Synthetic Pyrazole derivatives as growth inhibitors of some phytopathogenic fungi

The present study was carried out to investigate the antifungal activity of pyrazole/isoxazole-3-carboxamido-4-carboxylic acids, 4-oxo-5-substituted pyrazolo[3,4-d]pyrimidine-6-thiones, and N-alkyl/aryl-N′-(4-carbethoxy-3-pyrazolyl)thioureas against Pythium ultimum, Botrytis cinerea, and Magnaporthegrisea. The results on growth inhibition showed differences in the sensitivity of the threefungi to the tested substances, and in general P. ultimum was shown to be the most sensitive. On allphytopathogens the best results within the pyrazole/isoxazolecarboxamide series are given bythe compounds with the carboxamide and carboxylic groups in positions 3 and 4; the presence ofthese groups seems to be critical for biological activity in this series of compounds. Among thepyrazolopyrimidines the derivative supplied with the benzylic group was the most active on the threefungi and in particular against P. ultimum. Several compounds belonging to the thiourea series areable to inhibit selectively M. grisea at 50 and 10 μg mL-1, doses at which the reference commercialcompound tricyclazole had low or no effect.