Bacteria disinfection of rice seeds by ultraviolet light irradiation in a biosafe flow cabinet

Authors: Jia, Yulin; Read, Quentin

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/9/2023
Publication Date: 11/1/2023
Citation: Jia, Y., Read, Q.D. 2023. Bacteria disinfection of rice seeds by ultraviolet light irradiation in a biosafe flow cabinet. Plant Health Progress. https://doi.org/10.1094/PHP-02-23-0017-RS.
DOI: https://doi.org/10.1094/PHP-02-23-0017-RS

Interpretive Summary: Field-harvested rice seeds contaminated with bacteria is a concern for rice distribution. User-friendly methods to remove microbes are currently not available. Here we report the effects of 274 nanometer ultraviolet proton treatments for 1-7 days on rice seeds. Seeds were placed without a barrier, in a sterilized mesh bag, or a sterilized coin envelope. Each day for seven days after UV irradiation, 10 seeds were removed and placed in a nutrient agar medium in a dark incubator at 29°C for three days. Bacterial and/or fungal infected seeds were counted. At the same time, 10 seeds were removed and placed onto a moistened filter paper for five days in an incubator at 40 °C for germination assays. The rate of germination was counted at five days after incubation. Across all treatments, bacterial infection rate declined significantly over time. Fungal infection rate also declined significantly over time but at a slower rate. However, germination rate did not change significantly over time. When comparing the treatments, there was no significant difference between treatments for germination rate or fungal infection rate. Interestingly, the mesh bag UV had the strongest effect on reducing bacterial infection rate over time, even compared to the direct UV treatment. We suggest that UV irradiation of seeds in mesh bag be used to reduce seed bacterial contamination.

Technical Abstract: Plant seeds are known to carry many microbes, and some of them are harmful to plant health. Easy-to-use methods to disinfect bacteria without negative impacts on germination are not available. In the present study, rice seeds were irradiated by 274 nanometer germicidal ultraviolet proton in a biosafe flow cabinet. Seeds were placed without any barrier, in a sterilized mesh bag, or in a sterilized coin envelope. Ten seeds were removed each day for seven days after UV irradiation and placed in nutrient agar media. The seeds were incubated in a dark incubator at 29°C for three days, after which the number of seeds contaminated with bacteria and/or fungi were counted. At the same time, 10 seeds were removed, kept on a wet filter paper in a dark incubator at 40 °C for five days, at which time the germination rate was measured. Across all treatments, the average bacterial infection rate declined significantly over time. The fungal infection rate also declined significantly over time but at a slower rate. The germination rate did not change significantly over time. There was no significant difference among treatments for germination rate or fungal infection rate. Interestingly, the UV irradiation of seeds in mesh bags had the strongest effect on reducing bacterial infection rate over time, whereas the direct UV irradiation had a weaker effect on bacterial infection rate than the UV irradiation of seeds in mesh bags. We suggest that UV irradiation of seeds in mesh bags be used to reduce seed bacterial contamination.