Inhibition of fungal growth by plant growth retardants

Abstract

Ancymidol, Amitrole, and Phosphon-D, three plant growth retardants known to interfere with isoprenoid synthesis in plants, were found to be fungitoxic. Of nine fungi tested, five were highly sensitive to ancymidol (concentration required to cause 50% inhibition of mycelial growth (ED50) less than 50 mg/L) and a different set of five was highly sensitive to Amitrole. Ancymidol was more toxic than Captan to Fiisarium graminearum and at a concentration of 100 mg/L prevented growth of Bipolaris sorokiniana from infected barley seed. Phosphon-D inhibited growth of seven fungi by 50% at concentrations less than 300 mg/L. Since the isoprenoid pathway occurs in a wide range of organisms and generates many metabolically important compounds it is suggested that commercially available chemicals which inhibit this pathway, whether they be used as herbicides, plant growth regulators, insecticides, fungicides, etc., may be broad-spectrum biocides.