Assessment of antimicrobial potential of iron on phytopathogenic isolates of Nocardia sp. and their effect on tobacco false broomrape symptom expression

Abstract

Tobacco crop is affected by false broomrape caused by phytopathogenic isolates belonging to the Nocardia genus, present in the soil. Both persistence and incidence levels of its causal agent are lower in soils with red to reddish tonalities. These tones are associated with the presence of oxidized iron forms. The aim of this research was to assess the antimicrobial potential of different chemical forms of iron on phytopathogenic isolates of Nocardia sp., and evaluate its effect on the symptom expression of false broomrape in tobacco plants. Susceptibility to iron salts of four isolates was assessed in vitro by the minimal inhibitory concentration test. In in vivo experiments, soil inoculated with phytopathogenic isolates was treated with FeSO4.7H2O and symptom expression of false broomrape was evaluated as the average degree of affection, which considers grades of growth of tumours and buds developed on roots. We found that phytopathogenic isolates from four tobacco areas of Cuba with high incidence of the disease showed in vitro susceptibility to free iron in its oxidized forms of Fe+2 and Fe+3. It was shown that the application of 1000 ppm of FeSO4.7H2O on the roots of tobacco seedlings and in the soil where they were transplanted reduces expression of the symptoms of false broomrape.