QUANTITATIVE STRUCTURE-ACTIVITY-RELATIONSHIPS OF FLUAZINAM AND RELATED FUNGICIDAL N-PHENYLPYRIDINAMINES - PREVENTIVE ACTIVITY AGAINST SPHAEROTHECA-FULIGINEA, PYRICULARIA-ORYZAE AND RHIZOCTONIA-SOLANI

Quantitative structure-activity relationships (QSAR) analyses of fungi cidal activity of 3-chloro-2[N-(3-substituted-2, uoromethylphenyl)]ami no-5-trifluoromethylpyridines against Sphaerotheca fuliginea, Pyricula ria oryzae and Rhizoctonia solani were carried out and the results wer e compared. In the case of S. fuliginea, a usual QSAR equation with Ha mmett's electronic parameter (sigma(m)) and hydrophobicity (pi) was ob tained, suggesting that the uncoupling mechanism might be involved in the mode of action. In the cases of P. oryzae and R. solani, QSAR equa tions were consisted of sigma(m), pi and the activity rank against Bot rytis cinerea as independent variables, indicating both of uncoupling and SH-inhibition were working in the action mechanism. Molecular orbi tal calculations clarified that the charge delocalization coupled with structural relaxations of the torsion angles between the C-N-C plane and the benzene and pyridine rings were responsible for strong acidity of fluazinam even in the less polar environment, which was reported a s an important feature of shuttle-type uncoupling mechanism. More than one mode of action may be working behind the broad fungicidal spectru m of fluazinam.