Abstract

The ability of benzothiadiazole (BTH), humic acid (HA) and their combination when used in seed soaking to induce systemic resistance against a pathogenic strain of Fusarium oxysporum was examined in four soybean cultivars under greenhouse conditions. Both inducers and their combination were able to protect soybean plants against damping-off and wilt diseases compared with check treatment. These results were confirmed under field conditions in two different locations that is, Minia and New Valley governorates, Egypt. The tested treatments significantly reduced damping-off and wilt diseases and increased growth parameters, except number of branches plant^-1, and seed yield. Application of BTH (0.25) + HA (4 g/L) was the most potent in respect to this treatment. Soybean seed soaking in BTH+HA recorded the highest activities of oxidative enzymes followed by BTH in four soybean cultivars. Whereas, HA treatment recorded the lowest increase of these oxidative enzymes. Also, similar results were obtained in case of total phenol but HA increased the total phenol more than BTH in all tested cultivars.

Key words: Induce systemic resistance, soybean, wilt disease, benzothiadiazole (BTH), humic acid (HA).