Dickeya zeae, Pantoea ananatis e Xanthomonas vasicola pv. vasculorum: detecção em sementes de milho e controle com o uso de nanopartículas

Abstract

Bacterial diseases that cause losses to the maize crop are: white spot, caused by Pantoea ananatis, bacterial streak, caused by Xanthomonas vasicola pv. vasculorum and stem rot, caused by Dickeya zeae. The objectives of these works are (i) to evaluate the use of semi-selective culture media for the detection of D. zeae, P. ananatis and X. vasicola pv. vasculorum; (ii) to evaluate bacterial survival in inoculated corn seeds; (iii) evaluate culture media for the detection of D. zeae in naturally contaminated corn seeds; (iv) to evaluate the in vitro antibacterial activity of nanoparticles (NPs) in inhibiting the growth of D. zeae, P. ananatis and X. vasicola pv. vasculorum, and (v) evaluate the use of ZnO NPs, NiO and Ag-doped ZnO NPs in preventive and curative application in the control of white spot and bacterial stripe in maize. Culture media 523, TSA and XTS with the addition of cyclohexamide can be recommended for the simultaneous detection of D. zeae, P. ananatis and X. vasicola pv. vasculorum. The bacteria survive in the seeds and can be detected up to 120 days after storage. There is a difference in the sensitivity of the culture media for the detection of P. ananatis and X. v. pv. vasculorum in the evaluated storage periods. And, among the media, the TSA medium is the most suitable with better performance and greater sensitivity. Dickeya zeae was detected in all three seed lots. The TSA culture medium, with the addition of cyclohexamide, can be recommended for the detection of D. zeae in maize seeds, in routine analysis. Prior seed disinfestation favors the identification of isolates and reduces the growth of contaminants. ZnO and ZnOCl NPs did not show antibacterial activity against D. zeae, P. ananatis and X. vasicola pv. vasculorum. Ag-doped ZnO and ZnOCl NPs, K and Mo-doped ZnO NPs and Ag, Cu and Ni oxides inhibited in vitro growth with greater antibacterial activity for D. zeae isolates P. ananatis and X. vasicola pv . vasculorum. Copper hydroxide showed antibacterial activity only for D. zeae. Ag-doped ZnO NPs at different concentrations and NiO NPs reduced the severity of maize white spot and bacterial streak in preventive and curative applications. Copper hydroxide increased white spot severity and reduced maize bacterial streak severity.