Significant ultrastructure changes in Ralstonia solanacearum cells were observed using transmission electron microscope (TEM) after exposure to extremely low frequency (ELF) electromagnetic (EM) (1 Hz QAMW for 1 h) as well as DNA mutations and genetic alterations using RAPD PCR technique were detected. TEM was used to examine the changes in R. solanacearum cells exposed to 1 Hz QAMW (quantitative amplitude modulated waves) for 1 h in which elongation, deformation, heterogeneous appearance of cytoplasm disruption, disintegration of cell wall and retraction of cytoplasmic membrane were observed. Three of five RAPD PCR primers screened showed the appearance of new bands at 600, 450 and 550bp in the RAPD patterns for primers, P2, P3 and P4, respectively, after the exposure of R. solanacearum to 1 Hz QAMW. Potato tubers were kept immersed, for 30 minutes at room temperature, in bacterial suspension that exposed to QAMW at resonance frequency of growth inhibition then dried for 10 minutes and planted under greenhouse
conditions. Symptoms of wilt disease did not appear on plants treated with exposed bacteria compared with those treated with non-exposed. Although, the tubers of plants treated by exposed bacteria were small compared with healthy one, the disease did not appear in these tubers. The results indicated that, extremely low frequency of electromagnetic field modifies the cell structure and the DNA sequences which could inhibit the growth of R. solanacearum and affect the pathogenicity of the microbe.