Fungicidal activity of the polyamine analogue, keto‐putrescine

The polyamine analogue, keto‐putrescine, was shown to provide substantial control of infections by six economically important plant pathogens, with EC50 values ranging between 57 and 82 mg litre−1. However, keto‐putrescine was relatively less effective in vitro against Phytophthora infestans, Pyricularia oryzae and Pyrenophora avenae, with EC50 values ranging from 145 to 340 mg litre−1. In contrast, the polyamine analogue N‐acetylputrescine had to effect on in‐vitro growth of P. avenae or P. oryzae or infection of barley seedlings with powdery mildew. When P. avenae was grown in the presence of keto‐putrescine, there were small, insignificant reductions in ornithine decarboxylase activity, with more substantial, significant reductions in S‐adenosylmethionine decarboxylase activity. These changes were accompanied by a 43% reduction in spermidine concentration and increased concentrations of spermine and cadaverine.