Development and validation of a standard area diagram set as assessment aid for estimating the severity of bacterial spot on tri-lobed leaves of yellow passion fruit

  • Anne Pinheiro Costa Universidade de Brasília
  • José Ricardo Peixoto Universidade de Brasília
  • Luiz Eduardo Bassay Blum Universidade de Brasília
  • Michelle Souza Vilela Universidade de Brasilia
  • Wagner Vendrame University of Florida
Keywords: Passiflora edulis Sims, Xanthomonas axonopodis pv. passiflorae, phytopathometry

Abstract

Bacterial spot (Xanthomonas axonopodis pv. passiflorae) significantly reduces yellow passion fruit (Passiflora edulis Sims) yield and longevity. A standard area diagram set (SADs) for severity assessment of bacterial spot on tri-lobed leaves of yellow passion was developed and validated in this study. The SADs consisted of eight severity levels (2; 4; 9; 18; 35; 58; 80; and 94%). For its validation, 20 raters, who initially estimated the disease severity without the aid of the SADs, were divided into four groups (G1 and G3, inexperienced; G2 and G4, experienced). Subsequently, G1 and G2 performed the second evaluation without the SADs, and G3 and G4 completed the second evaluation with the proposed SADs. The accuracy and precision of the assessments were determined by simple linear regression and by the Lin’s concordance correlation coefficient (LCCC). The proposed SADs allowed accurate and precise quantification of bacterial spot severity, increasing the agreement between estimated and actual values. Inexperienced raters benefited the most from the use of the SADs. The increase in accuracy and precision in the non-aided groups, when present, was less pronounced than those increments observed in the SADs-aided groups. The LCCC confirmed the increases in accuracy and precision detected by the linear regression analysis.

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Author Biographies

José Ricardo Peixoto, Universidade de Brasília
Faculdade de Agronomia e Medicina Veterinária
Luiz Eduardo Bassay Blum, Universidade de Brasília
Departamento de Fitopatologia
Michelle Souza Vilela, Universidade de Brasilia
Faculdade de Agronomia e Medicina Veterinária
Wagner Vendrame, University of Florida
Tropical Research and Education Center
Published
2019-10-16
How to Cite
Costa, A. P., Peixoto, J. R., Bassay Blum, L. E., Souza Vilela, M., & Vendrame, W. (2019). Development and validation of a standard area diagram set as assessment aid for estimating the severity of bacterial spot on tri-lobed leaves of yellow passion fruit. Bioscience Journal - ISSN 1981-3163 , 35(6). https://doi.org/10.14393/BJ-v35n6a2019-42435
Section
Agricultural Sciences