Standard area diagram set for bacterial spot assessment in fruits of yellow passion fruit

Abstract This study developed and validated a standard area diagram set (SADs) for severity assessment of bacterial spot (Xanthomonas axonopodis pv. ) in passifloraefruits of yellow passion fruit (Passiflora edulis). The SADs consisted of eight severity levels (1%; 3%; 5%; 10%; 21%; 38%; 65%; and 80%). For its validation, 20 raters, who initially estimated the disease severity without the aid of the SADs, were divided into groups (G1 and G3, inexperienced; G2 and G4, experienced). Subsequently, G1 and G2 performed the second evaluation without the proposed SADs, and G3 and G4 completed the second evaluation using the proposed SADs. The accuracy and precision of the assessments were determined by simple linear regression and by the Lin’s concordance correlation coefficient. The increase in the accuracy was confirmed by the reduction in the constant and systematic errors, indicating that the estimated severities were close to the actual values when the SADs was used. Inexperienced raters benefited the most from the use of the SADs, and 60% and 100% of them presented constant and systematic error-free estimates, respectively. Precision increased with the increase in the coefficient of determination, the reduction in absolute errors, and the increase in the reproducibility of the estimates between pairs of raters.