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https://hdl.handle.net/2142/70590
Description
Title
Epidemiology of Soybean Pod and Stem Blight
Author(s)
Sohn, Cheong Yeol
Issue Date
1983
Department of Study
Plant Pathology
Discipline
Plant Pathology
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Agriculture, Plant Pathology
Abstract
Experiment I was conducted during 1978 and 1979 to investigate the development of pod and stem blight (PSB) of soybeans in the field as affected by soil fumigation, application of benomyl, and inoculations with Phomopsis sp. and its effect on agronomic traits: plant height, lodging, yields, and seed quality of soybeans. Two soybean cultivars, Beeson and Woodworth, were used. Only in 1978, Phomopsis sp. infection on stems and pods was significantly greater in the inoculated plots when compared with the check plots. Both stem and pod infection in plots protected with benomyl were significantly lower than those in check and inoculated plots. Plant height and lodging were not affected by inoculation. Inoculations did not affect yields, but the seed weight of Woodworth in 1979 was significantly reduced by inoculation over the check. However, results suggested that yields could be reduced by severe infection. Seed weight was negatively correlated with stem infection. In 1978, seed germination of Beeson was greatly reduced by inoculation over the check, but was increased by benomyl applications, which caused mainly by Phomopsis sp. control. The recovery of Phomopsis sp. and Diaporthe from seeds were significantly greater in the inoculated plots when compared to the check plots. In 1978, the plots protected with benomyl, showed a significant decrease in the recovery of Phomopsis sp. over the check plots.
Experiment II was to investigate the effects of two cropping systems, as corn soybean rotation and continuous soybeans, in the development of PSB. Two cultivars, Wells and Williams, were used. In 1978 and 1979, stem infection in the continuous soybean field was greater than in the corn-soybean rotation field with no difference in pod infection, indicating that crop residue- or soil-borne inoculum of Phomopsis sp. contributed greatly to stem infection. Stem infection in 1979 was extremely high as compared with 1978 due to inoculum carryover from 1978 (a high disease incidence year). In the continuous soybean field, the plant height of Wells was significantly reduced probably because of severe infection with Phomopsis sp. due to a high inoculum level. PSB did not cause lodging in either field. The seed weight was much lower in 1979 than in 1978 in both fields, because of severe stem infection in 1979 due to a carryover of inoculum. In general, seed quality was not greatly affected by the cropping systems.
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