Manganese Nanomaterials: A Green Solution to Suppress Xanthomonas oryzae in Rice

Due to the environmental concerns surrounding widely used antimicrobial agents, the use of nanotechnology to suppress crop diseases has attracted increasing attention in the agricultural field. This paper investigated the inhibitory effects of manganese-based nanomaterials (NMs) on rice leaf blight. In vitro experiments showed that manganese oxide (MnO2) NMs and manganese tetroxide (Mn3O4) NMs directly inhibited Xanthomonas oryzae (Xoo) with a maximum OD value of 0.177, which was 11.5% lower than the control. In vivo experiments demonstrated that spraying MnO2 NMs and Mn3O4 NMs reduced the diseased leaf length to 22–28% and 25–26%, respectively. This is due to Mn-based NMs inducing enhanced plant resistance by increasing the activity of phenylalanine ammonia–lyase in rice leaves by 36–61%. Single particle inductively coupled plasma mass spectrometry showed that Mn3O4 NMs are more frequently retained as NMs in rice than MnO2 NMs, resulting in enhanced antimicrobial effects. Mn-based NMs exhibit strong antimicrobial activity and hold significant promise as alternatives for plant protection and agricultural applications; however, careful consideration must be given to their concentrations and application methods.