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Bacterial wilt is a serious problem affecting many important food crops. Recent studies have 12
indicated that treatment with biotic or abiotic stress factors may increase the resistance of 13
plants to bacterial infection. Here, we investigated the effects of magnesium oxide 14
nanoparticles (MgO NP) on disease resistance in tomato plants against Ralstonia 15
solanacearum as well as its antibacterial activity. The roots of tomato seedlings were 16
inoculated with R. solanacearum and then immediately treated with MgO NP; the treated 17
plants showed very little inhibition to bacterial wilt. In contrast, when roots were drenched 18
with MgO NP suspension prior to challenge-inoculation with the pathogen, the incidence of 19
disease was significantly reduced. Rapid generation of reactive oxygen species such as O 2−• 20
radicals was observed in tomato roots treated with MgO NP. Further O 2−• was rapidly 21
generated when tomato plant extracts or polyphenols were added to the MgO NP suspension, 22
suggesting that the generation of O 2−• in tomato roots might be due to a reaction between