be pathogenic according to the length of the necrotic lesions that they caused and their reisolation frequencies from the infected plant tissues. Differences in the length of necrosis were detected among isolates, thus revealing the existence of different virulence levels in the species.     

First record of Peronospora sparsa on Prunus laurocerasus

Peronospora sparsa Berkeley was identified on cherry laurel ( Prunus laurocerasus ) which was being propagated in four nurseries across England and Wales in 1987. This is the first record of a downy mildew on Prunus laurocerasus.     

云南辣椒疫病的分子诊断及其病原菌群体特征研究

 对2005~2007年分离自云南省辣椒疫病的病原菌进行分子生物学鉴定,并对病原菌的群体特征进行研究。PCR特异性扩增表明,引起云南辣椒疫病的病原菌是辣椒疫霉。交配型测定显示,234个云南辣椒疫霉菌株由A1、A2和A1A2(自育型)3种交配型组成,以A2和A1A2交配型为主。其中,A2占45.3%,A1A2占43.2%,A1仅占11.5%。大部分产区3种交配型共存,在田间进行有性生殖的可能性很大。甲霜灵敏感性测定的200个菌株中,甲霜灵敏感菌株是主要菌系,占测定菌株的95.5%,中抗和抗性菌株比例较低,分别为2.0%和2.5%。抗药性菌株的出现与甲霜灵的选择压力有关。云南辣椒疫霉群体组成较为复杂,A1A2交配型可能在云南辣椒疫霉的有性生殖中起到了重要的作用,成为影响群体结构的一个重要途径。     

Molecular characterization of a phytoplasma causing Phyllody in Clover and other herbaceous hosts in Northern Italy

Red clover (Trifolium pratense) and Ladino clover (Trifolium repens) plants showing phytoplasma-associated symptoms (yellowing/reddening, virescence and phyllody) have been recovered in Friuli-Venezia Giulia, Italy. Using AluI RFLP analysis of PCR amplified 16S rDNA we showed that the disease can be caused independently by two phylogenetically distinct phytoplasmas. One of them showed the very typical 16S rDNA RFLP pattern of the agent of Clover Phyllody in Canada (CCPh). The 16S rDNA of the other phytoplasma (Italian Clover Phyllody phytoplasma, ICPhp) has been PCR amplified, cloned and sequenced. The sequence revealed high similarity (>98%) with phytoplasmas belonging to the X disease cluster, which includes organisms not reported to cause phyllody on their hosts. The analysis by AluI RFLP of the PCR amplified pathogen 16S rDNA from other herbaceous plants (Crepis biennis, Taraxacum officinale, Leucanthemum vulgare) collected nearby with phytoplasma-associated symptoms showed similar patterns. Southern blot hybridization of their EcoRI digested total DNA revealed identical RFLP patterns, suggesting that the causative agent may be the same organism.Abbreviations PCR Polymerase Chain Reaction - rDNA gene for the small subunit ribosomal RNA - RFLP Restriction Fragment Length Polymorphism     

Molecular characterization of a new bipartite begomovirus that infects okra plants in guerrero,Mexico

Journal of Plant Diseases and Protection - In Mexico, okra (Abelmoschus esculentus L.) is grown mainly for export, but its production is affected by various pests and diseases. Plants with mosaic...     

甘肃省定西市马铃薯疮痂病新病原Streptomyces galilaeus的分离、鉴定及生物学特性研究

对甘肃省定西市安定区的马铃薯疮痂病病原进行了分离、鉴定和生物学特性研究。结果表明,菌株5T-1具有较强致病性,菌落表面呈灰色,有金属光泽,平均直径为4.68mm,可产生黄褐色素,孢子圆形或圆柱形,孢子丝松散,革兰氏染色呈阳性。5T-1的16SrDNA序列与加利利链霉菌Streptomyces galilaeus菌株的相似度为99%,结合形态特征将菌株5T-1鉴定为Streptomyces galilaeus,为甘肃省新报道病原菌。菌株5T-1生长最适温度为30℃,最适光照条件为全黑暗,最适pH为8.5,最佳碳源和氮源分别为肌醇和天冬氨酸。该研究结果为甘肃省马铃薯疮痂病诊断和综合防治提供了依据。     

Functional characterization of a new pathogen induced xylanase inhibitor (RIXI) from rice

Rice xylanase inhibitor RIXI is a XIP-type inhibitor that belongs to the glycoside hydrolase family 18 (GH18), which includes plant class III chitinases (EC 3.2.1.14) known as PR-8 proteins. The aim of this study was to elucidate whether RIXI had any effect on rice endoxylanase and its role(s) in plant defence. RIXI encoding sequence was cloned from rice (Oryza sativa cv. Nipponbare), and was expressed in Escherichia coli. The activity of recombinant RIXI was investigated – among the tested xylanases, the GH11 xylanase from Aspergillus niger was the most inhibited, while rice endogenous xylanase OSX was least inhibited. Semi-quantitative real-time polymerase chain reaction (PCR) and quantitative real-time PCR showed that the xylanase inhibitor gene RIXI was up-regulated in rice seedlings infected by Magnaporthe grisea. The increased RIXI expression was also accompanied by significantly elevated expression of pathogenesis-related protein gene (PR-1) and class III chitinase gene (Cht-3). This suggested that RIXI might be involved in environmental responses such as defense against phytopathogens.     

Phytophthora oleae,a new root pathogen of wild olives

Wild olive (Olea europaea subsp. europaea var. sylvestris) is an important component of Mediterranean forests and a key genetic source for olive improvement programmes. Since 2009, a severe decline caused by Phytophthora cryptogea and P. megasperma has been detected in a protected wild olive forest of high ecological value (Dehesa de Abajo, Seville, Spain). In this natural forest, sampling of roots and soil was carried out on 25 wild olives with symptoms in 2014 and 2015. Apart from the already known P. cryptogea A1 and P. megasperma, a third Phytophthora species was consistently isolated from wild olive rootlets with symptoms. These isolates conformed morphologically with the newly described species P. oleae and were confirmed by analysis of their ITS regions and cox1 sequences. Temperature–growth relationships showed a maximum growth at 19.9 °C on carrot agar medium, making it the lowest temperature Phytophthora species infecting wild olive roots. Pathogenicity was confirmed on 1-year-old healthy wild olive seedlings and was similar to the previously known pathogenic phytophthoras. As temperature requirements are quite different, the three Phytophthora species may be active against wild olive roots in different seasons. However, the prevalence of P. oleae infecting wild olives in recent years could be due to its introduction as a new invasive pathogen. The probable invasive nature of P. oleae, together with increasing rain episodes concentrated in short periods frequent in southern Spain, would allow the outbreak of infections in wild olive forests, and also put cultivated olive orchards at risk.     

Monilia mumecola, a new brown rot fungus on Prunus mume in Japan

In 1982, an anamorphic fungus in the genus Monilia was first isolated as the causal agent of brown rot disease of Japanese apricot or mume (Prunus mume) in Oita Prefecture, Kyushu, Japan. Inoculation of flowers, shoots, and fruit of P. mume with the fungus reproduced brown rot disease symptoms similar to those found in nature. The fungus somewhat resembled the colony appearance of Monilinia (anamorph Monilia) laxa, the apricot brown rot fungus, on PSA plates, but it differed from the latter and the other two brown rot fungi, M. fructigena and M. fructicola, in terms of growth rate, temperature optima for mycelial growth and sporulation, morphology and germination pattern of conidia, nuclear number in the conidium, and nucleotide sequences in the ITS region of ribosomal DNA. It is newly described as Monilia mumecola Y. Harada, Y. Sasaki & T. Sano. A key to anamorphic states of four brown rot fungi of fruit trees is provided.     

Molecular and serological characterization of iris yellow spot virus, a new and distinct tospovirus species

ABSTRACT A new tospovirus was identified in iris cultivations in the Netherlands. Both serological comparisons and sequence determination of the S RNA demonstrate that this virus represents a new and distinct species, belonging to a separate serogroup, and for which the name iris yellow spot virus (IYSV) is proposed. The disease symptoms on iris are characterized by yellow spots on the leaves. Its experimental host range is very narrow and, in addition to iris, only includes Nicotiana benthamiana and Datura stramonium. The nucleoprotein of IYSV shows only 30 to 44% sequence identity with those of other tospoviruses identified so far; the highest homology being found with the tospovirus species of serogroup IV.     

一种新的香蕉黑斑病病原菌鉴定及生物学特性研究

 在广西香蕉种植区发现一种引起香蕉黑斑病的新病原。通过对病原菌分离培养、致病性测定、形态学观察、分子生物学鉴定及对该病原菌生物学特性进行初步研究,表明引起该病害的病原菌为芒果球座菌(Guignardia mangiferae A.J. Roy)。该病原菌菌落为深橄榄色,产生棒状子囊、梭形子囊孢子及倒梨形分生孢子;其最适生长温度为28℃,最适pH 值为6;病原菌生长较好的碳源为果糖和阿拉伯糖,氮源为蛋白胨和酵母膏;在全光条件下,病原菌菌丝扩展速度最快;菌丝的致死温度为54℃。由G. mangiferae引起的香蕉黑斑病,在国内外为首次报道。     

布朗李叶枯病病原鉴定及药剂筛选

布朗李叶枯病在湖南布朗李树上一般株发病率为20％～35％,叶发病率10％～25％,病情指数10～25;严重地区株发病率达100％,叶发病率50％～70％,病情指数25～35。病原菌为Macrophoma kawatsakai Hara。病菌从叶尖或叶缘侵入,形成叶枯或半圆形的病斑。实验室药剂筛选证实,抑制该菌菌丝生长效果良好的化学药剂有:70％代森锰锌可湿性粉剂、40％菌克星可湿性粉剂、50％退菌特可湿性粉剂、55％疫霜锰锌可湿性粉剂、80％新万生可湿性粉剂等;抑制孢子萌发效果良好的化学药剂有:70％代森锰锌可湿性粉剂、55％疫霜锰锌可湿性粉剂、50％退菌特可湿性粉剂、80％新万生可湿性粉剂、70％甲基硫菌灵可湿性粉剂、45％石硫合剂可湿性粉剂等。     

Detection and molecular characterization of a phytoplasma affecting Prunus persica L. in Jujuy, Argentina

Peach (Prunus persica L.) plants with symptoms of yellowing, reddening, curling and leaf necrosis, premature defoliation and internode shortening were observed in production fields in Jujuy province (Argentina). A phytoplasma was detected by PCR using the universal primer pairs P1/P7 and R16F2n/R16R2 in all the symptomatic samples analysed. The RFLP profile of PCR products, amplified with R16F2n/R16R2 primers, shows that this phytoplasma, named Argentinean Peach Yellows (ArPY), belongs to subgroup 16Sr III-B. The phylogenetic analysis of the 1244 bp 16S rDNA cloned sequence, grouped the ArPY phytoplasma into the X-disease group with a closer relationship with CFSD, PssWB and ChTDIII phytoplasmas. This is the first report of a phytoplasma infecting peach trees in Argentina.     

Molecular Variability Among Isolates of Prunus Necrotic Ringspot Virus from Different Prunus spp

ABSTRACT Viral sequences amplified by polymerase chain reaction from 25 isolates of Prunus necrotic ringspot virus (PNRSV), varying in the symptomatology they cause in six different Prunus spp., were analyzed for restriction fragment polymorphisms. Most of the isolates could be discriminated by using a combination of three different restriction enzymes. The nucleotide sequences of the RNA 4 of 15 of these isolates were determined. Sequence comparisons and phylogenetic analyses of the RNA 4 and coat proteins (CPs) revealed that all of the isolates clustered into three different groups, represented by three previously sequenced PNRSV isolates: PV32, PE5, and PV96. The PE5-type group was characterized by a 5' untranslated region that was clearly different from that of the other two groups. The PV32-type group was characterized by an extra hexanucleotide consisting of a duplication of the six immediately preceding nucleotides. Although most of the variability was observed in the first third of the CP, the amino acid residues in this region, which were previously thought to be functionally important in the replication cycle of the virus, were strictly conserved. No clear correlation with the type of symptom or host specificity could be observed. The validity of this grouping was confirmed when other isolates recently characterized by other authors were included in these analyses.