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1.
In two successive seasons, the effect of treatment of geranium stock plants with the competitive saprophytic fungus Ulocladium atrum as a biocontrol agent against Botrytis cinerea was compared to a fungicide treatment with Euparene M. B. cinerea incidence and severity on the stock plants, B. cinerea spore load in the air around stock plants and death of cuttings due to B. cinerea were scored. B. cinerea incidence and severity were much stronger in the second than the first experiment. This was quantitatively expressed by higher numbers of conidia of B. cinerea monitored in the second than the first year, both on necrotic (a maximum for the control of 27.5 × 106 spores per sample - all necrotic leaves of five plants - in experiment 1 against 86 × 106 in experiment 2) and green leaves, but numbers of conidia of B. cinerea recovered from the air were only slightly different. The death rate of cuttings was moderate in the first and extremely high in the second experiment. For the fungicide treatment, maximum sample values of 7% and 76% of 6-week old cuttings were killed in the first and the second experiment respectively. Treatment with U. atrum was effective in reducing all parameters studied. With the exception of the spore load of B. cinerea in the air and the success of cuttings, the effect of U. atrum varied from as good as the fungicide to half as effective. In the first trial, only Euparene M reduced spore load in the air, in the second trial only U. atrum consistently did so. In the first trial U. atrum reduced death of 4-week old cuttings, though less than fungicide (1.2, 20 and 38% killed with fungicide treatment, U. atrum treatment and control respectively). In the second trial only the fungicide reduced loss of cuttings. The impact of the data on the integration of U. atrum in a control system of B. cinerea in geranium is discussed.  相似文献   

2.
The objective of this study was to assess the genetic diversity and to infer the mode of reproduction of Botrytis elliptica and B. tulipae in the Netherlands. First, three molecular typing methods were compared for their ability to differentiate isolates of B. tulipae, B. elliptica, and B. cinerea. The methods compared were multilocus sequencing, restriction analysis of the ribosomal intergenic spacer (IGS) region, and amplified fragment length polymorphism (AFLP) analysis. AFLP fingerprinting provided the most efficient method to differentiate isolates within each Botrytis species and therefore this method was used for population analyses of B. elliptica and B. tulipae. Isolates of both species were sampled during successive growing seasons in experimental field plots in Lisse and other locations in the Netherlands. Among 174 B. elliptica isolates, 105 genotypes could be discriminated and 87 genotypes were found only once, reflecting high genotypic variation. Clonal genotypes were found only within growing seasons and in one location. Linkage disequilibrium analyses indicated that between 9.4% and 19.3% of the loci in clone-corrected samples were linked. The multilocus association index provided no evidence for random mating. We conclude that sexual recombination occurs in the B. elliptica population. Among the 170 B. tulipae isolates, 25 genotypes could be discriminated and four genotypes were found only once, reflecting a low genotypic variation. Clonal genotypes were frequently found in different growing seasons and different locations. Linkage disequilibrium analyses indicated that between 25.2% and 48.6% of the loci in clone-corrected samples were linked. We conclude that the B. tulipae population is mainly clonal with some recombination.  相似文献   

3.
In this study, the hypothesis was tested that removal of substrate for sporulation ofBotrytis spp. may lead to a retardation of an epidemic if the majority of the inoculum is produced inside the treated crop. Suppression of sporulation ofBotrytis spp. could be an attractive option for biological control ofBotrytis leaf spot in onions. In a field experiment, necrotic leaf tissue was removed to simulate the effect of a biocontrol agent. By this means, the amount of substrate on whichBotrytis spp. sporulates was reduced. In the experiment, the spore load above the onion plots was significantly reduced and the epidemic of onion leaf spot was retarded. At the end of the growing season, the number of leaf lesions in the green leaf area was lower in plots with substrate removal than in control plots (0.6 and 1.1 cm–2, respectively). The results demonstrated that an epidemic of onion leaf spot largely depends on the rate of inoculum production inside a crop. Thus, suppression of sporulation on necrotic leaf tissue is a valid control strategy that could be applied by using sporulation suppressing antagonists.  相似文献   

4.
观赏百合叶枯病症状类型与病原菌鉴定   总被引：3，自引：0，他引：3  
徐琼  徐秉良  王芳 《植物保护》2006,32(5):61-64
引起甘肃省百合叶枯病的主要致病菌为椭圆葡萄孢[Botrytis elliptica(Berk.)Cooker],分离率为70.5%;其次是灰葡萄孢(Botrytis cinerea Peers),分离率为23.0%。该病原菌在不同品种百合叶片上造成的症状有4种类型。不同症状类型病斑分离的病原菌种类不同,其中紫缘黄褐斑型、褐色环纹型和黄缘褐斑型主要致病菌为椭圆葡萄孢,平均分离率为82.5%;叶缘干枯型的主要致病菌为灰葡萄孢,分离率达93.7%。温度为15℃时,易产生菌核;菌核萌发最适温度为15~20℃。  相似文献   

5.
Sixty isolates of saprophytic microorganisms were screened for their ability to reduce the severity of grey mould (Botrytis cinerea) infection and sporulation. Isolates of the bacteriaXanthomonas maltophilia, Bacillus pumilus, Lactobacillus sp., andPseudomonas sp. and the fungusGliocladium catenulatum reduced germination of conidia of the pathogen and controlled disease on bean and tomato plants. Their activity under growth room conditions was good, consistent, and similar to the activity of the known biocontrol agent,Trichoderma harzianum T39 (non-formulated). Although the tested isolates may for nutrients with the germinating conidia ofB. cinerea, resistance induced in the host by live or dead cells were also found to be involved. Inhibitory compounds were not detected on treated leaves. Sporulation ofB. cinerea after its establishment on leaves was also reduced by the above mentioned isolates and byPenicillium sp.,Arthrinium montagnei, Ar. phaeospermum, Sesquicillium candelabrum, Chaetomium globosum, Alternaria alternata, Ulocladium atrum, andT. viride. These sporulation-inhibiting fungi did not reduce the infection of leaves byB. cinerea. Most of these selected fungi and bacteria were capable of reducing lesion expansion.  相似文献   

6.
Botrytis cinerea is a non-specific, necrotrophic pathogen that attacks many plant species, including Arabidopsis and tomato. Since senescing leaves are particularly susceptible to infection by B. cinerea, we hypothesized that the fungus might induce senescence as part of its mode of action and that delaying leaf senescence might reduce the severity of B. cinerea infections. To examine these hypotheses, we followed the expression of Arabidopsis SAG12, a senescence-specific gene, upon infection with B. cinerea. Expression of SAG12 is induced by B. cinerea infection, indicating that B. cinerea induces senescence. The promoter of SAG12, as well as that of a second Arabidopsis senescence-associated gene, SAG13, whose expression is not specific to senescence, were previously analyzed in tomato plants and were found to be expressed in a similar manner in the two species. These promoters were previously used in tomato plants to drive the expression of isopentenyl transferase (IPT) from Agrobacterium to suppress leaf senescence (Swartzberg et al. in Plant Biology 8:579–586, 2006). In this study, we examined the expression of these promoters following infection of tomato plants with B. cinerea. Both promoters exhibit high expression levels upon B. cinerea infection of non-senescing leaves of tomato plants, supporting our conclusion that B. cinerea induces senescence as part of its mode of action. In contrast to B. cinerea, Trichoderma harzianum T39, a saprophytic fungus that is used as a biocontrol agent against B. cinerea, induces expression of SAG13 only. Expression of IPT, under the control of the SAG12 and SAG13 promoters in response to infection with B. cinerea resulted in suppression of B. cinerea-induced disease symptoms, substantiating our prediction that delaying leaf senescence might reduce susceptibility to B. cinerea. Contribution from the Agriculture Research Organization, The Volcani Center, Bet Dagan, Israel, No. 127/2006 series.  相似文献   

7.
In June 1998, leaf spots caused by Botrytis elliptica (Berkeley) Cooke were found on Taiwanese toad lily (Tricyrtis formosana Bak.) in Kanagawa Prefecture, Japan. This is the first report on Botrytis blight of T. formosana caused by B. elliptica.  相似文献   

8.
Mutants of Botrytis cinerea and Ustilago maydis highly resistant to fludioxonil were isolated at a high frequency, after nitrosoguanidine or UV mutagenesis, respectively, and selection on media containing fludioxonil. Tests on the response of mutant strains to high osmotic pressure resulted in the identification of two fludioxonil-resistant phenotypes (FLDosm/s and FLDosm/r), regarding the sensitivity to high osmolarity. Approximately 95% of fludioxonil-resistant mutants were found to be more sensitive to high osmotic pressure than the wild-type parent strains. Genetic analysis of phenylpyrrole-resistance in the phytopathogenic basidiomycete U. maydis, showed that fludioxonil-resistance was coded by three unlinked chromosomal loci (U/fld-1, U/fld-2 and U/fld-3), from which only the U/fld-1 mutation coded an osmotic sensitivity similar to that of the wild-types. Cross-resistance studies with fungicides from other chemical groups showed that the mutations for resistance to phenylpyrroles affect the sensitivity of mutant strains to the aromatic hydrocarbon and dicarboximide fungicides, but not to the benzimidazoles, anilinopyrimidines, phenylpyridinamines, hydroxyanilides or the sterol biosynthesis inhibiting fungicides. A study of fitness parameters in the wild-type and fludioxonil-resistant mutants of B. cinerea, showed that all osmotic sensitive (B/FLDosm/s) isolates had significant reductions in the characteristics determining saprophytic fitness such as mycelial growth, sporulation, conidial germination and sclerotial production. Contrary to that, with the exception of mycelial growth, the fitness parameters were unaffected or only slightly affected in most of the osmotic resistant (B/FLDosm/r) isolates. Tests on cucumber seedlings showed that the osmotic-sensitive strains were significantly less pathogenic compared with the wild-type and B/FLDosm/r strains of B. cinerea. Preventative applications of the commercial products Saphire 50 WP (fludioxonil) and Rovral 50 WP (iprodione) were effective against lesion development on cotyledons by the wild-type and the mutant strains of B. cinerea that were resistant to the anilinopyrimidine cyprodinil (B/CPL-27) and to the hydroxyanilide fenhexamid (B/FNH-21), but ineffective, even at high concentrations, against disease caused by the fludioxonil-resistant isolates (B/FLD) and a mutant strain resistant to the dicarboximide iprodione (B/IPR-1). Experiments on the stability of the fludioxonil-resistant phenotype showed a reduction of resistance, mainly in osmotic-sensitive isolates, when the mutants were grown on inhibitor-free medium. A rapid recovery of the high resistance was observed after mutants were returned to the selection medium. Studies on the competitive ability of mutant isolates against the wild-type parent strain of B. cinerea, by applications of a mixed conidial population, showed that, in vitro, all mutants were less competitive than the wild-type strain. However, the competitive ability of osmotic-resistant mutants was higher than the osmotic-sensitive ones. Furthermore, competition tests, in planta, showed a significant reduction of the frequency of both phenylpyrrole-resistant phenotypes, with a respective increase in the population of the wild-type strain of the pathogen.  相似文献   

9.
Saprophytic antagonists were evaluated for suppression of sporulation ofBotrytis allii andB. cinerea on artificially killed segments of onion leaves that were pre-inoculated with the pathogens. During incubation of the antagonisttreated leaf segments in moist chambers, periods of leaf wetness and leaf dryness were alternated to simulate conditions in the field. Interruption of humid conditions with dry periods had a differential effect on antagonists.Alternaria alternata, Chaetomium globosum, Ulocladium atrum andU. chartarum suppressed sporulation ofB. allii almost completely under continuously wet conditions, and when the leaf wetness periods were interrupted with drying periods of 9h imposed 16, 40, and 64 h after the antagonists were applied. When leaf wetness was interrupted 16 h after antagonist application, the number of conidia ofB. allii produced cm–2 leaf surface after eight days was under the detection limit of 5.2 × 103 conidia on leaves treated with these antagonists compared to 3.7 × 105 conidia on leaves that were not treated. On the other hand,Gliocladium roseum, G. catenulatum andSesquicillium candelabrum, all highly efficient under continuously wet conditions, were of low to moderate efficiency when leaf wetness periods had been interrupted 16 h after application of the antagonists. The antagonists showed the same differentiation and sensitivity to interrupted wetness periods when tested withB. cinerea.  相似文献   

10.
In 1995, conidia of Ulocladium atrum were applied to a canopy of green lily (Lillium spp.) leaves in order to investigate its survival, colonisation of artificially induced necrotic leaf tissues and competitive ability against Botrytis spp. and naturally occurring saprophytes. U. atrum conidia density cm-2 at the top and middle canopy levels was not significantly different following application of the antagonist with a propane powered backpack sprayer. In repeat experiments, conidia density on leaves at the lower canopy level was 18% to 20% of that deposited onto leaves at the top of the lily canopy. There was a significant (P < 0.001) linear decline of U. atrum conidia over time and after 21 days conidia density had declined by up to 73%. Germination of U. atrum on green leaves in the field reached a maximum of 81%, seven days after antagonist application. Conidial viability, measured as germination potential, declined slightly (100% to 88%) after seven days exposure to field conditions but there were no further changes in the germination potential even after 21 days of field exposure. The germination potential was not affected by canopy level. The ability of surviving U. atrum conidia to colonise necrotic tissues, artificially induced with paraquat, was measured. U. atrum colonisation was consistently highest on necrotic leaves at the top level of the canopy and consistently lower on leaves from the bottom canopy level. Necrotic leaf colonisation by U. atrum decreased over time from 51% (necrosis induced immediately after antagonist application) to 21% when necrosis was induced 21 days after antagonist application. A significant (P < 0.001) linear relationship (R2 = 0.713) between colonisation of necrotic tissues and conidia density prior to induction of necrosis was detected. When necrosis was induced immediately after antagonist application, U. atrum outcompeted commonly occurring saprophytic Alternaria spp. and Cladosporium spp. The ability of U. atrum to significantly reduce colonisation by Alternaria spp. was maintained for up to 21 days. Botrytis spp. did not occur in these field experiments. It was concluded that U. atrum had the ability to survive and persist in the phyllosphere for up to 21 days in the field and provided further evidence that U. atrum has the necessary survival characteristics to be a successful biological control agent of Botrytis spp.  相似文献   

11.
The epidemiology of Botrytis cinerea was studied in five annual strawberry crops using waiting-bed transplants, a system widely adopted in the Netherlands. On dead leaves of transplants the incidence of B. cinerea varied from 26.7% to 52.6%, but the leaf area with potential sporulation was low (3.5–15.6%). During each crop cycle, the availability of necrotic leaf substrate for spore production of B. cinerea was generally low and varied between seasons and with the quality of transplants. B. cinerea sporulated on a maximum of 15.5 cm2 of leaf area per plant, measured as potential sporulation. The aerial concentration of B. cinerea conidia in untreated plots did not differ from the concentration in plots where all dead leaves had been removed, nor from the concentration at 25–50 m distance from the strawberry plots. B. cinerea incidence on flowers ranged from 5% to 96%, but no correlation was found with the potential spore production on necrotic leaves. Grey mould at harvest varied from 1.4% to 11.3% and was correlated with the average precipitation during the harvesting period but not with B. cinerea incidence on flowers. Post-harvest grey mould ranged from 2.1% to 32.6% and was correlated with petal colonisation by B. cinerea. The results suggest that in the annual cropping system with waiting-bed transplants, necrotic leaves are not a significant source of B. cinerea inoculum, unlike in other strawberry production systems. Therefore, control measures of grey mould in this annual system should focus on protection of flowers and young developing fruits, and not on the reduction of inoculum production on leaf debris.  相似文献   

12.
An unknown disease abruptly appeared on hydroponic cultures of common ice plant (Mesembryanthemum crystallinum) in the greenhouse, causing catastrophic damage. Although the symptoms of the plant were unlike typical Botrytis lesions on leaves and stems of other plants, fungi isolated from the necrotic lesions on the plant were similar to genus Botrytis in terms of conidial shape, colony color and nature. A representative isolate, Ice-2, caused similar symptoms on the host plants after inoculation with conidia, and the same fungus was isolated from the lesions. The conidia and conidiophores of Ice-2 were morphologically similar to those of B. cinerea but not to those of B. allii, B. fabae or B. squamosa. The tested Botrytis fungi grew at temperatures between 5 and 30°C. Ice-2 grew faster than the others at the lower end of the temperature range. Ice-2 was also more virulent than B. cinerea (Bay-1) in artificial inoculations, especially on common ice plant leaves. The glyceraldehyde-3-phosphate dehydrogenase gene (G3PDH) sequence of Ice-2 was determined and compared with those from four Botrytis species. The gene sequence of Ice-2 appeared to be identical to that of B. cinerea. In leaf tests on common ice plant and kidney bean, the diseases caused by Ice-2 and Bay-1 were controlled equally well by the primary Botrytis fungicides. Based on the results of the present studies, Ice-2 is thought to be Botrytis cinerea Person: Fries.  相似文献   

13.
ABSTRACT A technique was developed to localize and quantify the internal mycelial colonization of necrotic leaf tissue of cyclamen (Cyclamen persicum) or lily (Lilium) by pathogenic Botrytis spp. and the antagonist Ulocladium atrum. This technique allows investigation of competitive substrate colonization by both fungi, which is a key process for biological control of Botrytis spp. by U. atrum. A combination of differential fluorescent labeling and image analysis was applied on cryostat sections of necrotic leaf tissue. Botrytis mycelium was labeled specifically by indirect immunofluorescence using a monoclonal antibody specific for Botrytis spp. And an antimouse fluorescein conjugate. Wheat germ agglutinin conjugated to the fluorochrome TRITC was used to label mycelium of both fungi. Image analysis was used to measure the relative surface area of the cryostat section covered by fluorescing hyphae of Botrytis spp. and by fluorescing hyphae of both fungi. A mathematical conversion was derived and used to calculate the relative mycelial volume of each fungal species in the necrotic tissue based on the measured relative surface areas. Temporal aspects of substrate colonization were studied in a short time series. An analysis of components of variance provided insight into spatial colonization patterns for the fungal species involved and allowed the design of efficient sampling strategies for future experiments.  相似文献   

14.
Köhl J  Molhoek WM 《Phytopathology》2001,91(5):485-491
ABSTRACT The saprophytic fungus Ulocladium atrum was selected for its ability to competitively exclude Botrytis spp. from aboveground necrotic plant tissues which can play a crucial role in the epidemiology of diseases caused by necrotrophic Botrytis spp. Fungal growth in necrotic aboveground tissues can be hampered by fluctuating water availability. Adaptation to these adverse conditions is a key factor for the successful establishment of an antagonist population in this niche. Conidia of U. atrum germinated at water potentials between -1 and -7 MPa on water agar. Germinated conidia survived one to three interruptions of moist incubation by periods at -10 or -42 MPa. The speed of germination was significantly slower with interruption of the moist period as compared with the control, which had continuously moist incubation. However, the maximum germination percentage was the same for conidia incubated with or without interruption of the moist incubation. In bioassays with necrotic cyclamen leaves at -1, -3, and -7 MPa, U. atrum significantly reduced the sporulation of B. cinerea by more than 80%. The results demonstrate that U. atrum tolerates water stress during competitive substrate colonization with B. cinerea. The antagonist is, therefore, an attractive candidate for field applications on aboveground tissues.  相似文献   

15.
Survival- ofBotrytis cinerea was monitored during two summer seasons. Mycelium and conidia were found dead on the surface of plant debris within 2 months of incubation, whereas a high level of viability was detected in thallus of the pathogen which was 1–2 mm inside the dry host tissue. Of the 148 samples of infected senescing cucumber female fruits, 8% survived seven warm months; half of these isolates ofB. cinerea were resistant to dicarboximides (5 (μ/ml iprodione). Of the stems of cucumber infected withB. cinerea in winter, 18% yielded the pathogen at the beginning of the following winter; 15% of the surviving isolates were resistant to dicarboximides. Cucumber seedlings artificially infected byB. cinerea did not yield the pathogen longer than 9 weeks after establishment of infection, even when incubated in the shade. Plant debris with symptoms of gray mold were kept in the shade during the summer; at the beginning of winter it was possible to establish infection ofB. cinerea from the dry debris.  相似文献   

16.
In a collection of 735 Botrytis isolates sampled from Australian wine grape-growing regions, a single isolate from clade I and group I (based on Bc-hch RFLP analysis) was found. As many Botrytis species are known to live sympatrically, it was hypothesized that this isolate might be a new Botrytis species. After phenotypic and molecular assays supported this hypothesis, the species was designated B. medusae. Phylogenetic analyses using the nuclear genes G3PDH, HSP60, RPB2, NEP1 and NEP2 consistently placed B. medusae in an early-diverging clade I Botrytis spp. lineage. Botrytis medusae produced white aerial mycelium, grew faster at 30 °C and produced long-branched conidiophore extensions, compared with B. cinerea and B. pseudocinerea. Botrytis medusae was only able to infect wounded grape leaves and was significantly less virulent on wounded leaves and berries than B. cinerea. Botrytis medusae also lacked villiform appendages on the conidial surface and long conidiophores, which are defining features of B. sinoviticola and B. californica, respectively. Identification and characterization of new cryptic Botrytis species living in sympatry on grapevines could potentially provide information to assist disease management strategies for B. cinerea.  相似文献   

17.
植物内生枯草芽孢杆菌Em7菌株对葡萄灰霉病菌的抑菌活性   总被引：2，自引：0，他引：2  
通过室内皿内对峙抑菌试验、分生孢子萌发抑制试验、离体果实接种试验以及电镜技术,研究测定了分离自小麦根部的植物内生枯草芽孢杆菌Em7菌液对葡萄灰霉病菌Botrytiscinerea Pers.的抑制作用及抑菌机理。结果表明:用Em7菌液处理葡萄灰霉病菌后,在PDA培养基上形成了明显的抑菌圈,直径达2.81 cm;菌液对分生孢子萌发的抑制率达到88.65%;经Em7菌液处理后,离体果实病情指数明显低于空白对照,相对防治效果达到78.92%。电镜观察发现,处理组菌丝生长异常,体表凹凸不平,局部膨大成结或缢缩,分枝变多,菌丝体内液泡增多,细胞壁增厚,细胞膜透性发生变化。表明植物内生枯草芽孢杆菌Em7菌株对葡萄灰霉病菌有良好的抑制作用,并且可以有效控制葡萄灰霉病的发生。  相似文献   

18.
Botrytis spot or ghost spot on tomato fruits occurs after penetration of germ tubes ofB. cinerea into epidermal cells. A few days after the penetration a halo appears around the infected necrotic cells. These symptoms can be reproduced by inoculating young fruits with a few dry conidia. When many conidia alight on the epidermis of the fruit, scab-like symptoms develop, while under conditions of high humidity, blisters can be formed on the fruit surface before the fungus spreads through the fruit parenchyma. Under conditions of low humidity, necrotic areas are formed.In the necrotic cells, developed after inoculation with many or with a few conidia, no mycelium could be found by the histological methods so far used. However,B. cinera can be reisolated, implying that theBotrytis spot is a latent infection by the fungus. No renewed growth takes place when the fruit is fully ripe.Samenvatting Botrytis-stip op tomatevruchten ontstaat na binnendringen van kiembuizen vanB. cinerea in epidermiscellen van een jonge vrucht. Enkele dagen na de infectie treden celdelingen op in het onderliggende parenchymweefsel. De geïnfecteerde cel en enkele aangrenzende cellen sterven af, terwijl rondom dit necrotische plekje een zilverwit gekleurde ring ontstaat. Worden veel conidiën bijeen op een vruchtwand gebracht, dan krijgt de epidermis binnen 24 uur een schurftig uiterlijk. Blijft de luchtvochtigheid na de inoculatie hoog, dan kunnen daarentegen kleinere en grotere blaasjes in de vruchtwand ontstaan. Deze barsten na enkele dagen open, terwojl mycelium zich door de vrucht verbreidt. Daalt de luchtvochtigheid circa 16 uur na de inoculatie, dan blijft de aantasting beperkt tot de epidermis. Hoewel in het necrotische weefsel geen mycelium vanB. cinerea kon worden aangetoond, blijkt herisolatie van de schimmel gemakkelijk te zijn. Ook uitBotrytis-stippen van uit de praktijk afkomstige vruchten kanB. cinerea geïsoleerd worden. Dit betekent, dat het hier om een latente infectie gaat, waarbij evenwel geen hernieuwde groei plaats vindt als de vrucht geheel rijp is.  相似文献   

19.
Botrytis cinerea, which causes grey mould, is a major pathogen of many crops. On strawberry, isolates of Trichoderma spp. can effectively control B. cinerea, but frequent application is necessary. Bees can be used to disseminate biological control agents to the target crop. We tested the ability of honey bees to disseminate Trichoderma harzianum T39 to control B. cinerea in strawberry in the field during the winter in Israel over two consecutive seasons. We used the recently developed ‘Triwaks’ dispenser for loading the bees with the T. harzianum inoculum. During both years, grey mould developed in late January in untreated control plots; at low to medium disease levels it was partially controlled by fungicide treatment, and was best controlled in bee-visited plots. At high disease levels neither chemical nor biological control was effective. To assess the spatial distribution of inoculum by bees, we sampled flowers up to 200 m from the hives and found effective levels of T. harzianum even at 200 m. The approach used in this study provides an effective control of grey mould in strawberry in conditions of low to medium grey mould incidence.  相似文献   

20.
Basal rot is a common disease in lettuce greenhouses. A 3-year study on the diversity of pathogens associated with basal rot in Belgium was carried out. A total of 150 isolates were collected originating from 56 greenhouses. Four pathogens appeared to be involved. Rhizoctonia solani was found to be the causal agent at 23 locations, Sclerotinia spp. at 14, Botrytis cinerea at 17 and Pythium spp. at seven. The isolates of R. solani were further characterised to anastomosis groups and subgroups using morphological characteristics, pectic zymogram and PCR-RFLP. Five anastomosis groups could be distinguished: AG1-1B, AG4 HGI, AG10, AG2-1, AG2-1 Nt and AG3, with isolates of AG4 HGI and AG1-1B being the most prevalent and the most aggressive. Sclerotinia sclerotiorum was found at 13 locations, while S. minor was found at only one location. Based on ITS-sequencing Pythium isolates were assigned to three different species. At 20°C, isolates of all pathogens were able to cause lesions on detached lettuce leaves, except isolates of R. solani AG3 and AG2-1 Nt. A correlation could be found between the occurrence of the pathogens and the growing season. Botrytis cinerea was the most common pathogen in winter, whereas R. solani was most frequently isolated in summer. Sclerotinia spp. and Pythium spp. were isolated in spring, summer and autumn. The information obtained in this study will be most useful in the development of an alternative control strategy for causal agents of basal rot.  相似文献   

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