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1.
ABSTRACT The prevalence of brown stem rot (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae in the north central United States was investigated during the fall of 1995 and 1996. Soybean fields were randomly selected using an area-frame sampling design in collaboration with the National Agricultural Statistics Service. Soil and soybean stem samples, along with tillage information, were collected from 1,462 fields in Illinois, Iowa, Minnesota, Missouri, and Ohio. An additional 275 soil samples collected from Indiana were assessed for H. glycines. For each field, the incidence and prevalence of brown stem rot was assessed in 20 soybean stem pieces. The prevalence and recovery (expressed as the percentage of leaf disks colonized) of P. sojae and the prevalence and population densities of H. glycines were determined from the soil samples. The prevalence of brown stem rot ranged from 28% in Missouri to 73% in Illinois; 68 and 72% of the fields in Minnesota and Iowa, respectively, showed symptomatic samples. The incidence of brown stem rot was greater in conservation-till than in conventional-till fields in all states except Minnesota, which had few no-till fields. P. sojae was detected in two-thirds of the soybean fields in Ohio and Minnesota, whereas 63, 55, and 41% of the fields in Iowa, Missouri, and Illinois, respectively, were infested with the pathogen. The recovery rates of P. sojae were significantly greater (P 相似文献
2.
ABSTRACT Bayesian ideas have recently gained considerable ground in several scientific fields mainly due to the rapid progress in computing resources. Nevertheless, in plant epidemiology, Bayesian methodology is not yet commonly discussed or applied. Results of a logistic regression analysis of a 4-year data set collected between 1995 and 1998 on soybean Sclerotinia stem rot (SSR) prevalence in the north-central region of the United States were reexamined with Bayesian methodology. The objective of this study was to use Bayesian methodology to explore the level of uncertainty associated with the parameter estimates derived from the logistic regression analysis of SSR prevalence. Our results suggest that the 4-year data set used in the logistic regression analysis of SSR prevalence in the north-central region of the United States may not be informative enough to produce reliable estimates of the effect of some explanatory variables on SSR prevalence. Such confident estimations are necessary for deriving robust conclusions and high quality predictions. 相似文献
3.
ABSTRACT Investigations were conducted to determine whether the effects of tillage practices on the prevalence of brown stem rot of soybean (caused by Phialophora gregata), Heterodera glycines, and Phytophthora sojae were confounded by soil texture in samples collected in the fall of 1995 and 1996. Soil and soybean stem samples, along with tillage information, were collected from 1,462 randomly selected fields in Illinois, Iowa, Minnesota, Missouri, and Ohio in collaboration with the National Agricultural Statistics Service. The incidence of brown stem rot was determined from 20 soybean stem pieces collected from each field in a zigzag pattern. The detection frequency of P. sojae (expressed as percent leaf disks colonized) and population densities of H. glycines were determined from soil cores also collected in a zigzag pattern. The soil samples were grouped into various textural classes, and the effect of soil texture and tillage relations on the activities of each pathogen were determined. Both tillage and soil texture affected the incidence of brown stem rot; however, there was no interaction between tillage and soil texture. Conservation tillage had a greater (P < 0.05) incidence of brown stem rot in clay loam and silty clay loam than did conventional tillage. The detection frequency of P. sojae was not affected by tillage, but a tillage x texture interaction (P = 0.013) indicated that the effect of tillage depended on soil texture. There was a greater (P < 0.05) detection frequency of P. sojae in conservation tillage than in conventional tillage in silt loam and loam soils. However, in sandy loam, the detection frequency of P. sojae was greater (P = 0.0099) in conventional tillage than in conservation tillage. Population densities of H. glycines were significantly affected by both tillage and soil texture, but overall, there was no tillage x texture interaction. There was an inverse relationship between population densities of H. glycines and percent clay (r = -0.81, P = 0.01) in no-till fields, but little or no change in nematode densities was observed with increasing clay content in tilled fields. Population densities of H. glycines were less (P < 0.05) in no-till fields than in tilled fields in silty clay loam and clay soils. There was no difference in H. glycines densities between the tillage categories in soils sandier than silty clay loam or clay. The findings emphasize the need for cautious interpretation of the effects of tillage practices on diseases and pathogens in the absence of information on soil texture. 相似文献
4.
Characterization and Distribution of Two Races of Phialophora gregata in the North-Central United States 总被引：1，自引：0，他引：1
ABSTRACT Genetic variation and variation in aggressiveness in Phialophora gregata f. sp. sojae, the cause of brown stem rot of soybean, was characterized in a sample of 209 isolates from the north-central region. The isolates were collected from soybean plants without regard to symptoms from randomly selected soybean fields. Seven genotypes (A1, A2, A4, A5, A6, M1, and M2) were distinguished based on DNA fingerprinting with microsatellite probes (CAT)(5) and (CAC)(5), with only minor genetic variation within the A or M genotypes. Only the A1, A2, and M1 genotypes were represented by more than one isolate. The A genotypes dominated in the eastern Iowa, Illinois, and Ohio samples, whereas the M genotypes were dominant in samples from western Iowa, Minnesota, and Missouri. In growth chamber experiments, isolates segregated into two pathogenicity groups based on their aggressiveness toward soybean cvs. Kenwood and BSR101, which are relatively susceptible and resistant, respectively, to brown stem rot. In both root dip inoculation and inoculation by injecting spores into the stem near the ground line (stab inoculations), isolates of the A genotypes caused greater foliar symptoms and more vascular discoloration than isolates of the M genotypes on both cultivars of soybean. All isolates caused foliar symptoms in both cultivars and in three additional cultivars of soybean with resistance to brown stem rot. Greater differences between the A and M genotypes were seen in foliar symptoms than in the linear extent of xylem discoloration, and greater differences were seen in Kenwood than in BSR101. Inoculation of these genotypes into five cultivars of soybean with different resistance genes to brown stem rot showed a genotype x cultivar interaction. A similar distinction was found in an earlier study of the adzuki bean pathogen, P. gregata f. sp. adzukicola, and consistent with the nomenclature of that pathogen, the soybean pathogens are named the aggressive race (race A) and the mild race (race M) of P. gregata f. sp. sojae. 相似文献
5.
ABSTRACT Severity of Sclerotinia stem rot of soybean after treatment with lactofen (Cobra) and other herbicides was assessed in field experiments conducted in Michigan from 1995 to 1997. At sites where disease pressure was high, disease severity was reduced 40 to 60% compared with controls when lactofen was applied at the V3 (1995 and 1996) or R1 (1997) growth stages. Corresponding seed yields were unchanged or up to 20% greater when lactofen was applied at the R1 stage in 1997. Disease severity was not reduced by lactofen treatments in years and at sites where disease pressure was low to medium, and corresponding yields often were reduced by 10%. High levels of glyceollin accumulated in lactofen-injured leaves collected from field plots in 1996 and 1997. High glyceollin content in lactofen-treated leaves was associated with significant reductions in lesion size when leaves were challenge-inoculated with Sclerotinia sclerotiorum. 相似文献
6.
ABSTRACT Regional prevalence of soybean Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum, was modeled using tillage practices, soil texture, and weather variables (monthly air temperature and monthly precipitation from April to August) as inputs. Logistic regression was used to estimate the probability of stem rot prevalence with historical disease data from four states of the north-central region of the United States. Potential differences in disease prevalence between states in the region were addressed using regional indicator variables. Two models were developed: model I used spring (April) weather conditions and model II used summer (July and August) weather conditions as input variables. Both models had high explanatory power (78.5 and 77.8% for models I and II, respectively). To investigate the explanatory power of the models, each of the four states was divided into small geographic areas, and disease prevalence in each area was estimated using both models. The R(2) value of the regression analysis between observed and estimated SSR prevalence was 0.65 and 0.71 for models I and II, respectively. The same input variables were tested for their significance to explain the within-field SSR incidence by using Poisson regression analysis. Although all input variables were significant, only a small amount of variation of SSR incidence was explained, because R(2) of the regression analysis between observed and estimated SSR incidence was 0.065. Incorporation of available site-specific information (i.e., fungicide seed treatment, weed cultivation, and manure and fertilizer applications in a field) improved slightly the explained amount of SSR incidence (R(2) = 0.076). Predicted values of field incidence generally were overestimated in both models compared with the observed incidence. Our results suggest that preseason prediction of regional prevalence would be feasible. However, prediction of field incidence would not, and a different site-specific approach should be followed. 相似文献
7.
Journal of Plant Diseases and Protection - Sclerotinia stem rot, caused by Sclerotinia sclerotiorum (Lib.) de Bary, is a major disease in soybean in many parts of the world. Sustainable control... 相似文献
8.
黑龙江省大豆疫霉根腐病调查与病原分离 总被引：10，自引：0，他引：10
１９９６年对黑龙江省东部和中部大豆产区２３个市、县的大豆苗期疫霉根腐病进行了调查、研究,应用ＰＢＮＩＣ疫霉选择性培养基分离大豆疫霉根腐病病原菌,从牡丹江、穆棱、林口和佳木斯豆田具疫霉根腐症状的大豆植株上分离到大豆疫霉根腐病菌,并从根腐病株上单独或与大豆疫霉菌同时分离到终极腐霉菌,研究进一步证实我国黑龙江省有大豆疫霉根腐病。调查发现,大豆疫霉根腐病和终极腐霉根腐病主要发生在土质粘重、土壤含水量高或易积水的田块。 相似文献
9.
广东省新推广大豆品种病害的初步调查 总被引：1，自引：0，他引：1
本文采用普查和定点调查以及传统的植物病害鉴定方法,在2006年6月至2010年10月对广东省新推广高产优质大豆品种的病害种类、发生危害及分布进行了调查.发现病害共有12种,其中真菌病害9种,分别是锈病、霜霉病、红冠腐病、丝核菌叶枯病、炭疽病、白绢病、白粉病、镰刀菌根腐病和煤烟病;细菌性病害、线虫病害和病毒病害各1种,分别为细菌性叶斑病、根结线虫病和花叶病.主要病害为锈病、霜霉病、红冠腐病、花叶病、丝核菌叶枯病和炭疽病等.不同季节大豆的主要病害发生情况不同.春大豆以霜霉病发生较为严重;而夏大豆则以红冠腐病、锈病、花叶病毒病和丝菌核叶枯病发生较严重. 相似文献
10.
Liu Shengming Fu Liuyuan Chen Jinpeng Wang Shuan Liu Jinliang Jiang Jia Che Zhiping Tian Yuee Chen Genqiang 《Phytoparasitica》2021,49(1):123-130
Phytoparasitica - Sclerotinia stem rot, caused by Sclerotinia sclerotiorum, is a devastating fungal disease in oilseed rape. Chemical control with fungicides is the primary method of controlling... 相似文献
11.
ABSTRACT Sclerotinia sclerotiorum, the causal agent of potato stem rot, is prevalent and poorly managed on potatoes in the Columbia Basin of Washington. Because of the ubiquitous nature of the fungus and high crop diversity within the Columbia Basin, understanding the population structure and the potential for outcrossing of the pathogen would be helpful in developing disease management strategies. The population structure of S. sclerotiorum in the Columbia Basin from potato was examined using microsatellite markers and mycelial compatibility. Analysis of molecular variance revealed that 92% of the variability among 167 isolates was found within subpopulations, with limited, yet statistically significant impact of the collection date, but not the year or location of collection. Linkage disequilibrium and index of association analyses noted a potential for outcrossing in two locations, which was substantiated by the discovery of recombinant ascospores in three field-generated apothecia from the 12 apothecia examined. Microsatellite haplotypes were not correlated with mycelial compatibility groups. This high haplotypic diversity did not seem to impact pathologically important phenotypes. Greenhouse inoculations of potato plants exhibited no significant differences in aggressiveness on potato stems. Moreover, in vitro studies of response to fungicides and temperature stimuli yielded no significant differences among studied isolates. These findings illustrate the potential for outcrossing in warm temperate regions of North America, where a diversity of crops are planted simultaneously and in neighboring fields. This study also indicates that the unsatisfactory management of potato stem rot is likely not directly attributable to genetic factors, but to gaps in agricultural practices. 相似文献
12.
Pauline A. Donaldson Terry Anderson Byron G. Lane Andrea L. Davidson Daina H. Simmonds 《Physiological and Molecular Plant Pathology》2001,59(6):297
Sclerotinia stem rot (SSR) caused by Sclerotinia sclerotiorum (Lib.) De Bary is a serious fungal disease of soybean. Senescing petals provide a starting nutrient source for the invasion of healthy tissue by the advancing oxalic acid secreting fungal hyphae. Since oxalic acid is a major pathogenicity factor of SSR, transgenic soybean capable of degrading oxalic acid may be resistant to the pathogen. Transgenic soybean plants were produced byAgrobacterium -mediated transformation with the wheat germin gene (gf-2.8) encoding an oligomeric protein, oxalate oxidase (OxO), which oxidizes oxalic acid to carbon dioxide and hydrogen peroxide (H2O2). Transgenic soybean homozygous for 35S- gf-2.8 produced an approx. 130 kDa protein indistinguishable from wheat germin, and with OxO activity. OxO activity was prominent in cell walls proximal to the site of pathogen attack. The transgenics had greatly reduced disease progression and lesion length following cotyledon and stem inoculation with S. sclerotiorum indicating that the germin gene product conferred resistance to SSR. This is the first report of plant resistance to the fungal pathogen S. sclerotiorum in transgenic plants expressing OxO. 相似文献
13.
14.
Sclerotinia rot caused by Sclerotinia sclerotiorum is one of the most important diseases of processing tomatoes in Central Brazil. Yield losses in tomato cultivars (cv.) IPA-5 were assessed in mature plants from 1995 to 1997, and related to different disease intensities, in a naturally infested area irrigated by centre pivot. Over the 3 years, there were no differences (Tukey at 5%) in fruit numbers between plants without symptoms (NS) and with intermediate symptoms (IS), which yielded higher numbers than plants with severe symptoms (SS). The greatest reduction in fruit number was 56.8% in 1997. Significant differences were observed in fruit weight and size among NS, IS and SS plants in 1995 and 1997. In 1996, NS and IS plants were similar, but different from SS, which yielded significantly less. Weight and size reductions in SS plants reached 84.3% and 62.0%, respectively, in 1997. In 1996 and 1997, yield losses related to time of symptom appearance and physiological age were also assessed. Significant correlations were found ( P < 0.01), with nearly total losses observed when plants were infected from early to mid bloom, as opposed to plants infected near harvest, which had lower disease incidence and produced economically acceptable yields. Quadratic and exponential models best fitted the relationship between yield and time of symptom appearance, and yield vs physiological age could be explained by logistic and Gompertz functions. 相似文献
15.
Hui-Xia Ma Yu Chen Jian-Xin Wang Wen-Yuan Yu Zheng-He Tang Chang-Jun Chen Ming-Guo Zhou 《Phytoparasitica》2009,37(5):421-429
Carbendazim (MBC) was widely used to control Sclerotinia stem rot routinely during the 1980s in China, but development of
MBC resistance in the causal agent Sclerotinia sclerotiorum led to control failures of this disease. In this study it was found that the MBC resistance in S. sclerotiorum populations was widespread throughout Jiangsu Province with a resistance frequency of 29.54% in the 1786 collected isolates
during the growing seasons of 2006 to 2008. The resistance frequencies differed among sampled cities, ranging from 3.1% to
54.9%. The field MBC-resistant isolates showed comparable mycelial growth, sclerotia production and pathogenicity to the wild-type
sensitive isolates, which suggested that the field MBC-resistant isolates might have sufficient parasitic fitness to compete
with the field MBC-sensitive isolates in the field. In the in vitro sensitivity test, boscalid showed greater activity against S. sclerotiorum than dicarboximide fungicides (dimethachlon, iprodione and procymidone). The treatment 50% boscalid (WG) 125 g a.i. ha−1 was comparable in efficacy to the treatment 50% iprodione (WP) 600 g a.i. ha−1, and better than other treatments of 6% dimethachlon (WP) 690 g a.i. ha−1 and 50% procymidone (WP) 337.5 g a.i. ha−1, whereas MBC failed to control Sclerotinia stem rot (control efficacy only 16.0%). The most active agent for controlling
Sclerotinia stem rot was boscalid in our study. 相似文献
16.
Relationships between the spatial pattern and number of apothecia of Sclerotinia sclerotiorum and stem rot of soybean 总被引：1，自引：1，他引：0
Relationships between the spatial patterns and numbers of apothecia of Sclerotinia sclerotiorum and incidence of sclerotinia stem rot of soybean (Glycine max) were investigated in a field plot in 1981 and 1982. Apothecia and disease were both spatially aggregated and were most consistently described by the negative binomial distribution, although the Poisson-binomial and logarithmic with zeros distributions sometimes gave significant fits to data. Numbers of apothecia and disease incidence were correlated within quadrats of 1.4 m2 (r = 0.04-0.57), 36 m2 (r = 0.44-0.87) and 108 m2 (r = 0.44-0.99). The results suggest that disease incidence was determined primarily by inoculum produced within the field. This information may be important in developing models for disease production. 相似文献
17.
Journal of Plant Diseases and Protection - Sclerotinia stem rot (SSR), caused by Sclerotinia sclerotiorum (Lib.) De Bary, is one of the most devastating diseases of tomato. The control of the... 相似文献
18.
Elizabeth Dann Brian Diers Joe Byrum Ray Hammerschmidt 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(3):271-278
Field or greenhouse grown soybeans were treated with 2,6-dichloroisonicotinic acid or benzothiadiazole and subsequently assessed for severity of white mold disease caused by Sclerotinia sclerotiorum. Three or four applications of 2,6-dichloroisonicotinic acid to field plots in 1993–1995 reduced severity of white mold after natural infection by 20–70% compared with water-treated controls in soybean cultivars Elgin 87 and Williams 82, which are considered to be highly susceptible to the disease. The effect was not as large in the cultivars Corsoy 79 and NKS19-90 which are more resistant to white mold. Two or four applications of benzothiadiazole to field plots in 1995 and 1996 reduced white mold severity by 20–60%, with the greatest reductions again observed in the more susceptible cultivars. Corresponding yields were increased compared with controls, particularly for the susceptible cultivars under conditions of high disease pressure. In greenhouse trials multiple applications of either compound resulted in significantly smaller lesion diameters following subsequent leaf inoculations with the fungus. The compounds did not result in observable phytotoxicity or inhibit growth of Sclerotinia sp. in vitro. We hypothesize that the decrease in disease severity following treatment with INA or BTH is a result of resistance induction. 相似文献
19.
武夷菌素是一种核苷类农用抗生素,具有高效、广谱、低毒等优点,对大豆菌核病具有良好的防治效果。武夷菌素防治大豆菌核病包括抑制核盘菌和诱导大豆抗病性两方面的作用。本文分别从核盘菌生长发育、生理毒性和基因表达三个层面介绍了武夷菌素抑制核盘菌的作用机制,同时,从植物防御过程中的胼胝质沉积、防御相关酶活变化和激素信号传导途径三方面综述了武夷菌素诱导大豆抗病的作用机制。此外,本文分析并展望了今后深入研究武夷菌素防治大豆菌核病作用机制的工作重点。 相似文献
20.
农作物病害损失率估算方法探讨 总被引：1，自引：0，他引：1
本文以油菜菌核病为分析对象来研讨作物病害的损失率估算方法,得出当病害发病程度和损失呈直线关系时,损失率一般方程式可表示为Y= (a×发病率+b×K×病情指数) /?100,2012年经对36块油菜田菌核病损失率进行估算,并与观测值进行卡平方检验,结果理论值与实测值差异极小,表明此方程可靠性高,可用于病害损失率的准确估算。 相似文献