The effects of some factors on the growth and morphology of Naegleria sp. and three strains of the genus Acanthamoeba.

The effects of various biophysical and chemical factors on the cytology of vegetative stages of Naegleria sp., Vitek strain, Acanthamoeba culbertsoni, Acanthamoeba castellanii, Neff strain and Acanthamoeba polyphaga, No. 1289, were studied. The amoebae were cultured in a liquid medium under axenic conditions. The optimum temperature was 37 degrees C for pathogenic strains of Naegleria sp. and Acanthamoeba culbertsoni and 20 degrees C for A. castellanii. No changes were observed in the growth of A. polyphaga at the temperatures 20 degrees and 37 degrees C. The strains investigated grew at pH values of 5.6 to 7.7 using Soerensen's buffer. At the limit values the growth was inhibited and the morphology of cells was markedly changed. All of the four strains grew still at pH 8.4 kept by NaHCO3. A. polyphaga grew at partial anaerobiosis. The three tested strains of the genus Acanthamoeba grew in liquid axenic medium with 0.89% NaCl. The growth of Naegleria sp., Vitek was inhibited already at 0.2% concentration of this salt. The addition of 3 X 10(-2) m KCl to the culture medium had a harmful effect on the growth and morphology of three tested strains, except A. polyphaga. In the culture medium containing 2 X 10(-3) m CaCl2 the encystment of both pathogenic strains was stimulated. The cytological changes under experimental conditions were manifested by atypical movement of trophozoits and their intracellular structure.     

Gut bacteria associated with the Pacific Coast wireworm,<Emphasis Type="Italic">Limonius canus</Emphasis>, inferred from 16s rDNA sequences and their implications for control

A multitude of bacteria have been isolated from the guts of several insect species. Some of these have been modified to interfere with the development of the host insect or with the development and transmission of plant and animal pathogens transmitted by the host insect. We surveyed the gut flora of the Pacific Coast wireworm,Limonius canus LeConte, a serious pest of potato, at two sites in Oregon and Washington. Isolates were obtained from surface-sterilized triturated larvae by dilution plating on standard media. A rich diversity of species was found in 86 isolates, including spore-formers, non-spore-formers and aerobic and facultatively anaerobic species collected on four sampling dates at each location. Twenty-one of the isolates were identified to species based on rDNA sequence (nine distinct species). An additional 34 isolates were identified to genus from the sequence data while six isolates could be assigned only to family based on sequence comparisons. Twenty-seven additional isolates were identified to species (9), genus (17) or family (1) based on side-by-side morphological comparisons with isolates identified from rDNA sequence. The most frequently isolated bacterium wasBacillus megaterium, followed byRahnella aquatilis. A naturally occurring bacterium found in the gut and/or environment of a targeted insect that is modified to express toxins or other detrimental substances could provide certain advantages (such as persistence and recycling) over inundatively applied microbial control agents, particularly within soil habitats. The hypothesis that these species or others from the survey represent candidates for genetic modification to provide control options forL. canus is discussed.     

Morphological, pathogenic, and molecular characterization of alternaria isolates associated with alternaria late blight of pistachio

ABSTRACT Alternaria isolates were obtained from various pistachio tissues collected in five orchards in California. For all isolates, morphological characteristics of the colony and sporulation apparatus were determined and compared with those of representative isolates of A. alternata, A. tenuissima, A. arborescens, and A. infectoria. A selection of the pistachio isolates and the representative Alternaria isolates were evaluated for pathogenicity to pistachio. Molecular characteristics of these isolates were determined using random amplified polymorphism DNA (RAPD) analysis, polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis of nuclear intergenic spacer rDNA, and sequence analysis of nuclear internal transcribed spacer (ITS) rDNA. Based on morphological characteristics, the pistachio isolates were grouped as identical or very similar to either A. alternata, A. tenuissima, A. arborescens, or A. infectoria. Isolates from the alternata, tenuissima, and arborescens species-groups were pathogenic to pistachio and no significant differences in pathogenicity were observed. Isolates from the infectoria species-group were only weakly pathogenic to pistachio. Based on cluster analysis of RAPD and PCR-RFLP data, three distinct clusters were evident; the infectoria cluster, the arborescens cluster, and a combined alternata/tenuissima cluster. Based on analysis of ITS sequence data, the infectoria species-group was phylogenetically distinct from the other species-groups. Isolates of the alternata, tenuissima, and arborescens species-groups comprised a monophyletic clade in which the three species-groups could not be further resolved.     

Determination of Ralstonia (Pseudomonas) solanacearum rDNA subgroups by PCR tests

Rapid and sensitive polymerase chain reaction (PCR) methods are described for determination of the two 16 S rDNA subgroups of Ralstonia solanacearum, the causal agent of bacterial wilt. A third subgroup consisting of Indonesian R. solanacearum isolates belonging to Division II, the blood disease bacterium and Pseudomonas syzygii can also be identified. Primers were designed to sequences within R. solanacearum 16 S rDNA (equivalent to Escherichia coli 16 S rDNA positions 74–97, 455–475, 1454–1474), and the internal transcribed spacer region between the 16 S and 23 S rDNA genes. Different combinations of forward and reverse primers allowed selective PCR amplification of (a) R. solanacearum Division I (biovars 3, 4 and 5), (b) Division II (biovars 1, N2, and 2) including the blood disease bacterium and P. syzygii , or (c) amplification of Division II only except for five biovar 1, 2 or N2 isolates of R. solanacearum from Indonesia, P. syzygii and the BDB. A total of 104 R. solanacearum , 14 blood disease bacterium and 10 P. syzygii isolates were tested. Simultaneous detection of species and subdivision was achieved by designing a multiplex PCR test in which a 288-base pair (bp) band is produced by all R. solanacearum isolates, and an additional 409-bp band in Division I strains.     

花生白绢病菌ITS分型、菌丝亲和群分析及相关生物学特性比较

2013~2016年从全国12个省市采集不同花生白绢病样本,共分离获得39个分离物,对其ITS-r DNA序列进行了分析,表明它们均属于齐整小核菌(Sclerotium rolfsii);这39个分离物分为两个亚组,分别包含22个和17个菌株;对这39个菌株进行了菌丝亲和群分析及相关生物学特性比较,共鉴定出23个菌丝亲和群;8个亲和群包含2~6个菌株,其余的15个亲和群都只包含1个菌株;同一菌丝亲和群的菌株菌落形态相似,大多数菌株的菌丝生长速度、菌核大小比较相近,个别菌株差异较大;39个菌株均能产生草酸,在菌落形态、菌丝生长速度、菌核大小和重量上均有差异,生长速度为0.47~2.32cm·d~(-1),菌核直径为0.71~1.87 mm,单粒菌核干重为0.24~2.64 mg。     

黄瓜内生放线菌的分离、筛选及其活性菌株鉴定

 从植物内生放线菌中筛选拮抗活性菌株和寻找新的农用活性代谢产物,可为植物病害防治提供新的资源。本研究结果发现黄瓜幼苗的根、茎、叶中均有内生放线菌的存在,根组织中的数量、种类明显多于叶片和茎,占总分离株的72.7%,以链霉菌的淡紫灰类群、灰褐类群为主。活性筛选试验结果表明,黄瓜内生放线菌中对12种靶标真菌和6种细菌具有拮抗作用的菌株分别占46.8%和39.0%,主要为分离自根组织的链霉菌淡紫灰类群。分离自黄瓜叶片的gCLA4菌株抑菌谱较广,其发酵滤液对供试12种靶标真菌均具有较好的抑菌效果,但对靶标细菌有选择性抑制作用。形态学、细胞化学和16S rDNA序列分析鉴定该菌株为淡紫灰链霉菌(Streptomyces lavendularectus)。     

Strains of Botrytis cinerea resistant to dicarboximide and benzimidazole fungicides in New Zealand vineyards

In a survey of New Zealand vineyards at harvest 1985, isolates of Botrytis cinerea resistant to benzimidazole and to dicarboximide fungicides were common. The mean frequency of resistance in the major vine-growing districts ranged from 8 to 41% for benzimidazoles, and from 51 to 59% for dicarboximides. All benzimidazole-resistant isolates showed high levels of resistance (EC50 greater than 100 mg/l carbendazim based on radial growth response), and all dicarboximide-resistant isolates showed low levels of resistance. Two subgroups of dicarboximide-resistant isolates were recognized, distinguished in the first instance by their osmotic response. Low-level resistant isolates, which formed a dense margin on osmotically amended medium, exhibited an EC50 for mycelial growth on iprodione of c. 3-2 mg/l; ultra-low-level resistant isolates, which formed a fibrillose margin on osmotically amended medium identical to that of sensitive isolates, exhibited an EC50 of c. 1-3 mg/1. In agar culture, radial growth rate, and conidial and sclerotial production of both subgroups were similar to those of sensitive isolates. Virulence (lesion size) and conidial production on grape berries were highest in sensitive isolates, intermediate in ultra-low-level dicarboximide-resistant isolates, and lowest in low-level dicarboximide-resistant isolates. Evidence is presented indicating that ultra-low-level dicarboximide-resistant strains have progressively replaced low-level dicarboximide-resistant strains in the vineyard population. The presence of dicarboximide-resistant strains was linked with a partial loss of fungicide efficacy.     

北京地区芹菜细菌性软腐病菌鉴定及其致病力分析

 对从北京地区芹菜软腐组织中分离到的37株细菌性软腐病菌株,进行了微生物碳源利用(Biolog^TM)、生化特性、特异性PCR、ITS-RFLP带型以及基于16S rDNA完整序列遗传关系分析。结果如下:菌株革兰氏染色阴性、具周生鞭毛;可在5%和7% NaCl及28℃和37℃条件下生长;可分解柠檬酸盐及液化明胶;Biolog分析将这些菌株均鉴定为Pectobacterium carotovorum subsp. carotovorum (Pcc)。生化特性分析发现,其中36株菌株能利用D-山梨醇、D-阿拉伯糖醇、异麦芽酮糖和α-甲基葡萄糖苷,与对照菌株P. carotovorum subsp. odoriferum(Pco)S7一致;另外1株菌株Q34不能利用上述糖醇,与对照菌株P. carotovorum subsp. brasilience (Pcb)BC1和P. carotovorum subsp. carotovorum(Pcc)ECC71表现一致。利用pel(pectate lyase)基因特异性引物Y1/Y2在所有的37株菌株中均扩增出预期片段(434 bp),表明其基因组中均含有果胶酶基因。Pcb特异性PCR引物BR1f/L1r仅在Q34菌株与Pcb BC1中扩增出预期片段(322 bp),而Pcc特异性PCR引物EXPCCF/EXPCCR则在除Pcb BC1外所有菌株中均扩增出预期片段(550 bp)。Rsa I酶切16S-23S rDNA ITS片段结果显示,Q34酶切带型与Pcb BC1相同,其余36株带型与Pcc ECC71和Pco S7相同。基于16S rDNA基因完整序列,以Dickeya dadantii菌株582为外群,该37株菌株与已发表的Pectobacterium菌株系统发育树聚类分析结果表明,Q34与已发表的其他Pcb菌株形成了明显的Pcb类群,其余36株菌株则与已发表的其他Pco菌株形成了明显的Pco类群。综合多种鉴定结果,36株被鉴定为Pco,Q34被鉴定为Pcb。菌株致病力测试结果显示,36株Pco菌株中仅Q47表现为低等的致病力,其余24株和11株分别表现为中等和高等致病力;Pcb菌株Q34则表现出中等致病力。     

新疆加工型辣椒细菌性斑点病的发生和病原鉴定

 新疆加工型辣椒主要产区巴音郭楞蒙古自治州发生了一种严重危害辣椒的细菌性病害。从发病辣椒叶片中分离细菌,通过烟草过敏性反应、马铃薯软腐试验和接种辣椒等致病性测定,确定了13个致病菌株,各菌株之间致病力无明显差异。通过菌体形态、培养性状观察、生理生化反应、寄主范围测定,结合16S rDNA和rpoD基因扩增、序列测定和系统发育分析,将病原菌鉴定为丁香假单胞菌丁香致病变种(Pseudomonas syringae pv. syringae)。病原菌人工接种还能侵染番茄、茄子、马铃薯及黄瓜、四季豆、白菜、萝卜、芹菜等植物。P. syringae pv. syringae引起加工型辣椒细菌性斑点病在国内属首次报道。     

Molecular Characterisation of Alternaria linicola and its Detection in Linseed

Nucleotide sequences of the ribosomal DNA (rDNA) internal transcribed spacers (ITS) 1 and 2 and a 1068bp section of the beta-tubulin gene divided seven designated species of Alternaria into five taxa. Stemphylium botryosum formed a sixth closely related taxon. Isolates of A. linicola possessed an identical ITS sequence to one group of A. solani isolates, and two clusters of A. linicola isolates, revealed from beta-tubulin gene data to show minor variation, were as genetically similar to isolates of A. solani as they were to each other. We suggest, therefore, that A. linicola falls within the species A. solani. Similar results suggest that A. lini falls within the species A. alternata. RAPD analysis of the total genomic DNA from the Alternaria spp. concurred with the nucleotide sequence analyses. An oligonucleotide primer (ALP) was selected from the rDNA ITS1 region of A. linicola/A. solani. PCR with primers ALP and ITS4 (from a conserved region of the rDNA) amplified a c. 536bp fragment from isolates of A. linicola and A. solani but not from other Alternaria spp. nor from other fungi which may be associated with linseed. These primers amplified an identical fragment, confirmed by Southern hybridization, from DNA released from infected linseed seed and leaf tissues. These primers have the potential to be used also for the detection of A. solani in host tissues.     

水稻纹枯病生防内生菌糖蜜草固氮螺菌的分离与鉴定

 本文首先对砂仁内生细菌进行分离,以水稻纹枯病菌(Rhizoctonia solani)为靶标菌对获得菌株进行离体拮抗活性、盆栽及田间试验测定。结果表明：获得的27株内生细菌中有4株具有较好的离体抑菌活性,其中SRJ2-4抑菌效果最好,抑菌带达到18 mm;SRJ2-4的盆栽防效及田间防效分别为80.7%与79.4%,与其它菌株相比达极显著水平。SRJ2-4处理的亩产量为488.79 kg,高于其他药剂处理。对该菌株形态、生理生化及16S rDNA序列进行分析,将该内生菌鉴定为糖蜜草固氮螺菌(Azospirillum melinis)。     

广西地区葡萄黑痘病病原菌的分离与鉴定

采用常规组织分离法对广西南宁、河池两地的葡萄黑痘病菌进行分离、纯化,分别得到37和31株分离菌。经菌落形态观察及r DNA ITS序列分析,南宁37株分离菌为同一菌株,河池31株分离菌为同一菌株,以NN和HC分别代表两地菌株,对它们进行形态学、致病性鉴定及r DNA ITS区域序列分析。结果显示,两地菌株形态学与致病性存在较大差异,但都符合黑痘病菌生长形态。NN菌落为红棕色、近圆形,边缘光滑。菌落中心位置丘状凸起,表面有白色菌丝和透明粘稠的小液滴,周围边缘有较规则的褶皱。HC菌落呈浅橙色、近圆形,边缘光滑。菌落中心位置丘状凸起,表面有少量白色菌丝,无液滴,周围边缘有不规则褶皱隆起。人工接种葡萄后均能引起典型的黑痘病症状,NN致病性强于HC。使用r DNA ITS区域通用引物ITS1F/ITS4进行PCR扩增后,NN和HC分别得到1 124 bp和818 bp的片段。比对结果显示1 124 bp与Elsinoe ampelina(AY826763.1)序列覆盖率达92%,序列一致性达99%;818 bp与Elsinoe ampelina(AY826762.1)序列覆盖率达75%,序列一致性达99%。因此,NN和HC均是引起广西葡萄黑痘病的病原菌。     

广西蔗区甘蔗白条病菌的鉴定与致病力分析

甘蔗白条病是一种检疫性病害,在我国多个蔗区均有报道,严重威胁我国甘蔗生产.本研究对采自广西蔗区不同品种(系)的病原菌进行分离、鉴定、保存,并选取其中40份白条黄单胞菌分离物进行遗传多样性分析与接种试验,评价其致病性.根据三磷酸腺苷结合盒转运蛋白等管家基因和Ⅳ型分泌系统virB基因的序列差异和进化树分析,将40个菌株分为...     

Phylogenetic Analysis of 16S rRNA Genes and PCR Analysis of the nec1 Gene from Streptomyces spp. Causing Common Scab, Pitted Scab, and Netted Scab in Finland

ABSTRACT The sequences of the 16S rRNA genes (nucleotides 29 to 1,521) from various Streptomyces strains pathogenic to potato were compared. These included 10 pathogenic Streptomyces strains isolated from potato scab lesions in Finland, the type strains of S. aureofaciens NRRL 2209(T) and S. lydicus ATCC 25470(T), 'S. griseus subsp. scabies' ATCC 10246, and two S. griseus strains that were originally deposited to the collection as pathogens. The nucleotide sequence (>94.5% sequence identity [SI]) and length (1,469 to 1,481 nucleotides) of the analyzed region varied. Phylogenetic analysis of 16S rRNA genes placed Finnish strains into three species, supported by previously characterized morphological and physiological traits. Six Finnish strains, including two strains that deviated from the others in one trait (no spiral sporophores or D-xylose utilization), had identical 16S rRNA genes and were identified as S. scabies (99.9% SI to S. scabies ATCC 49173). Three Finnish strains were identified as S. turgidiscabies, a species previously described only in Japan (99.9% SI to S. turgidiscabies ATCC 700248). Finnish strain 317 and S. aureofaciens NRRL 2209 (99.8% SI) were placed in a distinct phylogenetic cluster together with Kitosatospora spp., which suggests that S. aureofaciens may belong to the recently revived genus Kitosatospora. In pathogenicity tests, S. scabies caused characteristic symptoms of common scab, S. turgidiscabies caused mainly pitted scab, and S. aureofaciens caused netted scab and necrotic lesions on stolons of potato cultivars Bintje and Matilda in the greenhouse. The nec1 gene and the intergenic region between nec1 and the 5' transposase pseudogene ORFtnp were successfully amplified by polymerase chain reaction from S. scabies ATCC 49173 and the pathogenic Finnish strains of S. scabies, but not from a nonpathogenic strain of S. scabies, three pathogenic and two nonpathogenic strains of S. turgidiscabies, and S. aureofaciens.     

进境澳大利亚豌豆细菌性萎蔫病病原菌的分离鉴定

 2008年3月自澳大利亚进口的豌豆种苗病变部位分离到致病性菌株,该菌株能引起豌豆茎部、卷须萎蔫腐烂,叶片褪绿等症状。针刺接种豌豆,发生的病变状态与自然发病的症状相同,且在接种发病植株中又分离到形态上一致的病原菌,得到了柯赫法则的验证。经形态特征、培养性状、生理生化及16S rDNA序列分析,鉴定其为桃色欧文氏菌(Erwinia persicina)。这是我国首次从进境豌豆中检出该病害。     

Toxin Profile, Fertility and AFLP Analysis of Fusarium verticillioides from Banana Fruits

Gibberella fujikuroi is composed of at least nine mating populations (MPs), corresponding to biological species and assigned letters (from A to I). Each MP possesses a specific toxicological profile and a preferential host. Members of Fusarium verticillioides and F. thapsinum, anamorphs respectively of MPs A (G. moniliformis) and F (G. thapsina), share identical morphological traits, but they have a different preferential hosts (maize and sorghum, respectively) and toxin profiles, beingable the only member of MP A to produce fumonisins and the only member of MP F to produce moniliformin. Isolates from banana fruits were identified morphologically as F. verticillioides. The isolates were analyzed for fumonisin and moniliformin production. While none of the isolates produced fumonisin, all the isolates produced moniliformin. The isolates were crossed with tester strains of MPs A and F, showing ability to produce fertile perithecia only when crossed by MP A tester strains isolated from maize. However, the time required for the formation of fertile perithecia and their size differed significantly from the usual fertile crosses of strains belonging to MP A. Pathogenicity tests using such isolates of F. verticillioides isolated from banana and a set of F. verticillioides isolates isolated from maize were also performed on banana fruits. The data showed that the isolates from banana were more pathogenic. Finally, isolates from banana and maize were compared using AFLP. The results revealed that isolates from banana and maize produced two distinctly different clusters. In conclusion, isolates of F. verticillioides from banana showed specific traits (toxin production, in vitro fertility, pathogenicity and molecular profiles), that were different to those of the same species from maize. This could reflect important differences in the ecology and natural history of the population from banana and should encourage further investigations into the mechanisms of toxin production and pathogenicity within the same MP.     

New data on aetiology of nodular gill disease in rainbow trout, Oncorhynchus mykiss

We studied amoebae associated with nodular gill disease (NGD) outbreaks in rainbow trout Oncorhynchus mykiss (Walbaum) in fish farms in South-Western Germany. Gills of 12 diseased rainbow trout were examined in fresh, by isolation attempts, histologically and using in situ hybridisation (ISH). A total of nine amoeba strains of the genera Acanthamoeba (1), Hartmannella (2), Naegleria (1), Protacanthamoeba (1) and Vannella (4) were isolated and determined using light microscopical, ultrastructural and molecular methods. Specific molecular probes designed from the SSU rDNA sequences of individual amoeba strains were used for non-radioactive ISH in histological sections. Association of Naegleria sp. with NGD and a direct ISH proof of Naegleria trophozoites attached to hyperplastic gill epithelium are novel findings, expanding the number of possible agents of NGD and supporting the hypothesis on multicausal aetiology of this disease.     

Two new species,Phytophthora nagaii sp. nov. and P. fragariaefolia sp. nov., causing serious diseases on rose and strawberry plants,respectively, in Japan

A new disease of rose was noticed in Chiba Prefecture of Japan in 1968, and the pathogen was initially identified as Phytophthora megasperma based on morphological characteristics. Similar Phytophthora isolates have since been collected from rose plants in Chiba, Kanagawa, and Shizuoka Prefectures. In 2005, several Phytophthora isolates were recovered from crowns of strawberry plants in Hokkaido Prefecture. These were considered to be members of a new species. In this study, we re-examined all these isolates using morphological and physiological studies and a multilocus phylogenetic analysis. The rose and strawberry isolates were mostly similar morphologically and physiologically, with some exceptions. The rose isolates differed significantly from P. megasperma sensu stricto and other related Phytophthora species. The rose and strawberry isolates had external proliferation of sporangia, characteristic funnel-shaped oogonia, predominantly paragynous antheridia, and fast growth rates of 10.5 mm/24 h at an optimum temperature of 28 °C. In the multilocus phylogenetic tree constructed using sequences from the rDNA ITS regions, rDNA LSU, and the translation elongation factor 1-α, β-tubulin and coxI genes, they formed a distinct monophyletic group in clade 7 with strong bootstrap support. The rose and strawberry isolates separated into two distinct groups. The results indicate that the rose and strawberry isolates constitute two separate species, designated here as Phytophthora nagaii and P. fragariaefolia.     

7种检疫性植物病原黄单胞菌III型分泌系统和效应蛋白编码基因的差异性分析

 γ-变形菌纲(γ-Proteobacteria)的黄单胞菌属(Xanthomonas)的大多数种类可引起植物病害,多数是我国检疫对象。与其他革兰氏阴性植物病原细菌一样,植物病原黄单胞菌可通过高度保守的III型分泌系统(type-III secretion system, T3SS)分泌效应蛋白(T3SS-secreted effectors, T3SEs)进入植物细胞,在非寄主植物和抗病寄主植物上产生过敏反应(hypersensitive response, HR)以及在感病寄主植物上具有致病性。尚不清楚哪些种类的黄单胞菌具有T3SS和缺少哪些T3SE是否可作为检疫的依据。搜集7种检疫性植物病原黄单胞菌,通过PCR和Southern杂交试验结果发现:香蕉细菌性青枯病菌(X. campestris pv. musacearum)的ICMP287和ATCC49084菌株、甘蔗流胶病菌(X. axonopodis pv. vasculorum)ATCC13901菌株、洋葱细菌性叶枯病菌(X. axonopodis pv. allii)的LMG576和LMG578菌株中不含有tale基因,并且ATCC13901菌株既不含有T3SS基因也不含有hpa1和xopQ基因;菜豆细菌性疫病菌(X. campestris pv. phaseoli)ATCC49119菌株不含有hpa1基因。相应地,推测含有2~12个tale基因的黄单胞菌有:大豆斑疹病菌(X. axonopodis pv. glycines)ICMP5732和ATCC43911菌株、豌豆细菌性疫病菌(X. axonopodis pv. vignicola)ATCC11648菌株、棉花细菌性角斑病菌(X. campestris pv. malvacearum)ATCC12131和(X. campestris pv. phaseoli)ATCC49119菌株。大豆细菌性斑疹病菌ATCC43911菌株尽管含有hpa1、xopQ和hrcC基因,但在非寄主烟草上不能激发HR反应;而甘蔗流胶病菌ATCC13901菌株不含有hpa1、xopQ和hrcC基因,却激发烟草产生HR反应。这些结果对于分析比较不同植物病原黄单胞菌的致病性因子和设计特定的植物检疫靶点提供了科学线索。     

山东省小麦赤霉病菌种群组成及其致病力分化

由禾谷镰孢菌群Fusarium graminearum clade引起的赤霉病是小麦的重要病害。为明确山东省小麦赤霉病菌的种群组成及其致病力,于2011年和2012年从山东省15地市分离了95株小麦赤霉病菌,在形态和分子生物学鉴定种的基础上,采用鉴定B型毒素化学型的特异性引物进行毒素化学型分析。在95个菌株中,93株分离物为禾谷镰孢菌F.graminearum,2株为燕麦镰孢菌F.avenaceum。94株分离物为脱氧雪腐镰孢菌烯醇(deoxynivalenol,DON)化学型,1株为雪腐镰孢菌烯醇(nivalenol,NIV)化学型。在94株DON毒素化学型菌株中,90株为15-乙酰脱氧雪腐镰孢菌烯醇(15-acetyldeoxynivalenol,15-AcDON)化学型,4株为3-乙酰脱氧雪腐镰孢菌烯醇(3-acetyldeoxynivalenol,3-AcDON)化学型。在小麦扬花期,采用单花滴注接种法对29个菌株进行了致病力测定,供试菌株的致病力分化明显。表明在山东省冬小麦产区,产15-AcDON毒素的F.gra-minearum是小麦赤霉病菌的优势种群。