INFLUENCE OF SOME FACTORS ON SUSCEPTIBILITY OF TWELVE VIRULENT ISOLATES OF RALSTONIA SOLANACEARUM TO FIVE NANOPARTICLES

ABSTRACT
Overall objective of the present study was to evaluate presence of pathogenic Ralstonia solanacearum isolates, the causative agent of wilt disease, which isolated from different sources in four Egyptian Goverovernorate. In addition, optimizing the environmental conditions necessary for the antibacterial activities of five nanoparticles In Vitro trials against the isolated pathogen isolates. The results indicated that, the highest bacterial incidence (87.2 %) was detected in the samples of      El-Behira Governorate, while, the lowest (26.7 %) was recorded in samples collected from El- Ismaelia Governorate. Only twelve isolates were virulent and subjected to further studies. The highest severity of disease incidence was recorded with (R9) isolate. Identification of the isolates from soil, irrigation water, tubers and weeds were carried out by immunofluorescent antibody staining of the pathogenic isolates which showed short rod shaped stained as bright green fluorescent in IF test confirmed that these isolates belong to R. solanacearum. Results of Polymerase Chain Reaction (PCR) technique on the twelve isolates, which gave the highest virulence showed that the samples visualize specific 718 bp PCR product under UV light pointing to the very close similarity between the twelve isolates tested of R. solanacearum. No variation could be detected as well in (Taq-Man) determination, Taq-Man is more specific test used to detect races and biovars of R. solanacearum by using reference bacteria (standard known bacterial isolates) and no variation could be noticed among the isolates, confirmed that these isolates belong to race 3 biovar2. Influence of different exposure times, temperature and pH values on R. solanacearum susceptipility to CuO-NPs and MgO-NPs, AgNPs, CsNPs and Ag/CsNC at 200 µg/mL concentration were carried out and the exposure of R. solanacearum to NPs for 2, 3 and 4 days demonstrates their pathogenicity efficacy and all NPs were superior for minimizing growth of R. solanacearum at 35^○C. Also it was found that, Ag/CsNC was more inhibitive for R. solanacearum at low temperature (less than 25^○C) and high temperature (45^○C). Ag/CsNC compeletly inhibited R. solanacearum growth when cultivated in growth medium with pH ranging from 5.6 to 8 than other NPs.