Research explores "arms race" between potatoes and pathogens post Irish potato famine

North Carolina State University researchers conducted a study involving genetic material from historic potato leaves, shedding light on the evolutionary dynamics between potato plants and the pathogen responsible for the Irish potato famine of the 1840s. Utilizing a targeted enrichment sequencing approach, the study analyzed both the plant's resistance genes and the pathogen's effector genes simultaneously, presenting a novel methodology.

To elucidate the genetic interactions, small fragments of historic leaves containing the pathogen and other bacteria were utilized. Allison Coomber, the lead author and former graduate student researcher at NC State, explained that short DNA fragments were employed as "magnets" to isolate similar genetic sequences amid the complex DNA mixture. This technique enabled the identification of both the plant's resistance genes and the pathogen's effector genes.

Unlike previous studies that focused on either the potato or the pathogen alone, the dual enrichment approach allowed researchers to study both entities concurrently. Jean Ristaino, corresponding author of a paper in Nature Communications and William Neal Reynolds Distinguished Professor of Plant Pathology, emphasized how technological advancements, such as genome sequencing, played a crucial role in making this pioneering study possible.

One significant finding of the study is that the pathogen, Phytophthora infestans, possesses a remarkable ability to overcome the potato's resistance to late blight disease. The FAM-1 strain of the pathogen demonstrated the capability to defeat the plant's R1 resistance gene, even before its deployment in cultivated potatoes. Coomber attributes this resistance to prior exposure of the pathogen in the wild to potatoes hosting the same resistance gene.

Furthermore, the research highlights the stability of many effector genes within the pathogen, albeit with different mutations enhancing its infectivity as plant breeders sought resistance. Notably, between 1845 and 1954, the pathogen acquired additional chromosomes, as demonstrated by the plant samples collected during this period.

The study's implications extend to plant breeding practices. With an improved understanding of effector gene alterations over time, breeders may select more stable resistance genes or combine multiple resistance genes from diverse wild hosts. Ristaino believes that this approach holds promise for studying and managing changes affecting pathogen virulence and traits such as fungicide resistance.

In conclusion, this comprehensive study provides valuable insights into the ongoing evolutionary "arms race" between potatoes and pathogens, paving the way for improved plant breeding practices and enhanced disease management strategies. By unraveling the genetic complexities involved, researchers strive to mitigate the impact of pathogens on potatoes and advance sustainable agriculture practices.

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