Uso de nanopartículas no controle da cercosporiose em mudas de cafeeiro (Coffea arabica L.)

Abstract

Brown eye spot (Cercospora coffeicola) is one of the main diseases of coffee (Coffea arabica) and represents a serious phytosanitary problem for the crop. Among the management strategies of the disease, the nutritional balance of plants is recommended. In this context, the supply of micronutrients and elements in the nanoparticle form has become the target of study due to its unique properties. In contrast, information about the use of this technology in the management of brown eye spot in coffee plants is scarce. The objective of this study was to evaluate the effect of nanoparticles of silver, copper, cerium, manganese, zinc and boron (Ag, Cu, Ce, Mn, Zn and B) on this disease management. The nanoparticles were evaluated on spore germination and mycelial growth rate (MGR) of C. coffeicola in vitro. The experiment was carried out in a completely randomized design with four replicates and the variance analysis in a 7x5 factorial scheme, with seven treatments (Cu, Ce, Mn, Zn, Ag and B nanoparticles and the fungicide azoxystrobin + cyproconazole) tested in five doses (3, 50, 100, 250, 500 mg L -1 ) and an additional treatment (control). It was observed that the nanoparticles of silver and copper at the 250 mg L -1 significantly reduced spores germination of C. coffeicola in 99% and 100% (trial 1), 100% and 93% (trial 2) when compared to the control. The boron, copper, zinc and manganese nanoparticles, at the 500 mg L -1 provided reduction of the MGR of 100%, 94%, 79% and 93% respectively, when compared to the control. For the in vivo experiment, the effective dose of nanoparticles in vitro, 500 mg L -1 , which were applied to coffee seedlings Mundo Novo 376/4 cultivar inoculated with C. coffeicola. The area under the disease progress curve (AUDPC), SPAD index (Soil Plant Analysis Development), dry weight, soluble phenol and lignin content were quantified. The trial was conducted in a randomized block design with eight treatments (nanoparticles- Cu, Ce, Mn, Zn, Ag and B, fungicide azoxystrobin + cyproconazole and control treatment) and four replicates. SPAD index and dry weight did not differ significantly between treatments. The preventive application of silver, cerium, boron and copper nanoparticles provided a significant (p <0.05) reduction in AUDPC in 58%, 31%, 25%, 16% respectively. Higher lignin content was quantified with application of copper, silver, zinc nanoparticles and fungicide.