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1.
ABSTRACT Leaf rust uredospore production and lesion size were measured on flag leaves of adult wheat plants in a glasshouse for different lesion densities. We estimated the spore weight produced per square centimeter of infected leaf, per lesion, and per unit of sporulating area. Three levels of fertilization were applied to the plants to obtain different nitrogen content for the inoculated leaves. In a fourth treatment, we evaluated the effect of Septoria tritici blotch on leaf rust uredospore production. The nitrogen and carbon content of the spores was unaffected or marginally affected by lesion density, host leaf nitrogen content, or the presence of Mycosphaerella graminicola on the same leaf. In leaves with a low-nitrogen content, spore production per lesion was reduced, but lesion size was unaffected. A threshold effect of leaf nitrogen content in spore production was however, evident, since production was similar in the medium- and high-fertilizer treatments. In leaves inoculated with M. graminicola and Puccinia triticina, the rust lesions were smaller and produced fewer spores. The relationships among rust lesion density, lesion size, and uredospore production were fitted to a model. We determined that the density effect on spore production resulted mainly from a reduction in lesion size, the spore production per unit of sporulating surface being largely independent of lesion density. These results are consistent with those obtained previously on wheat seedlings. The main difference was that the sporulation period lasted longer in adult leaves.  相似文献   

2.
ABSTRACT To develop mechanistic yield loss models for biotrophic fungi, we need better account for the export of dry matter, carbon, and nitrogen from the leaf into the spores. Three experiments in controlled environment chambers were performed to study the dynamics of uredospores production of Puccinia triticina on seedling leaves of wheat in relation to time, lesion density, and sporulating surface area. The detrimental effect of lesion density on the sporulation capacity of brown rust lesions was confirmed. When lesion density increased, spores production per lesion strongly decreased. However, our results showed that increasing lesion density also greatly reduces lesion size. A model was developed to summarize these relationships. Our main conclusion is that the density effect on spore production per lesion is accounted for by lesion size. When sporulation was related to the sporulating surface area, it became independent of density. As well, carbon and nitrogen contents of the spores were independent of lesion density. Our data suggest that when nitrogen available in the host is limiting, spore production is reduced but nitrogen content of spores tend to remain stable.  相似文献   

3.
The pathogenicity-related traits of biotrophic plant pathogens are usually measured on the individual host plant, at the scale of a single pathogen life cycle, whereas epidemic development in the field encompasses a succession of cycles. It remains unclear which traits make the greatest contribution to pathogen fitness in the field and to epidemic severity. The objective of this study was to determine the contributions of elementary pathogenicity traits to epidemic development in field conditions. We challenged a set of wheat cultivars with three different leaf rust isolates, under both controlled and field conditions, in 3 consecutive years. Infection efficiency, latent period, lesion size, spore production per lesion and spore production capacity were measured in the greenhouse, whereas disease severity was measured in the field. Most, but not all, of the pathogenicity traits were related to each other. All traits contributed to epidemic development in the field, but to different extents. Surprisingly, lesion size and spore production per lesion were inversely correlated with epidemic severity. Conversely, there was a strong positive correlation between spore production capacity and pathogen fitness in the field, in accordance with the concept of propagule pressure as a strong determinant of invasion success. Severe epidemics were mostly associated with small lesions with a high spore production capacity, high infection efficiency and a short latent period.  相似文献   

4.
Gilles T  Kennedy R 《Phytopathology》2003,93(4):413-420
ABSTRACT Controlled environment experiments were conducted to study the effects of inoculum density, temperature, and their interaction on germination of Puccinia allii urediniospores and infection of leek leaves. Percent germination of P. allii urediniospores and percent branching of germ tubes increased with 3 density of urediniospores and approached a plateau for densities above approximately 20 spores cm(-2) of leaf area. Percent germination was highest at 12 to 21 degrees C, a wide-range temperature optimum. Branching occurred at temperatures ranging from 5 to 25 degrees C, but there were few germ tubes branching at 25 degrees C. P. allii successfully infected leek leaves at temperatures ranging from 7 to 22 degrees C. The number of pustules produced increased with urediniospore density on leek leaves. At low spore densities, pustule production was little affected by temperature; at higher spore densities, pustule production was greatest between 9 to 11 degrees C, and numbers of pustules decreased greatly with temperature increasing above this optimum. Latent period was affected by temperature, with latent period being shortet between 19 and 22 degrees C, and latent period increasing when temperature decreased. Latent periods became approximately 1.8 days shorter for every 10-fold increase in spore density. The rate of pustule production increased with increasing spore density on leaves and was greatest between 11 to 14 degrees C. Computer simulation of leek rust progress based on the found relationships suggested that at optimal temperatures the development of leek rust epidemics may be little affected by initial spore density and density caused by each pustule, but that at sub- and supra-optimal temperatures the development is greatly affected by these variables.  相似文献   

5.
The aim of this study was to investigate the potential diversity and pathogen‐specificity of sources of quantitative resistance to leaf rust caused by Puccinia triticina in French wheat germplasm. From a set of 86 genotypes displaying a range of quantitative resistance levels during field epidemics, eight wheat genotypes were selected and challenged in a greenhouse with three isolates of the pathogen, belonging to different pathotypes. Five components of resistance were assessed: infection efficiency, for which an original methodology was developed, latent period, lesion size, spore production per lesion, and spore production per unit of sporulating tissue. High diversity and variability for all these components were expressed in the host × pathotype combinations investigated; isolate‐specificity was found for all the components. The host genotypes displayed various resistance profiles, based on both the components affected and the isolate‐specificity of the interaction. Their usefulness as sources of quantitative resistance was assessed: line LD7 probably combines diversified mechanisms of resistance, being highly resistant for all the components, but displaying isolate‐specificity for all the components; cv. Apache did not show isolate specificity for any of the components, which could be related to the durability of its quantitative resistance in the field over more than 11 years.  相似文献   

6.
In controlled near-optimum conditions (18 °C), monocyclic sporulation capacity and spore infection efficiency were assessed for faba bean rust on the first and second leaves of field bean. After a latency period of 8–10 days, lesions sporulated duringc. 50 days. Spore production on the second leaf,c. 9×104 spores per lesion, was two times as high as spore production on the first leaf. Infection efficiency was similar for both leaf layers, with a mean value of 0.11 lesion per inoculated spore. Infection efficiency decreased strongly when spores originated from mother lesions older than 20 days. Three life-table statistics (the net reproduction numberR o , the mean generation timeT g , and the maximum relative growth rater max ) were calculated.R o was larger andT g was longer for the second than for the first leaf, butr max was nearly the same for both leaf layers (0.31–0.33 day–1).r max was compared with the exponential growth rater measured in a field experiment. From the difference between the two rates, the fraction of inoculum lost in field conditions was estimated at 0.54–0.94. The life-table statistics were also compared to those of other legume rusts, and implications of life-table analysis for comparative epidemiology were discussed.  相似文献   

7.
ABSTRACT Rain splash dispersal of Gibberella zeae, causal agent of Fusarium head blight of wheat, was investigated in field studies in Ohio between 2001 and 2003. Samplers placed at 0, 30, and 100 cm above the soil surface were used to collect rain splash in wheat fields with maize residue on the surface and fields with G. zeae-infested maize kernels. Rain splash was collected during separate rain episodes throughout the wheat-growing seasons. Aliquots of splashed rain were transferred to petri dishes containing Komada's selective medium, and G. zeae was identified based on colony and spore morphology. Dispersed spores were measured in CFU/ml. Intensity of splashed rain was highest at 100 cm and ranged from 0.2 to 10.2 mm h(-1), depending on incident rain intensity and sampler height. Spores were recovered from splash samples at all heights in both locations for all sampled rain events. Both macroconidia and ascospores were found based on microscopic examination of random samples of splashed rain. Spore density and spore flux density per rain episode ranged from 0.4 to 40.9 CFU cm(-2) and 0.4 to 84.8 CFU cm(-2) h(-1), respectively. Spore flux density was higher in fields with G. zeae-infested maize kernels than in fields with maize debris, and generally was higher at 0 and 30 cm than at 100 cm at both locations. However, on average, spore flux density was only 30% lower at 100 cm (height of wheat spikes) than at the other heights. The log of spore flux density was linearly related to the log of splashed rain intensity and the log of incident rain intensity. The regression slopes were not significantly affected by year, location, height, and their interactions, but the intercepts were significantly affected by both sampler height and location. Thus, our results show that spores of G. zeae were consistently splash dispersed to spike heights within wheat canopies, and splashed rain intensity and spore flux density could be predicted based on incident rain intensity in order to estimate inoculum dispersal within the wheat canopy.  相似文献   

8.
 以12个全国大面积种植的小麦生产品种和1个高感品种为试材,利用抗性组分法研究了中国小麦条锈菌(Puccinia striiformis f.sp.tritici,Pst)4个主要流行小种条中32号、条中31号、水源11-14和水源11-4的寄生适合度。因子分析结果表明,病害量是度量条锈菌生理小种寄生适合度最重要的参数,其次是夏孢子生活力、产孢能力、产孢面积、产孢期,由此提出寄生适合度=(产孢量×侵染概率×夏孢子堆密度×夏孢子萌发率)/潜育期。研究还发现,条中32号的寄生适合度最高,致病性最强,与目前该小种为优势小种的事实相符;水源11-14的寄生适合度较高,有较大的发展潜力,在抗病育种中应予以高度重视。  相似文献   

9.

Studies were conducted on the effect of pruning time, host age, urediniospore release and weather parameters on the incidence and intensity of mulberry leaf rust (Peridiopsora mori). Rust severity significantly increased with increasing shoot age, irrespective of pruning time. Maximum disease severity was observed in plants pruned during the third week of October, and minimum severity in plants pruned during last week of November. Apparent infection rate was higher in younger shoots. Infection rate was higher in plants pruned during the last week of November. Urediniospore release was influenced by prevailing climatic conditions. A higher rate of spore release was noticed during sunny days. Maximum spore release was found between 12.00 h and 14.00 h. Spore release was positively correlated with temperature and negatively correlated with relative humidity. Rust severity (34.97%) was higher in January and least (1.03%) during May. Rust severity was negatively correlated with both temperature and rainfall. An exponential model was developed for the prediction of rust severity which was accurate up to 96.60%.  相似文献   

10.
The infection process of Septoria nodorum was studied on the flag and second leaves of wheat plants at the flag-leaf emergence growth stage (GS 39), after pre-inoculative fumigation with different doses of ozone (0, 80, 180 or 240 μg/m3) for 7 h daily over 7 days. On ozone-treated plants, formation of appressoria occurred earlier, leading to a greater number and density of appressoria and faster growth of superficial infection hyphae than on plants grown without ozone amendment. Additionally, on leaves treated with 180 and 240 μg/m3 ozone, the percentage of papillae per appressorium was only half that on control plants. The number of germ tubes per conidium was not significantly affected by any treatment. Effects of increasing leaf age on the infection process were similar to those obtained with ozone. These results provide further evidence for similarities in the physiological effects of ozone and leaf ageing, which support the hypothesis that disease alterations due to ozone are strongly determined by the senescing effects of the pollutant.  相似文献   

11.
 为了解空气中引起玉米南方锈病病原菌多堆柄锈菌孢子数量与田间病情的关系以及气象因素对孢子和病情的影响,于2017年6 ~9月,在中国农业大学开封实验站,监测空气中多堆柄锈菌的孢子动态,并调查病情和记录气象数据,分别利用Pearson 和Spearman等级相关分析孢子数量与病情以及气象因素与孢子数量和病情的相关性,进一步利用多元逐步回归分析构建病害预测模型。结果表明,在调查日期内(8 月 5~26日),孢子数量呈现先升后降的趋势;孢子的空间分布和扩散方向与风向基本一致。8 d前和3 d前的孢子数量均与病情呈显著正相关(P＜0.01),相关系数分别为0.720和0.755。孢子浓度与温度(≥27℃)、日照时数呈显著负相关;8d 前的气象因素能够显著影响田间病情的发生。建立了玉米南方锈病病害预测模型:Y= 70.938+ 0.009 SC-2.180 MT(其中Y表示的是病情指数, SC表示孢子数量,MT表示日平均气温,R2为0.716),为病情预测提供指导。  相似文献   

12.
应用HYSPLIT-4模式分析小麦条锈病菌远程传播事例   总被引：5，自引：0，他引：5  
 小麦条锈病的发生及大区流行与病原菌的远程传播密切相关。预测小麦条锈病大区流行的关键是搞清病原菌的远程传播路线和孢子云浓度变化规律。气流是菌源传播的主要动力,因此,气流运动的物理模型是对小麦条锈病菌远程传播事例分析的有力工具。本研究利用再分析格点资料(NCEP/NCAR Reanalysis Data),基于HYSPLIT-4模式,对历史上我国小麦条锈病菌远程传播的经典事例(分别发生于1960、1964、1975和1983年)进行了分析,着落区孢子浓度时间序列模拟结果与观察到病害发生前几天的降雨事件是相符的,结果表明小麦条锈病的远程传播及发生时间可通过计算大气环流运动来预测,病原菌孢子的沉降除由于孢子自身重力而引起的沉降外,很大程度上还受到降雨引起的湿沉降的影响。HYS-PLIT-4模式可用于探讨我国小麦条锈病区域间菌源传播关系问题,进行病害的预测预报,进一步指导我国小麦条锈病越夏和越冬调查以及菌源区综合治理和小麦品种布局。该研究在方法和技术上也可为研究其它病原菌远程传播提供借鉴。  相似文献   

13.
为明确酸雨对小麦条锈病菌孢子萌发及病害流行学组分的影响,采用不同酸度的模拟酸雨(p H值分别为2.5、3.5、4.5和5.6)处理小麦条锈病菌Puccinia striiformis f.sp.tritici生理小种CYR32和CYR33的夏孢子,并将不同酸度模拟酸雨处理后的夏孢子接种小麦感病品种铭贤169,采用组分分析法研究酸雨对病害发展过程的影响。结果表明,随着模拟酸雨酸度的增强,生理小种CYR32和CYR33的夏孢子萌发率均显著降低,萌发24 h后对照组生理小种CYR32和CYR33的夏孢子萌发率分别为93.7%和79.8%,在p H 3.5模拟酸雨处理后萌发率仅为13.1%和8.6%。温室内接种试验结果显示,不同酸度模拟酸雨对生理小种CYR32和CYR33的侵染概率、潜育期和病情指数均有显著影响,对生理小种CYR32和CYR33病斑扩展率影响不显著;与对照相比,p H 3.5模拟酸雨处理后生理小种CYR32和CYR33的侵染概率分别下降79.9%和79.8%。结果表明强酸雨(p H 3.5)显著延长小麦条锈菌潜育期,减少病斑产孢量,降低病情指数和病害进展曲线下面积。  相似文献   

14.
The onset of adult plant resistance (APR) to Puccinia striiformis was examined in seven Australian wheat cultivars under field conditions and in 14 cultivars under controlled environmental conditions. In most cultivars under field conditions the percentage leaf area affected by stripe rust at mid-tillering (GS 22–26; third leaf) was significantly less ( P < 0.05) than on the more susceptible cultivar Teal. The expression of APR was more conspicuous during tillering to node formation; at these growth stages chlorosis and/or necrosis developed in association with rust colonies on the most resistant cultivars. Under controlled conditions, the primary leaves of all cultivars except Olympic and Flinders displayed some resistance when compared with Teal (lower infection types, longer latent periods and/or less percentage leaf area affected). Studies on the spread of stripe rust from infection foci established in selected cultivars in the field indicated that the resistance detected at early growth stages in Suneca in controlled environmental studies also appeared to be effective in the field.  相似文献   

15.
ABSTRACT While it is generally accepted that dense stands of plants exacerbate epidemics caused by foliar pathogens, there is little experimental evidence to support this view. We grew model plant communities consisting of wheat and wild oats at different densities and proportions and exposed these communities to Puccinia recondita to induce wheat leaf rust. Wild oats was included because it is a common competitor of wheat and may act as a barrier to the dispersal of P. recondita spores among wheat plants. Disease severity was estimated as percentage of wheat flag leaves covered by rust lesions. Seeding density rarely had a significant influence on rust severity, probably because of compensation due to increased tillering at low seeding densities. In contrast, increasing the proportion of wheat in mixtures with wild oats consistently increased wheat leaf rust severity. Regression parameters describing wheat leaf rust severity as a function of wheat seeding density did not differ significantly between pure wheat stands and wheat-wild oat mixtures and, thus, failed to support an effect of wild oats on wheat leaf rust other than through its competitive impact on wheat tiller density.  相似文献   

16.
The mechanism by which foliar application of potassium chloride solution reduces symptoms of powdery mildew disease (Erysiphe graminis f.sp. tritici) of wheat was investigated. The hypothesis that potassium chloride reduces mildew by an osmotic effect on spore germination was tested in three glasshouse experiments. Either potassium chloride solution or the osmoticum polyethylene glycol 200 was sprayed on wheat at the three- or four-leaf stage. The plants were inoculated with spores and spore germination and leaf area affected by mildew were assessed. Leaf water potential was determined as a measure of the osmotic effect of the treatments. Spore germination and leaf area affected by mildew were related to leaf water potential using regression analysis in groups on the data averaged over the three experiments. Both spore germination on the leaf and leaf area affected by mildew were reduced as leaf water potential decreased. There was no difference between potassium chloride or polyethylene glycol in the relationship between spore germination and leaf water potential, but polyethylene glycol was slightly less effective at reducing mildew symptoms at any given leaf water potential. The results are compatible with the hypothesis that potassium chloride reduces symptoms of powdery mildew by an osmotic effect on spore germination.  相似文献   

17.
Experiments were performed in controlled conditions to compare several aggressiveness components of an isolate of Puccinia triticina on different wheat ( Triticum aestivum ) genotypes. Latency period, urediniospore production per lesion and per unit of sporulating surface, lesion size, and nitrogen and carbon content of the spores were measured on four host genotypes. Three of the host cultivars (Soissons, Altria and Isengrain) were susceptible and the fourth (Trémie) was resistant to the isolate used in the experiments, producing a mesothetic infection type. In all the analyses, lesion density was used as a covariable. The latent period was identical on the susceptible host cultivars, and there were no marked differences in the urediniospore production capacity when related to the sporulating surface area. In cv. Isengrain, differences in lesion size relative to the other susceptible cultivars resulted in lower urediniospore production per lesion. Urediniospore production per lesion and lesion size were density dependent and decreased exponentially with increasing lesion density. Urediniospore production per unit of sporulating surface was either independent of lesion density or marginally dependent (decreased linearly with a limited rate). On the resistant cultivar, Trémie, the latent period was longer and of a much greater variance compared with the susceptible cultivars. Urediniospore production per lesion was considerably reduced, but this reduction was fully accounted for by a reduction in lesion size, the urediniospore production capacity of the diseased tissue remaining equivalent to that observed in the susceptible cultivars. In all cultivars the C and N contents of the urediniospores were considered unchanged, even if minor differences were detected.  相似文献   

18.
ABSTRACT Using mathematical models, we investigated how infection and sporulation characteristics of competing plant pathogens determine the density and frequency dependence of relative fitness. Two models, one for the infection stage and one for the sporulation stage of a pathogen's life cycle, describe reproductive output of pathogen strains in mixture as a function of the strains' population densities. Model parameters include infection and sporulation efficiencies, carrying capacities on leaves for sporulating lesions and spore production, and coefficients of interstrain competitive effects in both life cycle stages. Although the models were originally developed for rust fungi, they are generally applicable to any organism with distinct colonization (e.g., infection) and propagative (e.g., sporulation) life cycle stages. In this work, paired hypothetical strains were assigned equal baseline parameter values. Parameters were then altered one at a time for one or both strains, and relative fitness was calculated over a range of densities and strain frequencies. Except for infection efficiency, the fitness benefit conferred by an advantage in a single parameter was always density dependent. Relative fitness was frequency dependent whenever inter- and intrastrain competitive effects were not equal. These results suggest that the fitness of pathogens in nature is rarely fixed, but, rather, may typically be highly dependent on the densities and frequencies of all coexisting strains in a habitat.  相似文献   

19.
为了解甘谷县春季空气中小麦条锈菌Puccinia striiformis f.sp.tritici夏孢子的动态变化、孢子密度与病情的关系以及气象因素对孢子密度和病情的影响,利用孢子捕捉器和定量PCR法对2013—2015年春季甘谷县南山和北山地区空气中小麦条锈菌夏孢子密度的动态变化进行监测,同时调查病情和记录相同时间段的气象因素,并利用Pearson和Spearman等级相关进行相关分析。结果显示,甘谷县南山和北山地区春季夏孢子动态变化趋势相似,均在5—6月出现孢子密度的峰值。南山和北山地区空气中的孢子密度与各地区田间病情指数显著相关,且相关系数分别达到0.851和0.931。除2013年外,空气中孢子密度与温度、光照呈正相关,而与相对湿度、降水量呈负相关;南山地区田间病情指数与光照、温度和降水天数显著相关,北山地区田间病情指数则仅与平均相对湿度显著相关。根据空气中小麦条锈菌夏孢子的监测并结合当地的气象因素有助于制定合理的病害防治策略,实现对小麦条锈病的定点和定期防治。  相似文献   

20.
 应用14C同位素示踪分析法研究叶锈病(Puccinia hordei)在花期后(GS71)侵染对大麦植物光合作用的影响,结果表明,给叶片接菌后0至8天内无明显的光合病变,8天之后叶片的总光合量下降而单位绿叶面积光合效率提高,且这种下降%和提高%分别与锈病严重度呈显著的直线相关(r2 ≥ 0.980,P<0.001);植株上单叶发病后其它器官的光合作用略有增强,全株叶片发病后穗部光合作用的增加达到显著水平(P<0.05)。
叶锈病在抽穗期(GS55)侵染后,植株籽粒产量和千粒重减低(P<0.01),而病叶干物重则显著增高(P<0.01),本文分析讨论了这些变化的生理机制。  相似文献   

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