Effects of powdery mildew and weather on winter wheat yield. 2. Effects of mildew epidemics

Wheat yield losses caused by powdery mildew were computed based on effects of the disease on leaf photosynthesis. Powdery mildew was introduced in a crop model of wheat by quantification of five parameters, taking the vertical and horizontal distribution of mildew in the crop into account. The most important parameters were those of the mildew intensity, the distribution of mildew in the crop, and the effect of mildew on assimilation at light saturation. Measured mildew epidemics in field experiments in three different years, were used to compute yield losses. Computed losses were compared to measured losses. On average, computed yield loss approached measured, but measured yield loss was underestimated, especially in early mildew epidemics due to the computation of partitioning and reallocation of assimilates. Other processes which may cause an underestimation are described. The use of crop models as a method to upgrade disease management systems is discussed.Samenvatting Opbrengstderving van wintertarwe werd berekend aan de hand van het effect dat meeldauw heeft op de blad-fotosynthese. Een rekenmodel voor de gewasgroei van tarwe werd uitgebreid met meeldauw. Met inachtneming van de vertikale en horizontale verdeling van meeldauw in het gewas, werd meeldauw in het model gekwantificeerd door vijf parameters. De belangrijkste parameters waren die van de meeldauwintensiteit, de verdeling van meeldauw in het gewas en het effect van meeldauw op de assimilatie bij een overvloed aan licht. Epidemieën van meeldauw, gemeten in veldproeven in drie verschillende jaren, werden gebruikt om opbrengstdervingen te berekenen. Gemiddeld kwam deze redelijk overeen met de in de veldproeven gemeten opbrengstderving. De gemeten opbrengstderving werd echter onderschat, vooral bij vroege epidemieën van meeldauw door de wijze waarop de (her)verdeling van assimilaten wordt berekend. Andere mechanismen, die een onderschatting van opbrengstderving kunnen veroorzaken worden besproken. Of deze modellen als methode gebruikt kunnen worden om systemen voor de geleide bestrijding van ziekten te verbeteren wordt bediscussieerd.     

Damage components of powdery mildew in winter wheat

Abastract The photosynthesis and transpiration rates of winter wheat leaves were measured at different developmental stages and at various levels of mildew infection. Even at low levels of infection, circa 4% leaf area being covered, both the assimilation and transpiration rates at light satiation were considerably reduced. Light use efficiency and dark respiration were not significantly affected. The physiological background of these effects was analysed by photosynthesis measurements at different external CO₂ concentrations. It was shown that the carboxylation resistance was increased due to mildew infection and that stomatal resistance, boundary layer resistance and transport resistance in the mesophyll were only indirectly affected.A simulation model was used to compute the consequences of these effects on daily growth rate of a winter wheat canopy at different development stages and with different levels of mildew severity. These computations show that a low infection level may result in a considerable reduction of the crop growth rate. This effect was more pronounced when the sky was clear than overcast.Samenvatting Bepalingen van fotosynthese en verdamping werden verricht bij verschillende ontwikkelingsstadia van wintertarwe, die in verschillende mate was aangetast door meeldauw. Zelfs bij vrij lage infectiepercentages (circa 4%) was er al een aanzienlijke reductie van assimilatie en verdampingssnelheid bij lichtverzadiging. Lichtbenuttingsefficiëntie en donkerademhaling werden niet significant beïnvloed.De fysiologische achtergrond van deze effecten werd onderzocht door fotosynthesemetingen bij verschillende externe CO₂ concentraties. Er werd aangetoond dat de carboxylatieweerstand werd verhoogd door meeldauwinfectie en dat de huidmondjesweerstand, grenslaagweerstand en transportweerstand in het mesofyl indirect werden beïnvloed.De gevolgen van deze effecten op de dagelijkse groeisnelheid van een wintertarwegewas in verschillende ontwikkelingsfasen en met verschillende LAI werd nagegaan met een simulatiemodel. Deze berekeningen tonen aan dat een geringe meeldauwaantasting resulteert in een aanzienlijke reductie van de groeisnelheid van het gewas. Dit effect was duidelijker bij heldere dan bij bewolkte hemel.     

Disease-weather relationships for powdery mildew and yellow rust on winter wheat

Key weather factors determining the occurrence and severity of powdery mildew and yellow rust epidemics on winter wheat were identified. Empirical models were formulated to qualitatively predict a damaging epidemic (>5% severity) and quantitatively predict the disease severity given a damaging epidemic occurred. The disease data used was from field experiments at 12 locations in the UK covering the period from 1994 to 2002 with matching data from weather stations within a 5 km range. Wind in December to February was the most influential factor for a damaging epidemic of powdery mildew. Disease severity was best identified by a model with temperature, humidity, and rain in April to June. For yellow rust, the temperature in February to June was the most influential factor for a damaging epidemic as well as for disease severity. The qualitative models identified favorable circumstances for damaging epidemics, but damaging epidemics did not always occur in such circumstances, probably due to other factors such as the availability of initial inoculum and cultivar resistance.     

A simulation model for the development of brown rust epidemics in winter wheat

A model simulating the progress of Puccinia recondita severity, expressed as a percentage of rusted leaf area (both as average and its 95% confidence interval) on individual wheat leaves over the course of a growing season, with a time step of one day, was elaborated using laboratory and field data from literature. Data on the stages of each infection cycle (uredospore germination, penetration, latency, uredium eruption and infectiousness) were transformed into model parameters by curve fitting, Montecarlo stochastic procedures, corrections and empirical assumptions. Data on host growth, like the timing of all phenological stages, the dynamic of the green area of each leaf from appearance to complete senescence, and tillering were obtained from a specific sub-model. Model validation was performed on actual data not used in model building and representing a wide range of conditions (several winter wheat cultivars grown at eight locations in northern Italy between 1990 and 1994) by using subjective, non-parametric and parametric tests: it revealed a satisfactory agreement between the data simulated by the model and actual data.     

A host-pathogen simulation model: powdery mildew of grapevine

An epidemiological model simulating the growth of a single grapevine stock coupled to the dispersal and disease dynamics of the airborne conidia of the powdery mildew pathogen Erysiphe necator was developed. The model input variables were either climatic (temperature, wind speed and direction) or related to the pathogen (location and onset of primary infection). The environmental input variables dictated plant growth and pathogen spread (latent period, infection, lesion growth, conidial spore production and release). Input parameters characterized the crop production system, the growth conditions and the epidemiological characteristics of the pathogen. Output described, at each time step, number, age and pattern of healthy and infected organs, infected and infectious leaf area and aerial density of spores released. Validation of the model was achieved by comparing model output with experimental data for epidemics initiated at different times of host growth. Epidemic behaviour for two contrasting years of crop development and 7 phenological stages at the time of primary infection (PI) was examined. For PI occurring at day 115 a vine with late budbreak (1998) showed 58% of primary leaves diseased at flowering compared with only 19% for a vine with early budbreak (2003). Depending on the phenological stage at PI (1–4 leaves), the proportion of diseased primary leaves decreased from 42% to 6% at flowering. Simulations suggested that differences resulted from the interplay between the timing of the first sporulation event, the phenological stage at the time of initial infection, and the age structure and spatial distribution of the leaf population.     

小麦白粉病与温度的定量关系研究

温度对小麦白粉病影响试验的结果表明,此病害适宜发生的温度为15～20℃,低于10℃或高于25℃对该病有明显抑制作用。当温度高于26℃时,试验显示随着温度的升高,终止小麦白粉病病程的时间缩短,据此建立了不同温度(x)与相应终止病程的时间(y)的关系模型为y=21 900e^{-0.303 5x}(χ²=1.65<χ²_0.05,7=14.07)。同时,根据高温区病害的严重度(y)与温度(x)的试验数据,建立了其关系模型为:y=-3.00x+76.60(r²=0.922 1^**),由此计算获得了连续10 d(一个病程时间)温度为25.53℃即可终止此病害的病程。该试验结果将为小麦白粉病的越夏区划提供基础数据。     

基于随机森林模型的小麦白粉病遥感监测方法

正小麦白粉病是危害我国小麦生产的主要病害,及时高精度地监测其发生发展状况对有效制定病害防控策略十分重要。基于目测手查的传统病害调查方式,耗时费力且无法实时监测。随着空间遥感技术的发展,利用遥感开展病害监测已成为及时获取作物病害信息的重要方式。目前作物病害监测方法大致分为统计模型和物理模型,前者灵活易用、操作简单;后者能定量分析病害发生情况,但输入变量较     

创建BP神经网络模型预测小麦白粉病

阐述了主分量分析法的原理与步骤,分析了河南省中原地区1990～2007年小麦白粉病病情及相关气象资料,得出影响其流行的主要分量,最后利用得到的主要分量作为BP神经网络的输入,对中原地区2008～2010年小麦白粉病流行情况进行预测,并与未进行主分量分析而建立的全要素BP网络模型进行比较。结果表明,该模型可以快速准确地预测小麦白粉病的流行程度,有效地减少小麦产量损失。     

河南省主推小麦品种白粉病发生程度及流行动态研究

经１９９５～１９９７年的试验表明,河南省近几年推广的小麦品种６７％以上为感白粉病品种。极感品种（豫麦１３号）白粉病发生早,发病全盛期长,约３０ｄ,表观侵染速率（ｒ）达０.１１～０.１６,最终病指和病指曲线下面积（ＡＵＤＰＣ）都最高;高感品种豫麦２５等的最终病指及ＡＵＤＰＣ值分别比极感品种低１９％～６６％、４０％～７３％,发病早,发病全盛期２５～３０ｄ,ｒ值０.１～０.１５;中抗品种豫麦２１号、２４号、中育４号占３３％,没有免疫品种。中抗品种的最终病指及ＡＵＤＰＣ值比极感品种分别低８３％～９１％、８９％～９４％,且发病较晚,发病全盛期只有１０ｄ,ｒ值０.０６～０.１１。     

A major gene for powdery mildew resistance transferred to common wheat from wild einkorn wheat

ABSTRACT A major gene for resistance to wheat powdery mildew (Blumeria graminis f. sp. tritici = Erysiphe graminis f. sp. tritici) has been successfully transferred into hexaploid common wheat (Triticum aestivum, 2n = 6x = 42, AABBDD) from wild einkorn wheat (Triticum monococcum subsp. aegilopoides, 2n = 2x = 14, AA). NC96BGTA5 is a germ plasm line with the pedigree Saluda x 3/PI427662. The response patterns for powdery mildew resistance in NC96BGTA5 were tested with 30 differential isolates of B. graminis f. sp. tritici, and the line was resistant to all tested isolates. The analyses of P(1), P(2), F(1), F(2), and BC(1)F(1) populations derived from NC96BGTA5 revealed two genes for wheat powdery mildew resistance in the NC96BGTA5 line. One gene, Pm3a, was from its recurrent parent Saluda, and the second was a new gene introgressed from wild einkorn wheat. The gene was determined to be different from Pm1 to Pm21 by gene-for-gene and pedigree analyses. The new gene was identified as linked to the Pm3a gene based on the F(2) and BC(1)F(1) populations derived from a cross between NC96BGTA5 and a susceptible cultivar NK-Coker 68-15, and the data indicated that the gene was located on chromosome 1A. It is proposed that this new gene be designated Pm25 for wheat powdery mildew resistance in NC96BGTA5. Three random amplified polymorphic DNA markers, OPX06(1050), OPAG04(950), and OPAI14(600), were found to be linked to this new gene.     

小麦白粉病纯化菌种保存方法

利用经初选确定的5种具有较好保鲜能力的配方,采用离体叶段滤纸保存法、离体叶段琼脂保存法和试管苗保存法对小麦白粉病菌纯化菌系保存效果进行了研究.结果表明,对小麦幼苗第一叶叶段保鲜效果最好的配方是沈保6号,当使用40～60μg/mL最适浓度时,第25天叶段绿色仍可达到90%以上.保存菌种的最适环境条件研究结果表明,在4℃冰箱中,以离体叶片沈保6号琼脂保存和离体叶沈保6号浸润滤纸保存效果最佳,在第40天叶片绿色仍分别达到78.0%和68.0%,孢子萌发率可达26.7%和26.8%.     

小麦白粉病地理空间分布特征

依据农业部全国农业技术推广服务中心提供的1980～1998年小麦白粉病病情数据,运用地理信息系统软件Arcview3.0和地统计学工具软件GeoEAS提供的两种空间插值方法,即普通克里格法和反距离加权平均法,进行了地理空间分布特征初步分析。结果表明,小麦白粉病的主要监测指标在较大空间尺度的地理分布上存在空间自相关性。根据空间自相关性,可以用普通克里格法和反距离加权平均法生成插值图。所产生的多幅地图较合理地显示了小麦白粉病的地理空间分布格局。     

Effects of powdery mildew and weather on winter wheat yield. 1. Variation of weather between years

A vital question to upgrade disease management systems is whether damage functions, established in years with specific weather conditions, can be applied also in other years. A simulation approach was used to explore effects of weather on yield and damage. Two existing models of wheat and a third, a combination of both, were used to compute yield, first in absence of mildew. In a second paper, effects of mildew will be reported. Yields simulated for different years were not significantly correlated with yields harvested, adjusted for their increase over years, in the Netherlands. Differences in performance between the models could be attributed to the method of simulating development and growth early in the cropping season.Samenvatting Om systemen voor geleide bestrijding van ziekten te verbeteren, werd de vraag gesteld of schaderelaties, vastgesteld in jaren met specifieke weersomstandigheden, ook gebruikt kunnen worden in andere jaren. Twee bestaande modellen van tarwe en een combinatie van beide, werden gebruikt om het effect van weer op opbrengst te berekenen, eerst bij afwezigheid van meeldauw. De berekende opbrengsten in verschillende jaren toonden geen samenhang met de behaalde opbrengsten, gecorrigeerd voor een jaarlijkse toename, in Nederland. Verschillen tussen de modellen konden worden toegeschreven aan de wijze waarop de groei en ontwikkeling van tarwe vroeg in het seizoen wordt berekend.     

Modelling the interaction between powdery mildew epidemics and host dynamics of tomato

European Journal of Plant Pathology - A model simulating the progress of powdery mildew coupled to the growth dynamics of tomato, with a time step of 1&;nbsp;day, is developed. The model is...     

小麦白粉病预测模型的有效性评价

为全面了解现有小麦白粉病预测模型的有效性,本文收集整理了全国9个省31个县(市)46个小麦白粉病预测模型,在对其实用性、时效性和准确性评价的基础上,对其中6个模型进行了优化、简化或重建,共获得4省7市12个小麦白粉病预测模型,此研究结果对于这些模型在生产上应用提供了依据。     

Modelling and forecasting epidemics of apple powdery mildew (Podosphaera leucotricha)

A model developed to simulate epidemics of powdery mildew on vegetative shoots of apple generates two types of output. Firstly, it forecasts disease severity (percentage of host tissue infected) by incorporating effects on disease development of the amount of healthy susceptible tissue and current infectious (sporulating) disease, the level of initial inoculum (overwintered 'primary' mildew) and weather conditions. The effects of weather variables are considered on only two aspects of the fungal life cycle: initial spore germination and the subsequent development during the incubation period. Secondly, the model generates indices of the relative favourability of weather conditions on disease development by incorporating effects of weather on conidial production/dispersal and germination. On each day, forecasts of the (relative) severity of new infection and total current infectious disease are given for both types of output. The model was evaluated by comparing its predictions with the mildew epidemics observed in two unsprayed orchards over four years. In all the years, the temporal patterns of the predicted and the observed disease were generally similar. The pattern of the disease severity forecasts was marginally closer to the observed than that derived from two weather indices. Potential roles of the model in practical management of apple powdery mildew are discussed.     

小麦新品系抗白粉病基因分析

 本文对6个小麦新品系所含的抗白粉病基因进行了遗传分析。将感病品种Liaochun10分别与SM 20121、SM 203390、SM 20125、SM 200332、SM 20126、SM 20005杂交和自交,并将这6个品系互配成半双列杂交组合。用小麦白粉菌15号小种的单孢堆菌系对各杂交组合的亲本、F₁、F₂代群体及F₃代家系进行了苗期抗病性鉴定。遗传分析表明,供试的6个品系对小麦白粉菌15号小种的抗性均由1对显性基因控制。等位性分析推断:SM 20121、SM 203390、SM 20125和SM 200332含有抗白粉病基因Pm12;SM 20126含有抗白粉病基因Pm21;SM 20005含有抗白粉病基因Pm16。建议将这6个品系作为优良抗病亲本利用。     

陇南山区小麦白粉病流行程度预测模型

调查分析1990~2005年陇南山区小麦白粉病发生、流行资料,发现:陇南白龙江流域为小麦白粉病常发重发生区,徽成盆地为小麦白粉病易发区,西汉水流域为小麦白粉病轻发区;小麦感病品种面积、上年秋苗平均病叶率和病田率、当年早春平均病田率、上年7、10月和当年5月平均气温、当年4月和上年7、8、11月降水量与全市春季小麦白粉病流行程度相关十分显著,上年9月到次年3月平均气温和4~8月降水量与小麦白粉病流行程度呈正相关,4~8月平均气温和9月到次年3月降水量与小麦白粉病流行程度呈反相关。由此建立的预报模型,历史拟合率可达93.75%,2006年业务应用预报准确率100%。     

Natural compounds in the control of powdery mildew on Cucurbitaceae*

Powdery mildew, caused by Sphaerotheca fuliginea, is a major disease of Cucurbitaceae. The use of natural compounds as alternatives or complements to chemical fungicides would be helpful because the crops require continued prolonged harvesting, during which young unsprayed leaf tissues continuously become available for infection. Several natural compounds were tested on courgette and cucumber plants grown under glasshouse conditions and artificially inoculated with S. fuliginea. Both sodium bicarbonate (0.5%) and mineral oil (1%) proved to be effective in keeping infections under control. These compounds showed a remarkable effectiveness when used in combination. The best results were achieved when the plants were treated after infection but before the disease appeared. Other compounds tested, such as sodium silicate and azadiractin, showed some effectiveness, but satisfactory control of the disease was achieved only at doses causing phytotoxicity in the form of necrotic spots on the leaves, especially on cucumber.