The invention relates to novel RacB cDNA sequences from barley and to expression cassettes and vectors comprising these promoter sequences. The invention furthermore relates to transgenic plants transformed with these expression cassettes or vectors, to cultures, parts or transgenic propagation material derived from them, and to their use for the production of foodstuffs, feeding stuffs, seed, pharmaceuticals or fine chemicals. The invention furthermore relates to methods of generating or increasing a pathogen resistance in plants by reducing the expression of an RacB protein or of a functional equivalent thereof.