Rapid elimination of Xanthomonas campestris pv. campestris from cabbage seeds by high-frequency microwave

Elimination of seed-borne bacteria is essential to agriculture due to the high imperceptibility and quick transmission of seed diseases. In comparison to thermal or chemical seed disinfection, microwave treatment promises to be an optimal alternative due to its rapid, non-contact and chemical-free nature. Nevertheless, the currently-employed, low-frequency (2.45 GHz and below) microwave treatments encounter two difficulties. First, because of its higher surface-to-volume ratio, the bacterium on the seed surface has a much greater thermal dissipation to air. Hence, its temperature rises more slowly than the seed. This was overcome in this study by soaking the seed in shallow water so the bacteria were in a co-heated medium. Second, the long heating time (5–20 mins) caused thermal damage to the water-rich seed embryo and decreased the germination rate. This could be remedied by much faster treatment at a much higher frequency (24 GHz). In our study, under optimum treatment time and total microwave dose, 100% mortality of Xanthomonas campestris pv. campestris (Xcc) could be achieved within 1 second while maintaining a 90–100% of seed germination rate. We believe that these rapid heating results verify the practicability of using high-frequency microwave treatment to eliminate Xcc from cabbage seeds.