Wheat is vulnerable to fungal maladies, known as septoria-blotch diseases, that reduce the ability of the plants' leaves to carry out photosynthesis. For reasons unknown, the relative roles played by the two fungi that cause these diseases—Phaeosphaeria nodorum and Mycosphaerella graminicola—vary from country to country and from decade to decade.
To examine possible factors behind these variations, plant pathologist Bart A. Fraaije of Rothamsted Research in Harpenden, England, and his colleagues tested a library of wheat samples grown on a British farm and archived for most years since 1843. For each year, the team identified which pathogen's DNA was more plentiful.
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