Escala diagramática para quantificação da ferrugem da folha do trigo

Abstract

Wheat leaf rust caused by Puccinia triticina is among the diseases of wheat, the most important historical and economic world. Among rusts the wheat this is more geographically distributed. However in Brazil there are no epidemiological studies of this disease. For which standard methods are needed to quantify the severity of the field. So, the objective was to develop a diagrammatic to standardize the estimates of severity, to evaluate the leaf rust of wheat. The scale was made from symptomatic leaves collected at random from naturally infested area at the Federal University of Viçosa, Viçosa-MG. After collection the leaves were scanned, and with the help of the Quant determined the injured area for the construction of diagrammatic. Thus the proposed scale has 10 levels of severity: 0,1; 1; 2; 4; 8; 16; 32; 64;80 and 95%. Scale validation was performed by eight evaluators without experience in disease assessment. The evaluators initially estimated the severity of the disease without the use of the scale, soon after the same raters used the scale proposed. The accuracy and precision of the scale were evaluated using linear regression analysis. The proposed diagrammatic scale is now quick, easy, so accurate, precise and reproducible. This scale is recommended as a tool to aid in estimating the severity of leaf rust of wheat.