Fusarium oxysporum f. sp. radicis-lycopersici can Induce Systemic Resistance in Barley Against Powdery Mildew

Drench inoculation of the undisturbed roots of barley seedlings with Fusarium oxysporum f. sp. radicis-lycopersici (FORL) significantly reduced the primary infection frequency of Blumeria graminis f. sp. hordei (BGH) on the first leaves. The length of secondary hyphae and subsequent conidial production of BGH were also found to be significantly reduced by preinoculation with FORL. The reduction in infection frequency was observed as early as 48 h after inducer treatment, namely when plants were challenge-inoculated immediately following inoculation with FORL. The induced resistance continued up to 16 days after treatment as indicated by the reduction in infection frequency, up to 22 days after treatment when evaluated as a reduction in the length of secondary hyphae, and up to 35 days after treatment when evaluated as a reduction in conidial production. Characteristics of FORL that may explain its success as an inducer of resistance against barley powdery mildew are discussed.