The effect of ozone on Aspergillus niger causing black rot disease in onion was studied in culture. Ozone induced the spore germination in all treatments and few spores showed rapid swelling, resulting in the production of 2-3 germ tubes per spore compared to control. Although all the ozone treated spores germinated, all of them did not produce uniform colony morphology. Some colonies which developed from ozone treated spores failed to produce spores and such colonies appeared as gray patches of mycelia without spores amidst surrounding black sporulating colonies. Further work is in progress to study the mechanism involved in formation of sterile mycelia by ozone.
Aspergillus niger, a fungi causes black rot disease in onions causing damage to the onion while in storage and in transportation. It is visible on the surface of the onion in the form of black powdery spores. The sanitation and cleaning of onions is critical in maintaining its freshness and physical attributes for the consumer. Ozone is known as a powerful disinfectant with no toxic byproduct making it attractive method of sanitation for onions.
A test was done to see if different concentrations of ozone and exposure time have an adverse effect on the Apsergillus niger fungus. Ozone was distributed through a bubbling glass tube at a flow rate of 500 ml/minute on the onion scales with Aspergillus niger. Exposure time was set at 5, 10, and 15 with treatments of 1)ozone 2) ozone and 0.1% sucrose 3)0.1% sucrose 4)control with no ozone or 0.1% sucrose.
In this study ozone did not have a inhibitory effect on the germination of Aspergillus niger spores. However despite the expansion of these spores, some of these created non-sporulating colonies with appearance of gray patches and not black sporulating colonies. A previous study showed that ozone at a concentration of 2.2 mg/L (chynoweth et al., 1997) had a inhibitory effect on Asperigas Niger. The mechanism of action determines if ozone inhibits or acts after germination.
Effect of Ozone on Apergillus niger Causing Black Rot Disease in Onion. Ozone: Science and Engineering, 28: 347-350 2006 International Ozone Association ISSN: 0191-9512 print/ 1577-6545 online