Dynamics of Root Growth in Potato Fields Affected by the Early Dying Syndrome

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Abstract
Root growth dynamics of potato cv. 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 5 soil cores (10 cm in diameter) per plant in 1981 and 1982. Treatments in 3 .times. 12-m field plots were the following: 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.