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.

Standard Area Diagram Set for Scab Evaluation in Fruits of sour Passion Fruit

“…Linear regression is one of the most frequently used strategies for the validation of disease estimate methods and the evaluation of the accuracy and precision of disease severity estimates in leaves, fruits, and pods Costa et al, 2018). Nevertheless, some authors suggest that statistical tests for estimate errors may be highly influenced by the precision of the raters in the linear regression (Lin, 1989;Shoukri & Pause, 1999).…”

“…15°30′15.08″ W, and 955 m asl). The image obtention process, SADs elaboration and validation procedures, and data analyses were performed according to previously described by Costa, Pires, Peixoto, Blum, and Faleiro (2018).…”

“…The accuracy and precision of the raters were determined by linear regression between the actual severity (independent variable) and the visually estimated severity (dependent variable), as well as by the Lin's concordance correlation coefficient (LCCC; ρ c ) (Costa et al, 2018). The most accurate raters were those whose estimates provided linear regression equations with intercept ("a") not significantly different from 0 (constant error-free estimates); and slope coefficient ("b") not significantly different from 1 (systematic error-free estimates), based on the t-test applied to "a" and "b" (Nutter & Schultz, 1995).…”

Standard Area Diagram Set for Bacterial Spot Quantification in Entire-Margined Leaves of Sour Passion Fruit

“…Fifty entire-margined leaves of sour passion fruit (BRS Gigante Amarelo, Yellow Master FB200, and genotypes in breeding process) showing symptoms of bacterial spot were collected from 3-month-old seedlings kept under protected cultivation at University of Brasilia's (UnB) Experiment Station (15°44′13″ S and 47°52′57″ W, 1010 m), located in Brasilia, DF, Brazil. The procedures of image obtention, SADs development and validation, as well as data analyses were performed as stated by Costa, Pires, Peixoto, Blum, & Faleiro (2018).…”

Standard area diagrams to assess scab severity of entire‐margined leaves of sour passion fruit

“…After the SADs are developed, it is mandatory to validate them before their use to improve accuracy and precision during disease severity assessments (Capucho, Zambolim, Duarte, & Vaz, 2011). In passion fruit, some SADs have been developed to assess anthracnose on fruits (Fischer et al., 2009), bacterial spot on fruits and leaves (Costa, Peixoto, Blum, de Oliveira, et al, 2019; Costa, Pires, Peixoto, Blum, & Faleiro, 2018; Monzani, da Silva, Nutter Junior, Duarte, & May‐De Mio, 2018) and scab on fruits (Costa, Peixoto, Blum, & Pires, 2019b).…”