Biocidal proteins capable of isolation from seeds have been characterized. The proteins have an amino acid sequence containing the common cysteine/glycine domain of Chitin-binding Plant Proteins but show substantially better activity against pathogenic fungi, a higher ratio of basic amino acids to acidic amino acids, and/or antifungal activity which results in increased hyphal branching. Antimicrobial proteins isolated from Amaranthus, Capsicum, Briza and related species are provided. The proteins show a wide range of antifungal activity and are active against Gram-positive bacteria. DNA encoding the proteins may be isolated and incorporated into vectors. Plants may be transformed with this DNA. The proteins find agricultural or pharmaceutical application as antifungal or antibacterial agents. Transgenic plants expressing the protein will show increased disease resistance.