Plant Fungal and Related Maladies
In the realm of plant diseases, fungi and fungal-like organisms (FLOs) have proven to be a formidable force, causing more plant diseases than any other group of plant pests. With over 8,000 species shown to cause disease, these microscopic organisms have left an indelible mark on agriculture and ecosystems throughout history.
One of the most infamous examples is the late blight of potatoes and tomatoes, caused by the oomycete (fungal-like organism) Phytophthora infestans. This notorious pathogen was responsible for the Irish Potato Famine in the 1840s, causing the death of more than 1 million people by starvation and initiating one of the largest human migrations on the planet.
Another significant example is gray mold disease, caused by the fungus Botrytis cinerea. This pathogen affects over 200 crop species worldwide and has historically caused billions of dollars in losses. Recent research has revealed its evolution in response to pesticide use and farming practices.
Black scurf disease, caused by the fungus Rhizoctonia solani AG-3 on potato, is another disease that has extended its geographic presence, with recent reports in Ecuador. Root rot disease, caused by fungi such as Alternaria tenuissima and Phytopythium vexans, also poses a significant threat to various plants.
Historically, Dutch elm disease, caused by the fungus Ophiostoma ulmi and related species, devastated elm tree populations globally in the 20th century. Wheat rusts, such as stem rust caused by Puccinia graminis, have caused severe crop losses historically and continue to challenge global wheat production.
Planting disease-free certified seed, implementing crop rotation strategies, maintaining a balanced fertility program, and growing crops in climates unsuitable for pathogenic fungi and FLOs are cultural practices for managing these diseases. Careful handling of the crop during harvest, transit, and storage, and the use of biological control organisms are also key strategies.
Fungicide applications are often essential for managing diseases caused by fungi and FLOs. Soil pasteurization is another method for managing these diseases. The implementation of strict quarantines that exclude or restrict the introduction or movement of fungal and FLO pathogens or infected plant material is a regulatory measure for managing diseases caused by these organisms.
Some beneficial fungi, such as those belonging to the genus Trichoderma, are effective biocontrol agents of plant pathogenic fungi. Notable examples of genetically resistant plants include certain hybrid potato cultivars resistant to late blight, soybean cultivars resistant to downy mildew, apple cultivars resistant to apple scab, and wheat cultivars resistant to stem rust.
The genus Phytophthora was named by Anton de Bary in 1876 as "plant destroyer." Fungi and FLOs obtain nutrients by absorption through tiny thread-like filaments called hyphae. They can penetrate a host via a wound or natural opening, but they can also actively penetrate via the production of specialized hyphal structures called appresoria.
These examples illustrate the broad impact fungi and FLOs have had on agriculture and ecosystems, causing large-scale food production challenges and prompting ongoing research into pathogen evolution and sustainable disease management strategies.
[1] Research Reviving 80-Year-Old Strains of Botrytis cinerea Reveals Its Evolution in Response to Pesticide Use and Farming Practices. (2020). Scientific Reports.
[3] Evolution of Botrytis cinerea in Response to Selection by Pesticides. (2019). Molecular Plant Pathology.
[5] Fungal and Fungal-Like Pathogens of Plants. (2019). Annual Review of Phytopathology.
