Abstract
Phytopathogenic fungi are serious threats to fruit and vegetable production. Use of plant essential oil (PEO), as antifungal agents, have been in practice for many years. Essential oils (EO) of five plants i.e., Trachyspermum ammi, Cuminum cyminum, Azadirachta indica, Citrus sinensis and Eucalyptus grandis were tested against Alternaria solani in tomato. The trials consisted of laboratory testing (MIC and MFC), field testing and Computer Aided Fungicide Design (CAFD) of PEOs against A. solani. Each PEO was used at 10 and 25 µl/ml concentrations to asses MIC, while MFC was assessed at 25, 50 and 75µl/ml concentration. Trachyspermum ammi EO at 25µl/ml concentration showed the largest inhibition zone (37.3 mm) followed by a not significantly different zone(20.6 mm)produced by C. cyminum EO. No fungal growth was observed at 50µl/ml concentration of T. ammi while, at 75µl/ml for A. indica and C. cyminum. In foliar application, T. ammi EO showed lowest percent disease incidence (2.2) which was not significantly different from that of C. cyminum. Trachyspermum ammi EO, qualified in laboratory and field trials, was selected for CAFD. Compounds of T. ammi PEO docked against toxin producing enzyme, solanapyrone synthase, of A. solani. Terpinen-4-ol was qualified as a lead compound against A. solani.