Sensitivity of Barley Leaves and Roots to Fusaric Acid, but not to H2O2, Is Associated with Susceptibility to Fusarium Infections

Fusarium head blight and rot root are among the most devastating plant diseases in modern agriculture. The causal pathogen, Fusarium spp., reduces plant yield and food quality in part because of mycotoxins, suggesting that breeding for resistance to Fusarium is an important control strategy. A simple and low-cost tactic in plant resistance breeding is testing the cultivars for their sensitivity to fungal metabolites and secretion products. We analysed barley cultivars with differential resistance to Fusarium culmorum KF350 for their sensitivity to 5-butylpicolinic acid [syn. fusaric acid (FA)], a product synthesized by Fusarium isolates of the Liseola section of the Gibberella fujikuroi species complex. We found similar sensitivity of first and second leaves of the cultivars to KF350 and to FA, as well as to head blight in the literature. Upon FA treatment, more resistant cultivars, Jolante and Chevron, compared with susceptible cultivars, Carola and Uschi, showed less necrosis and ion leakage in primary leaves and roots, suggesting that FA can possibly be used in breeding programs as a screening compound for improved cultivars. Importantly, sensitivity to H2O2 was not correlated with resistance to KF350 although it accumulated at penetration sites and in lesions associated with Fusarium infection in all cultivars.