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Iowa State University

Soybean

Plant Sciences

Graduate Theses and Dissertations

2010

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Epidemiological Studies On The Infection Process And Symptom Expression Of Soybean Sudden Death Syndrome, Carlos Cecilio Gongora-Canul Jan 2010

Epidemiological Studies On The Infection Process And Symptom Expression Of Soybean Sudden Death Syndrome, Carlos Cecilio Gongora-Canul

Graduate Theses and Dissertations

Sudden death syndrome (SDS) caused by Fusarium virguliforme (Aoki, O'Donnel, Homma & Lattanzi) is one of the most important soybean (Glycine max (L.) Merr.) diseases in the US. Management strategies currently available for this disease are not always effective, partly due to the high variability in symptom expression that occurs in field environments. To clarify the relationship between progress of root rot and foliar symptoms, soybean seedlings were inoculated at five inoculum densities and were destructively sampled over a 50 day period. Disease severity and area under disease progress curve (AUDPC) increased in response to increasing inoculum density (P < 0.01), particularly for foliar symptoms. Root rot severity evaluated 15 to 31 days after inoculation (DAI) was most highly correlated (r ...


Agronomic And Seed Traits Of Soybean Lines With The Rag1 Gene For Aphid Resistance, Justin Lee Mardorf Jan 2010

Agronomic And Seed Traits Of Soybean Lines With The Rag1 Gene For Aphid Resistance, Justin Lee Mardorf

Graduate Theses and Dissertations

Soybean [Glycine max (L.) Merrill] yields can be reduced significantly by infestations of the soybean aphid (Aphis glycines Matsumura). A dominant allele, Rag1, providing resistance to the aphid was identified in PI 548663. The objective of this study was to compare the agronomic and seed traits of 27 BC2F2-derived lines with the Rag1 allele to those of 27 lines with the rag1 allele from the same segregating population. The lines were evaluated under aphid-infested conditions at two Iowa environments in 2008 and under aphid-infested and aphid-free conditions at three Iowa environments during 2009. There were significant differences in mean yield ...


Tillage Effects On Soybean Growth, Development, And Yield, Alecia Marie Kiszonas Jan 2010

Tillage Effects On Soybean Growth, Development, And Yield, Alecia Marie Kiszonas

Graduate Theses and Dissertations

Profit margins of soybean [Glycine max (L.) Merr.] in the United States have recently declined as a result of an increase in production and land costs. Decreased profits coupled with increasing environmental concerns such as erosion and runoff prompts more cost-efficient production practices. No-tillage production practices offer a lower cost of production in addition to decreased soil erosion and runoff. Additionally, soil quality can be improved over time in a no-tillage system, greatly increasing the yield benefits over time. Today, only 41% of Iowa's soybean production is under no-tillage production (Conservation Technology Information Center, 2010), although even more of ...