拟轮枝镰孢菌EST-SSR信息分析与标记开发

为开发可用于拟轮枝镰孢菌Fusarium verticillioides及其近缘种遗传多样性分析的SSR引物,利用生物信息学方法和PCR技术,通过对从NCBI下载的87 086条拟轮枝镰孢菌的EST序列信息进行分析,设计EST-SSR引物,检测其在拟轮枝镰孢菌及其近缘种中的扩增情况,并用筛选出的多态性引物对15株拟轮枝镰孢菌进行SSR遗传多样性分析。结果表明,在EST序列中,共查找到11 952个SSR位点,592种重复基元,SSR出现频率为1.09%,重复基元出现数量最多的为三核苷酸(54.00%),其中(CAA/TTG)n基元出现频率最高。设计的25对EST-SSR引物在拟轮枝镰孢菌种内的有效扩增率和多态率分别为80.00%与32.00%,对5种近缘镰孢菌种的通用率和多态率分别为40.00%和8.00%。遗传多样性分析结果表明,在相似系数为0.664水平下,供试菌株可划分为4个SSR类群,但类群的划分与菌株的地理来源无关;不同菌株间存在明显的遗传分化。表明基于拟轮枝镰孢菌EST序列开发的SSR引物可用于拟轮枝镰孢菌及其近缘种的遗传多样性分析。     

基于转录组数据的印度谷螟微卫星位点分析

基于印度谷螟转录组测序数据筛选其功能微卫星(EST-SSR)分子标记,设计该虫的微卫星(SSR)引物并验证其适用性。用MicroSAtellite微卫星搜索软件查找印度谷螟转录组中微卫星的数量、重复次数以及所有微卫星的位置信息,采用Primer Premier 5软件设计SSR引物,并进行PCR验证。结果表明含EST-SSR的序列3 173个,占总搜索序列的8.52%,平均每13kb中就出现1个EST-SSR。共发现192种微卫星类型,其中重复单元为单碱基、二碱基和三碱基的比例较高,依次是28.21%、39.84%、25.43%。除单碱基重复单元外,出现频率最高的是AT/AT,有593次。在66对印度谷螟EST-SSR引物中,有28对PCR扩增成功。这说明基于印度谷螟转录组数据开发微卫星标记是可行的,本研究获得的印度谷螟EST-SSR位点为今后开展该虫的种群遗传学研究提供了基础数据。     

尖镰孢菌EST-SSR遗传多样性分析及通用性评价

为了解38株尖镰孢菌的遗传多样性并开发可在近缘镰孢菌种中通用的尖镰孢菌EST-SSR标记,利用设计和筛选的18对多态性EST-SSR引物对38株尖镰孢菌和5种近缘镰孢菌进行SSRPCR扩增,经6%非变性聚丙烯酰胺凝胶分离扩增产物,并用NTSYS软件分析供试尖镰孢菌的PCR扩增结果。结果表明,18对EST-SSR标记引物在38株尖镰孢菌中检测到75条多态性条带,多态性比率达92.6%,平均每对引物可扩增4.2条;各菌株间的遗传相似系数介于0.565~0.946之间,平均为0.721;来源于同科寄主植物群体的菌株间的平均遗传相似系数以葫芦科最大,锦葵科最小,依次为葫芦科兰科豆科亚麻科茄科锦葵科。在相似系数为0.756时,供试38株菌有35株按照不同科寄主植物聚为不同的类群,说明尖镰孢菌SSR类群的划分与其寄主来源具有一定的相关性。18对EST-SSR引物在近缘镰孢菌种中均能有效扩增的引物数及通用性比率为10对和55.6%,均显示多态性的引物有2对,占供试引物总数的11.1%。表明尖镰孢菌ESTSSR区域遗传多样性丰富,基于尖镰孢菌EST序列开发镰孢菌通用SSR标记是可行的。     

烟草疫霉SSR分子标记的开发与初步应用

 为开发烟草疫霉的SSR分子标记,利用MISA软件搜索烟草疫霉基因组序列中的 SSR位点,共发现1 311个SSR位点,优势SSR位点为二核苷酸和三核苷酸,分别占总 SSR 位点的56.45%和39.36%;根据分析到的SSR位点使用Primer 5.0软件设计48对SSR引物,以7株烟草疫霉的DNA 为模板对这些引物进行筛选,共获得扩增条带清晰且具有多态性的SSR引物20对,然后使用其中的6对SSR对32株烟草疫霉进行UPGMA聚类分析,遗传相似系数在 0.60~1.00 之间,在相似系数0.70水平上,可将其划分为3个类群,类群I包含29个菌株,类群II包含1个菌株,类群III包含2个菌株,显示出较低的遗传分化水平。这些SSR引物的开发将为研究我国烟草疫霉的遗传多样性、群体遗传结构以及遗传图谱构建等奠定基础。     

基于KASP技术的小麦条锈菌SNP分子标记开发与评价

为开发用于小麦条锈菌Puccinia striiformis f. sp. tritici群体遗传研究的竞争性等位基因特异性PCR-单核苷酸多态性(kompetitive allele specific PCR-single nucleotide polymorphism,KASPSNP)标记,以中国小麦条锈菌流行小种CYR32的基因组为参考,与美国小麦条锈菌流行小种PST78和印度小麦条锈菌流行小种38S102的基因组进行比对,根据比对到的SNP位点设计KASP-SNP引物,用64个中国小麦条锈菌标样对其进行筛选,同时用13对多态性引物组成的简单重复序列(sim‐ple sequence repeat,SSR)分子标记分析这64个标样,并利用Powermarker 3.25和Structure 2.3软件通过多态性指数和群体遗传结构分析来评价KASP-SNP和SSR两种分子标记。结果显示,共比对到29 929个SNP位点,设计出462对KASP-SNP引物,经64个中国小麦条锈菌标样筛选到43对多态性较好的引物,所开发的这43对KASP-SNP引物多态性信息含量指数平均为0.346,基因多样性指数平均为0.420,而SSR引物的2种指数分别为0.237和0.265,前者较后者分别高出46.0%和58.5%。2种标记结果的群体遗传结构分析可得到类似结果,最佳聚类数K值都为4,云南菌系是遗传结构相对最简单的菌系,湖北菌系是遗传结构相对最复杂的菌系,但个别菌株的遗传划分存在较大差异。表明本研究开发的KASP-SNP分子标记多态性较SSR分子标记更加丰富,具有较好的应用前景。     

基于转录组的小豆SSR分子标记开发及其应用

为了开发小豆SSR(Simple Sequence Repeats)分子标记,2019—2020年,利用微卫星识别工具MISA和软件Primer 3搜索小豆资源QH1转录组测序得到的Unigene,获得3 045个SSR分子标记,通过对标记的重复基序特点分析,发现标记的重复基序以单核苷酸重复、二核苷酸重复和三核苷酸重复为主,分别占标记总数的41.2%、26.4%和25.6%。利用可以锚定到小豆基因组并能成功设计引物的标记,构建了包括1 505个SSR分子标记的物理图谱。从以上1 505个标记中,随机选取分布于小豆11条染色体上的132个SSR标记进行有效性验证,发现有效扩增的标记为118个,有效率为89.4%。通过多态性标记筛选,获得6个多态性标记,利用这6个标记对36份小豆品种进行聚类分析,发现供试小豆材料可以分为4个类群。说明开发的SSR分子标记能够分析小豆的遗传背景差异,为小豆种质资源鉴定、遗传多样性分析以及优良性状基因定位研究提供可用的分子标记。     

亚洲玉米螟Bt抗性种群的遗传多样性分析

近20年来,在北美、西欧、南美、菲律宾等20多个国家大面积商业化应用Bt玉米防治欧洲玉米螟Ostrinia nubilalis(Hübner)等鳞翅目害虫的实践证明,其不可避免地胁迫靶标害虫产生遗传分化,出现新的抗性种群。研究精准有效的抗性检测方法,将为抗性监测和抗性治理策略的有效性提供科学依据。本研究基于高通量测序获得的亚洲玉米螟Ostrinia furnacalis(Guenée)转录组数据,应用MISA (MicroSAtellite)软件搜索SSR位点,从61 622条EST(Expressed Sequence Tag)序列中获得了3 467个SSR位点。通过设计、筛选,共获得3 316对特异性引物,从中挑选了150对引物进行PCR扩增,共有51对扩增出目的条带,对亚洲玉米螟敏感种群(ACB-BtS)及5个Bt毒素抗性种群(ACB-AbR、ACB-AcR、ACB-AhR、ACB-FR、ACB-IeR)进行多态性检测,最终得到20条高多态性引物。利用这20对微卫星引物共检测到126个等位基因,平均每个位点6.3个。不同Bt抗性种群间产生了一定程度的遗传分化,种群间的平均遗传分化系数(F_(st))为0.195 9,即说明种群间的遗传变异为19.6%。根据遗传距离建立了UPGMA系统发育树,显示6个种群的相似度,即ACB-AbR与ACB-AcR相似度高。种群变异相似度规律与已报道的亚洲玉米螟对各Bt毒素的交互抗性规律相一致。本研究发现的SSR位点可作为亚洲玉米螟不同Bt毒素抗性种群的分子检测方法。     

禾谷丝核菌基因组SSR标记的开发及评价

群体遗传学研究对于了解病原菌的流行、变异及进化规律具有重要意义。但是到目前为止,对小麦纹枯病菌禾谷丝核菌群体遗传结构的了解并不深入,缺乏有效的SSR标记是主要原因。本研究根据禾谷丝核菌全基因组序列进行了微卫星位点搜索并设计SSR引物,通过电泳筛选和测序验证,最终筛选出12个多态性较好且稳定可靠的SSR标记。利用这些标记对收集自我国安徽、江苏、河南三省的23个禾谷丝核菌菌株进行了多态性分析,结果发现禾谷丝核菌基因组中长片段微卫星位点较少。12对引物扩增出的等位基因数平均为6.1个,期望杂合度平均为0.651,观测杂合度平均为0.508,表明这些标记具有较高的多态性,能够满足禾谷丝核菌群体遗传学研究需要。本研究为进一步进行禾谷丝核菌的多样性、群体遗传结构分析及进化学研究提供了有效工具。     

大豆疫霉多态性SSR标记开发及遗传多样性分析

 用FastPCR软件在大豆疫霉全基因组中搜索到1 234个含2~4个重复基元精确SSRs。选择260个SSRs设计引物,经对大豆疫霉5个分离物的基因组DNA检测,有212对(81.5%)有效扩增出SSR特征条带,112对(52.8%)扩增多态性。用18对多态性SSR引物分析了来自美国、中国黑龙江省和福建省大豆疫霉分离物的遗传多样性,在73个分离物中共扩增出112个等位变异,变异范围为4~9,平均为6.22个,表明选择的引物对具有高的多态性。在3个大豆疫霉群体中,黑龙江省和福建省分离物的遗传距离最近,美国和福建省分离物的遗传距离最远。UPGMA聚类将73个分离物划分为6组,其中8个美国分离物(72.73%)和53个中国分离物(85.48%)被聚类在一起,表明大豆疫霉中国分离物与美国分离物可能具有共同的祖先,中国分离物可能为外来种。     

番茄资源对叶霉病的抗性鉴定和SSR标记遗传变异分析

 对62份番茄种质资源进行了抗番茄叶霉病鉴定, 共筛选出抗病材料17份, 其中对全部生理小种(1.2.3、1.2、2.3、1.2.3.4、1.2.4)均表现抗病或免疫的材料9份;抗3个生理小种的材料4份;抗2个生理小种的材料2份;抗4个生理小种的材料2份。并应用SSR标记技术对62份种质资源进行了遗传多样性分析, 50对SSR引物中筛选出11对多态性明显、条带清晰、反应稳定的引物, 共扩增出94条谱带, 平均每个引物扩增出8.55条带, 多态性条带比例达63.94%, 遗传相似系数在0~1之间, 表现出丰富的遗传多态性, 可将番茄野生种和栽培种分开, 反映了种间的遗传差异。     

Tumours of Begonia and some other ornamentals,induced by Corynebacterium fascians

In 1975 many tumours were observed in plants ofBegonia Schwabenland grown in Aalsmeer. Submersion of the roots ofNicotiana megalosiphon seedlings in a homogenate of tumorous tissue, induced tumours after two weeks. Short periods of submergence yielded results similar to those obtained after longer periods. Tumour homogenates lost their infectivity after ten min at 50°C. Aphids transmitted the infectious agent.Treatment with propylene oxide did not inhibit infectivity completely. Filtration through a 450 nm filter removed the infectious agent.Tobacco tumor virus or a viroid could not be isolated. Cultures ofCorynebacterium fascians, isolated from tumours ofN. megalosiphon were highly infectious and induced tumours in healthyN. megalosiphon andBegonia. Tumorous tissue homogenates ofPelargonium zonale, Dahlia sp.,Gladiolus sp., andLilium sp. also caused tumours inN. megalosiphon, from whichC. fascians was isolated. It was not possible to produce tumours inN. megalosiphon with homogenates from roses with symptoms of bud proliferation.Samenvatting In 1975 werden vele tumoren waargenomen inBegonia Schwabenland op Aalsmeerse bedrijven (Fig. 1). De infectiositeit van tumorweefsel kon goed en snel worden vastgesteld door de wortels van zaailingen vanNicotiana megalosiphon in een homogenaat van tumorweefsel te dompelen. Tumoren ontstonden na twee weken, de eindbeoordeling geschiedde na een maand (Fig. 2). Ook verschillende andereNicotiana spp.,Melilotus officinalis (Fig. 3) enPisum odoratum (Fig. 4) werden aangetast.Bij de infectiositeitstoets gaven zeer korte dompeltijden even goede resultaten als langere (Tabel 1). Infectieus sap verloor zijn infectievermogen na 10 min verhitting bij 50°C. Bladluizen brachten de smetstof over. Propyleenoxide verminderde de infectiositeit wel, doch onderdrukte deze niet totaal. Bij filtratie door een 450 nm filter bleef het infectieuse agens op het filter achter. Het tumor-inducerende agens was ook aanwezig in die delen van planten met tumoren welke gezond leken en het ging voor een gering deel over met zaad (Tabel 2).Uit tumoren konden wij geen tabakstumorvirus of een viroïde isoleren. Culturen vanCorynebacterium fascians, geïsoleerd uit tumoren vanN. megalosiphon bleken zeer infectieus en veroorzaakten tumoren inN. megalosiphon enBegonia. Homogenaten van tumorweefsel vanPelargonium zonale, dahlia (Fig. 5), gladiool (Fig. 6) enLilium Mid Century Hybrid Enchantment (Fig. 7) veroorzaakten ook tumoren opN. megalosiphon, waaruitC. fascians werd geïsoleerd. Met sap van kroeskopzieke rozen konden wijN. megalosiphon niet besmetten.     

Plant Viruses Transmitted by Whiteflies

One-hundred and fourteen virus species are transmitted by whiteflies (family Aleyrodidae). Bemisia tabaci transmits 111 of these species while Trialeurodes vaporariorum and T. abutilonia transmit three species each. B. tabaci and T. vaporariorum are present in the European–Mediterranean region, though the former is restricted in its distribution. Of the whitefly-transmitted virus species, 90% belong to the Begomovirus genus, 6% to the Crinivirus genus and the remaining 4% are in the Closterovirus, Ipomovirus or Carlavirus genera. Other named, whitefly-transmitted viruses that have not yet been ranked as species are also documented. The names, abbreviations and synonyms of the whitefly-transmitted viruses are presented in tabulated form together with details of their whitefly vectors, natural hosts and distribution. Entries are also annotated with references. Whitefly-transmitted viruses affecting plants in the European–Mediterranean region have been highlighted in the text.     

Epidemiology and simulation of population development of Sitobion avenae in winter wheat

The epidemiology ofSitobion avenae and its natural enemies in winter wheat was studied in 1975, 1976 and 1977. Immigration was important until the end of flowering. The alate immigrants had apterous offspring. These became the driving force in population growth. Their offspring were mostly alatae which usually left the field. A model of the epidemic was developed. Quantitative relations between the aphids and their environment were obtained from literature or established in laboratory trials. The model simulated population development and population composition from the beginning of June till the population peak at the end of June or early in July. Because quantitative data on relations between aphids and their natural enemies and pathogens are scarce, and since the knowledge on wing formation is still limited, the population collapse could not be predicted. In the future, prognosis over a period of three weeks seems possible.Samenvatting De toenemende betekenis van graanbladluizen (vooralSitobion avenae) gepaard gaande met een sterke toename van het gebruik van insecticiden op granen maakte verbetering van de prognose over het schadelijk optreden wenselijk. Door gedetailleerde tellingen in het veld (Fig. 1–7) werden gegevens verkregen over het verloop van de epidemie en het optreden van natuurlijke vijanden in 1975, 1976 en 1977.Een immigratieperiode tot in de bloei kon worden vastgesteld. Daarna lijkt de aantrekkelijkheid van het gewas voor alate luizen te verminderen. De alate immigranten krijgen aptere nakomelingen. Deze vormen de stuwende kracht van de populatiegroei. De nakomelingen van apteren zijn merendeels alaat. Zij verlaten het gewas.Een model van de populatieontwikkeling gedurende de epidemie werd opgesteld. De relatiediagrammen Fig. 9 en 10 laten groei en ontwikkeling vanS. avenae en een predator (Syrphus corollae) zien. Kwantificering van de betrekkingen werd mogelijk door literatuurgegevens en laboratoriumexperimenten.Met het model kon de populatieontwikkeling vanS. avenae vanaf begin juni tot aan de populatiepiek in 1975, 1976 en 1977 vrij goed worden gesimuleerd (Fig. 12). Ook de populatieopbouw kon worden gesimuleerd (Fig. 14). De teruggang van de populatiedichtheid blijkt moeilijker te voorspellen door het ontbreken van gegevens over natuurlijke vijanden.Het lijkt waarschijnlijk dat in de toekomst met het model een prognose over de piek van de bladluispopulatie circa 3 weken tevoren mogelijk zal zijn.     

Broad bean mottle virus in Morocco; curculionid vectors,and natural occurrence in food legumes other than faba bean (Vicia faba)

Broad bean mottle virus (BBMV) was transmitted from infected to healthy faba-bean plants by the curculionid weevilsApion radiolus Kirby,Hypera variabilis Herbst,Pachytychius strumarius Gyll,Smicronyx cyaneus Gyll, andSitona lineatus L. The latter appeared to be an efficient vector: acquisition and inoculation occurred at the first bite, the rate of transmission was c. 41%, and virus retention lasted for at least seven days.S. lineatus transmitted the virus from faba bean to lentil and pea, but not to the three genotypes of chickpea tested. This is the first report on the generaHypera, Pachytychius, andSmicronyx as virus vectors, and onA. radiolus, H. variabilis, P. strumarius, andS. cyaneus as vectors of BBMV.Out of 351 samples of food legumes with symptoms suggestive of virus infection, 16, 11, 19, and 17% of the samples of chickpea, lentil, pea, and common bean, respectively, were found infected when tested for BBMV in DAS-ELISA. This is the first report on the natural occurrence of BBMV in chickpea, lentil, pea, and common bean. The virus should be regarded as a food-legume virus rather than a faba-bean virus solely, and is considered an actual threat to food legume improvement programmes.     

Relationships of <Emphasis Type="Italic">Barley yellow dwarf virus</Emphasis>-PAV and <Emphasis Type="Italic">Cereal yellow dwarf virus</Emphasis>-RPV from Iran with viruses of the family <Emphasis Type="Italic">Luteoviridae</Emphasis>

Barley yellow dwarf disease is one of the most important problems confronting cereal production in Iran. Barley yellow dwarf virus-PAV (BYDV-PAV) and Cereal yellow dwarf virus-RPV (CYDV-RPV) are the predominant viruses associated with the disease. One isolate of BYDV-PAV from wheat (PAV-IR) and one isolate of CYDV-RPV from barley (RPV-IR) were selected for molecular characterisations. A genome segment of each isolate was amplified by PCR. The PAV-IR fragment (1264 nt) covered a region containing partial genes for coat protein (CP), read through protein (RTP) and movement protein (MP). PAV-IR showed a high sequence identity to PAV isolates from USA, France and Japan (96–97%). In a phylogenetic analysis it was placed into PAV group I together with PAV isolates from barley and oats. The fragment of RPV-IR (719 nt) contained partial genes for CP, RTP and MP. The sequence information confirmed its identity as CYDV. However, RPV-IR showed 90–91% identity with both RPV and Cereal yellow dwarf virus-RPS (CYDV-RPS). Phylogenetic analyses suggested that it was more closely related to RPS. These data comprise the first attempt to characterise BYD-causing viruses in Iran and southwest Asia. The nucleotide sequence data reported appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers AY450425 and AY450454     

Identification,incidence and characterization of <Emphasis Type="Italic">Fusarium proliferatum</Emphasis>on ornamental palms in Spain

During a survey conducted from 1998 to 2002, Fusarium proliferatum was found associated with young and adult palms belonging to the genera Chamaerops, Phoenix, Trachycarpus and Washingtonia showing symptoms of wilt and dieback. The fertility and toxicological profile of 36 strains representing different locations and hosts were studied. All of them except two, which were infertile, belonged to mating population D. Both mating types (MATD-1 and MATD-2) were isolated from the same host species, showing a high potential of genetic recombination in the field. Additionally, eight strains were fertile once crossed as female. Toxin analysis showed differences in the ability of strains to produce fumonisin B₁, moniliformin, beauvericin, fusaric acid and fusaproliferin. Only 17 of them produced all the toxins analyzed. Pathogenicity tests were conducted on Phoenix dactylifera and P. canariensis using nine F. proliferatum Spanish strains and two reference strains from Saudi Arabia. Eight months after inoculation all strains caused disease, with palms showing lesions on the bases of leaves and development of wilt symptoms similar to those originally observed in affected plants. This is the first report on the occurrence of F. proliferatum on P. dactylifera in Spain and also the first report of this pathogen on C. humilis, P. canariensis, P. reclinata, T. fortunei, W. filifera and W. robusta.     

Pathogenic fungi involved in root rot of peas in the Netherlands and their physiological specialization

Research on root rot pathogens of peas in the Netherlands has confirmed the prevalence ofFusarium solani, F. oxysporum, Pythium spp.,Mycosphaerella pinodes andPhoma medicaginis var.pinodella. Aphanomyces euteiches andThielaviopsis basicola were identified for the first time as pea pathogens in the Netherlands. Other pathogens such asRhizoctonia solani andCylindrocarpon destructans were also found on diseased parts of roots. F. solani existed in different degrees of pathogenicity, and was sometimes highly specific to pea, dwarf bean of field bean, depending on the cropping history of the field.A. euteiches was specific to peas, whereasT. basicola showed some degree of physiological specialization.     

Recent observations on leafy gall in Liliaceae and some other families

Corynebacterium fascians, which causes leafy gall, has been shown to be responsible for the unusual symptoms recently found in lilies. The symptoms are described and the different bacterial isolates compared by biochemical, serological and pathogenicity experiments. No evidence could be found for the existence of specialized strains even though considerable variation in virulence could be demonstrated. Although the role of variation in susceptibility of the different lily cultivars should not be underestimated, it would appear that high inoculum levels ofC. fascians in the soil may be largely responsible for these outbreaks.Also included in this study are the results of biochemical, serological and pathogenicity experiments ofC. fascians which has been isolated fromKalanchoe, Euphorbia, Brodiaea, Hebe andVerbascum.Samenvatting Reeds een aantal jaren was in lelies een woekering in stengelbollen bekend, die echter sporadisch voorkwam en economisch van weinig betekenis was. Tijdens de zomer van 1977 echter trad de ziekte op één enkel perceel zo ernstig op dat zeer aanzienlijke oogstderving het gevolg was. Behalve de stengelbol kan ook de hoofdbol misvormd zijn. Bovendien kunnen misvormde stengelbollen lange spruiten vormen, zgn. sabeltandvorming. Soms is het wortelstelsel gereduceerd; in de kas zijn verdikte stengels waargenomen. De ziekte staat nu bekend onder de naam woekerziekte.Door de PD te Wageningen en het LBO te Lisse werd de bacterieCorynebacterium fascians (Tilford) Dows. uit het zieke materiaal geïsoleerd. In gezamenlijk onderzoek werd nagegaan of de bacterie de veroorzaker is van bovengenoemde symptomen en of hier sprake is van een op lelie gespecialiseerde stam.Biochemische en serologische vergelijkingen tussen isolaten vanC. fascians uit lelie,Kalanchoe, Euphorbia, Brodiaeea, Hebe enVerbascum laten zien dat er zeer weinig verschillen bestaan. Alle isolaten reageren op een standaard antiserum met titers variërend tussen 1: 640–1: 5120.Een oriënterende inoculatieproef werd uitgevoerd op het LBO in 1977. Daarna werden op de PD 10 van de 25 isolaten uit lelie en 8 uit andere waardplanten getoetst op lelie, chrysant en lathyrus. Uit de inoculatieproeven blijkt, dat de bacterie de veroorzaker is van de waargenomen symptomen. Tussen de isolaten blijkt een groot verschil in pathogeniteit te bestaan (12–100% aantasting), zonder dat dit aan herkomst gebonden is. Het voorkomen van op lelie of andere waardplanten gespecialiseerde stammen is daarom niet aan te nemen.In hoeverre de hevige aantasting een gevolg is van een opbouw van de bacterie-populatie door een te nauwe vruchtwisseling en mechanische rooimethoden moet worden nagegaan.     

Nematicidal Activity of Chrysanthemum coronarium

Organic amendments and green manure are potential alternatives to the harmful chemical control means currently used against plant-parasitic nematodes. In this work, Chrysanthemum coronarium was applied to the soil as a green manure to control the root-knot nematodes Meloidogyne incognita and M. javanica. Chrysanthemum coronarium significantly reduced nematode infection of tomato roots and improved plant-top fresh weight, both in the greenhouse and in microplots. Other green manures, derived from Anthemis pseudocotula, wild chickpea (Cicer pinnatifidum), Geranium spp. and wheat, were not as effective as C. coronarium. Chrysanthemum coronarium, retained its nematicidal activity even when applied as a dried material. Only mature C. coronarium plants, in their flowering stage, exhibited nematode control activity, but the green plant parts were more effective than the flowers. An aqueous extract of C. coronarium exhibited in vitro, nematostatic activity towards M. incognita and M. javanica second-stage juveniles and inhibited their hatching from eggs and egg-masses; its nematostatic activity was expressed also against other phytonematode species such as Heterodera avenae and Pratylenchus mediterraneus, but did not affect the beneficial entomopathogenic nematode Steinernema feltiae.     

A new <Emphasis Type="Italic">Rhizoctonia</Emphasis> sp. closely related to <Emphasis Type="Italic">Waitea circinata</Emphasis> causes a new disease of creeping bentgrass

Isolates of an unidentified Rhizoctonia sp. (UR isolates) were obtained from creeping bentgrass and Kentucky bluegrass with reddish brown sheath and foliar rots. Because the UR isolates anastomosed with isolates of three varieties of Waitea circinata (var. oryzae, var. zeae, and var. circinata), colony morphology, hyphal growth rate at different temperatures, pathogenicity, sequence analysis of the internal transcribed spacers (ITS) region of ribosomal RNA genes (rDNA) were compared. The colony color of mature UR isolates was distinct from isolates of the other three varieties of W. circinata. In pathogenicity tests on creeping bentgrass, the severity of the disease caused by UR isolates was significantly higher than that caused by the three varieties of W. circinata. Sequence similarities of the rDNA-ITS region between UR isolates and between isolates within each variety were high (97–100%), but they were lower among isolates from UR and the varieties of W. circinata (88–94%). In a phylogenetic tree based on the rDNA-ITS sequences, UR isolates formed a cluster separate from each of the clusters formed by the three varieties of W. circinata. These results indicate that the UR isolates clearly differ from the three varieties of W. circinata. We therefore propose that the UR isolates be classified as new Rhizoctonia sp. that are closely related to W. circinata and that the disease on creeping bentgrass should be called Waitea reddish-brown patch disease (Sekikasshoku-hagusare-byo in Japanese).