不同体色瓜蚜耐药性差异及其生化机制

试验结果表明,在黄瓜上的绿色瓜蚜(Aphis gossypii Glov.)种群对氧化乐果、抗蚜威和氰戊菊酯的耐性明显高于黄色瓜蚜种群。这两种颜色的瓜蚜乙酰胆碱酯酶(ACHE)具有明显的不同,在绿色种群中,有60.7%的个体AChE活性大于0.8(OD_(412)/mg蛋白质,分钟),而在黄色种群中则仅有25.3%的个体AChE活性大于0.8;氧化乐果(终浓度为1.69×10~(-2)mol/L)对单个蚜虫AChE的抑制率,前者仅有19%的个体AChE抑制率在30%以上,而后者则有46%的个体在30%以上。α-乙酸萘酯羧酸酯酶的活性大于25(×10~(-2)μmol/蚜,15分钟)的个体在绿色种群中占56%,而在黄色种群中仅有20%;β-乙酸萘酯羧酸酯酶活性大于25(×10~(-2)μmol/蚜,15分钟)的个体在绿色瓜蚜中占45%,而在黄色种群中仅有7%。说明绿色和黄色瓜蚜耐药性的差异可能是由于AChE敏感性和羧酸酯酶活性的不同造成的。     

不同寄主植物棉蚜酯酶对杀虫剂不敏感性的频率分布

通过生物测定和生化分析研究了花椒棉蚜(HA)和棉花棉蚜(MA)种群对杀虫剂的抗性及其α-乙酸萘酯(α-NA)酯酶和乙酰胆碱酯酶(AChE)对杀虫剂的不敏感性。结果表明,MA种群对甲基对硫磷、辛硫磷和灭多威的耐药性均高于HA种群;MA种群中具有高α-NA酯酶活力的个体比HA种群多,甲基对硫磷对HA和MA种群α-NA酯酶的抑制率达30％时的个体累计频率分别为37％和65％;抑制率大于50％时的累计频率分别为18％和1％;灭多威对HA种群棉蚜AChE的抑制作用高于MA种群。说明MA种群对有机磷的抗性可能与α-NA酯酶活力的增高和对杀虫剂的不敏感性有关,对灭多威的抗性与AChE敏感度的降低有关。滤纸酯酶反应法和微量滴度酶标板法均能快速、有效地测定棉蚜个体酯酶的频率分布,准确地反映两种群棉蚜酯酶活力的差异。     

瓜-棉蚜对有机磷及氨基甲酸酯杀虫剂抗性机制研究

从1983年开始就北京及河北省廊坊、香河和涿鹿县四个地区瓜-棉蚜(Aphis gossypiiGlov.)对18种有机磷及2种氨基甲酸酯杀虫药剂进行了抗性系统监测,与苏联瓜蚜(A.gos-sypii Glov.)敏感系毒力值(LC_(50))进行比较,抗蚜威最高达7887.7倍,马拉硫磷357.8倍,乐果128.6倍,敌敌畏83.5倍,乙酰甲胺磷72.1倍;而对喹硫磷、甲基辛硫磷、呋喃丹及溴氯磷则相当敏感,LC_(50)值在45.2—186.0 ppm之间。其抗性谱大致呈交叉型交互抗性。酶系测定结果表明,瓜-棉蚜的乙酰胆碱酯酶(AChE)敏感性降低与抗药性关系最为密切,氧化乐果和抗蚜威对AChE的I_(50)值与其Log LC_(50)(ppm)呈显著相关(P<0.05)。四个地区的瓜-棉蚜AChE对底物(乙酰硫代胆碱ATCh)的米氏常数(Km)及最大反应速度(Vmax)值均无明显差异,但ATCh浓度超过10~(-2)mol/L时,对AChE还没有明显的抑制作用。瓜-棉蚜α-乙酸萘酯羧酸酯酶与对久效磷的抗性呈正相关,面与抗性较高的乐果则无相关性。多功能氧化酶活性的高低与抗药性水平有关,乐果加PB(1:1)也有一定增效作用。GSH-S-转移酶活性与瓜-棉蚜抗性不相关。     

北京及河北省北部瓜-棉蚜对拟除虫菊酯抗药性的研究初报

1983—1986年就北京及河北省廊坊、香河、涿鹿等地区的瓜-棉蚜(Aphis gossypii Glov.)对拟除虫菊酯杀虫药剂的抗药性作了系统监测。试验结果表明,北京、廊坊及香河等地区的瓜-棉蚜种群对氰戊菊酯及溴氰菊酯已产生了一定程度的抗性。以LC50及LC95进行抗性比较,对氰戊菊酯分别为519和6416倍;对溴氰菊酯为401和14805倍。蚜体中水解α-乙酸萘酯酶(以下简称酯酶)的活性与其对氰戊菊酯及溴氰菊酯的抗性程度密切相关,相关系数均大于0.9,均在显著水平以上。因此、酯酶是瓜-棉蚜抗拟除虫菊酯的主要抗性机制之一。     

哒螨灵对抗吡虫啉棉蚜种群的负交互抗性及对其生物学特性的影响

为明确哒螨灵对抗吡虫啉棉蚜Aphis gossypii种群的防治效果,采用浸渍法、微量点滴法、生化测定法和系统观察法,研究了哒螨灵对抗吡虫啉棉蚜种群(RF27)、敏感棉蚜种群(SS)和夏津种群(XJ)的负交互抗性及对其生物学特性的影响。结果表明:哒螨灵对RF27、XJ和SS的LD50分别为1.065×10-5、6.616×10-5和4.862×10-5μg/头;抗吡虫啉棉蚜种群与哒螨灵、吡蚜酮具有明显的负交互抗性,与啶虫脒、烯啶虫胺等具有交互抗性;CarE、GST和AChE比活力的提高是引起棉蚜对吡虫啉产生抗性的主要生化原因;哒螨灵对棉蚜的AChE和GST均有显著抑制作用;哒螨灵处理的抗吡虫啉棉蚜种群表现出明显的生殖缺陷,相对适合度较小,为0.67。     

寄主植物对棉蚜乙酰胆碱酯酶的影响

通过生物测定和生化分析研究了5种不同寄主植物上的棉蚜种群对灭多威的敏感性，乙酰胆碱酯酶（AChE)活性及灭多威对AChE的抑制作用，结果发现，取食石榴和花椒的棉蚜AChE活性最高，是冬青上棉蚜（最低）的2．00倍和3．33倍，说明寄主植物可以影响棉蚜AChE的活性，灭多威对不同寄主植物上的棉蚜个体的AChE进行抑制后，发现棉花和冬青上的棉蚜种群中AChE对灭多威不敏感的棉蚜个体多于花椒，木槿和石榴上的棉蚜种群，这与棉花及冬青上的棉蚜对灭多威耐药性较其它三种强的趋势近似，表明AChE敏感度的降低是棉蚜对灭多威产生抗药性的原因之一。     

呼伦贝尔盟农田杂草分布、发生规律与防治策略的研究

以生物测定及羧酸酯酶活性测定的方法,检测了上海地区菜缢管蚜对有机磷的抗药性。测定结果表明,金山群体对乐果、杀螟松和马拉硫磷的抗药性分别是梅陇的5.7、4.0和1.8倍。金山群体的羧酸酯酶活性高于梅陇。说明其抗性与羧酸酯酶活性增高有关。单个蚜虫的羧酸酯酶活性测定是检测抗性及抗性个体在群体内分布的一种既迅速又精确的方法。如把蚜虫的羧酸酯酶活性分成3类:低羧酸酯酶活性(OD<0.3)、中等羧酸酯酶活性(OD:0.3—0.5)和高羧酸酯酶活性(OD>0.6),则金山与梅陇种群低羧酸酯酶活性个体分别占8％、30％;中等活性个体分别占85％、68％;高活性个体分别占7％、2％。     

棉蚜对吡虫啉抗性的初步研究

用吡虫啉对棉蚜进行室内抗性筛选,用药处理25次后抗性是筛选前的20.03倍;2007年对田间棉蚜进行抗性调查,发现不同地区种群对吡虫啉的抗性差异显著,江苏南京种群最为敏感,河南安阳、山东泰安和北京地区棉蚜与之相比,抗性分别为2.21、7.63和9.53倍;抗、感品系解毒酶活力分析发现,抗性品系的谷胱甘肽S-转移酶活性增加很少(比活力1.12倍),但酯酶活力显著高于敏感品系(比活力1.71倍);增效试验结果表明,顺丁烯二酸二乙酯(DEM)在抗、感品系中对吡虫啉均没有明显的增效作用,而磷酸三苯酯(TPP)和增效醚(PBO)虽然在敏感品系中对吡虫啉的增效作用较小(SR 1.24和1.29),但在抗性品系中的增效作用显著增高(SR 2.13和1.74);此外还发现,吡虫啉处理可提高棉蚜群体的酯酶活力。由此认为,棉蚜至少具有对吡虫啉产生中等水平抗性的风险,其抗性可能是由于棉蚜的酯酶和P450单加氧酶的解毒能力提高所致。     

棉蚜不同抗性品系羧酸酯酶比较

用分光光度计终点测定法和酶标仪动力学测定法对3个抗性水平不同的棉蚜品系和1个敏感品系的羧酸酯酶进行了研究。棉蚜的不同抗性品系羧酸酯酶对α-乙酸萘酯(α-NA)和β-乙酸萘酯(β-NA)的水解活性具有极显著的相关性(r=0.95,n=400)。两种测定法均显示出R1、R2和R3品系的羧酸酯酶比活力明显高于S品系。以α-NA为底物时,用酶标仪动力学测定法研究表明,S、R1、R2和R3棉蚜品系羧酸酯酶活性分别为38、85、198和762mOD·min~(-1)·aphid~(-1);与4个品系的抗性程度比较,酶动力学方法的测定结果更可靠。     

桃蚜高效氯氰菊酯抗药性与乙酰胆碱酯酶的关系

于室内对桃蚜进行高效氯氰菊酯抗药性筛选,选育至10代后抗性倍数增长到49.9倍。生化分析表明,抗性品系乙酰胆碱酯酶(AChE)活性均显著高于敏感品系。比较两个品系乙酰胆碱酶活性个体频率分布发现,更多的桃蚜个体向酶活性高的区域分布。酶动力学测定结果显示,抗性桃蚜酯酶对底物的Vmax、Km显著大于敏感品系。     

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.     

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     

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.     

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.     

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.     

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).     

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.     

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.