| 【Objective】Ultrasound wave (USW) treatment of rice seeds can promote seed germination and seedling
growth, but its bactericidal effect is not clear. In this study, we intend to investigate the effects of USW on fungi and bacteria
on the surface of rice seeds, and to evaluate the antimicrobial efficacy of different USW treatments and the influencing
factors. We also try to analyze the reasons of the promotion of rice germination and seedling growth by USW. 【Methods】 Using the rice cultivar, Xiangyaxiangzhan, as material, three treatments, 25-50 kHz USW wet method (Twet), 50 kHz USW drying
method (Tdry1) and 25 kHz USW drying method (Tdry2), were set up. The conventional wet method (CK1) and dry method (CK2)
were taken as controls. The experiments were repeated three times. Microorganisms on the seed surfaces were separated by
PDA plates. The fungi and bacteria were identified by combining colony features, microscopic structures and ITS sequences
analysis. 【Results】USW had substantial bactericidal and fungicidal effects on seed surfaces. Wet treatment of USW (Twet)
was better than dry treatment (Tdry1, Tdry2), and the 50 kHz USW (Tdry1) was better than 25-kHz USW (Tdry2). Among the 15
species of bacteria detected on seed surfaces, USW had the significant bactericidal effects on low abundance bacterial species
such as Xanthomonas sacchari, Pseudomonas aeruginosa, Chryseobacterium gleum, Pantoea agglomerans and Stenotrophomo
maltophilia, but USW had not effects on the higher abundance bacteria such as Enterobacter cloacae and Klebsiella pneumoniae.
Eleven fungi were detected on the seed surfaces, USW had better fungicidal effects on Fusarium proliferatum, F. oxysporum,
F. moniliforme, F. equiseti and Phoma sp. But USW had not apparent effects on Sarocladium oryzae and Penicillium
oxalicum with the relatively higher richness. 【Conclusion】USW has antimicrobial effects on rice seed surfaces, but the
effects are related to the treatment ways of USW, microorganism species and their abundance. USW treatment on wet seeds has
better bactericidal and fungicidal effects than those of USW treatment on dry seeds. USW has significant fungicidal effects on
Fusarium spp with low abundance, which may be one of the reasons for promoting rice germination and seedling growth. |
