A timeline of destruction and discovery: 180 years of “plant destroyer” research

A microscopic “plant destroyer” not only helped trigger one of the deadliest famines in modern history but also reshaped global agriculture and gave birth to an entirely new scientific discipline. Now, nearly 180 years after the Irish Potato Famine devastated Ireland and altered the course of human history, researchers are tracing the remarkable scientific journey of the organism behind it: Phytophthora infestans and the larger genus, Phytophthora.

In a new feature article published in Plant Disease, researchers Z. Gloria Abad and Jorge A. Abad present a comprehensive 180-year timeline of the taxonomy and identification of Phytophthora species. The review explores how scientists progressed from early theories about mysterious crop failures in the 1840s to today’s advanced genomic technologies capable of decoding entire pathogen genomes.

The genus Phytophthora—whose name literally means “plant destroyer”—contains 261 species and includes some of the world’s most destructive plant pathogens. These organisms attack crops, forests, ornamental plants, and natural ecosystems, causing billions of dollars in annual agricultural losses and threatening global food security. The best-known species, Phytophthora infestans, was the causal pathogen behind the Irish Potato Famine between 1845 and 1852, when approximately 1.5 million people died and another 1.5 million emigrated due to starvation.

Abad and Abad recount how pioneering scientists such as Miles Joseph Berkeley and Heinrich Anton de Bary helped establish the science of plant pathology by demonstrating that microorganisms could cause plant disease. Their work transformed scientific thinking and laid the foundation for modern disease diagnosis and crop protection.

The article also highlights the dramatic technological evolution in identifying Phytophthora species. For more than a century, researchers relied primarily on morphology to distinguish species. However, since 2000, DNA sequencing and high-throughput genomic technologies have revolutionized the field. The review also presents information of mayor international taxonomic resources and updates data from the "Revision of Phytophthora" (Abad et al. 2023) including databases from 212 to 261 species and emphasizes the importance of “ex-type” cultures, the original reference specimens used to define species identities.

“This timeline of 180 years of the taxonomy and identification of Phytophthora is truly fascinating,” the authors noted. “There were many challenges, but also many important technological contributions that have cemented Phytophthora as a solid and unique genus of plant pathology.”

The authors also revisit a long-running debate over the geographic origin of P. infestans. While some 20th-century researchers argued for a Mexican origin, the review discusses historical and modern evidence supporting the Peruvian Andes as the pathogen’s center of origin, including recent genomic studies involving more than 1,700 pathogen genotypes from around the world.

By documenting the evolution of Phytophthora research from early microscopy to whole-genome sequencing, the article demonstrates how advances in science continue to strengthen global efforts to monitor, identify, and manage destructive plant diseases. The review also carries a personal dimension for the authors, who recently retired after nearly 5 decades working in plant pathology. Gloria and Jorge Abad acknowledge the many researchers who contributed to the field over generations.

To learn more, read “Phytophthora: Timeline of Taxonomy and Identification From Plant Pathology’s Origin to Molecular Technologies”—freely available in Plant Disease.

About Plant Disease

Published by The American Phytopathological Society, Plant Disease is the leading international journal for rapid reporting of research on new, emerging, and established plant diseases. The journal publishes papers that describe translational and applied research focusing on practical aspects of disease diagnosis, development, and management in agricultural and horticultural crops.