Effects of two pathogens on the performance of Cirsium arvense in a successional fallow

Biological control of weeds by natural antagonists is of increasing interest. To reduce densities of the weed Cirsium arvense (creeping thistle) in a successional fallow, we applied spores of two pathogens, the biotrophic rust Puccinia punctiformis and the perthotrophic Phoma destructiva, for three consecutive years individually at different dates and combined. The proportion of systemically Puccinia punctiformis-infected C. arvense was not influenced by the treatments, but local rust infection was a good predictor of systemic infection in the following season. Artificial inoculations with P. destructiva increased the incidence of this pathogen in the third year as a result of synergistic effects, when co-inoculated with P. punctiformis. Inoculations with either pathogen had little effect on C. arvense shoot density, although there were transient reductions after combined inoculations with both fungi compared with the fungicide treatment. Cirsium arvense decreased from 60% to 5% cover within 3 years, while the cover of the co-occurring fallow vegetation increased. Under field conditions, with an already high degree of natural P. punctiformis infection, the effects of inoculations of the single pathogens were minor, but reductions in shoot density after combined inoculations indicate that this inoculation may have the potential to cause a decline of this weed.     

<Emphasis Type="Italic">Brassica napus</Emphasis> plants infected by <Emphasis Type="Italic">Leptosphaeria maculans</Emphasis> after the third to fifth leaf growth stage in south-eastern Australia do not develop blackleg stem canker

Blackleg (Phoma stem canker) caused by Leptosphaeria maculans is the most damaging disease of Brassica napus (canola, rapeseed, colza) worldwide and is controlled by sowing blackleg resistant cultivars and crop management strategies that reduce exposure to inoculum and fungicide application. In experiments in south-eastern Australia, canola cultivars inoculated after the three to five leaf growth stage did not develop stem canker. Although mature canola plants are known to be less susceptible to blackleg than seedlings, this highlights for the first time the specific importance of protecting seedlings up to the three to five leaf growth stage in Australia. This would typically correspond to a period of four to six weeks after emergence. Canola plants are likely to be significantly less vulnerable to infection after this growth stage. However, this timing may vary due to the influence of environmental conditions.     

A Survey of Trunk Disease Pathogens within Rootstocks of Grapevines in Spain

Grapevine trunk disease pathogens, and specifically Petri disease pathogens, can be spread by planting infected plants. Due to the increasing incidence of Petri disease and other young grapevine declines reported lately in Spain, a sampling of plants used before for new vineyards were carried out in 2002 and 2004. A total number of 208 plants (grafted and non grafted) were collected, of which 94 plants (45.2%) were infected with at least one of the following pathogens: Phaeomoniella chlamydospora, and species of Phaeoacremonium, Botryosphaeria, Cylindrocarpon, and Phomopsis. Species of the genera Phaeoacremonium and Botryosphaeria isolated in 2004 were identified using morphological and molecular characters. Species of Phaeoacremonium identified were P. aleophilum and P. parasiticum; and those of Botryosphaeria were B. obtusa, B. dothidea and B. parva. This is the first report of P. parasiticum and B. parva occurring on grapevines in Spain. Distribution of pathogens within the plants was studied in 2004. Phaeomoniella chlamydospora was not detected in the graft union of any plant; however, species of Botryosphaeria and Phomopsis were detected along the plant, but mainly in the graft union; Phaeoacremonium aleophilum was detected along the grafted plants, but not in rooted rootstocks. The results suggest that infected plants used for new plantings in Spain are an important source of primary inoculum of the pathogens associated with grapevine trunk diseases in the field.     

Phomopsis cirsii: a potential biocontrol agent of Cirsium arvense

Cirsium arvense is a noxious perennial weed which has become an increasing problem in north European countries. Biological control by natural antagonists is of increasing interest to supplement mechanical and chemical control. Several attempts to use fungi such as Alternaria cirsinoxia, Puccinia punctiformis and Sclerotinia sclerotiorum as biocontrol agents have been initiated. No mycoherbicides against C. arvense have been developed and the search for aggressive pathogens continues. In a Danish survey, several fungi were isolated from C. arvense. Four are new records in Denmark: the white rust fungus Pustula andropogonis, the leaf spot fungi Ramularia cirsii, Septoria cirsii and Phomopsis cirsii. Our study shows that P. cirsii is pathogenic to C. arvense, causing stem canker and die back, and that it may have potential as a mycoherbicide against its host. Growth characteristics of P. cirsii on artificial media are described, as well as a scale measuring severity of visible symptoms of P. cirsii on C. arvense. The taxonomic characteristics of Phomopsis spp. are compared and discussed in relation to other records of Phomopsis spp. found on Cirsium spp. and C. arvense.     

Sympatric ascochyta complex of wild Cicer judaicum and domesticated chickpea

The aim of this study was to isolate, identify and characterize ascochyta blight pathogens from Cicer judaicum , a wild annual Cicer species which grows in Israel and other Mediterranean countries in sympatric distribution with legume crops, and determine their virulence and aggressiveness to other wild and domesticated legumes. Native C. judaicum plants exhibited symptoms resembling ascochyta diseases of grain legume crops. Two distinct pathogens were isolated and identified as Phoma pinodella and Didymella rabiei using morphological and molecular tools; their infectivity was verified using Koch's postulates. The virulence of these pathogens was examined on 13 legume species, of which P. pinodella was virulent to Pisum sativum , P. fulvum , C. judaicum , C. arietinum , C. reticulatum , C. pinnatifidum and C. bijugum . Didymella rabiei infected all these Cicer species, but not the other legume species tested. Aggressiveness of the pathogens was tested on wild and domesticated chickpea and pea. Didymella rabiei isolated from C. judaicum had significantly higher ( P  < 0·001) aggressiveness than P. pinodella from C. judaicum on both wild and domesticated chickpea. Disease severity on the former species ranged from 62·5% to 70% and on the latter from 41% to 56%. Phoma pinodella isolates from C. judaicum were more aggressive on C. arietinum and P. sativum than on C. judaicum and P. fulvum . Results of the current study suggest that C. judaicum may serve as an alternative host to ascochyta pathogens that endanger chickpea and possibly other crops and wild species growing in close proximity.     

枣铁皮病病原鉴定

 枣铁皮病主要为害大枣果实,可导致果实腐烂和提早落果,据症状特点可分为铁皮型和缩果型2种类型。1993~1995年对河北和河南2省6个不同枣区大枣铁皮病病果进行分离、接种和再分离,证实枣铁皮病病原为:链格孢Alternaria alternata(Fr.) Keissler;实腐茎点霉Phoma destructiva Plowr,壳梭孢属一种真菌Fusicoccum sp.3种病原真菌可以单独或混合侵染。     

Host specificity of Fusarium oxysporum Schlect (isolate PSM 197), a potential mycoherbicide for controlling Striga spp. in West Africa

The ability of Fusarium oxysporum (PSM 197), a potential mycoherbicide for control of Striga hermonthica, to control different Striga species (S. hermonthica, S. asiatica and S. gesneroides) and another parasitic weed, Alectra vogelli, was investigated under glasshouse conditions. Significant reductions in the total number of emerged plants of S. asiatica (91.3%), S. gesneroides (81.8%) and S. hermonthica (94.3%) were achieved in the presence of F. oxysporum (PSM 197). The pathogen only caused a reduction of 8.5% in A. vogelli. This high susceptibility of the three Striga species provides a possible opportunity to control these parasites simultaneously with this mycoherbicide.     

Evaluation of the grapevine nursery propagation process as a source of <Emphasis Type="Italic">Phaeoacremonium</Emphasis> spp. and <Emphasis Type="Italic">Phaeomoniella chlamydospora</Emphasis> and occurrence of trunk disease pathogens in rootstock mother vines in Spain

Five commercial nurseries were sampled in 2007 to evaluate the grapevine nursery propagation process as a source of Petri disease pathogens (Phaeoacremonium spp. and Phaeomoniella chlamydospora). Samples were taken at four stages of the propagation process: pre-grafting hydration tanks, scissors used for cutting buds, grafting machines and peat used to promote root development. All samples were analysed using two different techniques: nested PCR using specific primers for Phaeoacremonium spp. (Pm1/Pm2) and Pa. chlamydospora (Pch1/Pch2); and fungal isolation by culturing on semi-selective medium. Either Phaeoacremonium spp. or Pa. chlamydospora were detected at any of these stages, and more importantly they were viable since they were detected by isolating on culturing medium. Additionally, the importance of grapevine rootstock mother fields as sources of inoculum in the nurseries was studied. Fourteen grapevine rootstock mother fields were surveyed in 2006 and 2007 for the occurrence of fungal trunk pathogens. A total of 16.4% and 30% of the plants sampled in 2006 and 2007, respectively were infected. Petri disease pathogens (Pa. chlamydospora, Phaeoacremonium aleophilum, Pm. parasiticum) and several Botryosphaeriaceae species (Neofusicoccum parvum, Botryosphaeria dothidea, Lasiodiplodia theobromae, N. australe, N. mediterraneum and N. vitifusiforme) and Phomopsis viticola were isolated. This is the first time N. mediterraneum has been isolated from grapevines and the first report of N. australe, N. mediterraneum and N. vitifusiforme in Spain. This work shows that grapevine rootstock mother plants and the propagation process of grapevine plants should be considered as important sources of inoculum for fungal trunk pathogens, and especially of Petri disease pathogens.     

Relationship between ascochyta blight on field pea (Pisum sativum) and spore release patterns of Didymella pinodes and other causal agents of ascochyta blight

Ascochyta blight of field pea, caused by Didymella pinodes, Phoma medicaginis var. pinodella, Phoma koolunga and Didymella pisi, is controlled through manipulating sowing dates to avoid ascospores of D. pinodes, and by field selection and foliar fungicides. This study investigated the relationship between number of ascospores of D. pinodes at sowing and disease intensity at crop maturity. Field pea stubble infested with ascochyta blight from one site was exposed to ambient conditions at two sites, repeated in 2 years. Three batches of stubble with varying degrees of infection were exposed at one site, repeated in 3 years. Every 2 weeks, stubble samples were retrieved, wetted and placed in a wind tunnel and up to 2500 ascospores g^?1 h^?1 were released. Secondary inoculum, monitored using seedling field peas as trap plants in canopies arising from three sowing dates and external to field pea canopies, was greatest in early sown crops. A model was developed to calculate the effective number of ascospores using predictions from G1 blackspot manager (Salam et al., 2011b; Australasian Plant Pathology, 40 , 621–31), distance from infested stubble (Salam et al., 2011a; Australasian Plant Pathology, 40 , 640–7) and winter rainfall. Maximum disease intensity was predicted based on the calculated number of effective ascospores, soilborne inoculum and spring rainfall over two seasons. Predictions were validated in the third season with data from field trials and commercial crops. A threshold amount of ascospores of D. pinodes, 294 g^?1 stubble h^?1, was identified, above which disease did not increase. Below this threshold there was a linear relationship between ascospore number and maximum disease intensity.     

Occurrence and diversity of fungal pathogens associated with water hyacinth and their potential as biocontrol agents in the Rift Valley of Ethiopia

Water hyacinth poses serious socio-economic and environmental problems in Ethiopia. To integrate fungal pathogens into water hyacinth management, a survey was conducted in the Rift Valley of Ethiopia. Based on morphological characterization and DNA sequencing, 25 fungal species were identified that belong to nine genera. Alternaria tenuissima, A. alternata, Aspergillus niger, Phoma sp., Curvularia trifolii, Mucor fragilis, M. racemosus, A. fumigatus, Fusarium oxysporum, and F. equiseti were the most common fungi detected. However, their occurrence was influenced by water wave action, temperature, season, and altitude. Among the fungal pathogens, A. alternata, A. tenuissima, F. oxysporum, F. equiseti, and Neofisicoccum parvum were highly pathogenic to water hyacinth. Alternaria alternata and A. tenuissima did not cause disease symptoms on ecologically important plant species (e.g. Noug, Tef, and Coffee). Application of the fungal pathogens on water hyacinth plants also showed 11%–67%, 22%–72%, 15%–55%, and 12%–50% reduction in fresh weight, dry weight, plant height, and root length of water hyacinth, respectively. This study suggests that fungal species have the potential to control water hyacinth biologically and provides baseline data for biological control efforts in the future.     

Comparison of the epidemiology of ascochyta blights on grain legumes

Asochyta blights of grain legumes are caused by fungal pathogens in the genus Ascochyta. Different species infect the different legume species, and in pea three species including Phoma medicaginis var. pinodella have been implicated in ascochyta blight. The impact of the diseases varies between crops, countries, seasons and cropping systems, and yield loss data collected under well-defined conditions is scarce. However, ascochyta blights are considered major diseases in many areas where legumes are grown. Symptoms appear on all aerial parts of the plant, and lesions are similar for most of the species, except for M. pinodes and P. medicaginis var. pinodella. Infected seed, stubble and/or air-borne ascospores are major sources of primary inoculum. Their importance varies between species and also between regions. All Ascochyta spp. produce rain-splashed conidia during the cropping season which are responsible for the spread of the disease within the crop canopy. Only in pea are ascospores involved in secondary disease spread. Limited data suggests that Ascochyta spp. may be hemibiotrophs; however, toxins characteristic for necrotrophs have been isolated from some of the species. Modelling of ascochyta blights is still in the developmental stage and implementation of such models for disease forecasting is the exception.     

Phoma black stem severity and phytoestrogen production in annual Medicago spp. is primarily determined by interaction of cultivar and pathogen isolate

Phoma black stem and leaf spot disease (caused by Phoma medicaginis) not only diminishes forage and seed yield but stimulates production of detrimental phytoestrogens in annual Medicago spp. This study aimed to evaluate relationships between disease development from five isolates of P. medicaginis on 16 cultivars with production of coumestrol and 4′-O-methylcoumestrol. In the presence of P. medicaginis, Sava had the highest coumestrol and 4′-O-methylcoumestrol (640 and 85 mg/kg, respectively) followed by Caliph (253 and 15 mg/kg, respectively). In the absence of P. medicaginis, Jemalong and Paragosa showed highest and lowest coumestrol (137 and 0 mg/kg, respectively). 4′-O-methylcoumestrol was not produced in disease-free plants, but coumestrol was. Disease incidence and severity on leaves and on petiole/stems, and consequent leaf yellowing severity ranged from 5%–98.7%, 0%–100%, 4.4%–98.7%, 1.7%–100%, and 0%–85%. Sava, Paraponto, Harbinger, and Serena were most susceptible, while Tornafield and Caliph were least susceptible. There was significant overall positive correlation of disease incidence/severity factors across cultivars (p < 0.01) with both coumestrol and 4′-O-methylcoumestrol. Jemalong was least responsive and Paragosa and Sava most responsive to coumestrol production following P. medicaginis inoculation. Coumestrol in inoculated Paragosa increased to 373 mg/kg in comparison with 0 mg/kg in controls. These findings are of critical importance towards developing less disease-susceptible annual Medicago spp. producing less detrimental phytoestrogens. Least susceptible cultivars like Tornafield and Caliph can be used to manage yield loss, whilst least responsive cultivars to phytoestrogen production like Caliph also can help to reduce phytoestrogen production.     

Effects of fungicides on in vitro spore germination and mycelial growth of the phytopathogens Leptosphaeria maculans and L. biglobosa (phoma stem canker of oilseed rape)

BACKGROUND: Phoma stem canker, caused by the coexisting related fungal pathogens Leptosphaeria maculans (Des.) Ces. & de Not and L. biglobosa Shoemaker & H Brun, is a major disease of winter oilseed rape in the UK. Annually, over 90% of UK crops receive at least one foliar application of fungicide, but little is known about the sensitivity of the more damaging L. maculans and the less damaging L. biglobosa to these fungicides. The effects of flusilazole, tebuconazole and Methyl Benzimidazole Carbamate (MBC) fungicides (benomyl and carbendazim) on the germination of ascospores, conidia and germ tube growth of both species were examined. Isolates collected from different oilseed rape crops in England and Wales were assessed for their mycelial growth on fungicide‐amended medium, and ED₅₀ values were calculated. RESULTS: Leptosphaeria maculans and L. biglobosa differed in their sensitivity to fungicides. Conidial germination of L. maculans was more sensitive to these fungicides than that of L. biglobosa. Isolates of L. maculans had smaller ED₅₀ values for mycelial growth for all fungicides tested than isolates of L. biglobosa. CONCLUSION: These results suggest that fungicide applications might affect the structure of L. maculans/L. biglobosa populations in UK winter oilseed rape crops. Copyright © 2009 Society of Chemical Industry     

Fungi on roots and stem bases of asparagus in the Netherlands: species and pathogenicity

A survey was made to identify the most important soilborne fungal pathogens of asparagus crops in the Netherlands. Ten plants were selected from each of five fields with a young (1–4 y) first planting, five fields with an old (6–13 y) first planting and five fields with a young replanting. The analysis included fungi present in the stem base and the roots of plants with symptoms of foot and root rot or showing growth decline without specific disease symptoms. Isolates of each species were tested for pathogenicity to asparagus on aseptically grown plantlets on Knop's agar. Symptoms were caused byFusarium oxysporum, F. culmorum, Botrytis cinerea, Penicillium verrucosum var.cyclopium, Cylindrocarpon didymum, Phialophora malorum, Phoma terrestris andAcremonium strictum. F. oxysporum was by far the most common species and was isolated from 80% of the plants. Not all of its isolates were pathogenic to asparagus. Symptoms were caused by 67%, 78% and 93% of the isolates obtained from young first plantings, old first plantings and replantings, respectively.F. culmorum was isolated from 31% of the plants. Two other notorious pathogens of asparagus,F. moniliforme andF. proliferatum, did not occur in our samples.Species causing symptoms in the vitro test that were found on more than 5% of the plants were additionally tested for their pathogenicity in pot experiments.F. oxysporum f.sp.asparagi caused severe foot and root rot, significantly reduced root weights and killed most of the plants.F. culmorum caused lesions on the stem base often resulting in death of the plant.P. terrestris, a fungus only once reported as a pathogen of asparagus, caused an extensive root rot, mainly of secondary roots that became reddish. The fungus was isolated in only a few samples and is not to be regarded as an important pathogen in Dutch asparagus crops.P. malorum caused many small brown lesions on the stem base and incidentally also on the upper part of small main roots. This is the first report of its pathogenicity to asparagus. The fungus is one of the organisms inciting spear rust and it reduced crop quality rather than crop yield.P. verrucosum var.cyclopium andC. didymum did not cause symptoms in pot experiments.Because of its predominance on plants with foot and root rot and its high virulence,F. oxysporum f.sp.asparagi was considered to be the main soilborne pathogen of asparagus in the Netherlands.     

Control of clubroot of crucifers by Phoma glomerata and its product epoxydon

Phoma glomerata strain JCM9972 controls clubroot of cruciferous crops caused by Plasmodiophora brassicae and the activity depends upon epoxydon (5-hydroxy-3-(hydroxymethyl)-7-oxabicyclo [4.1.0]hept-3-en-2-one) produced by the strain.     

Verticillium wilt in nursery trees: damage thresholds,spatial and temporal aspects

Verticillium wilt can cause high losses in tree nurseries. To be able to predict disease and unravel disease dynamics over time and space, the relationship between verticillium wilt and soil inoculum densities of Verticillium dahliae and the nematode Pratylenchus fallax was studied in two 4-year field experiments with Acer platanoides and Catalpa bignonioides in the Netherlands. Best-fit regression equations showed that pre-planting inoculum densities of V. dahliae can be used to predict verticillium wilt over a period of at least 4 years. Pratylenchus fallax contributed significantly to disease severity in A. platanoides in some years. Disease can already occur at the detection limit of the pathogens. The 5% infection thresholds for V. dahliae were at 1 (A. platanoides) vs. 3 (C. bignonioides) colony-forming units (CFU) g⁻¹ soil. Analysis of spatial relationships indicated that diseased plants had a higher influence on neighbouring plants at low V. dahliae inoculum densities (<5 CFU g⁻¹ soil) than at high densities (≥5 CFU g⁻¹ soil). Seventy-four percent of the diseased plants recovered during the following year. After that year, recovered plants had a significantly higher probability of becoming diseased again than plants that were healthy during the two previous years, at high inoculum densities of V. dahliae, indicating that inoculum density in the soil, rather than incomplete recovery, was the most important factor for disease development.     

Impact of Foliar Diseases on Photosynthesis, Protein Content and Seed Yield of Alfalfa and Efficacy of Fungicide Application

Foliar pathogens attack alfalfa wherever the crop is grown, but their impact, especially on seed production, is poorly understood. In greenhouse trials, leaf spot injury caused by inoculation with various pathogens reduced the crude protein content of infected alfalfa leaves by 22% compared with a healthy control. There was a negative relationship between disease injury and the photosynthetic efficiency of alfalfa plants, as determined by measuring chlorophyll fluorescence in leaves from inoculated vs. non-inoculated seedlings. In field trials at two sites in Alberta from 2001 to 2003, inoculation with Phoma medicaginis increased disease incidence in four of six trials, Phoma sclerotioides increased incidence in four of five trials, and Leptosphaerulina trifolii and Stemphylium botryosum increased incidence in two of six trials. There was a trend for inoculation treatments to reduce seed yield, despite high levels of background infection by indigenous pathogens. The fungicides benomyl and propiconazole inhibited radial growth of Phoma spp. in vitro and reduced disease incidence in inoculated greenhouse experiments. In field trials, applications of benomyl and propiconazole reduced disease incidence, but did not always increase seed yield.     

Characterisation and detection of Pythium and Phytophthora species associated with grapevines in South Africa

Replant and decline diseases of grapevines not only cause quantitative and qualitative yield losses, but also result in extra costs when vineyards have to be replanted. This study investigated the role of Pythium and Phytophthora in the decline syndrome in South Africa by determining (1) the species associated with nursery and established vines, and (2) pathogenicity of Ph. sp. niederhauserii and P. vexans relative to known grapevine pathogens. Quantitative real-time PCR (qPCR) assays were also developed for detection of the most prevalent oomycete groups. In total, 26 Pythium and three Phytophthora species were identified from grapevine nurseries and established vineyards. The most common infections in sampled nursery vines were caused by P. vexans (16.7%), followed by P. ultimum var. ultimum (15.0%) and P. irregulare (11.7%). In established vineyards, P. irregulare (18.0%) and P. vexans (6.2%) were also among the three most prevalent species, along with P. heterothallicum (7.3%). Three Phytophthora species were also identified from the sampled established vines, of which Ph. cinnamomi (5.1%) was predominant, followed by Ph. sp. niederhauserii (1.1%). In established vineyards a higher incidence and more diverse species composition was observed in spring and winter, than in summer. Pathogenicity studies showed that some Ph. sp. niederhauserii and P. vexans isolates were as aggressive as the known grapevine pathogens Ph. cinnamomi and P. irregulare. Sensitive qPCR assays were developed for the detection of P. ultimum var. ultimum, P. irregulare, P. vexans and the genus Phytophthora. These assays will be invaluable in limiting pathogen dispersal through screening of nursery material. This is especially important since pathogenic species were also isolated from healthy looking vines in nurseries.     

Bean rust as a model system to evaluate efficieucy of teliospore induction, especially in the potential mycoherbicide Pucdni a punctiformis

The use of teliospores of the rust fungus Pucdnia punctiformis (Str.) Röhl., a potential mycoher-bicide against the dicotyledonous weed Cirsium arvense (L.) Scop, has shown promise. Methods to increase teliospore production for systemic infections were investigated using two dicotyle-donous host-pathogen systems, the thistle rust and the bean rust (Phaseolus vulgaris-Uromyces appendiculatus). Three different approaches (culture filtrate extracts of different Aphano-fadium album strains, application of Ajoen and dark periods) were tested for their capacity to induce teliospore production in the above-mentioned host-pathogen systems. The methods significantly increased the teliospore production in the model system (bean-rust), although differing in the order dark period > A. album extract ajoen. The effect of the A. album extract depends on the strain used. A two-day dark period increased the teliospore production of bean rust in addition to precipitating its onset. The same effect was noted for thistle rust using A. album extract. The advantage of bean rust as a model organism together with combined applications and host pathogen reaction mechanisms are discussed. La rouille du pois comme système modèle permettant d'évaluer l'efficacité de l'induction de téliosopores, en particulier chez le mycoherbicide potentiel Puccinia punctiformis L'utilisation de téliospores de la rouille Puccinia punctiformis (Str.) Röhl, un mycoherbicide potentiel, s'est montrée prometteuse pour la lutte contre la mauvaise herbe dicotylédone Cirsium arvense (L.) Scop. Des méthodes permettant d'augmenter la production de téliospores pour des infections systémiques ont étéétudiées sur deux systèmes hôte-pathogène de dicotylédones, la rouille du chardon et la rouille du haricot (Phaseolus vulgaris-Uromyces appendiculatus). Trois approches différentes (extraits de filtrats de culture provenant de différentes souches d'Aphanocladium album, application d'Ajoen et périodes obscures) ont été testées pour leur capacitéà induire les téliospores dans les systèmes hôte/pathogène précédents. Les méthodes accroissaient significativement la production de téliospores dans le système modèle (haricot-rouille) bien que différant en efficacité dans l'ordre: période obscure extraits d'A album Ajoen. L'effet de l'extrait d'A album dépendait de la souche utilisée. Une période obscure de deux jours accroissait la production de téliospores de la rouille du haricot et avanßait son démarrage. Le même effet était observé chez la rouille du chardon avec des extraits d'A album. L'avantage de la rouille du haricot comme organisme modèle, ainsi que d'applications combinées est discuté, de même que les mécanismes de la relation hôte/pathogène. Der Bohnenrost als Modellsystem zur Abschätzung der Effizienz unterschiedlicher Verfahren der Teleutosporeninduktion unter Berücksichtigung des potentiellen Mykoherbizids Puccinia punctiformis Die Verwendung der Teleutosporen des Rostes Puccinia punctiformis (Str.) Röhl. zeigt erfolgversprechende Ansätze als Mykoherbizid gegen das Unkraut Cirsium arvense (L.) Scop. Methoden, die für systemische Infektionen der Kratzdistel erforderliche Teleutosporenbildung zu steigern, wurden an 2 dikotylen Wirt-Pathosystemen, der Kratzdistel und der Bohne (Phaseolus vulgaris/Uromyces appendiculata), geprüft. Es wurden 3 unterschiedliche Methoden angewandt, um die Teleutosporenbildung in den erwähnten Systemen zu induzieren (Kulturfiltratextrakte unterschiedlicher Aphanocladium-album-Stämme, Ajoen und Dunkelperioden). Alle Anwendungen steigerten die Teleutosporenbildung im Modellsystem Bohnenrost signifikant, jedoch graduell unterschiedlich: Dunkelphase > A.-album-Extrakt > Ajoen. Dabei war der Effekt des A-album-Extraktes eindeutig von dem verwendeten Stamm abhängig. Die 2-tägige Dunkelphase steigerte die Teleutosporenproduktion des Bohnenrostes und bewirkte ein früheres Einsetzen der Teleutosporenbildung. Der gleiche Effekt konnte für den Kratzdistelrost auch unter Verwendung des A.-album-Extraktes festgestellt werden. Die Vorteile des Bohnenrostes als Modellorganismus sowie kombinierte Appli-kationen und mögliche Wirt-Pathogen-Reaktions-mechanismen werden diskutiert.     

Gummy stem blight of balsam pear caused by <Emphasis Type="Italic">Didymella bryoniae</Emphasis> and its anamorph <Emphasis Type="Italic">Phoma cucurbitacearum</Emphasis>

Gummy stem blight of balsam pear found in the Kanto district and in the Hokkaido Prefecture was demonstrated to be caused by Didymella bryoniae (Auerswald) Rehm based on inoculation experiments, molecular analysis, and morphological identification of the pathogenic fungus. This fungus was also pathogenic to related plants belonging to Cucurbitaceae. The imperfect stage of the fungus was identified as Phoma cucurbitacearum (Fr.: Fr.) Sacc. based on morphological similarities.