几丁质和杀菌剂对生物防治菌生长及其防治棉花病害效果的影响

 研究了化学杀菌剂对木霉菌生长的影响,探讨了几丁质添加物对绿色木霉菌菌株L R、LTR-2、哈茨木霉菌菌株Q1、Q2和粉红粘帚霉菌菌株GLR防治棉花病害效果的影响。多菌灵、苯菌灵和甲基硫菌灵在1.66μg/ml时可以完全抑制Q1和Q2的生长,但在2.68μg/ml时才能完全抑制LR和LTR-2的生长。几丁质添加物使L TR-2和Q1防治棉花立枯病的效果完全丧失,但是能使LR从没有防治效果提高到防治效果为34.6%,而对粉红粘帚霉菌的防治效果没有显著影响;对于防治棉花黄萎病来说,几丁质添加物使木霉菌LR、LTR-2和GLR的防治效果降低,但是提高了Q1的防治效果;对于防治棉花枯萎病来说,几丁质添加物能提高所有测定菌株的防治效果。说明不同的生物防治菌株、添加物和病害组合对于获得良好的防治效果是重要的。     

高效液相色谱串联质谱测定水果和蔬菜中的甲基硫菌灵和多菌灵残留

建立了同时测定水果和蔬菜中甲基硫菌灵、多菌灵的液相色谱串联质谱法。选取3种代表性水果鸭梨、苹果、西瓜和3种蔬菜菜花、芦笋、胡萝卜进行研究,先用乙腈提取,经石墨化碳氨基复合柱净化后,用C18柱分离,以乙腈和水为流动相进行梯度洗脱,四极杆串联质谱采用电喷雾正离子和多反应监测模式检测。结果表明:甲基硫菌灵在0.05~0.8μg/mL质量浓度范围内,多菌灵在0.005~0.08μg/mL质量浓度范围内线性关系良好,相关系数均不小于0.99;甲基硫菌灵、多菌灵的检出限分别为10μg/kg和1μg/kg。在3个不同的加标水平下,多菌灵的回收率在85%~106%之间,甲基硫菌灵的回收率在78~89%之间,相对标准偏差为分别为6.7%~7.6%和8.7%~9.8%。该方法能有效检测出多种水果和蔬菜中甲基硫菌灵、多菌灵的残留量,且稳定性好,结果可靠。     

芽孢杆菌(Bacillus spp.)与甲基硫菌灵混配对茄腐镰孢菌(Fusarium solani)的抑制作用

芽孢杆菌(Bacillus spp.)B1、B2、B6、B8与低毒化学农药甲基硫菌灵混配后对茄腐镰孢菌的抑制作用研究结果表明:甲基硫菌灵浓度为0.001mg/mL时,与4种生防菌混配对茄腐镰孢菌的抑制率达到78.21%～80.93%。较生防菌单独处理,混配的抑制率提高了43%～54%;较单独使用甲基硫菌灵,抑制率提高了14%～19%。当浓度为0.0005mg/mL时混配作用的抑制率为71.21%～68.48%,较生防菌单独作用,混配的抑制率提高了31%～44%;较甲基硫菌灵单独作用抑制率提高了12%～19%。当浓度继续降低后,4种生防菌分别和甲基硫菌灵混配对茄腐镰孢菌的抑制率与仅使用4种生防菌对茄腐镰孢菌的抑制率无显著差异,但较甲基硫菌灵单独作用抑制率提高27%。说明甲基硫菌灵在浓度为0.001、0.0005mg/mL时与4种生防菌混配,两者协同作用增强了抑制效果,对茄腐镰孢菌有很好的抑制作用。     

QuEChERS-超高效液相色谱-串联质谱法同时测定草莓中甲基硫菌灵、多菌灵和乙嘧酚残留

建立了QuEChERS-超高效液相色谱-串联质谱同时检测草莓中甲基硫菌灵、多菌灵和乙嘧酚残留的方法。样品经0.5%甲酸-乙腈提取,QuEChERS方法净化,以Agilent XDB-C18色谱柱(2.1 mm×150 mm,3.5 μm)进行UPLC分离,采用三重四极杆串联质谱以正离子多反应监测模式(MRM)进行测定。结果表明:在20~1 000 μg/L范围内,甲基硫菌灵、多菌灵及乙嘧酚的质量浓度与其相应的峰面积间呈现良好的线性关系,相关系数均大于0.997 8。在50~500 μg/kg添加水平下,草莓中甲基硫菌灵、多菌灵和乙嘧酚的平均回收率在86%~109%之间,相对标准偏差(RSD)在1.9%~13%(n=5)之间,检出限分别为2.5、0.50和1.0 μg/kg,定量限均为50 μg/kg。该方法样品前处理过程简单快速,分析时间短,灵敏度、准确度及精密度均符合农药残留检测要求,适用于草莓中甲基硫菌灵、多菌灵和乙嘧酚残留的检测。     

芒果炭疽病菌对多菌灵的抗药性

对来自广东和海南等不同果园的芒果炭疽病菌进行了对多菌灵的抗性测定.结果表明,敏感菌株的最小抑制浓度(MIC)为0.110μg/mL,而抗性菌株在多菌灵500μg/mL下仍生长良好.抗性菌株经继代培养10代后抗性几乎不变,说明其抗性稳定.对抗、感菌株的生物学特性进行测定,然后以产孢量和致病力分别用MIC做简单相关性分析,证明病菌的生物学特性、产孢量、致病力与抗药性无关,因此可以认为病菌对多菌灵的抗药性突变并不影响其正常的生理功能.抗性菌株对甲基硫菌灵、苯菌灵、噻菌灵表现正交互抗性,而对乙霉威和咪鲜胺敏感.病菌在含药培养基上测定的敏感性与在经多菌灵处理过的离体果实上的敏感性有较好的对应关系,可用于大田抗药性的初步检测.     

原生质体融合技术改良植病生防木霉菌株

以产孢量大，对苯菌灵有抗性，对潮霉素B敏感的哈茨木霉菌株T9和产孢量少，对潮霉素B有抗性，对苯菌灵敏感的康宁木霉菌株Tk7a为亲本，进行原生质体融合，筛选获得抗最高浓度杀菌剂的融合子。所有融合子的产孢量均比亲本菌株Tk7a大。融合子按照菌落形态的不同分成4组，大部分融合子的几丁质酶、葡聚糖酶和内切葡聚糖酶的活性比亲本菌株高。融合子对棉花猝倒病菌和小麦全蚀病菌的寄生能力基本等同于亲本菌株；融合子对小麦全蚀病的防效比亲本菌株稍好，其刺激麦苗根部生长的能力与亲本菌株相差不大。两个融合子根际竞争能力比亲本菌株T9强，和亲本菌株Tk7a相当。     

黄瓜白粉病菌对甲基硫菌灵的敏感性及室内抗性突变体生物学性状

为明确山西省黄瓜白粉病菌对甲基硫菌灵的抗药性现状,采用叶盘漂浮法测定了不同地区119株菌株对甲基硫菌灵的敏感性,用紫外线照射和药剂驯化方式诱导获得了甲基硫菌灵抗性突变体,并比较了亲本菌株与突变体的生物学性状。结果表明,119株菌株的EC50在0.48~14.37μg/m L之间,平均EC50为2.89±2.69μg/m L。不同地区菌株敏感性差异较大,采自未使用过任何杀菌剂的忻州市菌株敏感性最高,平均EC50为1.03±0.27μg/m L,可作为黄瓜白粉病菌对甲基硫菌灵的敏感基线;运城市菌株敏感性最低,平均EC50为7.02±3.12μg/m L,其中菌株YC01的EC50是敏感基线的13.98倍。3株室内诱导突变体均为高抗,突变体XZ11-2的抗性倍数达到94.96倍,抗性突变频率为1.5×10-3。无药剂处理条件下,突变体的侵染频率、病情指数、产孢量和孢子萌发率均显著低于亲本敏感菌株;抗∶感菌株分生孢子以80∶20混合培养7代后,抗性菌株频率变化不明显;以20∶80混合培养7代后,抗性频率降低甚至消失。表明黄瓜白粉病菌对甲基硫菌灵的抗性在选择压力低的情况下有可能丧失。     

柑橘甲基硫菌灵药剂在柑橘上的安全间隔期试验

2016年,宜都市柑橘深加工企业,在出口到美国的罐头中被检测出多菌灵超标(美国标准多菌灵含量不得≥10ppb),所有产品被退回。不仅给该公司带来了较大的经济损失,而且还造成了我市柑橘严重滞销,严重影响了我市柑橘声誉。为了检验在柑橘挂果期使用甲基硫菌灵对柑橘果实中的多菌灵残留值,探索出符合美国食品药品监督管理局(FDA)对食品中多菌灵10ppb的安全间隔期,指导柑橘深加工企业柑橘原料基地建设,为桔农提供安全用药技术指导,特进行了甲基硫菌灵药剂在柑橘上的安全间隔期试验。试验结果表明:70%甲基硫菌灵可湿性粉剂的安全间隔期为90d,即在6月20日后停止使用该农药,使用次数全年以1次～2次为宜。     

九种常用农药在桃树生长后期使用的安全性

为了评价桃生长后期使用农药的安全性,以桃早熟品种‘金陵黄露’为材料,分别在桃果收获前7和14 d,按最高推荐剂量及2倍最高推荐剂量混合施用9种农药,包括4种杀虫剂 (阿维菌素、氯虫苯甲酰胺、氯氟氰菊酯和吡虫啉) 和5种杀菌剂 (苯醚甲环唑、腈苯唑、嘧菌酯、甲基硫菌灵和多菌灵),研究了桃果中的农药残留量变化及不同农药在桃枝、桃叶、果皮和果肉中的分布规律,以及套袋在桃生长后期阻控农药吸收中发挥的作用。结果表明:在桃收获前7 d,按2倍最高推荐剂量施用其中3种杀菌剂 (苯醚甲环唑、腈苯唑、嘧菌酯) 和4种杀虫剂 (阿维菌素、氯虫苯甲酰胺、氯氟氰菊酯、吡虫啉),7种农药在桃全果中的残留量均低于中国国家农药残留限量标准(MRL);而过量施用多菌灵和甲基硫菌灵,桃全果中多菌灵残留量显著高于MRL标准,且随着施药后时间的延长,增加了多菌灵由果皮或枝叶向果肉迁移的风险。套袋处理后,桃全果中多菌灵的残留量远低于中国MRL标准,同时显著减少了桃全果中其他8种农药的残留量。9种供试农药在桃树不同组织中的分布规律一致,由高到低依次为果皮>全果>桃叶≥果肉≥桃枝。本研究表明,不同农药品种在桃生长后期消解规律存在差异,其中多菌灵和甲基硫菌灵超量使用会增加多菌灵在桃果中残留超标的风险,而套袋处理可减少桃果中的农药残留。该结果对去除桃果中农药残留、降低膳食摄入风险有一定指导意义。     

丁硫克百威在桃果实上残留的消解动态

每公顷桃园施用氨基甲酸酯杀虫剂了硫克百威（carbosulfan）乳油2kg（有效成分）进行其消解动态研究，结果表明：丁硫克百威的降解主要发生在两个连续的阶段（0～28天和28～57天），半衰期分别为7．4天和17．5天；施药后57天的残留量低于0．2ma／kg；果实成熟采收期前30、21、14天进行两种用药量（商品量1:0和2.0g／L）和两种喷洒量（750和1500L／ha）施药处理，测定其残留量介于0．122mg／ks（采收前30天）和0．4mg／kg（采收前14天）之间；整个试验中，丁硫克百威的主要代谢物克百威（carbofuran）的含量低于其检测极限值0.004mg／kg．     

Dermestid beetles in ‘evolution Canyon’, lower Nahal Oren, Mt. Carmel, including new records for Israel

Fifteen species of dermestid beetles were recorded at ‘Evolution Canyon’ (EC), Lower Nahal Oren, Mt. Carmel, Israel. They represent ~35% of known Israeli dermestid species. The following three species were recorded for the first time in Israel:Trogoderma svriaca Dalla Torre, 1911;Ctesias svriaca Ganglbauer, 1904; andAnthrenus (s.str.) jordaniens Pic, 1934. Adults of 13 species were collected on the more solar radiated, warmer and climatically more fluctuating south-facing slope (SFS); ten species were collected on the opposite, north-facing slope (NFS), which was cooler and climatically more stable. The abundance of adult dermestid beetles was 1.9 times higher on the SFS than on the NFS (86 and 47, respectively). Species richness and abundance distribution at EC (three collecting stations on each slope and one at the valley bottom) were significantly negatively correlated with the plant cover that consisted of trees and bushes (Spearmanr _s ,P=0.007 and 0.039, respectively) and perennials (Spearmanr _s ,P=0.039 and 0.077, respectively), indicating that non-woody plants were preferred by adult dermestid beetles.     

Epidemiology of Toxigenic Fungi and their Associated Mycotoxins for Some Mediterranean Crops

Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.     

A survey of the genera of<Emphasis Type="Italic">Microgaster</Emphasis> latreille and<Emphasis Type="Italic">Hygroplitis</Emphasis> thomson (Hymenoptera: Braconidae: Microgastrinae) from China

The genera ofMicrogaster Latreille 1804 andHygroplitis Thomson 1895 from China are presented systematically in this paper. Thirty-two species ofMicrogaster and three species ofHygroplitis are known in China. Diagnosis, character variation, distribution and host of each species among the two genera are presented, including its host and distribution. Keys to the species ofMicrogaster andHygroplitis are given. http://www.phytoparasitica.org posting Dec. 19, 2006.     

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.     

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.     

Characterization of potato potyvirus Y (PVY) isolates from seed potato batches. Situation of the NTN, Wilga and Z isolates

A collection of 38 PVY isolates from seed potato batches, originating from several Western European countries, was characterized by using current biological, serological and molecular tools differentiating PVY strains and groups. The correlation between the three kinds of tests was good but not absolute. No single serological or PCR method was able to discriminate among the five isolate groups found. Twenty-nine isolates belonged to the PVY^N strain and six to the PVY^O strain. No PVY^C was found. Two other isolates reacted serologically like PVY^O, but were unable to elicit a hypersensitive response from the Ny_tbr gene and probably represent the PVY^Z group. At the molecular level, these two isolates showed a combination of both PVY^O and PVY^N and could be recombinants of these strains. Another isolate reacted serologically like PVY^O, but induced vein necrosis in tobacco, like PVY^N-Wilga. Some PVY^N isolates caused tuber ring necrosis in glasshouse conditions. These might belong to the PVY^NTN group. The PVY^NTN, PVY^N-Wilga and PVY^Z groups probably represent pathotypes within strains PVY^N and PVY^O, respectively. The present study also confirms previous reports showing a high genetic variation at the 5 end within the PVYN strain.     

The autumn leafroller: Phenology,damage and parasitoids in a Dutch apple orchard

The phenology of the autumn leafroller,Syndemis musculana, a local pest of apple, was studied in order to forecast larval emergence. From 1983–1986, peak flight as determined with sexpheromone traps was always between 13–18 May. The duration of embryonic development was determined at various constant temperatures and used to estimate the periods of egg hatch in these four years. Each year, most eggs should have hatched in the second decade of June.Differences in attack rates between apple cultivars seem to be explained largely by the variation in picking time. Larvae are only half grown at the beginning of harvest (cv. James Grieve), and have gone into hibernation when the latest variety (cv. Golden Delicious) is picked. Moreover, the varieties Cox's Orange Pippin and Belle de Boskoop, picked about half time, are liable to receive additional damage by caterpillars brought with the picked fruits into storage.Various hymenopterous parasites were reared from caterpillars. As the only leafroller in the orchard which hibernates as mature larva,S. musculana may promote winter survival of some parasitoids, like the eulophidColpyclypeus florus.Samenvatting De fenologie van de herfstbladroller (Syndemis musculana Hübner), een incidentele plaag op appel, werd nader bepaald met het doel het uitkomen van de eieren te kunnen voorspellen. In 1983–1986 viel de piekvlucht, bepaald met behulp van feromoonvallen, steeds tussen 13 en 18 mei.De ontwikkelingsduur van de eieren bij verschillende constante temperaturen werd gebruikt om de periode van uitkomen te schatten. De meeste eieren zullen ieder jaar in de eerste helft van juni uitkomen.Geconstateerde verschillen in schade tussen appelrassen blijken goeddeels terug te voeren op verschillen in pluktijdstip. De rupsen van de herfstbladroller zijn pas half-was als de eerste appels eind augustus geplukt worden, terwijl tegen het einde van de oogst begin oktober de meeste al in winterslaap zijn. Met name tussentijdse rassen, als Cox's Orange Pippin and Schone van Boskoop, lopen extra schade op doordat grotere rupsen met de geplukte vruchten in de kist terecht komen.Uit de rupsen werden negen, al van andere boomgaardbladrollers bekende, sluipwespen gekweekt, Omdat deze bladrollersoort, als enige in de boomgaard, als volgroeide rups overwintert, lijkt zij bij uitstek geschikt als winterwaard.This study was carried out at the Experimental Orchard De Schuilenburg, Schuilenburg 3, 4041 BK Kesteren, the Netherlands, to which address correspondence should be addressed.     

Diagnostics,genetic diversity and pathogenic variation of ascochyta blight of cool season food and feed legumes

Molecular diagnostic techniques have been developed to differentiate the Ascochyta pathogens that infect cool season food and feed legumes, as well as to improve the sensitivity of detecting latent infection in plant tissues. A seed sampling technique was developed to detect a 1% level of infection by Ascochyta rabiei in commercial chickpea seed. The Ascochyta pathogens were shown to be genetically diverse in countries where the pathogen and host have coexisted for a long time. However, where the pathogen was recently introduced, such as A. rabiei to Australia, the level of diversity remained relatively low, even as the pathogen spread to all chickpea-growing areas. Pathogenic variability of A. rabiei and Ascochyta pinodes pathogens in chickpea and field pea respectively, appears to be quantitative, where measures of disease severity were based on aggressiveness (quantitative level of infection) rather than on true qualitative virulence. In contrast, qualitative differences in pathogenicity in lentil and faba bean genotypes indicated the existence of pathotypes of Ascochyta lentis and Ascochyta fabae. Therefore, reports of pathotype discrimination based on quantitative differences in pathogenicity in a set of specific genotypes is questionable for several of the ascochyta-legume pathosystems such as A. rabiei and A. pinodes. This is not surprising since host resistance to these pathogens has been reported to be mainly quantitative, making it difficult for the pathogen to overcome specific resistance genes and form pathotypes. For robust pathogenicity assessment, there needs to be consistency in selection of differential host genotypes, screening conditions and disease evaluation techniques for each of the Ascochyta sp. in legume-growing countries throughout the world. Nevertheless, knowledge of pathotype diversity and aggressiveness within populations is important in the selection of resistant genotypes.     

Characterization of Sclerotinia minor populations in Texas peanut fields

In the summer of 2004 an epidemic of sclerotinia blight of peanut, a disease caused by Sclerotinia minor, occurred in Texas in fields where the disease was never previously detected. The disease was observed on many plants within one of the fields (>3000 disease foci), although most foci were <1 m. It is hypothesized that these observations were inconsistent with the recent introduction of a monocyclic pathogen, even if disease developed under conducive environmental conditions. The pattern of disease is most suggestive of the presence of foliar (ascospore) infections, although air temperature was above the known limits for apothecia development if the pathogen had arrived in the field in 2004 peanut seed. To further examine this epidemic, 232 isolates were collected, across a variety of spatial scales spanning this field and other Texas peanut fields, and evaluated for aggressiveness, fungicide sensitivity and genotypic diversity. There was wide variation among isolates for the phenotypic characteristics measured, but there was no evidence that a genotypically unique, highly aggressive, and fungicide resistant isolate had been introduced or evolved. The predominant genotype, TX1, which contained 154 isolates, was found in every county and field population.     

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.