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Correlation of Growing Season Environmental Variables and the Effect of Early Dying on Potato Yield. L. J. Francl, Former postdoctoral research associate, Department of Plant Pathology, The Ohio State University (OSU), Ohio Agricultural Research and Development Center (OARDC), Wooster 44691, Present address: Nematology Laboratory, U.S. Department of Agriculture, Agriculture Research Service, Beltsville, MD 20705; L. V. Madden(2), R. C. Rowe(3), and R. M. Riedel(4). (2)(3)Associate professor, and professor, Department of Plant Pathology, The Ohio State University (OSU), Ohio Agricultural Research and Development Center (OARDC), Wooster 44691; (4)Professor, Department of Plant Pathology, OSU, Columbus 43210. Phytopathology 80:425-432. Accepted for publication 16 October 1989. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1990. DOI: 10.1094/Phyto-80-425.

Regression models for potato yield (Y) and yield relative to controls (RY) in relation to soil population densities of Verticillium dahliae and Pratylenchus penetrans at planting were developed based on 8 yr of data from Ohio microplot studies. The effect of environmental variables on variability in Y and RY left unexplained by models (i.e., residuals) then was investigated. Residuals for controls and treatments with P. penetrans, V. dahliae, and P. penetrans + V. dahliae were separately correlated with environmental variables calculated for various starting points and interval lengths of the growing season. Correlations of residuals with environmental variables for 12- to 18-day intervals were the most informative. Residuals of Y for all treatments were negatively correlated (P < 0.05) with several temperature variables over a 12- to 18-day period beginning 47-53 days after planting, suggesting a general depression of potato yield due to high temperature. Residuals of RY for treatments with V. dahliae and P. penetrans + V. dahliae were negatively correlated with several 18-day temperature variables beginning at 17?26 days after planting and again with some 18-day temperature variables at 68?71 days, suggesting a sensitivity of infected plants to high temperatures during these times. Total precipitation over an 18-day interval was negatively correlated with residuals of Y for the treatment with P. penetrans + V. dahliae beginning at 44 days after planting and again at 53?59 days. Residuals of RY for the treatment with V. dahliae were negatively correlated with precipitation accumulated over 12?18 days beginning at 38 days after planting and again at 62?65 days after planting. Six years of data from microplot experiments in a different Ohio location were analyzed similarly to assess the reliability of correlation results. There were sufficient similarities in correlation patterns for the two locations to suggest that periods of high temperature having a negative effect on yield of infected plants were correctly identified. If these relationships hold, it will be possible to forecast environmental impact on yield reduction due to potato early dying well in advance of symptom appearance.

Additional keywords: agrometeorology, Solanum tuberosum, yield loss models.