The Begomovirus Disease Tetrahedron: Weeds as the Missing Dimension in Virus Epidemiology.

Begomoviruses are among the most destructive plant viruses, causing substantial yield losses across diverse cropping systems. Their epidemiological success is driven by high genetic plasticity, broad host range, and efficient transmission by the whitefly vector Bemisia tabaci. Traditional epidemiological models based on the classical disease triangle (virus-host-vector) fail to fully capture the ecological and evolutionary complexity of begomovirus pathosystems. Increasing evidence highlights the critical role of non-cultivated plants, particularly weeds, as persistent reservoirs that maintain viral populations during off seasons, facilitate recombination, and act as primary inoculum sources for subsequent outbreaks. Here, we propose the Begomovirus Disease Tetrahedron, an integrative framework that expands the disease triangle by incorporating weeds as a fourth essential component. We synthesize current knowledge on begomovirus adaptive evolution, including genome plasticity, noncanonical protein functions, and virus-vector mutualism, alongside key ecological drivers such as seasonal dynamics, agricultural intensification, and landscape connectivity. By integrating molecular, ecological, and epidemiological perspectives, this framework provides a comprehensive understanding of begomovirus emergence and persistence, offering new insights for the development of sustainable and ecologically informed disease management strategies.