Mixed infections of <i>Zymoseptoria tritici</i> lead to reduced <scp>STB</scp> disease symptoms

Zymoseptoria tritici is the causal fungus of Septoria blotch (STB), a globally important foliar disease wheat. Infections by more than one strain pathogen, or co-infections, are known to be most prevalent form infection in field. The impact that co-infection Z. has on severity for plant host and its effect defence not fully understood. Here, isolates were extracted from STB-presenting leaves UK sites. Disease assays comparing single-isolate inocula mixed carried out three cultivars wheat, Flame, Stigg Longbow. Leaves infected with found show low symptoms, including lesion pycnidial coverage, compared those single isolates. Growing together liquid media did reveal evidence competition decreased growth inocula. Wheat mixture at least two (of differing aggressiveness) could induce Pr-1 (Pathogenesis-related 1) significantly higher level distal uninfected plants aggressive isolate. Expression was intermediate an isolate (lower expression) less (higher expression). This suggests wheat undergoes systemic “sensitization” during co-infection.