Abstract
Enterobacter cloacae SM10, which is an endophytic bacterium with the potential to suppress Fusarium wilt of spinach, produces indole-3-acetic acid (IAA) via indole-3-pyruvic acid. The effects of IAA production on disease suppression were studied. The strain SM10R, a spontaneous rifarapicin-resistant mutant of SM10, was used as the parental strain. The IAA-deficient mutant SM10RK was constructed by marker exchange mutagenesis, which introduced the kanamycin-resistance gene into the indolepyruvate decarboxylase gene of SM10R. SM10R significantly suppressed the disease incidence and severity, whereas SM10RK did not reduce the disease symptoms. These results suggested that IAA production in SM10 was essential for the suppression of Fusarium wilt of spinach.
