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Development and validation of a standard area diagram set to aid assessment of severity of loquat scab on fruit

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Abstract

A standard area diagram set (SAD) to aid visual assessment of loquat scab (caused by Fusicladium eriobotryae) severity on fruit was developed and evaluated for improving accuracy, precision and reliability of visual estimates. The SAD set contains eight black and white diagrams of diseased fruit with severity values from 2 % to 98 %. To evaluate the SADs, a group of 20 raters (comprising 10 ‘experienced’ and 10 ‘inexperienced’ raters) assessed the same set of 50 images three times, the first without SADs and the second and third using the SADs as an aid. Only for the group of inexperienced raters did SADs significantly improve accuracy (bias correction factor, C b = 0.93 without SADs and 0.98 with SADs), precision (correlation coefficient, r = 0.88 without SADs and r = 0.96 with SADs) and overall agreement (Lin’s concordance correlation coefficient, ρ c = 0.82 without SADs and ρc with SADs = 0.95) of the estimates. Accuracy and precision of the estimates by inexperienced raters were significantly higher than those obtained by the experienced raters, especially for the second assessment with SADs. Inter-rater reliability was improved when SADs were used by inexperienced raters, whereas a high degree of intra-rater reliability was obtained by both experienced and inexperienced raters when using SADs. The SADs developed in this study were useful for obtaining more accurate, precise and reliable assessments of loquat scab for inexperienced raters, and should be used as an aid for assessing scab in epidemiological studies or monitoring for decision-making purposes.

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Acknowledgments

This work was funded by Cooperativa Agrícola de Callosa d’En Sarrià (Alicante, Spain). Financial support was provided by CAPES (Brazil) for S. J. Michereff at the Universidad Politécnica de Valencia (Spain) and is gratefully acknowledged. The authors thank colleagues and students who assessed the diseased fruits images.

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Authors and Affiliations

  1. Instituto Agroforestal Mediterráneo, Universidad Politécnica de Valencia, Camino de Vera s/n, 46022, Valencia, Spain

    Elisa González-Domínguez, José García-Jiménez & Josep Armengol

  2. Campus Arapiraca, Universidade Federal de Alagoas, 57309-005, Arapiraca, AL, Brazil

    Ricardo Brainer Martins

  3. Departamento de Fitossanidade, Faculdade de Agronomia, Universidade Federal do Rio Grande do Sul, 91540-000, Porto Alegre, RS, Brazil

    Emerson Medeiros Del Ponte

  4. Departamento de Agronomia, Universidade Federal Rural de Pernambuco, 52171-900, Recife, PE, Brazil

    Sami Jorge Michereff

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  1. Elisa González-Domínguez
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Correspondence to Josep Armengol.

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González-Domínguez, E., Martins, R.B., Del Ponte, E.M. et al. Development and validation of a standard area diagram set to aid assessment of severity of loquat scab on fruit. Eur J Plant Pathol 139, 419–428 (2014). https://doi.org/10.1007/s10658-014-0400-2

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