When Does Spatial Diversification Usefully Maximize the Durability of Crop Disease Resistance?

Area of Science:

• Agricultural Epidemiology
• Plant Pathology
• Evolutionary Biology

Background:

• Maximizing crop disease resistance gene durability is crucial due to pathogen evolution.
• Spatial diversification of resistance genes (mixing susceptible and resistant fields) is hypothesized to reduce epidemic intensity.
• Understanding factors influencing this spatial effect is key for cost-effective strategies.

Purpose of the Study:

• To model the impact of spatial arrangement of resistant and susceptible fields on landscape-scale disease dynamics.
• To investigate how pathosystem parameters influence the effectiveness of spatial diversification.
• To identify conditions where spatial diversification is most cost-effective.

Main Methods:

• Developed a multiseason, semidiscrete epidemiological model.
• Tracked spatial spread of wild-type and resistance-breaking pathogen strains.
• Incorporated localized inoculum reservoirs and within/between-field transmission.

Main Results:

• Spatial diversification's effectiveness depends on pathogen dispersal, fitness costs of resistance-breaking strains, resistance efficacy, and timeframe.
• The strongest beneficial effect occurs at intermediate fitness costs of resistance-breaking traits.
• If resistance-breaking strains have low fitness, spatial diversification can paradoxically worsen epidemics.

Conclusions:

• Spatial diversification is a promising strategy for durable disease resistance, but its efficacy is context-dependent.
• Intermediate fitness costs for resistance-breaking pathogens maximize the benefits of spatial diversification.
• Further research should integrate genetic factors and landscape dynamics for pathosystem-specific evaluations.