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  • Vol. 2024, 42(1)
  • Phytopathological Note

Diagrammatic scale to quantify the severity of Ascochyta blight in broad bean crops

By Ernesto Alonso López Reyes, Álvaro Castañeda Vildózola*, Jesús Ricardo Sánchez Pale, Alejandra Contreras Rendón, Juyma Mayvé Fragoso Benhumea, Rómulo García Velasco

*Corresponding Author.

Received: 15/September/2022 – Published: 26/December/2023
DOI: https://doi.org/10.18781/R.MEX.FIT.2209-4

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    • López-Reyes EA, Castañeda-Vildózola Á, Sánchez-Pale JR, Contreras-Rendón A, Fragoso-Benhumea JM, García-Velasco R. 2022. Diagrammatic scale to quantify the severity of Ascochyta blight in broad bean crops. Mexican Journal of Phytopathology 42(1):. https://doi.org/10.18781/R.MEX.FIT.2209-4
    • López-Reyes, EA, Castañeda-Vildózola, Á, Sánchez-Pale, JR, Contreras-Rendón, A, Fragoso-Benhumea, JM y García-Velasco, R (2022). Diagrammatic scale to quantify the severity of Ascochyta blight in broad bean crops. Mexican Journal of Phytopathology 42(1):. https://doi.org/10.18781/R.MEX.FIT.2209-4
    • Ernesto López-ReyesA, Álvaro Castañeda-Vildózola, Jesús Sánchez-PaleR, Alejandra Contreras-Rendón, Juyma Fragoso-BenhumeaM y Rómulo García-Velasco. 2022. Diagrammatic scale to quantify the severity of Ascochyta blight in broad bean crops. Mexican Journal of Phytopathology 42(1):. https://doi.org/10.18781/R.MEX.FIT.2209-4
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Abstract Background/Objective. The objective of this study was to design and validate a diagrammatic severity scale of brown spot on broad bean.

Materials and Methods. We collected 120 leaflets with different level of brown spot damage from commercial crops in the Toluca Valley, which were visually selected based on the expressed symptomology. Sixty leaflets were scanned for evaluation with the software APS PRESS ©Assess 2.0 to determine the real severity value for each leaflet.

Results. The damage values allowed us to generate a diagrammatic scale consisting of six different classes: 0(0.0), 1(0.1-6.0), 2(6.1-10.0), 3(10.1-15.0), 4(15.1-40.0), 5(> 40.1-100). The leaflets were visually examined by evaluators who had no prior experience. The results from each evaluator were analyzed with a simple linear regression, obtaining r2 values from 0.0042 to 0.8748, β0 de 0.51 a 9.11, y β1 de 0.132 a 0.925. Using a scale, r2 values were obtained 0.9143 to 0.985, β0 de 0.001 a 0.911 y β1<0.001.

Conclusion. The generated diagrammatic severity scale was validated and reproducible, showing high reliability.

Keywords: Symptoms, damage, evaluation, reproducibility

Figure 1. Diagrammatic scale of brown spot severity (Ascochyta fabae) in broad bean. zLower limit-average-upper limit.
Figure 1. Diagrammatic scale of brown spot severity (Ascochyta fabae) in broad bean. zLower limit-average-upper limit.
Figure 2. Distribution of residuals (estimated severity-real severity) of the brown spot evaluations (Ascochyta fabae) in broad bean leaflets. A) Scaled evaluation. B) Unscaled evaluation.
Figure 2. Distribution of residuals (estimated severity-real severity) of the brown spot evaluations (Ascochyta fabae) in broad bean leaflets. A) Scaled evaluation. B) Unscaled evaluation.
Table 1. Values of the Intercept (β0), slope of the line (β1), coefficient of determination (r²) and margin of error (1-r²) of the simple linear regression equation in visual estimations of the severity in of brown spot in broad bean (Ascochyta fabae), with 20 unscaled evaluators and 10 scaled evaluators
Table 1. Values of the Intercept (β0), slope of the line (β1), coefficient of determination (r²) and margin of error (1-r²) of the simple linear regression equation in visual estimations of the severity in of brown spot in broad bean (Ascochyta fabae), with 20 unscaled evaluators and 10 scaled evaluators