scholarly journals Velocity of Spread of Wheat Stripe Rust Epidemics

2005 ◽  
Vol 95 (9) ◽  
pp. 972-982 ◽  
Author(s):  
Christina Cowger ◽  
LaRae D. Wallace ◽  
Christopher C. Mundt
Keyword(s):  
Disease Severity ◽  
Stripe Rust ◽  
Field Experiments ◽  
Average Rate ◽  
Spatial Scales ◽  
Management Strategies ◽  
Plant Diseases ◽  
Pure Stand ◽  
Wheat Stripe Rust ◽  
Competing Models

Controversy has long existed over whether plant disease epidemics spread with constant or with increasing velocity. We conducted largescale field experiments with wheat stripe rust at Madras and Hermiston, Oregon, where natural stripe rust epidemics were rare, to test these competing models. Data from three location-years were available for analysis. A susceptible winter wheat cultivar was planted in pure stand and also in a 1:4 or 1:1 mixture with a cultivar immune to the stripe rust race utilized in the experiments. Plots were 6.1 m wide and varied from 73 to 171 m in length. A 1.5 by 1.5-m focus was inoculated in either the center (2001) or upwind of the center (2002 and 2003) of each plot. Disease severity was evaluated weekly throughout the epidemics in each plot at the same points along a transect running upwind and downwind from the focus. Velocity of spread was calculated from the severity data and regressed separately on time and on distance from the focus. In all location-years and treatments, and at all levels of disease severity, velocity consistently increased linearly with distance, at an average rate of 0.59 m/week per m, and exponentially with time. Further, across epidemics there was a significant positive relationship between the apparent infection rate, r, and the rate of velocity increase in both space and time. These findings have important implications for plant diseases with a focal or partially focal character, and in particular for the effectiveness of ratereducing disease management strategies at different spatial scales.

scholarly journals Improved Evaluation of Wheat Cultivars (Lines) on Resistance to Puccinia striiformis f. sp. tritici Using Molecular Disease Index

Plant Disease ◽  
2019 ◽  
Vol 103 (6) ◽  
pp. 1206-1212
Author(s):  
Bingyao Chu ◽  
Lujia Yang ◽  
Cuicui Wang ◽  
Yilin Gu ◽  
Kai Yuan ◽  
...  
Keyword(s):  
Latent Period ◽  
Stripe Rust ◽  
Field Experiments ◽  
Puccinia Striiformis ◽  
Quantitative Polymerase Chain Reaction ◽  
Disease Index ◽  
Wheat Cultivars ◽  
Resistance Level ◽  
Seedling Resistance ◽  
Wheat Stripe Rust

Wheat stripe rust caused by Puccinia striiformis f. sp. tritici is one of the most destructive diseases of wheat worldwide. Sichuan Province plays an important role in interregional epidemics in China. Application of host resistance is important in disease management, and efficient approaches to evaluate resistance level are necessary to obtain useful varieties. In this study, 100 wheat cultivars (lines) growing in Sichuan were selected to evaluate their resistance to stripe rust. Field experiments were conducted with a mixture of three P. striiformis f. sp. tritici races for inoculations at seeding and adult stages in the 2014 to 2015 season and the 2016 to 2017 season. Leaf samplings were conducted four times during the latent period at early growth stage of wheat. The sampled leaves were processed to extract DNA. The DNA of both wheat and P. striiformis f. sp. tritici was quantified using real-time quantitative polymerase chain reaction, and the molecular disease index (MDI) was used to evaluate the resistance level. The area under the disease progress curve in terms of disease index (AUDPC-DI) was obtained for each studied cultivar (line) in the fields. Among the 100 studied cultivars (lines), 61% of them showed seedling resistance, and 63 and 65% showed adult resistance in the 2014 to 2015 and 2016 to 2017 seasons, respectively, based on the infection type. High consistency in resistance grouping by cluster analysis as the percentage of the studied cultivar (line) belonging to the same group based on AUDPC-DI data and based on MDI data was obtained. The correlations between AUDPC-DI and MDI from samples collected on 9 and 14 or 15 days after inoculation during the latent period were all significant at P < 0.01. This study provided a new and efficient method for evaluation of varietal resistance to wheat stripe rust.

Primary Disease Gradients of Wheat Stripe Rust in Large Field Plots

2005 ◽  
Vol 95 (9) ◽  
pp. 983-991 ◽  
Author(s):  
Kathryn E. Sackett ◽  
Christopher C. Mundt
Keyword(s):  
Stripe Rust ◽  
Power Law ◽  
Puccinia Striiformis ◽  
Exponential Model ◽  
Plant Diseases ◽  
Large Field ◽  
Data Sets ◽  
Wheat Stripe Rust ◽  
Primary Disease ◽  
Modified Power Law

Field data on disease gradients are essential for understanding the spread of plant diseases. In particular, dispersal far from an inoculum source can drive the behavior of an expanding focal epidemic. In this study, primary disease gradients of wheat stripe rust, caused by the aerially dispersed fungal pathogen Puccinia striiformis, were measured in Madras and Hermiston, OR, in the spring of 2002 and 2003. Plots were 6.1 m wide by 128 to 171 m long, and inoculated with urediniospores in an area of 1.52 by 1.52 m. Gradients were measured as far as 79.2 m downwind and 12.2 m upwind of the focus. Four gradient models—the power law, the modified power law, the exponential model, and the Lambert's general model—were fit to the data. Five of eight gradients were better fit by the power law, modified power law, and Lambert model than by the exponential, revealing the non-exponentially bound nature of the gradient tails. The other three data sets, which comprised fewer data points, were fit equally well by all the models. By truncating the largest data sets (maximum distances 79.2, 48.8, and 30.5 m) to within 30.5, 18.3, and 6.1 m of the focus, it was shown how the relative suitability of dispersal models can be obscured when data are available only at a short distance from the focus. The truncated data sets were also used to examine the danger associated with extrapolating gradients to distances beyond available data. The power law and modified power law predicted dispersal at large distances well relative to the Lambert and exponential models, which consistently and sometimes severely underestimated dispersal at large distances.

scholarly journals Effect of Plant Age and Leaf Position on Susceptibility to Wheat Stripe Rust

2017 ◽  
Vol 107 (4) ◽  
pp. 412-417 ◽  
Author(s):  
D. H. Farber ◽  
C. C. Mundt
Keyword(s):  
Disease Severity ◽  
Stripe Rust ◽  
Host Tissue ◽  
Plant Age ◽  
Disease Spread ◽  
Leaf Position ◽  
Mixed Effect ◽  
Wheat Stripe Rust ◽  
Successful Infection ◽  
Propagule Dispersal

In addition to pathogen propagule dispersal, disease spread requires successful infection of host tissue. In plant disease epidemiology, susceptibility of host tissue is often assumed to be constant. This assumption ignores changes in host phenology due to developmental stage. To examine this assumption, 3-, 4-, and 5-week-old wheat plants were inoculated with equal quantities of urediniospores of Puccinia striiformis f. sp. tritici, the causal agent of wheat stripe rust (WSR). Disease severity on each leaf was assessed and fit by mixed-effect linear model as a function of leaf position and plant age. Younger plants had significantly greater disease severity than older plants, with mean severities of 50.4, 30.1, and 12.9% on plants that were 3, 4, and 5 weeks old, respectively, at time of inoculation. This effect was greater on leaves higher on the plant. Within same-aged plants, younger leaves had significantly greater disease severity than older leaves, with mean severities of 40.2, 34.8, and 17.7% on the uppermost, second, and third leaf, respectively. These results suggest that the vertical distribution of WSR lesions in agricultural fields could be driven by differences in host susceptibility more so than propagule dispersal.

scholarly journals Biocontrol Effects of Paecilomyces variotii against Fungal Plant Diseases

2021 ◽  
Vol 7 (6) ◽  
pp. 415
Author(s):  
Alejandro Moreno-Gavíra ◽  
Fernando Diánez ◽  
Brenda Sánchez-Montesinos ◽  
Mila Santos
Keyword(s):  
Disease Severity ◽  
Biological Control Agent ◽  
Management Strategies ◽  
Severity Index ◽  
Control Agent ◽  
Plant Diseases ◽  
Paecilomyces Variotii ◽  
Strong Control

The genus Paecilomyces is known for its potential application in the control of pests and diseases; however, its use in agriculture is limited to few species. Research interest in new formulations based on microorganisms for the control of pathogens is growing exponentially; therefore, it is necessary to study new isolates, which may help control diseases effectively, and to examine their compatibility with established agricultural control methods. We analysed in vitro and in vivo the antagonistic capacity of Paecilomyces variotii against seven phytopathogens with a high incidence in different crops, and we examined its compatibility with 24 commercial fungicides. P. variotii was applied in the following pathosystems: B. cinereal—melon, Sclerotinia sclerotiorum—pepper, R. solani—tomato, F. solani—zucchini, P. aphanidermatum—melon, M. melonis—melon, and P. xanthii—zucchini. The results showed strong control effects on M. melonis and P. xanthii, reducing the disease severity index by 78% and 76%, respectively. The reduction in disease severity in the other pathosystems ranged from 29% to 44%. However, application of metabolites alone did not cause any significant effect on mycelial growth of phytopathogens, apart from F. solani, in which up to 12% inhibition was observed in vitro when the extract was applied at a concentration of 15% in the medium. P. variotii was compatible with most of the tested fungicides, and of the 24 fungicides tested at the maximum authorised dose, 6 acted as fungicides, 4 as fungistatics, and the remaining showed inhibition rates ranging from 18.2% to 95.8%. These results indicate that P. variotii is a potential biological control agent to be used against several aerial and soil diseases, thus it should be integrated into modern pest management strategies.

Screening of genotypes against Alternaria blight of rapeseed-mustard and its fungicidal management

2018 ◽  
Vol 5 (03) ◽  
Author(s):  
HK SINGH ◽  
SUDHAKAR SHUKLA ◽  
JAY KUMAR YADAV ◽  
MANISH KUMAR MAURYA ◽  
KN MAURYA
Keyword(s):  
Disease Management ◽  
Disease Severity ◽  
Field Experiments ◽  
Management Strategies ◽  
Alternaria Brassicae ◽  
Effective Management ◽  
Alternaria Blight ◽  
Maximum Test ◽  
Moderately Resistant ◽  
Disease Free

Alternaria blight is destructive disease of rapeseed- mustard caused by Alternaria brassicae (Berk) Sacc. and A. brassicicola (Schw). The field experiments were conducted during 2013-14 and 2014-15, with 200 genotypes for evaluation of their resistance to Alternaria blight, as well as to develop effective management strategies for this disease. None of the genotypes were found disease free or highly resistant, only 7 genotypes namely (DLSC-1, DRMR-261, DRMR-270, GSC-101, GSL-1, NPC-20 and PHR-2) were found resistant, 15 genotypes were rated as moderately resistant. Rest of the genotypes was either recorded susceptible or highly susceptible.For disease management, newly molecules of 6 fungicides were evaluated with 13 treatments combinations for their effectiveness. Propiconazole 25% EC @ 0.10% was found most effective in reducing the disease severity followed by same fungicide @ 0.05%. It was followed by Hexaconazole 5% SC @ 0.010%. Maximum test weight and yield was also recorded with the sprays of Propiconazole 25% EC @ 0.10% followed by same fungicide @ 0.05%. In comparison to other fungicides, the maximum B:C ratio was recorded with three sprays of Hexaconazole 5% SC @ 0.05% followed by Propiconazole 25% EC @ 0.05%.

Relationships between stripe rust severity and grain yield loss at Dooen, Victoria

1988 ◽  
Vol 39 (4) ◽  
pp. 563 ◽  
Author(s):  
JS Brown
Keyword(s):  
Grain Yield ◽  
Disease Severity ◽  
Stripe Rust ◽  
Growth Stage ◽  
Field Experiments ◽  
Yield Loss ◽  
Rust Severity ◽  
Cent Disease ◽  
The Relationship ◽  
Best Estimator

The relationship between stripe rust severity and grain yield loss in wheat was studied in two field experiments. Wheat cultivars varying in response to the disease were used to produce epidemics of differing severity. Regression models were used to examine the relationship between disease severity and yield loss. The best estimator of yield loss was an estimate of disease severity at the end of anthesis-early berry growth stage. The relationship between per cent yield loss (YL) and per cent disease severity (DS) at that growth stage was established to be YL = 0.479DS + 0.84.

scholarly journals Consequences of Long-Distance Dispersal for Epidemic Spread: Patterns, Scaling, and Mitigation

Plant Disease ◽  
2019 ◽  
Vol 103 (2) ◽  
pp. 177-191 ◽  
Author(s):  
Paul M. Severns ◽  
Kathryn E. Sackett ◽  
Daniel H. Farber ◽  
Christopher C. Mundt
Keyword(s):  
Stripe Rust ◽  
Power Law ◽  
Spatial Scales ◽  
Disease Outbreaks ◽  
Disease Spread ◽  
Epidemic Spread ◽  
Long Distance ◽  
Wheat Stripe Rust ◽  
Scaling Relationships ◽  
Animal Pathogens

Epidemics caused by long-distance dispersed pathogens result in some of the most explosive and difficult to control diseases of both plants and animals (including humans). Yet the factors influencing disease spread, especially in the early stages of the outbreak, are not well-understood. We present scaling relationships, of potentially widespread relevance, that were developed from more than 15 years of field and in silico single focus studies of wheat stripe rust spread. These relationships emerged as a consequence of accounting for a greater proportion of the fat-tailed disease gradient that may be frequently underestimated in disease spread studies. Leptokurtic dispersal gradients (highly peaked and fat-tailed) are relatively common in nature and they can be represented by power law functions. Power law scale invariance properties generate patterns that repeat over multiple spatial scales, suggesting important and predictable scaling relationships between disease levels during the first generation of disease outbreaks and subsequent epidemic spread. Experimental wheat stripe rust outbreaks and disease spread simulations support theoretical scaling relationships from power law properties and suggest that relatively straightforward scaling approximations may be useful for projecting the spread of disease caused by long-distance dispersed pathogens. Our results suggest that, when actual dispersal/disease data are lacking, an inverse power law with exponent = 2 may provide a reasonable approximation for modeling disease spread. Furthermore, our experiments and simulations strongly suggest that early control treatments with small spatial extent are likely to be more effective at suppressing an outbreak caused by a long-distance dispersed pathogen than would delayed treatment of a larger area. The scaling relationships we detail and the associated consequences for disease control may be broadly applicable to plant and animal pathogens characterized by non-exponentially bound, fat-tailed dispersal gradients.

scholarly journals Effect of Application Frequency and Reduced Rates of Acibenzolar-S-Methyl on the Field Efficacy of Induced Resistance Against Bacterial Spot on Tomato

Plant Disease ◽  
2012 ◽  
Vol 96 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Cheng-Hua Huang ◽  
Gary E. Vallad ◽  
Shouan Zhang ◽  
Amin Wen ◽  
Botond Balogh ◽  
...  
Keyword(s):  
Disease Severity ◽  
Untreated Control ◽  
Systemic Acquired Resistance ◽  
Field Experiments ◽  
Acquired Resistance ◽  
Foliar Spray ◽  
Field Trials ◽  
Plant Diseases ◽  
Bacterial Spot ◽  
Field Efficacy

Acibenzolar-S-methyl (ASM), a plant activator known to induce systemic acquired resistance, has demonstrated an ability to manage a number of plant diseases, including bacterial spot on tomato caused by four distinct Xanthomonas spp. The aim of this study was to evaluate application rate and frequency of ASM in order to optimize field efficacy against bacterial spot in Florida, while minimizing its impact on marketable yields. ASM was applied biweekly (once every 2 weeks) as a foliar spray at a constant concentration of 12.9, 64.5, and 129 μM throughout four field experiments during 2007–08. A standard copper program and an untreated control were also included. Overall, biweekly applications of ASM did not significantly reduce disease development or the final disease severity of bacterial spot compared with the copper-mancozeb standard or the untreated control. Only one experiment showed a significant reduction in the final disease severity on plants treated with ASM at 129 μM compared with the untreated control. Three additional field trials conducted during 2009–10 to evaluate the effects of weekly and biweekly applications of ASM at concentrations of 30.3 to 200 μM found that weekly applications provided significantly better disease control than biweekly applications. The tomato yields were not statistically improved with the use of ASM relative to the untreated control and standard copper program. Weekly ASM applications at rates as low as 75 μM (equivalent to 1.58 g a.i./ha in 100 liters of water or 0.21 oz. a.i./acre in 100 gallons of water) to 200 μM (equivalent to 4.20 g a.i./ha in 100 liters of water or 0.56 oz. a.i./acre in 100 gallons of water) were statistically equivalent in managing bacterial spot of tomato without significantly reducing yield compared with the untreated control.

scholarly journals Bacterial Coated Fertilizer Induced Resistance Against Wheat Stripe Rust

2021 ◽  
Vol 2 (2) ◽  
pp. 97-106
Author(s):  
Hasan Riaz ◽  
Zulqurnain Khan ◽  
Syed Shahid Hussain Shah ◽  
Muhammad Yasir Khurshid ◽  
Muhammad Asif Ali
Keyword(s):  
Disease Severity ◽  
Stripe Rust ◽  
Puccinia Striiformis ◽  
Limiting Factors ◽  
Wheat Crop ◽  
Resistant Variety ◽  
Wheat Stripe Rust ◽  
Coated Urea ◽  
Inducing Resistance

Wheat is the second largest consumed cereal by humans after Rice and its high yield and production is very critical for ever increasing global population. The wheat crop is grown all over Pakistan and threatened by several limiting factors. Stripe rust, caused by Puccinia striiformis, is the most destructive wheat pathogen and can reduce yield up to 70% in Pakistan. The present study aimed at exploring the role of Zabardast urea, a bacterial coated urea with zinc,  in inducing resistance against wheat stripe rust. The study involved the collection and maintenance of stripe rust inoculum on Morroco cultivar which later used to inoculate seedlings of Akbar-2019 and Galaxy-2019 resistant and susceptible varieties with three different fertilizer levels viz. specialty fertilizer zabardast urea, plain urea with zinc and plain urea. The results demonstrated the positive role of bacterial coated urea with zinc and reduced the disease severity by 10% and 5% in susceptible and resistant cultivars, respectively, leaving resistant variety asymptomatic. The plain urea with zinc also decreased disease severity in susceptible variety Galaxy-2013 by 6% in comparison with plain urea treatment underlying the role of zinc in combating stripe rust. The study underlines the importance of specialty fertilizers in inducing resistance against stripe rust in wheat and needs further experimentation exploring the mechanisms involved in disease resistance under field conditions.   

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