Biology, diversity, detection and management of Plasmopara viticola causing downy mildew of grapevine (Vitis spp.)

Grapevine downy mildew is a devastating disease that wreaks havoc on grapevines (Vitis vinifera L.) worldwide. The causal organism of this disease is Plasmopara viticola, a diploid obligate biotrophic oomycete native to North America. This pathogen has swiftly spread to grape-growing regions across the globe, particularly those blessed with warm, humid climates. Plasmopara viticola possesses a flexible mating system, employing both sexual and asexual means to propagate its lineage. Plasmopara viticola life cycle involves the production and dispersal of zoospores for grapevine infection. Zoospores produced within sporangia are released by rain or wind and swim in free water on the grapevine surface. They are attracted to stomata, where they encyst, germinate, and penetrate the host tissue. A substomatal vesicle develops, giving rise to intercellular mycelium. Under favorable conditions (warm, humid nights), sporulation occurs. Sporangiophores emerge through stomata, bearing sporangia that produce new zoospores. These zoospores are then dispersed by wind and rain to initiate new infection cycles on grapevine tissues. Meanwhile, P. viticola's resilience is further enhanced by its ability to produce thick-walled oospores, which can overwinter in infected leaf debris, ready to unleash a fresh wave of destruction in the following spring. Downy mildew's destructive reach extends to all green tissues of grapevines, leaving a trail of devastation in its wake. Infection of leaves cripples photosynthetic efficiency, leading to a decline in grape quality. The infection of inflorescences and berries directly translates into yield losses. The current mainstay of downy mildew control is a heavy reliance on fungicide treatments. However, this approach is riddled with drawbacks, including exorbitant expenses, potential threats to human health, environmental contamination, and the inevitable emergence of fungicide resistance. In light of these shortcomings, researchers are actively exploring alternative, ecologically sound strategies to curb downy mildew's rampage, aiming to strike an integrated disease management balance between effective disease control and environmental stewardship. This comprehensive review provides in-depth insights into P. viticola, encompassing its taxonomy, host-pathogen interactions, symptoms, economic impact, epidemiology, distribution, infection mechanisms, and control strategies, with a strong focus on sustainable methods.