四种杀菌剂对莴苣霜霉病的田间防效

使用4种杀菌剂不同剂量处理防治莴苣霜霉病田间药效试验,结果显示:4种杀菌剂对莴苣霜霉病均有一定的防治效果,且每种杀菌剂的防效随用药量增大而提高。试验药剂1%申嗪霉素SC 18 g/ha、80%代森锰锌WP 3 000 g/ha防效与对照药剂80%烯酰吗啉WP 300 g/ha防效相当;试验药剂30%吡唑醚菌酯EW 99 g/ha的防效略低于对照药剂80%烯酰吗啉WP的防效,但无显著差异;试验药剂20%霜脲氰SC 3个处理的防效均极显著低于对照药剂80%烯酰吗啉WP的防效。根据试验结果,试验药剂20%霜脲氰SC在试验中防效偏低,不作为田间防治莴苣霜霉病的推荐药剂,另外3种试验药剂1%申嗪霉素SC、80%代森锰锌WP、30%吡唑醚菌酯EW在试验过程中表现出较好的防治效果,可作为田间防治莴苣霜霉病的药剂轮换使用。推荐使用有效成分用量为1%申嗪霉素SC 15～18 g/ha、80%代森锰锌WP 2 400～3 000 g/ha、30%吡唑醚菌酯EW 99 g/ha。在发病前或发病初期开始喷雾,7～10 d后进行下一次施药,连续防治2～3次。用药液量750 L/ha,均匀喷雾于莴苣叶片正反面。     

Silicon and increased electrical conductivity reduce downy mildew of soilless grown lettuce

Downy mildew of lettuce, caused by Bremia lactucae, is difficult to control in soilless systems by using conventional methods of disease management because few chemicals are registered, while resistant cultivars face the problem of resistance break down; therefore other methods for disease control need to be investigated. The effect of silicon salt as well as increased electrical conductivities against downy mildew was evaluated in four experiments carried out in hydroponically systems, using the cultivar of lettuce “Cobham Green”, known for its susceptibility to the pathogen. Silicon, as potassium silicate, was added at 100 mg l⁻¹ of nutrient solution at three levels of electrical conductivity: 1.5–1.6 mS cm⁻¹ (EC1), 3.0–3.5 mScm⁻¹ (EC2, 0.70 g l⁻¹ NaCl) and 4.0–4.5 mS cm⁻¹ (EC3, 0.95 g l⁻¹ NaCl) respectively. Lettuce plants, grown for 14–20 (trials 1 and 2) and 36–45 (trials 3 and 4) days in the different nutrient solutions tested, were inoculated with B. lactucae conidia with a maximum of two inoculations before final disease assessment carried out 14–21 days after the inoculation able to give symptoms. EC and potassium silicate significantly influenced downy mildew incidence and severity, while their interaction was not a significant factor. The addition to the standard nutrient solution (EC1) of potassium silicate resulted in a significant reduction of downy mildew severity in trials 1 and 2 where plants were artificially inoculated 15 and 20 days after transplanting. This efficacy was slight on plants grown for 36 and 45 days before inoculation in a soil drenched with EC1 amended with potassium silicate. EC2 gave a significantly similar downy mildew reduction than EC2 added with potassium silicate in trial 3. Plants grown for 36 and 45 days at the highest electrical conductivity (EC3) showed a significant reduction in severity of downy mildew compared with that observed at EC2 level. The best results, in terms of disease control, were given by the addition of potassium silicate to the EC3 solution. This combination also led to a significantly increased plant biomass. The possibility and benefits of applying potassium silicate and increased EC amendments in practice is discussed.     

Spatial analysis and incidence–density relationships for downy mildew on hop

The spatial pattern of downy mildew (Pseudoperonospora humuli) on hop (Humulus lupulus) was characterized over 4 years to aid in deriving an appropriate incidence–density relationship. From 472 disease assessments (datasets), discrete distributions were fitted to the datasets to determine aggregation of disease density. Where distributions were able to be fitted, the Poisson distribution fitted 4% of the datasets and the negative binomial distribution fitted 87% of the datasets. Larger‐scale patterns of disease were assessed by autocorrelation and runs analysis; both indicated aggregation of diseased plants was less common than aggregation of disease within plants. Taylor’s power law indicated disease density was aggregated and related to mean disease density in all years. Disease incidence and density were linked by saturation‐type relationships based on the zero term of the negative binomial distribution or an empirical regression. Certain individual datasets were not described well by any incidence–density model, particularly when disease density was greater than about 0·8 diseased shoots per plant with the cultivar Cascade. When applied to 56 validation datasets, 88% of the variation in observed disease incidence was explained by the incidence–density models. Under conditions where sampling would be implemented for disease management, the requisite conditions appear to be in place for a binomial sampling plan for downy mildew.     

利用MAXENT预测玉米霜霉病在中国的适生区

玉米霜霉病是我国重要的对外植物检疫对象,本文用MAXENT软件对引起玉米霜霉病的5种检疫性病原菌Peronosclerospora maydis、P. sacchari、P. philippinensis、P. sorghi和Sclerophthora rayssiae var. zeae在我国的潜在分布进行了预测。结果表明,5种病原菌中P. sorghi在我国的适生范围最广,根据适生值的大小,其在华北平原、长江中下游平原、东北中部地区、两广、福建及云南西部,均有不同程度的发生风险。在这些地区内种植有大面积的玉米,为玉米霜霉病菌的定殖提供了良好的寄主。加强这些区域的调查监测和检疫对保护当地的玉米生产有重要意义。     

不同助剂提高烯酰吗啉防治莴苣霜霉病的效果研究

为研究不同喷雾助剂提高烯酰吗啉防治莴苣霜霉病的效果,采用喷雾法测定了有机硅助剂Silwet 408、阴离子表面活性剂捷成、植物源助剂克欧森和怀农特4种助剂对50％ 烯酰吗啉可湿性粉剂在莴苣上的沉积率及对霜霉病防治效果的影响.烯酰吗啉不添加助剂以及分别添加4种助剂后,第1次施药后1 d在莴苣植株内的沉积量分别为4.10、...     

Further characterization of field resistance in lettuce to Bremia lactucae (downy mildew)

The development of five Bremia lactucae isolates on the field-resistant crisphead lettuce cultivar Iceberg was compared under field conditions with that on the more susceptible crisphead cultivar Ithaca. With each of five isolates, the epidemic developed more rapidly on Ithaca than Iceberg; lesions on Ithaca were more numerous, larger and sporulated more profusely than on Iceberg. There was no evidence for adaptation of isolates to Iceberg, which provides some additional evidence that the resistance of this cultivar could be non-differential (horizontal). There was, however, evidence of non-specific differences between isolates in their quantitative virulence.     

The genetic control and expression of specificity in Bremia lactucae (lettuce downy mildew)

The inheritance of specific virulence in Bremia lactucae was studied in crosses involving 12 heterothallic isolates of the fungus. In one cross, virulence to eight of the II specific resistance factors examined segregated in the F₁ generation. Although there were exceptions, most of the data were consistent with the hypothesis that pathogenicity was controlled by independent single loci with avirulence dominant to virulence. Linkage between loci determining virulence on R2 and R11 was confirmed. Loci controlling virulence on R5 and R8 also appeared to be linked but these may be identical R-factors. Contrary to a previous suggestion, the locus determining virulence to R10 was independent of that for R5/R8. The expression of virulence to three R-factors (Rl, R4 and R5/R8) was influenced by independent second loci. The presence of a dominant allele at the second locus inhibited avirulence. The expression of avirulence on R6 seemed to be influenced by modifier genes and environment in some isolates. Although the cultivars Mildura, Bourguignonne, Sucrine and Captain were originally thought to contain a single resistance factor, these data suggest that Sucrine carries R5/R8 in addition to R10 whilst Mildura may carry Rl in addition to R3. The stock of Bourguignonne appeared to be a mixture of resistance genotypes. The data add additional support to the suggestion that Capitan (Rll) may carry two resistance factors.     

Incorporation of temperature and solar radiation thresholds to modify a lettuce downy mildew warning system

ABSTRACT The effect of temperature on infection of lettuce by Bremia lactucae was investigated in controlled environment studies and in the field. In controlled conditions, lettuce seedlings inoculated with B. lactucae were incubated at 15, 20, 25, or 30 degrees C during a 4-h wet period immediately after inoculation or at the same temperatures during an 8-h dry period after the 4-h postinoculation wet period at 15 degrees C. High temperatures during wet and dry periods reduced subsequent disease incidence. Historical data from field studies in 1991 and 1992, in which days with or without infection had been identified, were analyzed by comparing average air temperatures during 0600 to 1000 and 1000 to 1400 Pacific standard time (PST) between the two groups of days. Days without infection had significantly higher temperatures (mean 21.4 degrees C) than days with infection (20.3 degrees C) during 1000 to 1400 PST (P < 0.01) but not during 0600 to 1000 PST. Therefore, temperature thresholds of 20 and 22 degrees C for the 3-h wet period after sunrise and the subsequent 4-h postpenetration period, respectively, were added to a previously developed disease warning system that predicts infection when morning leaf wetness lasts >/=4 h from 0600 PST. No infection was assumed to occur if average temperature during these periods exceeded the thresholds. Based on nonlinear regression and receiver operating characteristic curve analysis, the leaf wetness threshold of the previous warning system was also modified to >/=3-h leaf wetness (>/=0900 PST). Furthermore, by comparing solar radiation on days with infection and without infection, we determined that high solar radiation during 0500 to 0600 PST in conjunction with leaf wetness ending between 0900 and 1000 PST was associated with downy mildew infection. Therefore, instead of starting at 0600 PST, the calculation of the 3-h morning leaf wetness period was modified to start after sunrise, defined as the hour when measured solar radiation exceeded 8 W m(-2) (or 41 mumol m(-2) s(-1) for photon flux density). The modified warning system was compared with the previously developed system using historical weather and downy mildew data collected in coastal California. The modified system was more conservative when disease potential was high and recommended fewer fungicide applications when conditions were not conducive to downy mildew development.     

Genetic dissection of Lactuca saligna nonhost resistance to downy mildew at various lettuce developmental stages

This study used the pathosystem of lettuce ( Lactuca spp.) and downy mildew ( Bremia lactucae ) as a model to investigate the inheritance of nonhost resistance, and focused on the contribution of quantitative trait loci (QTLs) to nonhost resistance at various developmental stages in the lettuce life cycle. A set of 28 backcross inbred lines (BILs) of L. saligna CGN05271 (nonhost) introgressions in a L. sativa cv. Olof (host) background identified 16 introgressions that contributed to resistance at various plant developmental stages: seedlings, young plants, adult plants in the greenhouse and adult plants in the field. This paper provisionally considered these introgressions to be 16 QTLs. Of these 16 QTLs, seven were identified previously and nine were new. For 15 QTLs ( Rbq1, Rbq2, rbq3–7 and Rbq8–15 ), the resistance alleles were derived from the nonhost L. saligna ; the resistance allele of the other QTL ( Rbq16 ) was from the susceptible L. sativa cv. Olof. Of the 15 QTLs in L. saligna , only two, rbq5 and rbq7 , were found to be effective at every plant developmental stage; the other 13 QTLs were only effective at certain developmental stages. Experiments with seven B. lactucae races did not provide evidence that any QTL was race-specific. The data suggest that nonhost resistance in L. saligna is the result of cumulative effects of many resistance QTLs operating at various developmental stages.     

Occurrence in Italy and characteristics of lettuce downy mildew (Bremia lactucae) resistant to phenylamide fungicides

Control of lettuce downy mildew (Bremia lactucae) with phenylamide fungicides has failed in some intensive lettuce-producing areas in Northern Italy since Spring 1993. Before then, these chemicals and particularly metalaxyl, provided the best disease control. The sensitivity of Bremia lactucae isolates collected in such areas to metalaxyl was evaluated in the laboratory. These strains grew and sporulated profusely on lettuce seedlings treated with 100 and 200 ppm of metalaxyl, whereas sensitive control strains were completely inhibited when treated with fungicide concentrations ranging from 0.5–1 ppm. Thus in Italy occurrence of resistance to phenylamide fungicides in Bremia lactucae has also been demonstrated, as in almost all the countries where these chemicals were previously authorised. Subsequently, a demonstration of occurrence of resistance was made and the virulence pattern of several strains (resistant and sensitive to metalaxyl) was characterised using differential NL series containing the 13 DM resistant genes or R factors. The results suggest the occurrence of a new pathotype in Italy different from all the 16 NL Bremia lactucae races studied.     

弱光胁迫下黄瓜霜霉病抗性评价与分析

为明确弱光胁迫下黄瓜霜霉病田间发病规律及遗传特性,筛选抗霜霉病黄瓜品种,以15份黄瓜自交系为试材,在弱光条件下通过子叶接菌诱导寄主植株发病,同时结合田间发病率及病情指数调查进行复合抗性鉴定,进而筛选抗病组合,并对其分离世代进行抗性鉴定与遗传特征分析。结果表明,供试15份材料中共筛选出4个典型品系HB1、HB2、HB3和HB4,其病情指数分别是14.17、28.71、63.33和78.33,分别属于高抗、抗病、感病和高感病类型。这4个亲本的F1代及分离世代群体中霜霉病抗性与亲本抗性均存在正相关关系,抗性亲本的后代表现出较强的抗性;F2代群体病株分离现象比较明显,呈偏态分布,有明显的主基因+多基因存在特征,表明弱光胁迫下黄瓜霜霉病受主基因+多基因控制,主基因效应值较大。经田间抗病性鉴定分析,初步筛选出组合HB12、HB13和HB21为抗霜霉病组合,可用于后续抗病品种的选育。     

Genetic analysis of factors for resistance to downy mildew (Bremia lactucae) in species of lettuce (Lactuca sativa and L. serriola)

Simultaneous genetic analysis of resistance in species of lettuce (Lactuca sativa and L. serriola) and a virulence in Bremia lactucae were made to characterize the genetic basis of resistance to downy mildew in 11 host cultivars and accessions. Four new downy mildew resistance genes (Dm13, Dm14, Dm15 and Dm16) were characterized. Other resistance phenotypes were conditioned by combinations of these or previously described Dm genes. New resistance genes, Dm 16 (from LSE/18), Dm14 (from Gelber Winterkonig) and Dm15 (from PIVT 1309), mapped to Dm linkage group I (Dm1, Dm2, Dm3 and Dm6) while Dm13 from Pennlake segregated independently of the three previously characterized linkage groups and therefore belongs to a fourth linkage group. Characterization of new resistance genes requires simultaneous consideration of host and pathogen genetics.     

Occurrence and molecular characterization of strobilurin resistance in cucumber powdery mildew and downy mildew

ABSTRACT Between 1998 and 1999, control failure of powdery mildew (Podosphaera fusca) and downy mildew (Pseudoperonospora cubensis) by the strobilurin fungicides azoxystrobin and kresoxim-methyl was observed in cucumber-growing areas of Japan. Results from inoculation tests carried out on intact cucumber plants and leaf disks clearly showed the distribution of pathogen isolates highly resistant to azoxystrobin and kresoximmethyl. Fragments of the fungicide-targeted mitochondrial cytochrome b gene were polymerase chain reaction amplified from total pathogen DNA and their sequences analyzed to elucidate the molecular mechanism of resistance. A single point mutation (GGT to GCT) in the cytochrome b gene, resulting in substitution of glycine by alanine at position 143, was found in resistant isolates of downy mildew. This substitution in cytochrome b seemed to result in high resistance to strobilurins in this pathogen. The same mutation was found in some but not all resistant isolates of powdery mildew. This study suggests that a mutation at position 143 in the target-encoding gene, resulting in an amino acid substitution, was probably a major cause of the rapid development of high strobilurin resistance in these two pathogens.     

黄瓜霜霉病生态防治技术研究

对大棚黄瓜设计了地膜覆盖双垄,膜下垄间浇水防治黄瓜霜霉病的生态防治措施.试验结果表明,这种防治措施可使大棚内的相对湿度在晴天时控制在85%以下,比膜外浇水显著降低了棚内的湿度,使感病和抗病品种的病情指数均控制在6.0以内,相对防效可达90%以上.与通常的明沟浇水相比,可提早上市1周,推迟拉秧30天,折合每亩增产3107.8kg,增收9323.4元.     

不同葡萄品种对霜霉病的抗性

葡萄霜霉病是葡萄生产上重要的病害之一,通过对辽宁省不同葡萄品种进行室内离体叶片接种和田间自然发病情况调查,以期为葡萄抗性品种的选育和葡萄霜霉病的防治提供科学依据。结果表明,在供试品种中,没有对霜霉病完全免疫的品种,室内离体叶片接种和田间调查结果基本一致,不同品种间霜霉病的抗性存在差异。供试的65个品种中,室内离体叶片接种评价高抗品种3个,抗病品种23个,感病品种24个,高感品种15个;田间自然发病调查评价高抗品种1个,抗病品种19个,感病品种35个,高感品种10个。欧美杂交品种(系)相对欧亚杂交品种(系)较抗病。     

Spatiotemporal analysis of epiphytotics of downy mildew of oilseed poppy in tasmania, australia

Downy mildew, caused by Peronospora arborescens, has become the major disease affecting oilseed poppy (Papaver somniferum) since its first record in Tasmania in 1996. Two field trials conducted in 2000 and 2001 studied the progression and spatial distribution of downy mildew epiphytotics. The logistic and exponential models best described the progression of disease incidence and severity, respectively. Incidence and severity increased rapidly following canopy closure. In 2001, incidence increased from 0.16%, prior to canopy closure, to 100% at late flowering (40 days). Spatial analyses of epiphytotics were conducted by fitting the beta-binomial and binomial distributions, median runs analysis, and the spatial analysis by distance indices. All analyses demonstrated that the distribution of incidence and severity was strongly spatially aggregated from canopy closure until at least late flowering. These results suggest that secondary spread from a few primary infections is the major factor in epiphytotics.     

Quantification of downy mildew (Peronospora sparsa) in Rubus species using real-time PCR

Downy mildew disease caused by Peronospora sparsa, also known as ‘dryberry’ disease, is a serious threat to the cultivation of arctic bramble (Rubus arcticus) and boysenberry (Rubus spp. hybrid). A quantitative and sensitive screening method is necessary for the breeding of downy mildew resistant cultivars and for determining efficient disease control methods. A quantitative real-time PCR method using SYBR^® Green I fluorescent dye was developed for the analysis of P. sparsa in arctic bramble, other Rubus species and roses. Primers were designed to amplify a P. sparsa specific 94-bp fragment from the internal transcribed spacer region (ITS1) and a 140-bp fragment from a conserved region of plant 5.8S ribosomal DNA, which served as an internal control in the samples. Linear amplification from genomic DNA and control plasmids was achieved with both primers, and even 37 fg of P. sparsa conidial DNA was detected. In the samples collected from the field, quantities as low as 0.2 ppm of P. sparsa DNA in plant DNA were detected, thus enabling the diagnosis of weak and latent infections. Arctic bramble cvs Pima, Mespi and Mesma, all showing distinct foliar symptoms, were tested to assess the relative amount of downy mildew DNA present. The symptoms and the amount of P. sparsa DNA detected correlated only in cv. Pima, indicating that visual inspection of symptoms is not a reliable method for assessing the extent of tissue infection. The number of conidiophores of P. sparsa on in vitro inoculated leaves of two arctic bramble cultivars correlated with the results obtained by real-time PCR.     

藜麦霜霉病病原菌鉴定

正藜麦原产于南美洲的安第斯山地区,具有适应恶劣环境的特性,在美洲、欧洲、亚洲、澳洲等地都有种植~([1])。联合国粮农组织推荐为适宜人类食用的"全营养食品"~([2,3])。我国的藜麦产业起步晚,2008年山西省最早实现了规模化种植藜麦~([4])。2016年山西省藜麦面积约5307hm~2,其中山西省     

The occurrence, characteristics and distribution in the United Kingdom of resistance to phenylamide fungicides in Bremia lactucae (lettuce downy mildew)

Failure to control Bremia lactucae (lettuce downy mildew) with metalaxyl in an intensive lettuce-producing region of Lancashire at the end of 1983 was shown to be due to the occurrence of a high level of resistance to this fungicide (isolates capable of growth at < 100 μg/ml metalaxyl). During most of 1984, metalaxyl-resistant isolates were obtained from numerous sites but all within a 20-km radius of the initial outbreak. Thereafter, at the end of 1984 and during 1985, metalaxyl-resistant isolates were recovered from most major lettuce-producing regions in the UK with protected crops more affected than field crops. AH metalaxyl-resistant isolates tested were identical in their response to fungicide, sexual compatibility type (B2) and virulence phenotype, probably representing a clone from a single origin. The resistant pathotype was virulent on resistance factors R 1-10 and 12-15 but lacked virulence for R 11 and 16-18. This was also the most common virulence phenotype among sensitive isolates collected at the same time. Cross-resistance to other phenylamide fungicides was demonstrated but isolates resistant and sensitive to phenylamide showed a similar response to the unrelated systemic fungicides propamocarb and fosetyl-Al. An F₁ sexual progeny isolate from a cross between a phenylamide-sensitive and a phenylamide-resistant isolate (presumed heterozygous at the locus or loci regulating response to phenylamide fungicides) exhibited an intermediate response to phenylamide fungicides. No isolates of this type were obtained from the field. At the high concentrations affecting spore germination, phenylamide fungicides exhibited lower activity against a resistant isolate compared with a sensitive isolate. The findings are discussed in relation to future control strategies, the population biology of the fungus and possible directions for lettuce breeding programmes.