Modeling effects of vector acquisition threshold on disease progression in a perennial crop following deployment of a partially resistant variety

Authors: Sisterson, Mark; Stenger, Drake

Submitted to: Plant Pathology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/7/2018
Publication Date: 1/18/2018
Citation: Sisterson, M.S., Stenger, D.C. 2018. Modeling effects of vector acquisition threshold on disease progression in a perennial crop following deployment of a partially resistant variety. Plant Pathology. 67:1388-1400.

Interpretive Summary: Disease management through use of resistant plants is a common goal of plant breeding programs. While resistant plants have lower pathogen titers than susceptible counterparts, arthropod vectors may be able to acquire the pathogen from resistant plants. As vectors move between fields, vectors could acquire the pathogen on farms maintaining resistant plants and then move to farms maintaining susceptible plants. A mathematical model was developed to predict effects of deploying a resistant variety of a perennial crop on disease progression in an area consisting of a mixture of resistant and susceptible varieties. Analytical manipulation of the model identified a vector acquisition threshold; with values of vector acquisition from resistant plants below the threshold, deployment of resistant plants resulted in little pathogen spread to susceptible plants. Acquisition rates from resistant plants can be directly measured by experimentation. Thus, identification of a theoretical threshold provides plant breeders with an estimate of acquisition rates that result in limited pathogen spread from resistant varieties to susceptible varieties.

Technical Abstract: Deployment of resistant varieties is a key strategy to mitigating economic losses due to arthropod-transmitted plant pathogens of perennial crops. Resistant plants have lower pathogen titers than susceptible counterparts, but often remain hosts for the pathogen. As resistant varieties maintain yield after infection, infected plants are unlikely to be rogued. During initial periods of deployment, agricultural landscapes will consist of a mixture of resistant and susceptible varieties and there is a risk that resistant plants could serve as a source of inoculum for pathogen spread to susceptible plants. Here, a coupled differential equation model that tracked spread of an arthropod-transmitted pathogen in a plant population consisting of a mixture of susceptible and resistant varieties was developed. A threshold acquisition rate from resistant plants that resulted in limited spread of the pathogen from resistant plants to susceptible plants was identified. The acquisition threshold from resistant plants varied with parameters influenced by management decisions such as number of vectors per plant, vector turnover, replacement of susceptible plants, and proportion of plants that were resistant. Thus, management decisions will affect acquisition rates from resistant plants that result in limited pathogen spread to susceptible plants. In model simulations, effects of deploying a resistant variety on disease incidence in a susceptible variety depended on the extent to which pathogen spread among susceptible plants was suppressed and acquisition rates from resistant plants. Deployment of a resistant variety that did not serve as an acquisition source generally decreased disease incidence in a susceptible variety, whereas deployment of a resistant variety that served as an acquisition source generally increased disease incidence in a susceptible variety. Collectively, the results indicate that risk of resistant plants serving as an acquisition source could be assessed prior to deployment, thereby enabling design of complementary tactics to minimize economic losses in susceptible varieties following deployment.