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Ecology and Epidemiology

Effects of Seed Quality, Seed Treatment, Soil Source, and Initial Soil Moisture on Soybean Seedling Performance. R. S. Ferriss, Department of Plant Pathology, University of Kentucky, Lexington 40546; R. E. Stuckey(2), M. L. Gleason(3), and M. R. Siegel(4). (2)(3)(4)Department of Plant Pathology, University of Kentucky, Lexington 40546, (3)Current address: Department of Plant Pathology, Seed and Weed Sciences, Iowa State University, Ames 50011. Phytopathology 77:140-148. Accepted for publication 1 July 1986. Copyright 1987 The American Phytopathological Society. DOI: 10.1094/Phyto-77-140.

Greenhouse experiments were conducted in which untreated and carboxin-thiram treated seeds from relatively high or low quality seed lots were incubated for 3 days in five soils adjusted to specific matric potentials. Soils were then adjusted to matric potentials near-optimum for germination. Greenhouse results were compared with results of concurrent field experiments. In general, seed lot quality and seed treatment had more effect on establishment (proportion of seeds producing seedlings with opened true leaves) than did soil source or nonsaturated soil moisture treatments. Seed treatment increased establishment more for lower than for higher quality seeds. Low soil moisture levels decreased establishment more from lower than from higher quality seeds. Establishment was greatly reduced after incubation in saturated soil compared with all nonsaturated soil moisture levels. Establishment after incubation in saturated soil was increased greatly by seed treatment, but was affected little by seed lot. Symptoms of root and hypocotyl disease were most severe after incubation at nonsaturated soil water potentials greater than approximately 1.0 bar, were reduced by seed treatment, but were not affected by seed lot. There was no discernible difference in the performance of seeds that had been treated before or after 5-mo storage. In general, field and greenhouse results were similar; however, soil pasteurization by methyl bromide-chloropicrin fumigation resulted in a greater increase in establishment in the field than in the greenhouse. These findings indicate that caution should be used in comparing the results of seed quality tests of fungicide treated seed lots with those for untreated seed lots, that seed treatment can improve the performance of both high and low quality seed lots, and that it may be advantageous to treat all soybean seeds at the time of cleaning.

Additional keywords: damping-off, Glycine max, Phomopsis longicolla, Phomopsis sp., pod and stem blight, seed vigor.