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Iowa State University

Soybean

Plant Pathology

Theses/Dissertations

Articles 1 - 13 of 13

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Studies On The Impact Of Cover Crops On Soybean Productivity And Root Diseases, Grazieli Da Araldi Da Silva Jan 2019

Studies On The Impact Of Cover Crops On Soybean Productivity And Root Diseases, Grazieli Da Araldi Da Silva

Graduate Theses and Dissertations

Soybean (Glycine max L.) and corn (Zea mays L.) are the two main field crops grown in the Midwest, and they are usually used in a rotation system (FAOSTAT, 2018). This cropping system contributes to the elevated nitrate levels found in the surface waters in the Midwest (David et al., 1997; Dinnes et al., 2002), along with higher risk of soil erosion (Pimentel et al., 1995) and loss of nutrients and organic matter (Burkart and James, 1999; David and Gentry, 2000). Cover crops, grown between soybean or corn harvest in the fall and planting of the subsequent crop in the ...


Soybean-Pythium Pathosystem: Search For Host Resistance And Interaction With Fusarium Species, Elizabeth Rose Lerch Jan 2017

Soybean-Pythium Pathosystem: Search For Host Resistance And Interaction With Fusarium Species, Elizabeth Rose Lerch

Graduate Theses and Dissertations

Seedling disease of soybean is an economically important disease that reduces crop stands and may reduce yield. Symptoms of seedling disease include pre- and post-emergence damping-off and root rot. Many species of Pythium and Fusarium cause seedling disease and are frequently recovered together from diseased soybean seedlings. Host resistance as a strategy to manage multiple pathogens has only briefly been explored in soybean and the interaction between these pathogens is unclear. To better understand the soybean-Pythium pathosystem, lab and growth chamber assays were conducted to accomplish the following objectives, 1) identify with resistance to seed and root rot caused by ...


Efficacy Of Soybean Seed Treatments In Iowa And The Effect Of Cold Stress On Damping-Off Caused By Pythium Sylvaticum, Mauricio Serrano Jan 2017

Efficacy Of Soybean Seed Treatments In Iowa And The Effect Of Cold Stress On Damping-Off Caused By Pythium Sylvaticum, Mauricio Serrano

Graduate Theses and Dissertations

Soybean (Glycine max (L.) Merr.) production is negatively affected by the occurrence of seedling diseases. In Iowa, the occurrence of seedling diseases is commonly associated with cool and wet weather soon after planting, and several Pythium spp. have been found as the predominant pathogens causing seedling disease. Increasing cost of the seed, risk of seedling diseases reducing stand in cold, wet soils, and the yield benefit sometimes provided by early planting have motivated an increase in the use of fungicide seed treatment. However, a positive effect of seed treatments on soybean plant stand and yield has not been clearly demonstrated ...


The Effect Of Fungicides And Pod Removal Alone Or In Combination On Green Stem Disorder Of Soybean And Further Investigation Of Genetic Components, Xavier Phillips Jan 2016

The Effect Of Fungicides And Pod Removal Alone Or In Combination On Green Stem Disorder Of Soybean And Further Investigation Of Genetic Components, Xavier Phillips

Graduate Theses and Dissertations

Green stem disorder (GSD) of soybean (Glycine max L. Merr.) is when stems remain green and fleshy after pods reach physiological maturity and are ready to harvest. Little is known about GSD and its causes. Although GSD has not been shown to directly impact yield, the immature green stems may lead to harvest issues. Harvesting at the right time is essential to preserve the quality of the seed. During 2014 and 2015, field experiments located in central Iowa were used to investigate the effect of fungicides, pod removal, and their interaction on GSD incidence. The objective of this research was ...


Soybean Vein Necrosis Virus: Impacts Of Infection On Yield Loss And Seed Quality And Expansion Of Plant Host Range, Melissa Irizarry Jan 2016

Soybean Vein Necrosis Virus: Impacts Of Infection On Yield Loss And Seed Quality And Expansion Of Plant Host Range, Melissa Irizarry

Graduate Theses and Dissertations

Soybean vein necrosis virus (SVNV) rapidly became a widespread soybean (Glycine max) virus within a few years of its initial confirmation in 2008. The economic impact of soybean vein necrosis (SVN) disease remains unknown. Soybean is a crop of global importance with nearly 4 billion bushels of soybeans produced in the United States in 2014. This study was designed to pursue two main questions; is there any yield loss or change in seed quality associated with SVN and are there horticultural or cover crop species that could be serving as sources of SVNV inoculum?

In order to determine if there ...


Identification And Characterization Of Brown Stem Rot Resistance In Soybean, Chantal Elaine Mccabe Jan 2016

Identification And Characterization Of Brown Stem Rot Resistance In Soybean, Chantal Elaine Mccabe

Graduate Theses and Dissertations

Breeding for pathogen resistance is an important objective to improve and protect soybean yields. In 2010, 14.4% of total soybean yield was suppressed by diseases. Brown stem rot (BSR), caused by the fungus Phialophora gregata, reduces yield by as much as 38%. To date, three dominant BSR resistance genes have been identified: Rbs1, Rbs2, and Rbs3. The objectives of my research were 1) to determine if plant introductions contained novel BSR resistance genes, 2) to determine the correlation between P. gregata hyphae growth and foliar symptoms as well as characterize the response of the three BSR resistance genes to ...


Studies On Cover Crops And Sudden Death Syndrome Of Soybean, Renan Kobayashi-Leonel Jan 2016

Studies On Cover Crops And Sudden Death Syndrome Of Soybean, Renan Kobayashi-Leonel

Graduate Theses and Dissertations

Soybean sudden death syndrome (SDS), caused by Fusarium virguliforme, is a major soybean disease affecting soybean production in the United States. In search for more diversified cropping systems, the adoption of cover crops in the corn-soybean rotation is being encouraged. However, there is lack of information regarding the impact that cover cropping can have on SDS. On the one hand, it is possible that the improvements in soil health caused by cover crop can create an environment that is not favorable to the disease. On the other hand, F. virguliforme is able to colonize many plant species and, if a ...


Genome-Wide Association And Epistasis Studies Of Sclerotinia Sclerotiorum Resistance In Soybean, Tara Catherine Moellers Jan 2016

Genome-Wide Association And Epistasis Studies Of Sclerotinia Sclerotiorum Resistance In Soybean, Tara Catherine Moellers

Graduate Theses and Dissertations

Sclerotinia stem rot or white mold (WM) [Sclerotinia sclerotiorum (Lib.) de Bary] is an important fungal disease affecting soybean [Glycine max (L.) Merr.] and causes yield and quality losses. WM is prevalent in cool and moist environments, particularly in the soybean growing regions of Northern United States and Canada. Although sources of complete resistance have not yet been identified, several quantitative trait loci (QTL) for partial resistance have been reported but generally using bi-parental mapping populations. Genome-wide association (GWA) studies have been used to dissect complex disease resistance traits in plants and to identify the genes controlling the expression. WM ...


Effects Of Ilevo® On Soybean Sudden Death Syndrome And Soybean Cyst Nematode, Edward R. Zaworski Jan 2014

Effects Of Ilevo® On Soybean Sudden Death Syndrome And Soybean Cyst Nematode, Edward R. Zaworski

Graduate Theses and Dissertations

Fusarium virguliforme, the causal agent of soybean sudden death syndrome (SDS), and Heterodera glycines, soybean cyst nematode (SCN), are two of the most important pathogens of soybean. Host resistance is currently the main management strategy for both pathogens, and there are few other options available for each pathogen. Seed treatments are now an option for farmers for use of pesticides in early plant development. Bayer CropScience recently registered a seed treatment, ILeVO® (fluopyram), with reported activity against both SDS and SCN. The research described in the following manuscript tested ILeVO® in different combinations with currently available seed treatment products for ...


Investigation Of The Arabidopsis Nonhost Resistance Mechanism Against The Soybean Pathogen, Phytophthora Sojae, Rishi Sumit Jan 2013

Investigation Of The Arabidopsis Nonhost Resistance Mechanism Against The Soybean Pathogen, Phytophthora Sojae, Rishi Sumit

Graduate Theses and Dissertations

Nonhost resistance (NHR) provides immunity to all members of a plant species against all isolates of a microorganism that is pathogenic to other plant species. Three Arabidopsis thaliana PEN (penetration deficient) genes, PEN1, 2 and 3 have been shown to provide prehaustorial NHR against the barley pathogen Blumeria graminis f. sp. hordei. Arabidopsis pen1-1 mutant is penetrated by the hemibiotrophic oomycete pathogen, Phytophthora sojae that causes root and stem rot disease in soybean. The P. sojae susceptible (pss) 1 mutant is infected by both P. sojae and the hemibiotrophic fungal pathogen, Fusarium virguliforme that causes sudden death syndrome in soybean ...


Fusarium Species Infecting Soybean Roots: Frequency, Aggressiveness, Yield Impact And Interaction With The Soybean Cyst Nematode, Maria Mercedes Diaz Arias Jan 2012

Fusarium Species Infecting Soybean Roots: Frequency, Aggressiveness, Yield Impact And Interaction With The Soybean Cyst Nematode, Maria Mercedes Diaz Arias

Graduate Theses and Dissertations

Fusarium root rot is a widespread and common disease in soybean. Several Fusarium species have been reported to infect soybean roots but their occurrence, aggressiveness and impact on yield have not been quantified. To gain a better understanding of the importance of root-infecting Fusarium species in soybean productivity in Iowa, a three year root survey, and greenhouse and field experiments were conducted in order to accomplish the following objectives, 1) characterize the frequency of Fusarium species associated with soybean roots from Iowa soybean fields, 2) determine aggressiveness of predominant Fusarium species towards soybean, 3) estimate the impact of Fusarium species ...


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 ...


Bacteria-Free Soybean Plants , Jerry Fred Strissel Jan 1970

Bacteria-Free Soybean Plants , Jerry Fred Strissel

Retrospective Theses and Dissertations

No abstract provided.