Colorimetry was evaluated as a method to assess pod disease in peanuts (Arachis hypogaea L.) caused primarily by Pythium myriotylum Drechs., Sclerotium rolfsii Sacc., and Rhizoctonia solani Kuhn. Data analyzed were from nineteen replicated tests conducted from 1982 to 1987, exclusive of 1985, in three South Texas locations. Each plot was scored for pod disease colorimetrically and visually. A negative linear relationship (R2>96%) was found between Hunter color values (L and b) and percent infection measured visually for samples hand selected to approximate eleven disease levels varying from 0-100%. Variability among readings was less at extremes of infection. Correlation both between visual ratings and between visual and colorimetric ratings was affected by soil differences, pathogens infecting the pods, pod genotype, and level of infection present. Correlation among visual raters was generally higher than that between color value ratings. Two-thirds of the lines in these tests classified visually as being in the best 50% for pod disease were also in the best 50% according to colorimetric scores. Use of colorimetry in conjunction with a single visual rating was estimated to increase efficiency and reduce costs of evaluation compared to multiple visual ratings.
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Keywords: Arachis hypogaea, Groundnut, Pythhim myriotylum, Rhizoctonia Solani, pod rot correlation, Sclerotium rolfsii, white mold, fiber optic light, disease assessment
How to Cite:
Parker, G. & Smith, O. & Grichar, W.,
(1989) “Colorimetric Assessment of Pod Disease in Peanuts: Comparison with Visual Methods and Efficacy of Use in Selection¹”,
Peanut Science 16(2),
01 Jul 1989
1Contribution from the Texas Agri. Exp. Stn., Texas A&M Univ., College Station, TA No. 24440. Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product and does not imply its approval to the exclusion of other products that may be suitable. This publication was partially supported by the Peanut CRSP, USAID grant number DAN-4048-G-SS-2065-00. Recommendations do not represent an official position or policy of USAID.