In vitro Effect of Alum on Microbes Associated with Foliar Phytoplasma Disease of Noni

Abstract

Foliar phytoplasma disease of Noni (Morinda citrifolia) has a devastating socioeconomic impact on host crop species and a huge problem to farmers and scientists. Therefore, this study investigates the in vitro effect of alum on microorganisms associated with foliar phytoplasma disease (FPD) of Noni. Bacteria and fungi were isolated and identified by culture-dependent technique using standard microbiological procedures and susceptibility of species were evaluated by disc and agar well diffusion techniques and inhibition zones (IZs) were measured in millimeter (mm). The microbes identified were Bacillus subtilis, B. tequilensis, Brevundimonas vesicularis, B. cereus, Staphylococcus aureus and Serratia species as well as Aspergillus flavus, A. fumigatus, A. niger and Penicillium species. Relative abundance (%) of bacterial species occurred in the order; S. aureus > B. tequilensis > B. cereus and least being Br. vesicularis whereas fungi were A. fumigatus (75%), A. niger and A. flavus (50%) respectively and Penicillium (25%) species. Susceptibility test efficacy of Alum was concentration dependent with Serratia sp. as (6.0mm) and S. aureus (4.0mm) whilst A. flavus (36.0mm), A. fumigatus (32.5mm), Penicillium (30.2mm) and A. niger (30.0mm) at 5.0% Alum concentrations as the largest IZs respectively. The minimum inhibitory concentration (MIC) of Alum against all the microflora were < 2.0gm/mL except for S. aureus which portends a good future prospects in agronomy. However, the higher concentrations of Alum compared favourably with Ketoconazole (control) but showed wide disparity with Ofloxacin (control). This study, however, may proffer solutions for the prevention and management of FPD or foliar related diseases by periodic spraying or fumigation with Alum.