Development and validation of diagrammatic scale for white mold on tobacco leaf discs
Sclerotinia sclerotiorum; Nicotiana tabacum; Diagrammatic scale.
Sclerotinia sclerotiorum is geographically cosmopolitan and has a broad ecological distribution, although it is most common in temperate regions. More than 400 species are susceptible to this pathogen, including most vegetables (e.g. potato, tomato, lettuce, and crucifers), tobacco, and others .The aim of this study was to develop and validate a diagrammatic scale to aid the visual assessment of white mold in Tobacco. The diagrammatic scale from 0 to 100% was analyzed according to precision, accuracy, and reproducibility. Six evaluators estimated the white mold severity level with and without the diagrammatic scale, considering six levels of disease severity using 50 leaf discs images. Without and with (1st and 2nd evaluation) the use of the scale, the evaluator 1 obtained coefficients of determination (R2) from 0,20 to 0,82 and 0,73, respectively. The variation coefficient (CV%) observed without the scale was 37.36% and after utilizing it were 5.97% and 10.47% , indicating a good homogeneity of the data. So, the proposed diagrammatic scale was considered appropriate to estimate the severity of Sclerotinia sclerotiorum in Nicotiana tabacum.