盾壳霉对核盘菌的拮抗作用研究

系统研究了菌核重寄生菌盾壳霉对核盘菌的拮抗作用,结果表明:盾壳霉可在核盘菌菌落上寄生,使核盘菌菌丝消解、原生质泄露,并抑制菌核的形成;而且盾壳霉提前6d接种,其分泌的抗生物质还可抑制核盘菌菌丝生长,并产生明显抑菌带。盾壳霉孢子液喷雾处理也证明:盾壳霉分生孢子即可在核盘菌子囊盘(柄)上萌发、寄生,使子囊盘(柄)萎缩枯死,而且还可以在核盘菌菌落上萌发、寄生,消解破坏菌丝体、抑制的菌核形成。     

Glasshouse trials of Coniothyrium minitans and Trichoderma species for the biological control of Sclerotinia sclerotiorum in celery and lettuce

Coniothyrium minitans, Trichoderma harzianum (HH3) and Trichoderma sp. (B1) were tested for ability to control disease caused by Sclerotinia sclerotiorum in a sequence of a celery crop and two lettuce crops in the glasshouse. In control plots, over 80% of celery and 90 and 60% of lettuce in first and second crops, respectively, were infected at harvest. Only the C. minitaris treatment in the first lettuce crop decreased disease and increased marketable yield. Nevertheless, C. minitans reduced the number of sclerotia recovered at harvest in the celery and first lettuce crops and decreased sclerotial survival over the autumn fallow periods following the celery and second lettuce crop. C. minitans survived in soil for over 1 year and spread to infect sclerotia in virtually all other plots. C. minitans infected sclerotia at all times of the year but sclerotia still failed to degrade during the summer months when the soil was dry. The Trichoderma species tested had no effect on disease and almost no effect on the survival of the sclerotia. even though they could be recovered from soil for the duration of the experiments.     

Effect of inoculum type and timing of application of Coniothyrium minitans on Sclerotinia sclerotiorum: control of sclerotinia disease in glasshouse lettuce

The effects of Coniothyrium minitans inoculum quality and an 8-week interval between inoculum application and crop planting on sclerotinia ( Sclerotinia sclerotiorum ) disease in three successive lettuce crops were investigated in a glasshouse trial. Spore suspensions of three isolates of C. minitans (Conio, IVT1 and Contans) applied at 10⁸ CFU m⁻² and a standard Conio maizemeal–perlite application (06 L m⁻², 10¹¹ CFU m⁻²) were assessed for their ability to control S. sclerotiorum . Only the maizemeal–perlite inoculum (isolate Conio) consistently reduced sclerotinia disease. In the third lettuce crop only, isolates IVT1 and Contans formulated by Prophyta and isolate IVT as an oil–water formulation, all applied as spore suspensions, reduced disease at harvest compared with the untreated control. Recovery, viability and C. minitans infection of sclerotia buried during the 8-week period prior to each of the three lettuce crops, and of sclerotia formed on the crop, were tested. Only the maizemeal–perlite inoculum (isolate Conio) reduced the recovery of sclerotia buried in soil for weeks between inoculum application and crop planting, reducing their viability and increasing infection by C. minitans . Eight weeks was sufficient to enable C. minitans to infect sclerotia of S. sclerotiorum , and may account for disease control. After harvest of the second and third crops, maizemeal–perlite treatment (isolate Conio) reduced the number and viability of sclerotia recovered on the soil surface and increased infection by C. minitans compared with spore-suspension treatments. The effect of inoculum concentration and the influence of soil temperature (varying with time of year) on infection of sclerotia by C. minitans are discussed.     

Antagonistic activity of fungi isolated from sclerotia of Sclerotinia sclerotiorum

Fungi isolated from soils in central Italy by a baiting technique with sclerotia of Sclerotinia sclerotiorum were evaluated for their antagonism in vitro to this fungus using dual cultures and tests with sclerotia. Trichoderma spp., Coniothyrium minitans and species of Fusarium and Penicillium all showed strong antagonistic activity. Morphological alterations were observed in the mycelium of S. sclerotiorum. Trichoderma spp. and Gliocladium catenulatum killed a very high percentage (96–100%) of the sclerotia.     

Interactions between Coniothyrium minitans and Sclerotinia minor affect biocontrol efficacy of C. minitans

Coniothyrium minitans, marketed as Contans, has become a standard management tool against Sclerotinia sclerotiorum in a variety of crops, including winter lettuce. However, it has been ineffective against lettuce drop caused by S. minor. The interactions between C. minitans and S minor were investigated to determine the most susceptible stage in culture to attack by C. minitans, and to determine its consistency on S minor isolates belonging to four major mycelial compatibility groups (MCGs). Four isolates of S. minor MCG 1 and 5 each from MCGs 2 and 3 and one from MCG 4 were treated in culture at purely mycelial, a few immature sclerotial, and fully mature sclerotial phases with a conidial suspension of C. minitans. Sclerotia from all treatments were harvested after 4 weeks, air dried, weighed, and plated on potato dextrose agar for recovery of C. minitans. S. minor formed the fewest sclerotia in plates that received C. minitans at the mycelial stage; C. minitans was recovered from nearly all sclerotia from this treatment and sclerotial mortality was total. However, the response of MCGs was inconsistent and variable. Field experiments to determine the efficacy of C. minitans relative to the registered fungicide, Endura, on lettuce drop incidence and soil inoculum dynamics were conducted from 2006 to 2009. All Contans treatments had significantly lower numbers of sclerotia than Endura and unsprayed control treatments, and drop incidence was as low as in Endura-treated plots (P > 0.05). Although the lower levels of lettuce drop in Contans treatments were correlated with significantly lower levels of sclerotia, the lower levels of lettuce drop, despite the presence of higher inoculum in the Endura treatment, was attributable to the prevention of infection by S. minor. A useful approach to sustained lettuce drop management is to employ Contans to lower the number of sclerotia in soil and to apply Endura to prevent S. minor infection within a cropping season.     

Effect of inoculum type and timing of application of Coniothyrium minitans on Sclerotinia sclerotiorum: influence on apothecial production

The effects of different inocula of the mycoparasite Coniothyrium minitans on carpogenic germination of sclerotia of Sclerotinia sclerotiorum at different times of year were assessed. A series of three glasshouse box bioassays was used to compare the effect of five spore-suspension inocula of C. minitans , including three different isolates (Conio, IVT1 and Contans), with a standard maizemeal–perlite inoculum. Apothecial production, as well as viability and C. minitans infection of S. sclerotiorum sclerotia buried in treated soil, were assessed. Maizemeal–perlite inoculum at 10⁷ CFU per cm³ soil reduced sclerotial germination and apothecial production in all three box bioassays, decreasing sclerotial recovery and viability in the second bioassay and increasing C. minitans infection of sclerotia in the first bioassay. Spore-suspension inocula applied at a lower concentration (10⁴ CFU per cm³ soil) were inconsistent in their effects on sclerotial germination in the three box bioassays. Temperature was an important factor influencing apothecial production. Sclerotial germination was delayed or inhibited when bioassays were made in the summer. High temperatures also inhibited infection of sclerotia by C. minitans . Coniothyrium minitans survived these high temperatures, however, and infected the sclerotia once the temperature decreased to a lower level. Inoculum level of C. minitans was an important factor in reducing apothecial production by sclerotia. The effects of temperature on both carpogenic germination of sclerotia and parasitism of sclerotia by C. minitans are discussed.     

Potential for Integrated Control of Sclerotinia sclerotiorum in Glasshouse Lettuce Using Coniothyrium minitans and Reduced Fungicide Application

ABSTRACT All pesticides used in United Kingdom glasshouse lettuce production (six fungicides, four insecticides, and one herbicide) were evaluated for their effects on Coniothyrium minitans mycelial growth and spore germination in vitro agar plate tests. Only the fungicides had a significant effect with all three strains of C. minitans tested, being highly sensitive to iprodione (50% effective concentration [EC(50)] 7 to 18 mug a.i. ml(-1)), moderately sensitive to thiram (EC(50) 52 to 106 mug a.i. ml(-1)), but less sensitive to the remaining fungicides (EC(50) over 200 mug a.i. ml(-1)). Subsequently, all pesticides were assessed for their effect on the ability of C. minitans applied as a solid substrate inoculum to infect sclerotia of Sclerotinia sclerotiorum in soil tray tests. Despite weekly applications of pesticides at twice their recommended concentrations, C. minitans survived in the soil and infected sclerotia equally in all pesticide-treated and untreated control soil trays. This demonstrated the importance of assessing pesticide compatibility in environmentally relevant tests. Based on these results, solid substrate inoculum of a standard and an iprodione-tolerant strain of C. minitans were applied individually to S. sclerotiorum-infested soil in a glasshouse before planting lettuce crops. The effect of a single spray application of iprodione on disease control in the C. minitans treatments was assessed. Disease caused by S. sclerotiorum was significantly reduced by C. minitans and was enhanced by a single application of iprodione, regardless of whether the biocontrol agent was iprodione-tolerant. In a second experiment, disease control achieved by a combination of C. minitans and a single application of iprodione was shown to be equivalent to that of prophylactic sprays with iprodione every 2 weeks. The fungicide did not affect the ability of C. minitans to spread into plots where only the fungicide was applied and to infect sclerotia. These results indicate that integrated control of S. sclerotiorum with soil applications of C. minitans and reduced foliar iprodione applications was feasible, did not require a fungicide tolerant isolate, and that suppression of Sclerotinia disease by C. minitans under existing chemical control regimes has credence.     

Effect of Coniothyrium minitans on sclerotial survival and apothecial production of Sclerotinia sclerotiorum in field-grown oilseed rape

In two field trials with oilseed rape, Coniothyrium minitans was applied to soil as a maizemeal-perlite preparation in order to determine its effect on sclerotial survival and apothecial production of Sclerotinia selerotiorum. The mycoparasite infected sclerotia and decreased sclerotial survival, carpogenic germination and production of apothecia. Effects were greatest when inoculum of C. minitans was applied in autumn, at the time of sowing, rather than when it was applied in spring. C. minitans survived in soil for 2 years and spread to adjacent control plots and infected sclerotia within those plots. However, despite the fact that the inoculum potential of S. selerotiorum was reduced by C. minitans treatment, no disease control was obtained either in trial 1, where disease levels were low (0-20% of plant stems affected), or in trial 2, where disease levels were high (up to 70% of plant stems affected). Possible reasons for this failure of C minitans to control sclerotinia disease in oilseed rape, and strategies to improve its efficacy in the field, are discussed.     

Impact of consumer-driven changes to crop production practices on lettuce drop caused by Sclerotinia sclerotiorum and S. minor

Increasing demands for value-added salad products have triggered revolutionary changes in the production practices of vegetable salad crops in recent years. One of the pivotal changes is the adaptation of 2-m-wide beds for increased vegetable biomass per unit area. The move away from the traditional 1-m-wide raised beds in cool-season vegetable production and the associated irrigation practices potentially can have a major influence on diseases affecting cool-season vegetables. To assess the potential impacts of this shift on lettuce drop caused by Sclerotinia minor and S. sclerotiorum, the two bed widths and different irrigation frequencies within each were compared in two separate field experiments over four lettuce crops in 2 years. Treatments included 1- and 2-m bed widths with twice-weekly, weekly and biweekly drip irrigation serving as subplot treatments that were begun immediately following thinning. Incidence of lettuce drop was evaluated weekly thereafter until maturity. For S. sclerotiorum, 36 half-liter soil samples were also collected once each season and assayed for the number of sclerotia, and apothecia were counted weekly in a 10-m(2) area for each plot. Regardless of the species, the effects of bed width and irrigation frequency were both significant. Twice-weekly irrigation and 2-m bed width resulted in higher lettuce drop incidence than other treatments. For S. sclerotiorum, twice-weekly irrigation and 2-m bed width also significantly increased the number of apothecia per unit area and the accumulation of soilborne sclerotia over multiple cropping seasons. Results demonstrated that the 2-m bed width combined with the practiced frequency of irrigations can result in higher lettuce drop caused by S. minor and increased incidence of airborne infection by S. sclerotiorum in the Salinas Valley where, historically, it has not been a serious threat. Increased incidence of S. sclerotiorum infection in commercial lettuce fields in the Salinas Valley between 2001 and 2006 validates these experimental results. These relatively new crop production practices can alter the balance of the two Sclerotinia spp. that has long existed in California.     

Germination of Sclerotinia minor and S. sclerotiorum Sclerotia Under Various Soil Moisture and Temperature Combinations

ABSTRACT Sclerotial germination of three isolates each of Sclerotinia minor and S. sclerotiorum was compared under various soil moisture and temperature combinations in soils from Huron and Salinas, CA. Sclerotia from each isolate in soil disks equilibrated at 0, -0.03, -0.07, -0.1, -0.15, and -0.3 MPa were transferred into petri plates and incubated at 5, 10, 15, 20, 25, and 30 degrees C. Types and levels of germination in the two species were recorded. Petri plates in which apothecia were observed were transferred into a growth chamber at 15 degrees C with a 12-h light-dark regime. All retrievable sclerotia were recovered 3 months later and tested for viability. Soil type did not affect either the type or level of germination of sclerotia. Mycelial germination was the predominant mode in sclerotia of S. minor, and it occurred between -0.03 and -0.3 MPa and 5 and 25 degrees C, with an optimum at -0.1 MPa and 15 degrees C. No germination occurred at 30 degrees C or 0 MPa. Soil temperature, moisture, or soil type did not affect the viability of sclerotia of either species. Carpogenic germination of S. sclerotiorum sclerotia, measured as the number of sclerotia producing stipes and apothecia, was the predominant mode that was affected significantly by soil moisture and temperature. Myceliogenic germination in this species under the experimental conditions was infrequent. The optimum conditions for carpogenic germination were 15 degrees C and -0.03 or -0.07 MPa. To study the effect of sclerotial size on carpogenic germination in both S. minor and S. sclerotiorum, sclerotia of three distinct size classes for each species were placed in soil disks equilibrated at -0.03 MPa and incubated at 15 degrees C. After 6 weeks, number of stipes and apothecia produced by sclerotia were counted. Solitary S. minor sclerotia did not form apothecia, but aggregates of attached sclerotia readily formed apothecia. The number of stipes produced by both S. minor and S. sclerotiorum was highly correlated with sclerotial size. These results suggest there is a threshold of sclerotial size below which apothecia are not produced, and explains, in part, why production of apothecia in S. minor seldom occurs in nature.     

Control of lettuce drop disease, caused by Sclerotinia sclerotiorum, with metham-sodium soil treatment and foliar application of benomyl

The effects of metham-sodium (MES) soil treatment, a varying number of benomyl foliar sprays (two, three and six) and combined treatments on control of lettuce drop disease were studied at two sites in Israel naturally infested with the pathogen Sclerotinia sclerotiorum. MES killed 85% of the S. sclerotiorum sclerotia in the top 10 cm of soil where initial populations were 0.6 and 1.6 viable sclerotia per kg soil at the two sites. Of the remaining viable sclerotia. only 30% produced apothecia. MES treatment alone reduced numbers of apothecia to 5% of those counted in the unsprayed control treatment. Numbers of ascospores deposited on the crop in the MES-treated plots were 7-20% of those deposited on control plots. Lettuce drop decreased the total yield by 30% in unsprayed control plots; MES application reduced the loss to 4% and also increased the number of marketable plants. Benomyl sprays alone also significantly reduced numbers of apothecia and disease development and consequently increased yield, although not to the extent observed with the MES treatment alone. Combined treatments produced the best disease control, but this improvement was not accompanied by any major increase in yield compared to that with MES treatment alone.     

Effects of soil temperature, moisture, and burial depths on carpogenic germination of Sclerotinia sclerotiorum and S. minor

Extensive studies have been conducted on the carpogenic germination of Sclerotinia sclerotiorum, but carpogenic germination in S. minor has not been studied adequately. It remains unclear why apothecia of this pathogen have seldom been observed in nature. In this study, a new method was developed to produce apothecia in the absence of soil or sand, and carpogenic germination without preconditioning was recorded for 95 of the 96 S. sclerotiorum isolates tested. Carpogenic germination of the two species was compared under a variety of temperature, soil moisture, burial depths, and short periods of high temperature and low soil moisture. The optimal temperatures for rapid germination and for maximum germination rates were both lower for S. minor than for S. sclerotiorum. The temperature range for carpogenic germination was also narrower for S. minor than for S. sclerotiorum. A 5-day period at 30 degrees C, either starting on the 10th or 20th day of incubation, did not significantly affect carpogenic germination of S. sclerotiorum. For both S. minor and S. sclerotiorum, the percentage of carpogenically germinated sclerotia increased as soil water potential increased from -0.3 to -0.01 MPa. In the greenhouse, a 10- or 20-day dry period completely arrested carpogenic germination of S. sclerotiorum, and new apothecia appeared after an interval of 35 days following rewetting, similar to the initial carpogenic germination regardless of when the dry period was imposed. In naturally infested fields, the number of sclerotia in 100 cc of soil decreased as depth increased from 0 to 10 cm before tillage, but became uniform between 0 and 10 cm after conventional tillage for both species. Most apothecia of S. minor were, however, produced from sclerotia located at a depth shallower than 0.5 cm while some apothecia of S. sclerotiorum were produced from sclerotia located as deep as 4 to 5 cm. These results provide the much needed information to assess the epidemiological roles of inoculum from sexual reproduction in diseases caused by the two Sclerotinia species in different geographical regions. However, more studies on effects of shorter and incompletely dry periods are still needed to predict production of apothecia of S. sclerotiorum in commercial fields under fluctuating soil temperature and moisture.     

A method for inducing apothecia from sclerotia of Sclerotinia sclerotiorum

An isolate of Sclerotinia sclerotiorum from oilseed rape was grown on sterilized wheat grain for 3 weeks at 20 C, followed by 4 weeks at 4^oC. Harvested sclerotia were buried 1 cm deep in compost in plastic containers and kept at 10^oC until apothecial stipes appeared (c. 6 weeks). When these dishes were placed under near-UV light (14 h/day) at 22^oC, apothecia matured in 5 days. The method also induced apothecia from sclerotia of 35 other isolates of S. sclerotiorum obtained from 17 different hosts.     

Forecasting sclerotinia disease on lettuce: toward developing a prediction model for carpogenic germination of sclerotia

ABSTRACT The feasibility of developing a forecasting system for carpogenic germination of Sclerotinia sclerotiorum sclerotia was investigated in the laboratory by determining key relationships among temperature, soil water potential, and carpogenic germination for sclerotia of two S. sclerotiorum isolates. Germination of multiple burials of sclerotia to produce apothecia also was assessed in the field with concurrent recording of environmental data to examine patterns of germination under different fluctuating conditions. Carpogenic germination of sclerotia occurred between 5 and 25 degrees C but only for soil water potentials of >/=-100 kPa for both S. sclerotiorum isolates. Little or no germination occurred at 26 or 29 degrees C. At optimum temperatures of 15 to 20 degrees C, sclerotia buried in soil and placed in illuminated growth cabinets produced stipes after 20 to 27 days and apothecia after 27 to 34 days. Temperature, therefore, had a significant effect on both the rate of germination of sclerotia and the final number germinated. Rate of germination was correlated positively with temperature and final number of sclerotia germinated was related to temperature according to a probit model. Thermal time analysis of field data with constraints for temperature and water potential showed that the mean degree days to 10% germination of sclerotia in 2000 and 2001 was 285 and 279, respecttively, and generally was a good predictor of the observed appearance of apothecia. Neither thermal time nor relationships established in the laboratory could account for a decline in final percentage of germination for sclerotia buried from mid-May compared with earlier burials. Exposure to high temperatures may explain this effect. This, and other factors, require investigation before relationships derived in the laboratory or thermal time can be incorporated into a forecasting system for carpogenic germination.     

Forecasting Sclerotinia Disease on Lettuce: A Predictive Model for Carpogenic Germination of Sclerotinia sclerotiorum Sclerotia

ABSTRACT A predictive model for production of apothecia by carpogenic germination of sclerotia is presented for Sclerotinia sclerotiorum. The model is based on the assumption that a conditioning phase must be completed before a subsequent germination phase can occur. Experiments involving transfer of sclerotia from one temperature regime to another allowed temperature-dependent rates to be derived for conditioning and germination for two S. sclerotiorum isolates. Although the response of each isolate to temperature was slightly different, sclerotia were fully conditioned after 2 to 6 days at 5 degrees C in soil but took up to 80 days at 15 degrees C. Subsequent germination took more than 200 days at 5 degrees C and 33 to 52 days at 20 degrees C. Upper temperature thresholds for conditioning and germination were 20 and 25 degrees C, respectively. A predictive model for production of apothecia derived from these data was successful in simulating the germination of multiple burials of sclerotia in the field when a soil water potential threshold of between -4.0 and -12.25 kilopascals (kPa) was imposed. The use of a germination model as part of a disease forecasting system for Sclerotinia disease in lettuce is discussed.     

Quantitative Aspects of Infection of Sclerotinia sclerotiorum Sclerotia by Coniothyrium minitans – Timing of Application, Concentration and Quality of Conidial Suspension of the Mycoparasite

White mould disease leads to production of sclerotia, which subsequently survive in soil and may be responsible for future epidemics. The effect of the mycoparasite Coniothyrium minitans in decreasing survival of sclerotia of Sclerotinia sclerotiorum was studied. Infection of sclerotia of S. sclerotiorum by C. minitans can be achieved by a single conidium. Under optimal conditions, 2 conidia per sclerotium produced 63% of the maximum infection (ca. 90%) of sclerotia produced by up to 1000 conidia. Similar results were observed on the infection of stem pieces infected by S. sclerotiorum. In field trials, application of conidial suspensions of C. minitans to a bean crop soon after white mould outbreak led to a higher percentage of sclerotial infection than later applications. Ninety per cent infection of sclerotia was obtained within 3 weeks of application by C. minitans suspensions in the range of 5 × 10⁵ and 5 × 10⁶ conidia ml^–1 at 1000 l ha^–1. The concentration of the conidial suspensions and the isolate used were of less importance. The result was marginally affected by the germinability of the conidia (75% against 61% infected sclerotia at 91% and 16% viability of isolate IVT1, respectively). Less apothecia of S. sclerotiorum developed in soil samples collected after 2 months from plots sprayed immediately after disease outbreak than from those treated 11–18 days later. It is concluded that a suspension of 10⁶ conidia ml^–1 in 1000 l ha^–1 (= 10¹² conidia ha^–1) sprayed immediately after the first symptoms of disease are observed, results in > 90% infection of sclerotia of S. sclerotiorum. The infection of sclerotia, which prevents their carry-over, occurs within a broad range of inoculum quality.     

除草剂精禾草克和乙草胺对油菜菌核病生防菌盾壳霉生长和寄生的影响

本文研究了油菜田间常用除草剂精禾草克和乙草胺对油菜菌核病生防菌盾壳霉Conio-thyrium minitans的影响。结果表明它们对盾壳霉菌丝生长和分生孢子萌发均有显著的抑制作用,其中精禾草克对盾壳霉菌丝生长和孢子萌发的抑制中浓度分别为2.95mg/L和7.80mg/L;乙草胺对菌丝生长和孢子萌发的抑制中浓度分别为137.45mg/L和120.90mg/L。精禾草克可以抑制盾壳霉寄生核盘菌Sclerotinia sclerotiorum菌核,当精禾草克的使用量达田间使用浓度时,盾壳霉不能寄生核盘菌菌核;而乙草胺对盾壳霉寄生菌核的影响较小,在田间使用浓度1250mg/L时,盾壳霉仍可寄生菌核;乙草胺和盾壳霉在田间使用浓度条件下混合使用,60d后菌核腐烂指数与单独使用盾壳霉没有显著差异,均大于75。上述结果表明在田间使用量条件下,乙草胺可以和盾壳霉生防制剂混用,而精禾草克不宜和盾壳霉混用。     

Interactions Between the Mycoparasite Pythium oligandrum and Sclerotia of the Plant Pathogen Sclerotinia sclerotiorum

Pythium oligandrum Drechsler is a mycoparasite which parasitizes hyphae of many fungal species. A detailed study of the interactions between P. oligandrum and the sclerotia of the plant pathogen Sclerotinia sclerotiorum (Lib.) de Bary is presented. Pythium oligandrum was present in Danish soils at concentrations between 4 and 26 cfu g^–1 soil. An increase in the natural population of P. oligandrum by addition of P. oligandrum zoospores to a soil reduced the ability of sclerotia of S. sclerotiorum to germinate myceliogenically and the sclerotia were colonized internally by P. oligandrum. This colonization and reduction of germination of sclerotia were also seen when sclerotia and P. oligandrum were incubated together in water. Small sclerotia were significantly more susceptible to parasitism by P. oligandrum than large sclerotia, and increasing the incubation time caused a further reduction in the germination ability of the sclerotia. P. oligandrum was able to pass through its entire life-cycle from zoospores to oogonia both with sclerotia as sole nutrient-source and in water containing exudates from the sclerotia. The cell wall degrading enzymes N-acetyl--D-glucosaminidase (NAGase), endo-chitinase, protease, -glucanase, -glucosidase and cellobiohydrolase were detected in culture filtrates of P. oligandrum cultivated with S. sclerotiorum. These findings suggest that P. oligandrum has a potential to reduce the survival of S. sclerotiorum sclerotia present naturally in soils, through mycoparasitic activity.     

Factors affecting the production of apothecia and longevity of sclerotia of Sclerotinia sclerotiorum

Sclerotia of Sclerotinia sclerotiorum produced naturally on winter oilseed rape and by an isolate from this host on sterile wheat grain were placed in two different soil types in pots, either on the soil surface or 1. 2, 3, 4 or 6 cm deep. Nitrogen (as TN 34, Thames Nitrogen Co.) was applied to one set of pots in autumn 1982 and spring 1983. Production of apothecia was recorded in this set in 1983 only. In pots without added N apothecia were counted in 1983 and 1984 and sclerotia were recovered from these pots at the end of the experiment.
Overall, production of apothecia was not affected by soil type. More apothecia formed from cultured sclerotia and they appeared earlier than from natural sclerotia. More apothecia were produced from sclerotia placed at 0–2 cm than from those buried deeper. Fewer apothecia were produced in pots with added N and their production was delayed. Fewer sclerotia were recovered from the upper layers of soil with a higher clay content, and when sclerotia were obtained from oilseed rape rather than from cultures.     

盾壳霉控制油菜菌核病菌再侵染及其叶面存活动态的研究

 本文评估了施于油菜(Brassica napus)叶片上的盾壳霉(Coniothyrium minitans)控制油菜菌核病菌再侵染能力,探讨了其作用机理,并测定了盾壳霉分生孢子在油菜叶面上的存活动态。结果如下:叶面上的盾壳霉对油菜菌核病菌的初侵染影响较小,但在高剂量(> 10⁶孢子/ml)时可以控制病斑的扩展。所有供试剂量的盾壳霉均可不同程度地控制再侵染。盾壳霉分生孢子可在叶面病部迅速萌发,48 h和72 h时孢子萌发率分别为51%和95%,而在健康叶面上6 d未能检测到萌发的孢子。自携带盾壳霉的叶面病部不能分离到核盘菌,表明叶面上的盾壳霉已寄生并破坏了核盘菌再侵染菌丝。自油菜叶面上分离到的盾壳霉菌落数随时间延长而降低,但其分生孢子至少可以在叶面上存活28 d。这即表明,在叶面上适时适量地添加盾壳霉可以控制油菜菌核病的为害。