In 19th century Ireland, a devastating disaster struck—an event that led to the deaths of around 1 million people. This catastrophe was tied to a potato disease, commonly linked to the Irish famine. However, there has been ongoing debate about where this pathogen originated.
Scientists have been divided on whether the culprit, a fungus-like organism known as Phtytophthora infestans, first appeared in the Andes of South America or in Mexico. Recently, a team of researchers claims to have resolved this debate. Their study involved a thorough analysis of the microbe’s genome and its relatives, leaning toward a South American origin.
Professor Jean Ristaino from North Carolina State University, a co-author of the research, emphasized that science is a process of questioning and testing hypotheses. The genetic data strongly indicates that the blight’s ancestry is linked to the Andes, aligning with historical accounts. In 1845, when the blight emerged, there were reports of the disease already existing among indigenous Andean potato growers.
Though Ristaino acknowledges that discussions may continue, she believes the wealth of data gathered makes it hard to dispute this finding.
In their paper published in the journal Plos One, Ristaino and her team detailed their findings, noting that the Mexican strains of the potato blight pathogen appeared to be more recent compared to those from South America. They observed a complex interplay among modern populations of the microbe, suggesting that strains from Mexico, the Andes, and Europe have mingled in recent times. However, they found that the oldest lineage does not originate from Mexico, contradicting the idea that it is the center of origin.
Potato blight remains a significant concern today. Ristaino highlighted that fungicide-resistant strains are present in Europe, forcing farmers to seek alternative chemical solutions. Research into breeding and gene-editing potatoes may offer long-term solutions, but the problem persists globally, particularly in developing regions of Africa, South America, and parts of England.
Understanding where potato blight started is vital. Ristaino explained that identifying the origin helps locate resistance to the disease. Ultimately, managing potato blight will hinge on breeding resistant varieties, with a focus on the genetic resources found in the Andes.
Dr. David Cooke from the James Hutton Institute, an expert on potato blight, praised the research. The ongoing debate about the pathogen’s origins is compounded by differences in how South American and Mexican populations reproduce. The South American strains reproduce mostly asexually, while the Mexican ones reproduce sexually, leading to greater genetic diversity. Cooke suggests that what’s really needed is a study in South America to find evidence of sexual reproduction in local populations, which could confirm a true center of origin.
