Date of Award
Master of Science
Plant and Soil Science
Soybeans [Glycine max (L.) Merrill] are a major commercial crop that originated in Eastern Asia, which date back 5,000 years ago in China and are still used worldwide today. Soybeans are considered an oil seed crop that averages twenty percent oil content and consists of thirty-five to forty percent protein. Soybeans are used in most aspects of the modern world as a source of protein for humans and animals alike. It is also used for its oils, which can be found in food, consumables, and plastic. Soybean production came about in the 18th Century in the United States as a hay crop and in some regions as an ornamental plant, but did not start being grown in large-scale production until the early 19th Century. Seed producing companies did not take interest in the plant until 1970, when Congress established the United States Plant Variety Act. This Act allows protection for companies against unauthorized use of proprietary material. Plant breeders focused on improving yield, drought tolerance, and disease resistance. Sudden Death Syndrome (SDS) is a disease of soybeans that affect soybean populations in the Western Hemisphere. SDS is a seedling disease in which a soil-borne fungal infection attacks the roots of a young soybean plant. This infection is more severe in soils highly saturated with water early in the planting year and then followed by cool weather before the soybean plant flowers in late summer. Yield losses commonly do not exceed ten to fifteen percent of a crop, but cases have occurred where yield was reduced over seventy percent due to SDS. Three species that affect the Western Hemisphere; Fusarium virguliforme (FV), formally know as Fusarium solani f. sp. Glycines (FSG); which mainly affects soybean production in the North American continent, Fusarium phaseoli and Fusarium tucumaniae, which affect the South American continent. SDS in the United States can account for yield losses occurring in primarily Arkansas, Iowa, Illinois, Indiana, Kentucky, Missouri, and Tennessee during 1999 to 2002 time period, with Iowa, Illinois, and Indiana having the most severe effects. SDS has rapidly spread throughout the United States and it was estimated to suppress the soybean yield in 2002, with damage that was valued at $157.4 million. There is not a 100 percent proven agronomic practice for controlling SDS, so the identification of host resistant genes are required in order to develop different varieties that will offer the producer the most economically efficient way to manage the disease.
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