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Dynamics of Root Growth in Potato Fields Affected by the Early Dying Syndrome. J. B. Kotcon, Former research assistant, Department of Plant Pathology, University of Wisconsin, Madison 53706, Present address: Department of Plant Pathology, Cornell University, Long Island Horticultural Research Laboratory, Riverhead, NY 11901; D. I. Rouse(2), and J. E. Mitchell(3). (2)(3)Assistant professor, and professor, respectively, Department of Plant Pathology, University of Wisconsin, Madison 53706. Phytopathology 74:462-467. Accepted for publication 9 November 1983. Copyright 1984 The American Phytopathological Society. DOI: 10.1094/Phyto-74-462.

Root growth dynamics of potato cultivars Norgold Russet and Russet Burbank were studied in field plots infested with pathogens associated with the “potato early dying” (PED) syndrome. Root growth was determined from estimates of root diameter and length in 14 soil cores (5 cm in diameter) per plant in 1980 and from five soil cores (10 cm in diameter) per plant in 1981 and 1982. Treatments in 3 × 12-m field plots were: untreated, artificially infested with Verticillium dahliae, fumigated with methyl bromide, or fumigated and infested with V. dahliae. Mean root diameter decreased through the season, but root length reached a maximum at 69- 105 days after planting, then declined as the plants senesced. Average total root length per plant was 502 m for Norgold Russet in 1980 and was not significantly affected by treatments. Total root length per plant of Russet Burbank in fumigated plots reached 1,248 m in 1981 and 1,154 m in 1982. Root length in fumigated plots infested with V. dahliae was 21% less than in fumigated, noninfested plots in 1981 (P = 0.10), but reductions were not statistically significant in 1982. Root surface areas and volumes were greater in fumigated plots than in unfumigated plots and were less in plots infested with V. dahliae than in noninfested plots.

Additional keywords: plant growth, soil microbiology.