ABSTRACT

The study was aimed at evaluating the antimicrobial activities of iron oxide and magnesium oxide nanoparticles against Helminthosporium heveae isolated from diseased rubber leaves. Green synthesis of iron oxide and magnesium oxide nanoparticles was done using extracts from Azadirachta indica and Moringa oleifera, respectively. The biologically-synthesized nanoparticles were characterized using Vis-spectrophotometer. H. heveae was isolated from diseased rubber leaves collected from Iyanomo, 6°36’0”N 5°29’0”E and Akwette, 4°53’14”N 7°21’26”E in Nigeria. Morphological identification was carried out by employing macroscopy and microscopy. In vitro antimicrobial activities of the biologically-synthesized nanoparticles were evaluated using the poison plate and agar well diffusion methods. Different concentrations (25%, 50%, 75% or 100%) of each nanoparticles were tested, and ketoconazole (antifungal agent) was used as a control. Zones of inhibition was observed and recorded. The results obtained from this research showed that iron oxide nanoparticles at a concentration of 100 % had the highest inhibitory effect on both isolates. Iron oxide nanoparticle had an average zone of inhibition value of 0.57±0.04 for the isolate obtained from Iyanomo, while 0.7±0.02 was recorded for isolate obtained from Akwette. However, biologically-synthesized magnesium oxide nanoparticle had no significant antimicrobial effect on both the test isolates. The findings obtained from this study revealed that biologically-synthesized iron oxide nanoparticles from Azadirachta indica had great potential in their use as an antifungal substance against H. heveae. The future direction to this study is to investigate the potential of using iron oxide nanoparticles in crop protection against H. heveae that causes a great threat to the growth and production of rubber.