Nanopartículas no controle da vassoura de bruxa do cacaueiro

Abstract

Nanoparticles (NPs) have been effective in controlling phytopathogens in vitro, but few studies have been developed in vivo. The objective of this work was to evaluate the effects of ZnO, CuO, MnO2, B, Si and Ag NPs on the inhibition of different phases of cacao witches broom (M. perniciosa) in vitro and in vivo. The experiment was conducted at CEPEC/CEPLAC in Ilhéus, southern Bahia. In the experiment of basidiospore germination inhibition, design was completely randomized in a 6x6 factorial scheme, with 6 NPs ZnO, CuO, MnO2, B, Si and Ag, 6 doses 0, 25, 50, 100, 200 and 400 mg/L- 1 and 16 repetitions. The NPs were diluted in agar culture medium and a 2x105 basidiospore suspension added, readings were taken after 6 hours. In the experiment mycelial growth inhibition the design was completely randomized in a 4x6 factorial scheme, with 4 NPs ZnO, CuO, B and Ag and 6 doses 0, 25, 50, 100, 200 and 400 mg/L-1 and 5 replications. NPs were diluted in BDA culture medium and a mycelium disc added to the center of the plates. Readings were taken every 3 days until 12 day. In the experiment basidiocarp inhibition the design was in randomized block in 5x4 factorial scheme, with 5 NPs ZnO, CuO, MnO2, Si and Ag and 4 doses 0, 100, 200 and 400 mg/L-1 and 3 replications. The dried brooms were soaked in NPs solutions for 1 hour shortly after they were taken to the broom. There were 3 readings 1 per week. In the experiment in seedling the design was a randomized block in a 2x4 factorial scheme, with 2 NPs Si and Ag and 4 doses 0, 100, 200 and 400 mg /L-1 and 4 replications. At 23 days after planting, 10 mL of NPs solutions were applied via leaf and 10 days after, 30 μL of 2x105 basidiospore viable was deposited on the apical meristem. Were taken readings of incidence, severity, chlorophyll, height and diameter. In the basidiospore of germination test the 200 mg/L-1 dose was more efficient than the others, reducing germination in 0,18% (ZnO), 0% (Ag), 0,05% (CuO), 0% (Si), 1,0%. (MnO2) and 37,73% (B). In the mycelial growth inhibition test the 400 mg/L-1 NPs of ZnO, Ag and CuO were more phytotoxic to M. perniciosa than the others, inhibiting 69,0, 89,0, and 82,2% respectively. In the experiment basidiocarp inhibition the dose of 400 mg/L-1 NPs inhibited above 92%. The AACPDI mean values were 38, 32, 24 and 0 and 34, 27, 19 and 7 at the doses of 0, 100, 200 and 400 mg/L-1 NP Si and Ag respectively. The AACPDS mean values were 81, 118, 108 and 0 cm² and 61, 102, 97 and 23 cm² at the doses of 0, 100, 200 and 400 mg/L-1 NP Si and Ag respectively. NP Si presented phytotoxic effects to M. perniciosa in vitro and in vivo, inhibiting in AACPD 100% of the severity in the 400 mg L-1 dose.