Genotyping of benzimidazole-resistant and dicarboximide-resistant mutations in Botrytis cinerea using real-time polymerase chain reaction assays

Botrytis cinerea, an economically important gray mold pathogen, frequently exhibits multiple fungicide resistance. A fluorescence resonance energy transfer-based real-time polymerase chain reaction assay has been developed to detect benzimidazole- and dicarboximide-resistant mutations. Three benzimidazole-resistant mutations-(198)Glu to Ala (E198A), F200Y, and E198K-in beta-tubulin BenA were detected using a single set of fluorescence-labeled sensor and anchor probes by melting curve analysis. Similarly, three dicarboximide-resistant mutations-I365S, V368F plus Q369H, and Q369P-in the histidine kinase BcOS1 were successfully distinguished. Unassigned melting profiles in BenA genotyping assay resulted in the identification of a new benzimidazole-resistant BenA E198V mutation. This mutation conferred resistance to carbendazim as do E198A and E198K mutations. The isolates with BenA E198V mutation showed a negative cross-resistance to diethofencarb, but to a lesser extent than the E198A mutants. A survey of 210 B. cinerea field isolates revealed that most of benzimidazole-resistant isolates possessed the E198V or E198A mutation in the BenA gene, and the I365S mutation in the BcOS1 gene was also frequently observed in Japanese isolates. However, benzimidazole-resistant isolates with BenA F200Y or E198K mutations, which confer the diethofencarb-insensitive phenotype, were rare. Our BenA and BcOS1 genotyping is a rapid and reliable method that is suitable for monitoring the fungicide-resistant field population.     

Strains of Botrytis cinerea resistant to dicarboximide and benzimidazole fungicides in New Zealand vineyards

In a survey of New Zealand vineyards at harvest 1985, isolates of Botrytis cinerea resistant to benzimidazole and to dicarboximide fungicides were common. The mean frequency of resistance in the major vine-growing districts ranged from 8 to 41% for benzimidazoles, and from 51 to 59% for dicarboximides. All benzimidazole-resistant isolates showed high levels of resistance (EC50 greater than 100 mg/l carbendazim based on radial growth response), and all dicarboximide-resistant isolates showed low levels of resistance. Two subgroups of dicarboximide-resistant isolates were recognized, distinguished in the first instance by their osmotic response. Low-level resistant isolates, which formed a dense margin on osmotically amended medium, exhibited an EC50 for mycelial growth on iprodione of c. 3-2 mg/l; ultra-low-level resistant isolates, which formed a fibrillose margin on osmotically amended medium identical to that of sensitive isolates, exhibited an EC50 of c. 1-3 mg/1. In agar culture, radial growth rate, and conidial and sclerotial production of both subgroups were similar to those of sensitive isolates. Virulence (lesion size) and conidial production on grape berries were highest in sensitive isolates, intermediate in ultra-low-level dicarboximide-resistant isolates, and lowest in low-level dicarboximide-resistant isolates. Evidence is presented indicating that ultra-low-level dicarboximide-resistant strains have progressively replaced low-level dicarboximide-resistant strains in the vineyard population. The presence of dicarboximide-resistant strains was linked with a partial loss of fungicide efficacy.     

Distribution and fitness of isolates of Botrytis cinerea with multiple fungicide resistance in Spanish greenhouses

Forty-nine greenhouses of vegetable crops were surveyed in southeast Spain at the beginning of the disease season in December 1992 to estimate frequencies of resistance to benzimidazoles, dicarboximides and N -phenylcarbamates (NPC) in B. cinerea . Out of 261 isolates collected, 28% were sensitive to both benzimidazoles and dicarboximides, 15% were benzimidazole-resistant and dicarboximide-sensitive, 8% were benzimidazole-sensitive and dicarboximide-resistant and 46% were benzimidazole- and dicarboximide-resistant. Resistance to benzimidazole, dicarboximide and N -phenylcarbamate was determined by measuring the ability of each isolate to grow in the presence of carbendazim, procymidone and diethofencarb fungicides respectively. Carbendazim- or procymidone- resistant isolates were found in all surveyed greenhouses. Three isolates were found with resistance to carbendazim, procymidone and diethofencarb collected in two adjacent greenhouses that were sprayed with the carbendazim and diethofencarb mixture. All other isolates were sensitive to the mixture because they were either sensitive to carbendazim and resistant to diethofencarb or vice versa. Fitness of 31 isolates of B. cinerea was determined in vivo by measuring their sporulation and lesion growth rate on leaf disks. No fitness costs were associated with resistance to iprodione (dicarboximide) and benomyl (benzimidazole). Isolates with EC₅₀ values higher than 101 mg/L for benomyl and 1.6 mg/L for iprodione were considered to be field resistant (they caused visible lesions on cucumber leaf disks treated with each fungicide).     

Effect of Combined Treatment of Pasteurisation and <Emphasis Type="Italic">Coniothyrium minitans</Emphasis> on Sclerotia of <Emphasis Type="Italic">Sclerotinia sclerotiorum</Emphasis> in Soil

Integrated control of soil-borne plant pathogens such as Sclerotinia sclerotiorum is becoming more important as the soil fumigant methyl bromide is being phased out of use. Two alternative methods of control that have been found to reduce viability of sclerotia are steam sterilisation (pasteurisation) of soil or the application of the mycoparasite Coniothyrium minitans. This work investigated the possibility of integrating these two control measures. Soil was pasteurised in an autoclave, using a temperature of 80 °C for 3 min to simulate the possible temperatures reached by soil steaming machines for field use. Coniothyrium minitans was subsequently applied to the pasteurised soil to assess the effects of the combination of control measures in reducing sclerotial viability of S. sclerotiorum. Similar results were found in two soil types. Either method used individually was effective in decreasing the number of viable sclerotia, but no further reduction in sclerotial viability was seen when the two methods were combined. Coniothyrium minitans was found to colonise pasteurised sclerotia significantly quicker than untreated sclerotia, and it was seen that there was an increase in number of C. minitans in pasteurised soil in the presence of sclerotia. Experiments were also conducted to investigate the effect of application timing of the biocontrol agent to soil following pasteurisation, in relation to sclerotial infection. Here, two different isolates of S. sclerotiorum were used, with similar results. Application of C. minitans to soil immediately following pasteurisation resulted in sclerotial infection by the mycoparasite, but application 7 days or more after soil pasteurisation resulted in low recovery of the biocontrol agent from sclerotia, possibly due to the mycoparasite being masked by the presence of other fungi which colonised the sclerotia first.     

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.     

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.     

Effects of cultivation, conditioning and isolate on sclerotium germination in Sclerotium cepivorum

Sclerotium germination in various isolates of S. cepivorum was studied following different cultivation and conditioning treatments. A simple and rapid laboratory test was developed to trigger sclerotial germination under unsterile conditions. In most isolates, sclerotia produced under sterile and unsterile conditions showed a constitutive dormancy immediately after maturing. In contrast to this, the sclerotia of some isolates germinated quite well as soon as they were mature. The dormancy of sclerotia from axenic cultures broke down after storage in soil for 12 weeks. In a few cases sclerotia produced under unsterile conditions germinated remarkably well. Freezing and thawing of sclerotia decreased the ability of most isolates to germinate.     

Formation of Sclerotia and Aflatoxins in Developing Cotton Bolls Infected by the S Strain of Aspergillus flavus and Potential for Biocontrol with an Atoxigenic Strain

ABSTRACT Aspergillus flavus can be divided into the S and L strains on the basis of sclerotial morphology. On average, S strain isolates produce greater quantities of aflatoxins than do L strain isolates. Sclerotia of the S strain were observed in commercial seed cotton from western Arizona. Greenhouse tests were performed to better define sclerotial formation in developing bolls. Eight S strain isolates were inoculated into developing bolls via simulated pink bollworm exit holes. All eight isolates formed sclerotia on locule surfaces, and seven of eight isolates produced sclerotia within developing seed. Boll age at inoculation influences formation of sclerotia. More sclerotia formed within bolls that were less than 31 days old at inoculation than in bolls older than 30 days at inoculation. Frequent formation of sclerotia during boll infection may both favor S strain success within cotton fields and increase toxicity of A. flavus-infected cottonseed. Atoxigenic A. flavus L strain isolate AF36 reduced formation of both sclerotia and aflatoxin when coinoculated with S strain isolates. AF36 formed no sclerotia in developing bolls and was more effective at preventing S strain isolates than L strain isolates from contaminating developing cottonseed with aflatoxins. The use of atoxigenic L strain isolates to prevent contamination through competitive exclusion may be particularly effective where S strain isolates are common. In addition to aflatoxin reduction, competitive exclusion of S strain isolates by L strain isolates may result in reduced overwintering by S strain isolates and lower toxicity resulting from sclerotial metabolites.     

影响盾壳霉寄生核盘菌菌核的几个生态因子的分析

 在室内测定了盾壳霉(Coniothyrium minitans)对不同寄主上的核盘菌(Sclerotinia sclerotiorum)菌核的寄生致腐作用,研究了温度、含水量和土壤类型等生态因子对核盘菌菌核的寄生致腐作用的影响,通过检测土壤的呼吸速率探讨了它在土壤中定殖与核盘菌菌核的关系。结果表明:盾壳霉能寄生致腐核盘菌属所有供试菌株的菌核;寄生致腐菌核的最适温度是20℃,最适相对含水量为50%~60%;盾壳霉在供试的8种土壤中均能寄生致腐菌核,对它们的pH值要求不严格,但土壤类型影响其寄生致腐速度;在土壤中添加菌核和菌核提取液都可不同程度地刺激它的生长。     

Effect of environmental factors and Sclerotium cepivorum isolate on sclerotial degradation and biological control of white rot by Trichoderma

Laboratory assays demonstrated that two isolates of Trichoderma viride and one isolate of Trichoderma pseudokoningii degraded up to 80% of sclerotia of four isolates of Sclerotium cepivorum in a silty clay soil, and also degraded up to 60% of sclerotia in three other soil types. Relationships were defined between the degree of sclerotial degradation by the two T. viride isolates in the silty clay soil and both temperature and soil water potential. Sclerotia were degraded between 10 and 25°C at −0·00012 MPa, but there was little activity of T. viride at 5°C or at −4 MPa. Degradation of S. cepivorum sclerotia also occurred in the absence of Trichoderma at soil water potentials approaching saturation . Experiments using onion seedling bioassays showed that the efficacy of Trichoderma isolates for the control of white rot using the same selection of soils and S. cepivorum isolates was variable, but that there was significant disease control overall. The importance of environmental factors and pathogen isolate in relation to effective biological control of white rot 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.     

Pectolytic and Cellulolytic Enzymes of Dicarboximide-sensitive and Resistant Strains of Botrytis cinerea1

Starting in 1979 the pathogenicity of dicarboximide-resistant and sensitive strains of Botrytis cinerea was regularly examined in greenhouse tests using grape plants. In these tests the proportion of resistant strains with low or nearly no pathogenicity was always higher than that of sensitive strains. This led to comparative studies on the enzyme activities of sensitive and resistant field isolates. Pectolytic and cellulolytic enzymes were chosen because of their importance in the infection process of B. cinerea. The results of these studies indicated that no correlation could be found between the activity of these enzymes and the pathogenicity of the tested isolates, and that resistant strains tended to have higher enzyme activities than sensitive ones. Comparison of the enzyme activities of laboratory-adapted isolates and the original sensitive ones gave similar results. Since enzyme activities do not seem to play an important role in explaining the general observations on the slow increase and spread of resistant strains in vineyards, other factors must be considered, such as the stability of the dicarboximide resistance, which apparently is very low.     

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.     

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.     

Comparative survival of Sclerotia of Sclerotinia minor and S. sclerotiorum

Survival of sclerotia of Sclerotinia minor and S. sclerotiorum was compared in irrigated fields during the summer in two major lettuce production areas in California. More than 50% sclerotia of S. sclerotiorum compared with 4 and 35% of S. minor remained viable after 24 weeks of burial at 15 and 5 cm depths, respectively, in the San Joaquin Valley while >80% of sclerotia survived in the Salinas Valley for both species. The results explain in part the lower infections from S. minor in the San Joaquin Valley. To identify factors that contribute to the rapid decline in the viability of sclerotia, the effects of soil moisture, temperature, and oxygen levels were studied in laboratory. More than 90% of sclerotia of both species survived for at least 3 months in sterilized dry soils at temperatures between 15 and 40 degrees C. Soil moisture did not affect survival at 15 and 25 degrees C. At 35 degrees C, however, survival rates were significantly lower at high (-0.3 to -0.01 MPa) water potential than at low (<-1.0 MPa) water potential. Incubation under ultralow oxygen concentration (0.01%) significantly reduced survival of sclerotia in nonautoclaved moist soils at 25 degrees C, with less than 2% sclerotia surviving over 4 weeks compared with about 45% sclerotia surviving at the ambient oxygen level (21%). The combination of high temperature, high soil moisture, and reduced oxygen in irrigated fields contribute to the lower survival of both Sclerotinia species and the responses of the two species to these conditions shape their relative geographical distribution.     

浙江省果蔬灰霉病菌对嘧菌酯的抗药性研究

采用菌丝生长速率法,连续监测了2010—2012年间浙江省果蔬灰霉病菌对QoI类杀菌剂嘧菌酯的敏感性变化。 结果表明:病菌群体中的低敏感性亚群体的比例明显上升,EC50值>5 mg/L 菌株的比例分别为12.5%、15.8%和28.3%;在菌丝生长阶段和孢子萌发阶段,旁路氧化在灰霉病菌对嘧菌酯敏感性中的平均相对贡献值(F)分别为2.91±0.89和5.72±2.82;嘧菌酯抗药性菌株的菌丝生长速率、产孢量、产菌核数和致病力与敏感菌株相比无显著差异。抗药性分子机制研究表明,灰霉病菌中存在2种类型的cyt b基因:Ⅰ型cyt b基因在第143位密码子后紧跟内含子;Ⅱ型cyt b基因在第143位密码子后没有紧跟内含子。大多数的灰霉病菌菌株属于Ⅱ型。Ⅰ型菌株均为嘧菌酯敏感菌株,Ⅱ型菌株为嘧菌酯敏感菌株或抗性菌株。抗性菌株的cyt b 基因的第143位密码子由甘氨酸(GGC)突变为了丙氨酸(GCC),抗药性机制为G143A。     

Inoculum potential of Sclerotinia sclerotiorum sclerotia depends on isolate and host plant

The soilborne fungus Sclerotinia sclerotiorum infects many important crop plants. Central to the success of this pathogen is the production of sclerotia, which enables survival in soil and constitutes the primary inoculum. This study aimed to determine how crop plant type and S. sclerotiorum isolate impact sclerotial production and germination and hence inoculum potential. Three S. sclerotiorum isolates (L6, L17, L44) were used to inoculate plants of bean, carrot, lettuce, oilseed rape (OSR) and potato, and the number and weight of sclerotia per plant quantified. Carpogenic germination of sclerotia collected from different hosts was also assessed for L6. Production of sclerotia was dependent on both crop plant type and S. sclerotiorum isolate, with OSR and lettuce supporting the greatest number (42–122) and weight (1.6–3.0 g) of sclerotia per plant. The largest sclerotia were produced on OSR (33–66 mg). The three S. sclerotiorum isolates exhibited a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced smaller numbers of large sclerotia, with L17 intermediate between the two. Germination rate and percentage was greatest for larger sclerotia (4.0–6.7 mm) and also varied between host plants. Combining sclerotial production data and typical field crop densities suggested that infected carrot and OSR could produce the greatest number (3944 m^?2) and weight (73 g m^?2) of S. sclerotiorum sclerotia, respectively, suggesting these crops potentially contribute a greater increase in inoculum. This information, once further validated in field trials, could be used to inform future crop rotation decisions.     

Reduced sclerotial viability of Stromatinia cepivora and control of white rot disease of onion and garlic by means of soil bio-solarization

The suppressive effects of soil bio-solarization, which is a new method of soil disinfestation that combines soil bio-fumigation with soil solarization, against the sclerotial viability of Stromatinia cepivora and the subsequent control of white rot disease of onion and garlic were evaluated. Soil was bio-fumigated with fresh amendments of cow manure, chicken manure, horse manure, cruciferous plant residues, or Allium waste, at 30,000 kg/ha. After bio-fumigation, the soil was irrigated and covered with a 200 μm transparent plastic sheet for 60 days. Plots that received fresh amendment and remained uncovered and untreated served as controls. Solarization alone increased the maximum soil temperature to 55.3 °C, 50.3 °C and 46.3 °C at 10, 20, and 30 cm depths, respectively, which led to significant reductions (98.0%, 89.3%, and 62.7%, respectively) in the sclerotial viability of S. cepivora. Soil bio-solarization with cruciferous plant residues or Allium waste resulted in the strongest negative effects on the sclerotial viability of S. cepivora, with reductions of 100.0%, 98.7%, and 87.3% or 100.0%, 99.3%, and 87.7%, at 10, 20, and 30 cm depths, respectively. Compared to the non-treated control, these treatments significantly reduced the incidence of white rot disease in onion and garlic, which led to increases in onion and garlic yield in fields that were heavily infested by S. cepivora.

     

啶菌噁唑对番茄灰霉病菌的抑菌作用研究

采用生物测定方法研究了啶菌噁唑对番茄灰霉病菌Botrytis cinerea不同发育阶段的影响。结果表明:其对菌落扩展、芽管伸长、分生孢子产生和菌核形成均具有显著的抑制活性,其中啶菌噁唑对P-9菌株菌丝生长和芽管伸长的EC50值分别为0.193和0.154 μ g/mL,0.5 μ g/mL的啶菌噁唑对菌丝生长和芽管伸长的抑制率大于77%,对分生孢子和菌核萌发的抑制率分别低于10％和40%,表明药剂对分生孢子萌发无明显抑制作用。紫外吸收分析显示,啶菌 NFDA1 唑可破坏细胞的膜结构,促使菌体核酸和蛋白外渗。离体叶片毒力测定结果表明,120 μ g/mL的啶菌 NFDA1 唑可有效抑制番茄灰霉病病斑扩展,抑制率达83.74%。     

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.