Diagrammatic scale for assessment of soybean rust severity

Abstract

A diagrammatic scale to assess soybean (Glycine max) rust severity, caused by the fungus Phakopsora pachyrhizi, was developed in this study. Leaflets showing different severity levels were collected for determination of the minimum and maximum severity limits; intermediate levels were determined according to "Weber-Fechner's stimulus-response law". The proposed scale showed the levels of 0.6; 2; 7; 18; 42, and 78.5%. Scale validation was performed by eight raters (four inexperienced and four experienced), who estimated the severity of 44 soybean leaflets showing rust symptoms, with and without the use of the scale. Except for rater number eight, all showed a tendency to overestimate severity without the aid of the diagrammatic scale. With the scale, the raters obtained better accuracy and precision levels, although the tendency to overestimate was maintained. Experienced raters were more accurate and precise than inexperienced raters, and assessment improvements with the use of the scale were more significant for inexperienced raters.

Inducers of resistance and silicon on the activity of defense enzymes in the soybean-Phakopsora pachyrhizi interaction

“…The severity of ASR was evaluated on the fourth, fifth and sixth leaves of each plant at V6 growth stage (Fehr and Caviness, 1977) per replication of each treatment at 18 days after inoculation (dai) according to the symptoms scale proposed by Godoy et al (2006).…”

Tolerância de genótipos de soja à ferrugem-asiática

“…Foram avaliados os graus médios de severidade, em porcentagem (SEV), com auxílio da escala diagramática elaborada por GODOY et al (2006). Cada dado de severidade foi obtido pela avaliação de 30 folíolos por parcela, igualmente distribuídos entre os terços inferior, médio e superior das plantas e coletados de forma distribuída na área útil da parcela, em duas avaliações: a primeira aos 20 dias após a primeira aplicação do fungicida e a segunda, sete dias após a segunda aplicação, em todos os tratamentos.…”

Efeito de herbicidas e fungicidas nas curvas de progresso e quantificação de danos causados pela ferrugem asiática da soja

“…Foi quantificada semanalmente a severidade de ferrugem asiática, com base na escala diagramática proposta por GODOY et al (2006). Estimou-se a severidade por meio da média das avaliações dos terços inferior, médio e superior, em quatro plantas por parcela.…”