Fig. 11
Lesion quantification and classification. A Image of artificially damaged and stained spinach leaf containing damage of different sizes. All detected lesions were divided into three classes, based on their area (measured as pixels (px)). B Definition and in planta demonstration of lesion classes: microlesion (smallest detectable area; 1 px or 1800 µm2) shown as a small yellow square, mesolesion (2–200 px; up to 360,000 µm2) shown as area within large dashed rectangle, and macrolesion (major damage, > 200 px or > 360 000 µm2) shown as the area outside the dashed rectangle. Images used for comparisons between methods, comprising C positive control images (N = 10) and D randomly chosen images from the experimental dataset (N = 10). Lesion classification by the LiMu program, the commonly used image analysis software IMAGEJ and manual assessment was compared. Significant differences (p ≤ 0.05) between methods (post hoc test) are indicated with different lower-case letters (a, b, c) (Additional file 7)