Master of Science / Department of Agronomy / Scott A. Staggenborg / Abstract Hard red winter wheat (Triticum aestivum L.) is the predominate crop grown in North Central Kansas; and no-till wheat production practices have gained popularity in this region. No-till advantages may include: increased stored soil moisture, decreased labor costs, and increased soil conservation compared with conventional cropping systems. Seeding rates and fertility rates are two important no-till management decisions for producers. Therefore, a two-year study was conducted to determine the optimum wheat seeding and fertility rates in north central Kansas comparing the winter wheat cultivars 'Overley' and '2145'. Treatments also included seeding rates (100 kg ha-1 vs. 134 kg ha-1) and fertility rates (0, 78, 112, 146 kg ha-1). A fungicide application study was also conducted with this two-year study but proved to be statistically insignificant during the two years. Overall, the variety selection and fertility rates affected grain yields. The higher fertilizer treatments increased wheat grain yields. However, the seeding rate yield differences were not significant either year of this study. In the fungicide study, 2145 responded more to fungicide applications than Overley in 2006; but in 2005 there was no statistical advantage for a fungicide treatment with either variety. For this study, wheat varieties were planted during the recommended optimum "fly-free" seeding date period (4 October through 10 October). Although this study did not record yield differences between wheat drilled at higher or lower seeding rate during the recommended seeding period, other research does indicate that seeding rates should be increased if planting dates are extended well beyond the optimum period. Further outcomes from this study indicate that nitrogen rates should be adjusted based on field yield expectations. Although timely rainfall and/or stored soil moisture are the most limiting yield factors in dryland wheat production in north central Kansas, research results indicate that wheat yields increase with higher fertility rates when moisture is not a limiting factor. This research may be applied to north central Kansas wheat fields particularly where no-till farming practices are being used in wheat following wheat fields.

Doctor of Philosophy / Department of Agronomy / William T. Schapaugh Jr / Harold N. Trick / Demands on value-added crops have been raised to improve agricultural, industrial, and economical value. Currently, transgene application is one of most effective methods to satisfy these demands. Success in herbicide-resistant soybean (Glycine max (L.) Merr.) has boosted genetic engineering to be used for biochemical, nutritional, cultural, and physiological improvements. The objectives of this study were to establish transgenic soybean lines with attenuated phospholipase D[Alpha] (PLD[Alpha]) activity in the seed, test the alteration of fatty acid profiles affected by transgene and somaclonal variation, and evaluate the physiological alteration of transgenic lines by both transgene and somaclonal variation. To change fatty acid profile in soybean seed, we attenuated PLD[Alpha] enzyme activity by an RNA interference construct using the PLD[Alpha] gene sequence. Two transgenic soybean lines were established by particle inflow gun bombardment of co-bombarding pSPLDi and pHG1 transgenes, and evaluated for the presence and expression of transgenes thoroughly through the T[subscript]5 generation. PLDα-suppressed soybean lines were characterized by decreased PLD[Alpha] enzyme activity and PLD[Alpha] protein both during seed development and in mature seeds. The PLD[Alpha]-attenuated transgenic lines, SW1-7-1-1 and SW1-7-1-2, contain 36% and 49% oleic acid in the filed and greenhouse evaluations, respectively, which are equivalent to the mid-oleic acid soybean lines improved by conventional breeding and mutagenesis. Phenotypic and genetic analysis of the transgenic lines suggested the possibility that the multi-copy transgene integration formed direct or indirect repeats by random ligation during integration and organization of transgenes in the soybean genome, and the transgene cluster with tandem repeats may consequently increase the probability of transgene silencing. Various factors, such as high humidity and temperature, result in the loss of seed viability. Fayette seed stored for two months since harvest exhibited about 95% viability; however Fayette seeds stored for 33 months at room temperature and uncontrolled relative humidity become non-viable. PLDα-attenuated transgenic soybean seeds have been produced by transformation. PLD-suppressed transgenic soybean seeds have maintained viability when stored for 33 months at room temperature. Germination of transgenic seed stored for 33 months ranged from 30 to 50%. Increased leakage of electrolytes associated with the loss of viability was observed in null-transgenic and background seeds versus transgenic seed. The increase in electrolyte leakage may have been induced by lipid peroxidation and free radical formation which can generate oxidative damage in the cell and subsequently decrease seed viability. Differences in the ultrastructure of cotyledon tissue were observed between PLD[Alpha]-suppressed soybean and the background cultivar. The loss of viability in the background cultivar was consistent with observations of the plasma membrane being detached from the cell wall complex and disorganization of oil bodies. Stresses caused by temperatures higher or lower than ambient are one of agricultural problems that reduce crop productivity in many areas and diverse species. To overcome the uncertainty of environmental fluctuations, efforts continue to improve high and low temperature tolerance in crops. PLD[Alpha]-suppressed transgenic events were produced by antisense suppression driven by constitutive and seed-specific promoters using the particle inflow gun (PIG) bombardment method. Nine fertile transgenic events suppressed the expression of PLD[Alpha] protein. PLD{Alpha] enzyme activity in T[subscript]1 seed was observed to be reduced by 25 percent compared to the non-transgenic control. When soybean seedlings were exposed to lethal freezing temperature, increased electrolyte leakage associated with oxidative damage and biophysical changes were observed in non-transgenic soybean, whereas membrane stability and integrity were maintained in transgenic soybean seedlings. The early growth of PLD[Alpha]-attenuated soybean seedlings was recovered from extreme heat-shock (45 °C) and freezing treatments (-8 °C). The disruption of the plasma membrane and organelles was observed in freeze-stressed non-transgenic control seedlings. On the other hand, the structures of the plasma membrane, oil bodies, and cell organelles in transgenic seedlings were partially sustained after enduring freezing and thawing stresses.

Master of Science / Department of Agronomy / William T. Schapaugh Jr / The soybean cyst nematode (Heterodera glycines) (SCN) is an important pathogen of soybean in the United States. Annual yield losses from SCN are estimated to be over $2 billion worldwide. However, SCN virulence or the ability of a nematode to grow on resistant soybean genotypes varies widely among SCN populations. Fortunately there are several genetic sources of resistance to decrease the virulence of the pathogen on soybean. The objectives of this research were to: 1) characterize the genetic diversity of soybean cyst nematode populations in Kansas, 2) determine the frequency of Kansas SCN populations virulent on PI88788, 3) determine which plant introductions used in the HG Type Test provide the best level resistance, and 4) compare the performance of commercial soybean cultivars to the plant introduction from which their SCN resistance was derived. Soil samples were collected from SCN-infested fields across the state. Each soil sample was taken to the greenhouse and planted to a susceptible soybean cultivar to increase SCN population. Following an SCN population increase, a HG Type Test was planted. H. glycines field populations were highly variable, not only in population densities, but also in their abilities to develop on soybean genotypes. Collected from a diverse range of environments, ten HG types were identified. About 50% of the H. glycines populations were virulent on PI 88788, and most of the populations were virulent on commercial SCN resistant lines which derived their resistance from PI 88788. The commercial lines tended to be more susceptible to SCN than the lines from which they derived their resistance, but few HG populations were virulent on PI 437654 or the commercial line that derived its resistance from PI 437654. These results suggest that sources other than PI 88788 should be used in the development of H. glycines resistant cultivars for Kansas. One possible source of resistance is PI 437654. Information about SCN diversity in Kansas will improve decisions regarding cultivar development and selection for SCN management.

Doctor of Philosophy / Department of Agronomy / Johanna A. Dille / Success of plants depends largely on their environment. A survey, field and greenhouse studies were conducted from 2006 to 2010 to characterize the dynamics of giant ragweed (AMBTR) and common sunflower (HELAN) in KS through determining their distribution, plant-soil feedback response and demography. The survey revealed a distinct distribution pattern within the state with HELAN being more dominant than AMBTR. Populations of AMBTR and HELAN from KS could be grouped by their emergence characteristics. Plant-soil feedback response of AMBTR and HELAN varied across sites with HELAN having a consistent positive feedback response while AMBTR had negative feedback response in IL, KS, MI-a, MI-B, OR and SD but not in MT. Interaction coefficient analysis was neutral for IL, KS and MI-b while positive for OR and SD and negative for MI-a and MT. Plant-soil feedback response of KS-derived populations of AMBTR and HELAN indicated that both KS-AMBTR and KS-HELAN seemed to grow best in soil preconditioned by another species. Seed survivorship over winter and summer, emergence, and population growth rates of both weed species varied over three years with HELAN having higher growth rates that AMBTR. This study showed that demographic success of HELAN and AMBTR was greatly influenced by the climatic conditions more than any other factors. AMBTR from IL, if introduced to the state can adapt to KS conditions. Further studies including impacts of soil biota, nutrient dynamics and biochemical processes such as allelopathy are needed to better understand the mechanism behind the plant-soil feedback response of the two weed species and its contribution to the demographic success of AMBTR and HELAN.

Master of Science / Department of Agronomy / Guihua Bai / Stem rust, caused by Puccinia graminis f. sp. tritici, has successfully prevented rust epidemics by Deployment of resistant cultivars in the past several decades. Unfortunately, race TTKS (termed Ug99) has defeated most stem rust resistance genes existing in commercial cultivars. Sr40, a stem rust resistance gene from Triticum timopheevii ssp. araraticum, was transferred to wheat and provides effective levels of seedling and adult plant resistance against Ug99. To characterize Sr40 in wheat, two mapping populations were developed from the crosses RL6088 / Lakin and RL6088 / 2174. RL6088 is an Ug99-resistant parent with Sr40. Since race TTKS is a quarantined pathogen, a US stem rust isolate RKQQ that is avirulent to Sr40 was used to evaluate the rust resistance in the F[subscript]2 and F[subscript]2:3 populations at the seedling stage. A total of 83 simple sequence repeats (SSR) primers on chromosome 2B were used to screen the parents for polymorphism. Each F[subscript]2 population was analyzed with the markers polymorphic between two parents. Marker Xwmc344 was the most closely linked to Sr40, at 0.7 cM proximal, in the linkage map constructed from the population RL6088 / Lakin, while Xwmc474 and Xgwm374 were also tightly linked. Xwmc474 was mapped 2.5 cM proximal to Sr40 in the RL6088 / 2174 population. Xwmc474 and Xwmc661 were flanking markers for Sr40 in both populations. Markers linked to Sr40 will be useful for marker-assisted integration of Sr40 into elite wheat breeding lines. In addition, a unknown stem rust resistance gene from another source, OK01307, a breeding line from Oklahoma State University shows partial resistance to Ug99, and was characterized using SSRs in this study. Two mapping populations were developed from cross OK01307 / Chinese Spring and OK01307 / LMPG-6. A total of 1300 SSR primers were screened for polymorphism between OK01307 and Chinese spring, and 1000 SSR primers were screened for polymorphism between OK01307 and LMPG-6. Polymorphic primers between parents and between bulks were used to screen the corresponding population. One Sr gene in OK01307 was mapped on chromosome 1BS of the both populations, which was closely linked to Sr24. Whether the gene is Sr24 per se or a new Sr gene that closely linked to Sr24 needs further investigation.

Master of Science / Department of Electrical and Computer Engineering / Steven Warren / The greenhouse in Throckmorton Hall at Kansas State University (KSU) has a temperature and humidity monitoring system. The system updates its measurements every thirty minutes online, and air temperature is controlled by an automated system. Each room has one temperature and humidity sensor box, which provides a suitable reference but is insufficient for more detailed plant research. To provide a distribution of temperature and humidity, a sensing system should be composed of a collection of sensors that gather data simultaneously. The new multi-point greenhouse monitoring system presented here can be helpful for plant research on a low budget. The demonstration system uses 27 sensor boxes in a 3x3x3 sensor grid (nine sensors at the same height and three different heights). Each sensor box contains temperature, humidity and light sensors that record data once per minute. MATLAB plots of these data indicate that temperature varied between 20 and 25 °C at night. Daytime temperatures are increased by sunlight, and rise to a maximum around noon. Sun-lit areas have higher temperatures than shaded areas, and during cloudy days all areas were almost the same temperature. Relative humidity is inversely related to temperature changes; when the temperature is stable, humidity is also stable. Humidity drops at noon because of increasing temperature and rises again at night. When researchers water the plants, humidity increases immediately. Greenhouse light intensity depends on the room design and the angle of the sunlight. Direct sunlight makes an obvious difference in shaded areas, and cloudy days promote even light distribution. Lighting at night time diffuses well at lower heights.

Master of Science / Department of Agronomy / David B. Mengel / Anhydrous ammonia (AA) is one of the most commonly used nitrogen (N) fertilizer sources for corn (Zea mays L.) in the US. Traditional knife applicators are slow, have high power requirements and create substantial soil disturbance. Thus, there is considerable interest in high speed, shallow placement, and low draft AA applicators like the newly introduced JD 2510 series, particularly for no-till production systems. The objective of this project was to compare a prototype high speed, low draft applicator (JD) with a traditional knife type AA applicator (TRAD) for irrigated and dryland corn production in the Kansas River Valley. Field studies were conducted from 2007 through 2009. Six N rates ranging from 0 – 224 kilograms N per hectare, in 45 kilogram increments, were applied at 3 application timings, Fall (FALL), Preplant (PRE), and Sidedress (SD) with both type applicators. Gaseous AA emissions were collected over a seven to nine day period after each application for both the TRAD and JD applicators for all application timings. The impact of applicator, timing and N rate was also measured on plant stand, earleaf N content, total N uptake, nitrogen use efficiency and grain yield. Statistically higher post application losses of ammonia at high N application rates were seen at all application timings with the JD applicator. However, these N losses were not of agronomic significance, and did not affect grain yield in 2007 or 2008. In 2009, there did appear to be a significant difference between applicators in grain yield, however this was primarily due to a significant yield decrease at the JD SD 224 kilograms N per hectare treatment from high application loss and resulting plant tissue damage. A significant response to N application was seen every year. Optimum N rate varied between years. FALL and PRE treatments had significantly higher grain yield than SD applications in 2008. However, in 2009 there was no significant difference in N application timing.

Master of Science / Department of Agronomy / Loyd R. Stone / Corn (Zea mays L.) yields are often reduced by limited pumping capacity of irrigation wells drawing from the High Plains Aquifer. As a result of decreased well capacities in this region, many irrigation systems no longer have the ability to meet peak irrigation (water) needs during the growing season. The purpose of this study was to measure easily identifiable plant characteristics of corn hybrids and relate those characteristics with the ability to maintain yield under water-limited conditions. This study involved measuring several plant characteristics of 18 corn hybrids grown under irrigated and dryland conditions near Tribune, KS during the growing seasons of 2005, 2006, and 2007. During each year, hot and dry conditions occurred during silking which resulted in large differences, and many poor yields, in the dryland plots. The number of days and growing degree days (GDD) to initiation of silking were the variables most strongly correlated with grain yield in the dryland environment. The shorter the time it took to reach initiation of silking the greater the grain yield. The number of days, or the GDD, to initiation of silking in irrigated environments did not have a significant correlation with corn grain yield. Other characteristics including canopy temperature, PAR (photosynthetically active radiation), color, leaf angle, number of internodes, number of leaves, and leaf N had no significant correlation with corn grain yield for either dryland or irrigated environments in 2005 and 2006. In this study using hybrids with maturity ratings between 98 and 118 d, there were no significant differences in grain yield in the irrigated environment. In the dryland environment, the hybrids used (98 – 118 d) in this study resulted in a decrease in grain yield with an increase in maturity. By considering the maturity of a hybrid, a producer will potentially be able to better select a variety that will perform well in a growing season with potential or likely severe water cutbacks as a result of limited water supply or reduced well capacity.

Master of Science / Department of Agronomy / Scott A. Staggenborg / Current demand for ethanol production is stressing feedstock production. Previous research has shown sweet sorghum and photoperiod sensitive sorghum [Sorghum bicolor (L.) Moench] as viable feedstocks which may supplement or replace current feedstocks. Studies were conducted at two dryland locations in north central and northeast Kansas in 2008 and 2009 to determine the effects of cultivar, nitrogen fertilizer rate, plant density, and harvest date on sweet sorghum juice and biomass yields. The cultivar study indicated the cultivar ‘M81E’ generally had the greatest yield. Other cultivars were not well suited for this region. No significant results were found in the nitrogen rate trial, indicating sweet sorghum may be insensitive to nitrogen fertilizer applications. The plant density trial results indicated that sweet sorghum possess a great ability to compensate for plant spacing. No differences were found in juice yields across densities, and the only difference found in total dry biomass was at the highest plant density. Results from the harvest date study indicate that sweet sorghum harvest should be delayed until at least the grain soft dough stage and can be continued for at least 10 days after a killing freeze without a yield penalty. Delaying harvest allowed for an increase in total dry matter and fermentable carbohydrates without a decrease in juice yield. Two studies were conducted at two dryland locations in northcentral and northeast Kansas in 2008 and 2009 to determine the effects of plant density on photoperiod sensitive sorghum yields, with an additional study to determine the effects of winter weathering. Photoperiod sensitive sorghum was found to be similarly insensitive to plant density, with few differences found in total dry biomass yield. Yields were found to decrease significantly due to winter weathering. A final study was conducted to examine a variety of sorghums as biofuel feedstocks. Photoperiod sensitive sorghum yielded the greatest in 2008 while sweet sorghum yielded less. In 2009, sweet and photoperiod sensitive sorghum yielded less than the cultivar TAMUXH08001. Sweet sorghum yields are generally the greatest with ‘M81E’ and when harvested after soft dough. Yields of both sorghums are occasionally influenced by plant density.

Doctor of Philosophy / Department of Agronomy / Charles W. Rice / Atmospheric concentrations of the greenhouse gases (GHG) carbon dioxide (CO2), nitrous oxide, and methane have been increasing since the Industrial Revolution. An expanding human population, increased fossil fuel use, extensive ecosystem disturbance, and intensive production agriculture have contributed to this increase. Storing carbon (C) in soil in natural and agricultural ecosystems has the potential to offset a portion of the future atmospheric increases in CO2 levels. Laboratory and field studies were conducted to evaluate basic mechanisms of C sequestration. The research reported here focuses on identifying strategies to reduce C loss from soil by (1) slowing plant residue decomposition rates, or (2) increasing soil fungal dominance and physical protection of soil C. Grain sorghum (Sorghum bicolor) hybrids were used in a laboratory experiment to determine the effect of varied amounts of lignin on plant residue C mineralization. The different levels of lignin in the hybrids was not strongly correlated with plant residue C mineralization. Another laboratory experiment investigated larger differences in lignin content between crop plants. Plant residue exhibiting the natural mutation referred to as brown midrib (bmr) also had lowered total lignin and different lignin chemistry. The bmr plants decomposed faster than the normal isolines, and the addition of nitrogen lowered overall mineralization. Nitrogen additions also significantly impacted the microbial community by lowering total phospholipid fatty acids (PLFA) and shifting fungal energy storage physiology. A field experiment was conducted to measure the soil microbial response to adding grain sorghum residue in both tillage (CT) and no-tillage (NT) agricultural ecosystems. The residue mineralized similarly in both systems, but the NT microbial population was stimulated significantly greater than CT. The fungal PLFA in NT 0-5 cm was higher than NT 5-15 cm, CT 0-5 cm, or CT 5-15 cm. A significantly greater amount of plant residue C was found in soil macroaggregates, as compared to microaggregates, at the conclusion of the experiment, regardless of tillage. More N was found in NT macroaggregates than in CT macroaggregates. The experiment identified two mechanisms for increased C storage in NT soils, as compared to CT soils.