Effects of cyproconazole, azoxystrobin and mineral oil on soybean leaf anatomy Efeitos de ciproconazole, azoxistrobina e óleo mineral sobre a anatomia foliar da soja

A fungicide composed of a triazole (cyproconazole), a strobilurin (azoxystrobin) and a mineral oil (nimbus) is used for disease control, Asian Rust mainly, currently considered one of the major soybean diseases in Brazil. With the purpose of studying the effect of the fungicide and its constituents on histological characteristics of soybean (Glycine max cv. Pintado) leaves, the fungicides plus mineral oil, cyproconazole, azoxystrobin plus mineral oil and just mineral oil, were applied at R1 stage (anthesis), R3 and R5 stages. Fourteen days after the last application, central leaflet of each trifoliate leaf were harvested from five plants. Leaf anatomy variables were measured in four leaves collected in each of five plants per treatment. Histological analysis showed that the fungicide plus mineral oil increased leaf blade thickness, midrib, xylem, phloem and the width of the midrib. Azoxystrobin plus mineral oil increased the thickness of midrib, xylem, phloem and the width of the midrib. Cyproconazole increased the thickness of xylem and phloem. Finally, mineral oil reduced the thickness of leaf blade and midrib.