The recent occurrence of bacterial leaf streak of corn caused by Xanthomonas vasicola pv. vasculorum represents a potential threat to the maize crop in Brazil. This study aimed to develop and validate a diagrammatic scale for the assessment of leaf streak severity in corn leaves. Linear regression and Lin’s coefficient approaches were used to explore the intra- and inter-rater reliability and accuracy of experienced and inexperienced evaluators. In cornfields in Cafelândia, Paraná state, 450 leaves that were naturally infected by the bacterium were collected from plants in stages V12 to R2. APS Assess software was used to measure the disease severity. The proposed scale consisted of eight levels: 0.5, 1, 3, 6, 11, 18, 37 and 67%. Validation was performed by five experienced and five inexperienced evaluators. The use of the scale improved the precision of inexperienced (R²₌ 0.66 and 0.88, with and without the scale) and experienced (R²₌ 0.81 and 0.97, without and with the scale) evaluators. In general, inexperienced evaluators overestimated (β_{0 =} 5.7) disease severity without the scale, and experienced evaluators underestimated (β_{0 =} − 2.1) disease severity without and with the scale. The agreement (pc = 0.83 and 0.94, without and with the scale, respectively) and accuracy (Cb = 0.93 and 0.98, without and with the scale, respectively) improved with the use of the scale. The overall concordance correlation coefficient (OCCC) showed the improvement of the concordance between experienced evaluators. The use of the proposed diagrammatic scale proved to be adequate for evaluating the severity of the bacterial leaf streak and improved the inter- and intrarater reliability and accuracy of experienced and inexperienced evaluators.

Xanthomonas vasicola pv引起的玉米细菌性叶条纹最近发生。血管对巴西的玉米作物构成潜在威胁。本研究旨在开发和验证用于评估玉米叶片中叶片条纹严重程度的图解量表。线性回归和林氏系数方法用于探讨经验丰富和经验不足的评估者在评估者内部和评估者之间的可靠性和准确性。在Paraná州Cafelândia的玉米田中，从V12到R2阶段的植物中收集了450片自然被细菌感染的叶子。APS评估软件用于测量疾病严重程度。拟议的量表包括八个级别：0.5％，1、3、6、11、18、37和67％。验证由五名经验丰富的评估者和五名经验不足的评估者进行。秤的使用提高了经验不足的精度（R ² ₌0.66和0.88（有和没有标度）和经验丰富的（R ² ₌ 0.81和0.97，有和没有标度）评估者。通常，没有经验的评估者高估了疾病严重程度（β0 ₌ 5.7），而没有量表，而经验丰富的评估者则低估了（β0 ₌ − 2.1）疾病严重程度，无等级，无等级。使用刻度尺，一致性（pc分别为0.83和0.94，无刻度和带有刻度）和准确性（Cb = 0.93和0.98，分别为无刻度和带有刻度）提高了。总体一致性相关系数（OCCC）显示了经验丰富的评估者之间一致性的提高。事实证明，使用拟议的比例尺足以评估细菌叶片条纹的严重程度，并提高经验丰富和经验不足的评估者之间和评估者之间的可靠性和准确性。