The inventors provide the use of a chelating agent and an antimicrobial agent that is effective against a plant pathogenic microorganism to inhibit the growth of and/or kill a plant pathogenic microorganism on a plant； the use of a chelating agent to increase the activity of an antimicrobial that is effective against a plant pathogenic microorganism； a method of inhibiting the growth of and/or killing a plant pathogenic microorganism comprising administering to a plant in need thereof a chelating agent and an antimicrobial agent that is effective against a plant pathogenic microorganism； and a method of increasing the activity of an antimicrobial that is effective against a plant pathogenic microorganism comprising using said antimicrobial with a chelating agent. Also provided is a composition comprising a chelating agent and an antimicrobial agent that is effective against a plant pathogenic microorganism, use of said composition to inhibit the growth of and/or kill a plant pathogenic microorganism on a plant, and a method of inhibiting the growth of and/or killing a plant pathogenic microorganism comprising administering to a plant in need thereof said composition. Further provided is the use of a composition comprising an antimicrobial polypeptide comprising Blad or an active variant thereof to kill, or inhibit the growth of a plant pathogenic bacterium on a plant, and a method of killing, or inhibiting the growth of a plant pathogenic bacterium on a plant, said method comprising administering to said plant a composition comprising an effective amount of an antimicrobial polypeptide comprising Blad or an active variant thereof.本発明者らは、植物上で植物病原性微生物の増殖を阻害する、および／またはそれを殺滅するための、キレート剤および植物病原性微生物に対して効果的である抗微生物剤の使用；植物病原性微生物に対して効果的である抗微生物剤の活性を増加させるためのキレート剤の使用；それを必要とする植物にキレート剤および植物病原性微生物に対して効果的である抗微生物剤を投与するステップを含む、植物病原性微生物の増殖の阻害および／または殺滅方法；ならびに抗微生物剤をキレート剤とともに用いるステップを含む、植物病原性微生物に対して効果的である抗微生物剤の活性の増加方法を提供する。キレート剤および植物病原性微生物に対して効果的である抗微生物剤を含む組成物、植物上で植物病原性微生物の増殖を阻害する、および／またはそ
