Seed treatment of barley with Idriella bolleyi causes systemically enhanced defence against root and leaf infection by Bipolaris sorokiniana

Inoculation of barley seed with the saprophytic fungus Idriella bolleyi caused systemically improved resistance on both leaves and roots of young plants to subsequent infection with the necrotrophic fungus Bipolaris sorokiniana. Lesion sizes were reduced by up to 50% as a result of the seed treatment. Seed and root inoculation with I. bolleyi induced biochemical defence responses in the plants as shown by slight accumulation of pathogenesis-related (PR) proteins, but the accumulation was not as great as when the roots were inoculated with B. sorokinina. Conidia of I. bolleyi applied to seed survived well during storage, with no significant reduction in colony forming units (CFUs) occurring at 15degreesC after 2 months. However, storage at 28degreesC decreased the viability of the applied conidia. The fungus colonized the seed and roots during Weld conditions as indicated by high numbers of CFUs. Two months after sowing, frequencies of I. bolleyi were higher on plants treated with the fungus than on control plants where colonization occurred naturally from Weld soil. The implications of the results are discussed in relation to earlier reports of biological control of cereal root diseases by I. bolleyi and induced resistance.