Abstract Color photographs represent the symptoms of the disease as observed in the field, favoring the visual estimation of severity. In order to increase the accuracy, repeatability and reproducibility of Coffea canephora L. rust severity estimates, this study was carried out to elaborate and validate a standard area diagram (SAD) constructed with color photographs (SADcp). To do so, we collected leaves with different intensities of symptoms in crops, and the actual severity was determined with the aid of the software QUANT. The intermediate levels of the scale were determined based on the frequency distribution of severity values. The validation of the diagram was performed by 13 raters who estimated disease severity in 50 leaves of C. canephora with different intensity of symptoms. One assessment without the standard area diagram and two assessments with the diagram were performed at intervals of seven days. Data were analyzed by linear regression and Lin's concordance correlation coefficient. The accuracy, precision, repeatability and reproducibility of the estimates were evaluated. To compare the efficiency of SADcp with the existing scale constructed with two-color diagram (SAD2col), these procedures were performed with both scales. Without the scale and with the SAD2col diagram, the raters overestimated the severity of the disease. With the use of SADcp, the raters presented better levels of accuracy, precision, reproducibility and repeatability in the estimates, compared to when they did not use SAD, or when they used SAD2col. Therefore, SADcp was suitable for estimating the severity of coffee leaf rust in C. canephora.

中文翻译：

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带有彩色照片的标准面积图，用于估计咖啡豆中咖啡叶锈病的严重程度

摘要 彩色照片代表了在现场观察到的疾病症状，有利于对严重程度的视觉估计。为了提高 Coffea canephora L. 锈病严重程度估计的准确性、可重复性和再现性，本研究旨在阐述和验证由彩色照片 (SADcp) 构建的标准面积图 (SAD)。为此，我们收集了作物中具有不同症状强度的叶子，并借助软件 QUANT 确定了实际严重程度。量表的中间级别是根据严重性值的频率分布确定的。该图的验证由 13 位评估者进行，他们估计了 50 片具有不同症状强度的 C. canephora 叶子的疾病严重程度。每隔 7 天进行一次没有标准面积图的评估和两次有图表的评估。数据通过线性回归和林氏一致性相关系数进行分析。评估了估计的准确度、精密度、重复性和再现性。为了将 SADcp 的效率与用双色图 (SAD2col) 构建的现有量表进行比较，这些程序在两种量表上都进行了。在没有量表和 SAD2col 图的情况下，评估者高估了疾病的严重程度。与不使用 SAD 或使用 SAD2col 时相比，使用 SADcp 后，评估者在估计中呈现出更高水平的准确度、精确度、再现性和可重复性。因此，SADcp 适用于估计咖啡叶锈病的严重程度。