Mathematical Models of Cross Protection in the Epidemiology of Plant-Virus Diseases

Mathematical models of plant-virus disease epidemics were developed where cross protection occurs between viruses or virus strains. Such cross protection can occur both naturally and through artificial intervention. Examples of diseases with continuous and discontinuous crop-host availability were considered: citrus tristeza and barley yellow dwarf, respectively. Analyses showed that, in a single host population without artificial intervention, the two categories of host plants, infected with a protecting virus alone and infected with a challenging virus, could not coexist in the long term. For disease systems with continuous host availability, the virus (strain) with the higher basic reproductive number (R0) always excluded the other eventually; whereas, for discontinuous systems, R0 is undefined and the virus (strain) with the larger natural transmission rate was the one that persisted in the model formulation. With a proportion of hosts artificially inoculated with a protecting mild virus, the disease caused by a virulent virus could be depressed or eliminated, depending on the proportion. Artificial inoculation may be constant or adjusted in response to changes in disease incidence. The importance of maintaining a constant level of managed cross protection even when the disease incidence dropped was illustrated. Investigations of both pathosystem types showed the same qualitative result: that managed cross protection need not be 100% to eliminate the virulent virus (strain). In the process of replacement of one virus (strain) by another over time, the strongest competition occurred when the incidence of both viruses or virus strains was similar. Discontinuous crop-host availability provided a greater opportunity for viruses or virus strains to replace each other than did the more stable continuous cropping system. The process by which one Barley yellow dwarf virus replaced another in New York State was illustrated.

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Estimating Yield Losses Due to Barley Yellow Dwarf on Winter Wheat in Kansas Using Disease Phenotypic Data

Plant Health Progress ◽

10.1094/php-rs-14-0039 ◽

2015 ◽

Vol 16 (1) ◽

pp. 1-6 ◽

Cited By ~ 9

Author(s):

Genna M. Gaunce ◽

William W. Bockus

Keyword(s):

Winter Wheat ◽

Yield Loss ◽

Disease Incidence ◽

Relative Yield ◽

Yellow Dwarf ◽

Wheat Cultivars ◽

Grain Yields ◽

Barley Yellow Dwarf ◽

Winter Wheat Cultivars ◽

The Impact

Barley yellow dwarf (BYD) is one of the most important wheat diseases in the state of Kansas. Despite the development of cultivars with improved resistance to BYD, little is known about the impact that this resistance has on yield loss from the disease. The intent of this research was to estimate yield loss in winter wheat cultivars in Kansas due to BYD and quantify the reduction in losses associated with resistant cultivars. During seven years, BYD incidence was visually assessed on numerous winter wheat cultivars in replicated field nurseries. When grain yields were regressed against BYD incidence scores, negative linear relationships significantly fit the data for each year and for the combined dataset covering all seven years. The models showed that, depending upon the year, 19–48% (average 33%) of the relative yields was explained by BYD incidence. For the combined dataset, 29% of the relative yield was explained by BYD incidence. The models indicated that cultivars showing the highest disease incidence that year had 25–86% (average 49%) lower yield than a hypothetical cultivar that showed zero incidence. Using the models, the moderate level of resistance in the cultivar Everest was calculated to reduce yield loss from BYD by about 73%. Therefore, utilizing visual BYD symptom evaluations in Kansas coupled with grain yields is useful to estimate yield loss from the disease. Accepted for publication 1 December 2014. Published 9 January 2015.

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Yield Loss Assessment of Barley Yellow Dwarf Disease on Spring Oat in Illinois

Plant Disease ◽

10.1094/pdis.1997.81.5.485 ◽

1997 ◽

Vol 81 (5) ◽

pp. 485-488 ◽

Cited By ~ 4

Author(s):

Ellen M. Bauske ◽

Suzanne M. Bissonnette ◽

Adrianna D. Hewings

Keyword(s):

Yield Loss ◽

Barley Yellow Dwarf Virus ◽

Disease Incidence ◽

Rhopalosiphum Padi ◽

Maximum Yield ◽

Quantitative Relationship ◽

Yellow Dwarf ◽

Loss Assessment ◽

Barley Yellow Dwarf ◽

Yellow Dwarf Virus

The quantitative relationship between yield of spring oat cvs. Ogle and Noble and incidence of barley yellow dwarf (BYD) disease caused by barley yellow dwarf virus (BYDV-PAV-IL) was studied. Field plots were infested with Rhopalosiphum padi vectoring BYDV-PAV-IL. A linear critical point regression model was developed that related percentage of maximum yield to BYD incidence, assessed by estimating the percentage of plants with BYD symptoms at Feekes growth stage 10.5 in each plot. The model y = 96.9 - 0.45x (r2 = 0.53) best explained the relationship. Test weight was unaffected by BYD. Although Noble consistently sustained higher disease incidence than Ogle, covariate analysis indicated that the effect of BYD on yield was similar for both cultivars. Studies of random versus focus inoculation of Noble oat, designed to determine the importance of compensation in reducing yield loss associated with BYD, indicated that compensation did not play an important role.

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