A time series analysis of brown eye spot progress in conventional and organic coffee production systems

Brown eye spot (BES), caused by Cercospora coffeicola, is an important coffee disease in Brazil. Losses related to this disease have increased over the last few years. Because the factors associated with the disease dynamics are not fully understood, it is important to gather information about this in different cropping systems. BES epidemics were compared from three production systems: organic (OS), organic under shade (OSS) and conventional under full sun (CS). This study was conducted in Ervália‐MG, Brazil, from November 2004 to October 2008. Disease progress was modelled with all 4 years of data in a time series analysis. Disease intensity (severity (SEV) and incidence (INC)), leaf setting (LS) and leaf fall (LF) were assessed on a monthly basis. The highest values for SEV, INC, LF, LS, as well as a larger area under the disease progress curve and maximum disease occurred in CS and in the upper branches, whereas the lowest values for all variables occurred in OSS and in the lower branches. The highest values occurred for SEV and INC from May to July, for LF from July to September, and for LS from October to January. The disease progress was successfully modelled via a time series analysis. The seasonal behaviour of disease progress for all years and production systems was modelled with a nonlinear sinusoidal model with autoregressive moving average (ARMA) errors. Estimated parameters were generated which could be useful for comparative epidemiology, and it was shown that shade could be used in the field for BES management.     

黄帚橐吾提取物对棉铃虫的生物活性

为掌握贵州甘蔗真菌病害种类及发生情况,采用随机踏查、定点调查、症状诊断与病原菌形态特征观察等方法对贵州甘蔗产区7个县进行真菌病害调查;采用菌丝生长速率法,对甘蔗褐斑病进行了5种杀菌剂室内毒力测定和田间防效试验。结果表明,贵州甘蔗主要真菌病害有褐斑病、褐锈病、赤腐病、黄斑病、轮斑病、褐条病、煤烟病、黑穗病,其中褐斑病、轮斑病、褐条病发生较重,煤烟病发生严重;5种杀菌剂中,325 g/L苯甲· 嘧菌酯悬浮剂对甘蔗褐斑病毒力最高和防效最好,EC50为0.0025 mg/L,第3次药后10 d防效达86.46%。其他4种杀菌剂对褐斑病均有较好的防治效果,可应用于甘蔗生产防治褐斑病。     

花生褐斑病和网斑病田间混发流行过程及其产量损失研究

 通过田间小区人工接种试验,分析比较了花生褐斑病和网斑病单独及混合发生的流行过程及对花生产量损失的影响。结果表明,在病害混发初期,病害间无明显的相关性,随着病情加重,病害间的负相关性逐渐增大并达到显著水平,说明病害间有明显的抑制作用。在不同生育期接种发病情况有所差异,在开花初期和盛花期接种,褐斑病和网斑病的病情较重,而在开花末期接种的病情较轻,但都能表现病害间的抑制作用。病害混发时造成的产量损失小于各病害单独造成损失之和,对白沙1016和四粒红接种2种病菌,病害混合发生所造成产量损失约为各病害单独引起损失之和的77.2% ~ 85.7%和76.1% ~ 79.6%。在不同生育期接种2种病菌,2个品种产量的损失均随着侵染时期的推迟而逐渐降低。     

Early detection and classification of plant diseases with Support Vector Machines based on hyperspectral reflectance

Automatic methods for an early detection of plant diseases are vital for precision crop protection. The main contribution of this paper is a procedure for the early detection and differentiation of sugar beet diseases based on Support Vector Machines and spectral vegetation indices. The aim was (I) to discriminate diseased from non-diseased sugar beet leaves, (II) to differentiate between the diseases Cercospora leaf spot, leaf rust and powdery mildew, and (III) to identify diseases even before specific symptoms became visible. Hyperspectral data were recorded from healthy leaves and leaves inoculated with the pathogens Cercospora beticola, Uromyces betae or Erysiphe betae causing Cercospora leaf spot, sugar beet rust and powdery mildew, respectively for a period of 21 days after inoculation. Nine spectral vegetation indices, related to physiological parameters were used as features for an automatic classification. Early differentiation between healthy and inoculated plants as well as among specific diseases can be achieved by a Support Vector Machine with a radial basis function as kernel.The discrimination between healthy sugar beet leaves and diseased leaves resulted in classification accuracies up to 97%. The multiple classification between healthy leaves and leaves with symptoms of the three diseases still achieved an accuracy higher than 86%. Furthermore the potential of presymptomatic detection of the plant diseases was demonstrated. Depending on the type and stage of disease the classification accuracy was between 65% and 90%.     

玉米灰斑病脉冲Logistic模型研究

[目的]采用脉冲Logistic模型模拟玉米灰斑病流行过程。[方法]在不同品种玉米上接种玉米灰斑病菌并观察记录发病情况,采用脉冲Logistic模型对该病发展过程进行模拟,并与实际发病情况进行比较。[结果]人工接种验证结果表明,脉冲Logistic模型能够反映玉米灰斑病病害时间动态。推导得到,玉米灰斑病指数增长期从玉米出苗开始到每年7月上旬,逻辑斯蒂期从7月上旬到8月下旬,衰退期从9月上旬到玉米生育期结束。[结论]由模型推导的结果符合玉米灰斑病发展的生物学规律。     

长豇豆资源的遗传距离估测和聚类分析

对３９份长豇豆品种进行了煤霉病抗性鉴定。并对其１４个重要农艺性状进行考查，以综合性状组、丰产性状组和早熟性状组的遗传相关矩为基础矩阵，分别进行主成分转换并计算欧氏遗传距离，用最长距离法进行品种聚类。结果表明，３９份品种中，有７份对煤霉病表现免疫、高抗或抗病。通过主成分分析、测试、确定了具有较优综合性状的品种１１个，丰产性较优或早熟性较优的品种各９个，试验结果还表明，选择不同的性状组分析，遗传距离及     

大豆灰斑病粒率的遗传表现

大豆高抗灰斑病品种与抗性不同的品种杂交，Ｆ_１代各个组合的灰斑病粒率均表现高抗，其病粒率值的大小与另一亲本的抗性程度呈正相关，并相关极显著。中抗品种与感病品种杂交，或双亲皆为感病品种，Ｆ_１代病粒率多倾向双亲之间。５个正反交组合Ｆ_１代灰斑病粒率表现，经ｔ值测定差异不显著。高抗品种与感病品种杂交的４个组合，Ｆ_２代灰斑病粒率表现出不同抗性的变异趋向。呈偏态分布。     

大豆灰斑病接种体来源及接种条件的研究

比较种子带菌和土壤带菌作为接种体来源的田间试验,结果证明,土壤带菌是田间接种体的主要来源。不同带病水平的种子,即使100%带病,引起病害的严重度没有多大差别,在发病初期调查,连作地的平均病指为2.98%,而与玉米轮作的地块仅为0.98%,病害降低了67.11%。室内进行的接种条件研究证明,接种体的浓度以每毫升悬浮液中含40000个孢子为宜。接种后,应立即保湿。孢子落到叶片上,没有足够湿度的情况下,6天后便失去侵染活力。孢子在饱和湿度下,2小时亦能侵入,2～8小时侵染率都很低,以保湿24小时的效果较好。     

大豆灰斑病1号生理小种抗性基因的SSR标记分析

针对中国大豆灰斑病1号生理小种,以抗所有生理小种的品系东农40566为母本,以感1号生理小种的品种东农410为父本配制杂交组合,杂交得到F2代后连续自交3代得到F5代群体.该群体经人工接种灰斑病1号生理小种后,利用BSA法对500个SSR标记进行筛选,其中3个标记Satt565、SOYGPATR和Satt396在抗、感池间表现出稳定的多态性,并且在F2代个体中表现出抗性与多态性协同分离的趋势.这3个标记与抗性基因的连锁顺序为Satt565-SOYGPATR-Hrcs1-Satt396,它们与抗性基因的连锁距离分别为12.7cM、6.5cM、14.7cM.推测抗大豆灰斑病1号生理小种的基因可能位于C1连锁群上.     

Sensitivity of Cercospora beticola isolates from Serbia to carbendazim and flutriafol

Cercospora beticola, causal agent of Cercospora leaf spot (CLS) of sugar beet, is primarily controlled by fungicides. Benzimidazole and demethylation inhibiting fungicides, including carbendazim and flutriafol, have been widely used in Serbia. Since these fungicide groups have a site-specific mode of action, there is a high risk for developing resistance in target organisms, which is the most important limiting factor in Cercospora leaf spot chemical control. A rapid identification of flutriafol and carbendazim resistance can help researchers in examining the potential of different fungicide resistance management practices, as well as in selection of fungicides for use in the areas where resistance has occurred. One hundred single-conidia isolates were collected from 70 representative locations of the sugar beet production region in Serbia. Evaluation of the isolates' sensitivity was based on the reduction of mycelial growth on medium amended with 1.25 μg mL⁻¹ flutriafol and 5 μg mL⁻¹ carbendazim. Resistance to flutriafol and carbendazim was detected in 16% and 96% of the tested isolates, respectively. All isolates resistant to flutriafol were resistant to carbendazim as well, which is the first report of a double resistance to fungicides in C. beticola. Detection of the isolates resistant to flutriafol and carbendazim using Cleaved Amplified Polymorphic Sequence (CAPS) markers confirmed the results of the in vitro tests. The efficacy of carbendazim, flutriafol, azoxystrobin, and tetraconazole at commercially recommended doses was evaluated in field trials where sugar beet plants in plots were inoculated with a mixture of isolates either sensitive and/or resistant to flutriafol and carbendazim. Carbendazim and flutriafol efficacy was very low in plots inoculated with isolates resistant to these fungicides. Presented results will contribute to development of a pathogen population sensitivity monitoring strategy that could be used for an effective CLS management in the region.