Foliar pathogenic fungi: growing threats to global food security and ecosystem health

Globally, foliar pathogenic fungi cause serious losses of annual and perennial crops, ornamentals, landscape plants and forest trees. Plant pathogens that infect foliage are a diverse assemblage of fungi representing both phyla: Ascomycota and Basidiomycota. Although most of the species found on living leaves have been well studied by mycologists and plant pathologists, recent studies have remarkably enhanced the current understanding of species numbers and their evolutionary relationships. The impact of global climate change, the increasing international exchange of plant material and the lack of proper phytosanitary practices have resulted in the potential re-emergences of formerly known destructive fungi, infecting new hosts in new geographic locations. Routinely inspecting diseased plants and accurately identifying and naming causative agents are vital for mitigating the impact of invasive and other non-indigenous pathogens on crops and native flora. It is also necessary to characterise foliar pathogenic fungi based on molecular phylogeny, morphology, pathogenicity and the comparative analysis of fungal genomic data. This review provides an overview of prevalent groups of foliar pathogenic fungi, their diversity and economic impact, while emphasising emerging and destructive species that threaten global food security and ecosystem health.