Biological efficacy of polyoxin D in crop protection

Polyoxin D is purified from the culture broth of actinomycetes and used as an agricultural fungicide. This compound shows antifungal activity against various plant pathogenic fungi, especially Rhizoctonia solani, by inhibiting germination, hyphal growth, and sporulation of the fungi. Its mode of action is thought to be via the competitive inhibition of chitin synthase, which causes incomplete cell wall formation and swelling in germ tubes, hyphae and septa. This action is unique and results in the suppression of diseases in various crops through fungistatic rather than fungicidal activity. Although the polyoxin complex shows not only fungicidal but also insecticidal activity, polyoxin D has less activity against insects, no negative impacts on the environment and is suitable for organic agriculture. Polyoxin D has the potential to control soil-borne and post-harvest diseases and to inhibit mycotoxin production via a new mode of action.