Doctor of Philosophy / Department of Agronomy / Kassim Al-Khatib / Growth chamber, greenhouse and field experiments using conventional grain sorghum were conducted to 1) evaluate the differential response of grain sorghum hybrids to POST application of mesotrione at various rates and application timings, and 2) determine the physiology of tolerance of grain sorghum hybrids to mesotrione. Sorghum response ranged from susceptible to tolerant. Mesotrione dose-response studies on four sorghum hybrids revealed that injury symptoms were greatest in Pioneer 85G01 and least in Asgrow Seneca. Mesotrione applied EPOST (early POST) injured sorghum more than when applied at MPOST (mid POST) or LPOST (late POST) timings. Observed injury symptoms were not well correlated with grain yield and were transient, thus injury did not reduce sorghum grain yield. Foliar absorption or translocation of mesotrione in tolerant hybrids did not differ with that of susceptible hybrids but metabolism was more rapid in tolerant than in susceptible hybrids. Initial grain sorghum injury was severe and will likely be a major concern to producers. Field and growth chambers studies were conducted on herbicide-resistant grain sorghum to 1) determine the effect of quizalofop rates, application timings, and herbicide tank mixes on acetyl-coenzyme A carboxylase (ACCase)-resistant grain sorghum injury and yield, and 2) determine if herbicide metabolism is an additional mechanism that could explain the resistance of ACCase- and acetolactate synthase (ALS)-resistant grain sorghum. Depending on rate, EPOST application caused the greatest injury while the least injury occurred with LPOST application. Crop injury from quizalofop was more prominent at rates higher than the proposed use rate (62 g ha [superscript]-1) in grain sorghum. Sorghum grain yield was not affected by quizalofop regardless of rates or application timings. Weed control was greater when quizalofop was applied with other herbicides than when applied alone. Herbicide treatments except those that included 2,4-D caused slight to no sorghum injury. Results of the quizalofop metabolism study do not support the involvement of differential metabolism in the observed response of grain sorghum to quizalofop. Rimsulfuron metabolism by ALS-resistant sorghum is more rapid than the susceptible genotypes, thus explaining the observed rapid recovery of grain sorghum plants from rimsulfuron injury in the field.

Doctor of Philosophy / Department of Entomology / James F. Campbell / Phillip E. Sloderbeck / Robert "Jeff" J. Whitworth / Knowledge of factors influencing the establishment, persistence and distribution of stored-product pests aids the development of effective Integrated Pest Management (IPM) programs in food storage and processing facilities. This research focused primarily on Tribolium castaneum, which is one of the most important pests of mills. Populations of T. castaneum from different food facilities can potentially be interconnected by either their own dispersal behavior or by human transportation. Population genetic structure analyses based on microsatellites and other insertion-deletion polymorphisms (“indels”) showed that populations from different mills around the US are genetically distinct from each other, but the level of differentiation was not correlated with the geographic distance. A potential source of insect infestation within a food facility is spillage that accumulates outside or movement from bulk storage facilities on site. Results from three facilities showed that most stored-product species were captured both inside and outside buildings, but T. castaneum was rarely captured outside of the facilities. Spatial distribution of all species outside was associated with the proximity of buildings, not necessarily with areas with accumulated spillage. T. castaneum populations inside facilities are potentially exposed to frequent genetic bottlenecks resulting from structural fumigations. Changes in allele frequencies through time, based on the analysis of microsatellites and other indels in individuals collected in a mill, confirmed bottleneck effects. To understand how spatial distribution of T. castaneum within a mill could be influenced by environmental and physical factors, a range of variables were measured at each trap location. There was significant variation among trap locations regarding beetle captures and the variables measured, but increase in beetle captures correlated only with increase in temperature and spillage production. Tribolium castaneum response to visual cues could influence attraction to pheromone and kairomone olfactory cues used in traps. Results of laboratory experiments showed that adults respond to tall narrow black shapes and placing traps in front of these shapes can increase captures. This research provides new insights into factors influencing the spatial distribution of T. castaneum and could help in improving monitoring programs for this important pest of the food industry.

Master of Science / Department of Agronomy / Scott A. Staggenborg / In recent years, subsurface drip irrigation (SDI) acres have increased substantially. The use of SDI on corn (Zea Mays L.) in the Great Plains has increased due to increased land costs, reduced irrigation water availability, and higher commodity prices. Applying phosphorus (P) fertilizer through a SDI system becomes a major advantage, but further investigation of the interaction between water and fertilizer is needed. Sub-surface drip irrigation systems can be used to better improve the application efficiencies of fertilizers, applying in wet soil-root zones can lead to better uptake of soil applied materials. The objectives of this study were to determine how corn responds to P fertilizer applied via SDI and to create methodologies to simulate fertilizer and irrigation water compatibility tests for use in SDI systems. A plot sized SDI system was installed near Manhattan, KS to evaluate P treatments. Eight separate P fertilizers were applied via SDI mid-season at a rate of 34 kg P2O5 ha-1 and split-plots were created with 2x2 starter band at planting. Nitrogen was a non-limiting factor, with 180 kg N ha-1 applied as urea. Both starter fertilizer and injected fertilizer affected corn grain yield as indicated by the starter by treatment interaction. Split applying starter fertilizer at planting increased yield. A secondary laboratory study was conducted to evaluate the water and fertilizer interactions. A filtration system was used to simulate field conditions and each fertilizer/water mix was filtered through a 400 mesh filter paper to evaluate fertilizer precipitant formation. Sixteen common fertilizers were analyzed with different rates of Avail. Differences were observed between fertilizer treatments, visually and quantitatively. A secondary P soil movement field study was performed to quantify P concentrations around the SDI emitter. Soils were sampled in a 30.5 cm by 30.5 cm square adjacent to the emitter on a control treatment and a fertilized treatment, in both years of the study. Visual and quantitative differences were observed between the two treatments in both years of the study. When P fertilizers were added to the SDI system, higher P concentrations were found very close to the emitter orifice. Control treatments exhibited lower P concentrations around the emitter than fertilized treatments.

Master of Science / Department of Biology / Jesse B. Nippert / Jesse B. Nippert / Anthropogenic climate change is likely to alter the function and composition of ecosystems worldwide through increased precipitation variability and temperatures. To predict ecosystem responses, a greater understanding of the physiological and growth responses of plants is required. Dominant species drive ecosystem responses, and it is essential to understand how they respond to understand potential ecosystem changes. Dominant species, such as switchgrass (Panicum virgatum L.), posses large genotypic and phenotypic variability, which will impact the degree of responses to projected climate changes. I studied the physiological and growth responses of switchgrass, a common perennial warm-season C4 grass that is native to the tallgrass prairie, to alterations in precipitation amount and temperature. The first experiment I conducted focused on the responses of three ecotypes of P. virgatum to three precipitation regimes (average, 25% below, 25% above). I concluded that the physiological responses of photosynthesis, stomatal conductance, transpiration, dark-adapted fluorescence, and mid-day water potential in P. virgatum were explained by ecotypic differences. Robust responses to altered precipitation were seen in the water use efficiency, mid-day water potential, and aboveground biomass. Ecotypic differences were also seen in several aboveground biomass variables, and most strikingly in flowering times and rates. There were few interactions between ecotype and precipitation, suggesting precipitation is a strong driver of biomass production, whereas adaption of ecotypes to their local environment affects physiological processes. A second experiment studied the response of local populations of P. virgatum to nocturnal warming. Results showed significant differences in daytime E, daytime gs, and flowering phenology between treatments. Differences in aboveground biomass were between topographic positions. I concluded that water availability, based on topographic position, is a strong driver of P. virgatum aboveground biomass production, but nocturnal warming has the potential to impact flowering phenology, physiological responses, and exacerbate plant water stress. I also reviewed the literature on the ecological effects of implementing switchgrass cultivation for biofuel. From the literature review, I concluded that large-scale switchgrass cultivation will have widespread ecological impacts. If landscape heterogeneity is maintained through harvest rotations, no till farming, and mixed species composition, ecosystem services can be maintained while providing economic value.

Master of Science / Department of Agronomy / Curtis R. Thompson / Curtis R. Thompson / Postemergent herbicide options for grain sorghum are limited and increasingly challenged by the development of herbicide resistant weeds. The herbicide pyrasulfotole & bromoxynil (P&B) was evaluated for potential use in grain sorghum and for control of a suspected HPPD-resistant Palmer amaranth population. Field experiments were conducted near Manhattan and Rossville, KS, to evaluate grain sorghum response to P&B with and without 2,4-D applied to growth stages from 1-leaf through the flag leaf stage and tankmixed with 2,4-D ester, amine, or dicamba applied to 3- and 6-leaf sorghum. The addition of 2,4-D ester did not reduce sorghum injury from P&B alone. Increasing the rate of P&B increased injury. Treatments applied to 1- and 4-leaf sorghum were injured the most. All P&B treated sorghum, regardless of timing, yielded 8 to 20% less than the untreated check. Pyrasulfotole & bromoxynil applied alone or with dicamba injured sorghum less than 2,4-D applied at 3- or 6-leaf. Increasing the rate from 140 to 280 g ha[superscript]-1 2,4-D amine or ester increased injury by 6 to 11%. Yields were lowest when P&B was applied with 2,4-D amine at 140 g ha[superscript]-1 and 2,4-D amine or ester at 280 g ha[superscript]-1 compared to all other treatments. Increasing the rate of growth regulator herbicides decreased yields by 8% and did not reduce crop injury from P&B alone. Greenhouse and field experiments were conducted to evaluate the response of two suspected P&B-resistant (R1 & R2) and one susceptible (S) Palmer amaranth population to P&B, atrazine, and tembotrione. Herbicides were applied when plants were 7 to 19 cm tall. The S population was controlled with less than field use rates. A resistance index (RI) of 4.8 to 11.0 was determined for R1 and R2 in greenhouse and field experiments. Tembotrione controlled 100% of S in all experiments, while providing 63 to 86% injury to R1 and R2 populations. Atrazine did not control the resistant populations. Pyrasofotole & bromoxynil will be an valuable tool for weed control in sorghum, however, Palmer amaranth populations exist that will not be controlled.

Master of Science / Department of Agronomy / Johanna Dille / Nitrogen (N) fertilizer intended for the crop may benefit highly competitive weeds to the detriment of the crop. A field experiment was conducted in 2009 to determine the influence of increasing N fertilizer rates and increasing Palmer amaranth densities on weed biomass and grain sorghum biomass and yield. Three rates were 0, 67, and 134 kg N ha-1 and natural populations of Palmer amaranth were thinned to densities of 0, 0.5, 1, 2, 4, and 8 plants m-1 of row. Palmer amaranth biomass increased as weed density and N rates increased. Weed-free grain sorghum yields were similar across all three N rates, and parameter estimates of yield across Palmer amaranth densities were not different between N rates. Based on the parameter estimates from the rectangular hyperbola model, initial slope (I) as density approached zero was 16%. Maximum expected yield loss (A) at high Palmer amaranth densities was 68%. Palmer amaranth showed a high response to N and the higher N rate increased the ability of the weed to reduce grain sorghum yield. A greenhouse experiment was conducted to determine the influence of six N rates on growth of six selected plant species, including grain sorghum, soybean, yellow foxtail, velvetleaf, Palmer amaranth and shattercane. Covariance analysis was performed with N rate as a covariate. Biomass of all species increased as N rate increased in both runs of the study. Soybean responded the least to N rate of all species in regards to biomass, height and leaf area production. In the first run, the biomass of three grass species (grain sorghum, yellow foxtail, shattercane) had similar estimates of slope and intercept of biomass across N rates. In the second run, the biomass slopes of grain sorghum and shattercane differed from soybean and were the only slopes that differed between species. Palmer amaranth had the highest rate of response as N increased but slopes of height were similar for Palmer amaranth, grain sorghum and shattercane. Soybean leaf area slopes were different from grain sorghum, yellow foxtail, and velvetleaf, but all other slopes were not different among species. Addition of N to grain sorghum increased weed growth and resulted in more yield loss as a result of weed density. The greenhouse study demonstrated that grain sorghum and Palmer amaranth increased in response similarly to the addition of N. Alternative N fertilizer management could play a role in minimizing Palmer amaranth impacts in grain sorghum production.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Jack D. Fry / Researchers and practitioners can use numerous techniques to measure or estimate evapotranspiration (ET) from turfgrass but little is known about how they compare to ET using standard lysimeters. An investigation was conducted to compare measurements of ET from lysimeters (LYS[subscript]E[subscript]T) with ET estimates from the FAO56 Penman-Monteith (PM[subscript]E[subscript]T) and Priestley-Taylor (PT[subscript]E[subscript]T) empirical models, atmometers (AT[subscript]E[subscript]T), eddy covariance (EC[subscript]E[subscript]T), and a canopy stomatal conductance model that estimates transpiration (COND[subscript]T). Methods were compared at the same site during the 2010, 2011, and 2012 growing seasons. Overall, PT[subscript]E[subscript]T and EC[subscript]E[subscript]T were not different from LYS[subscript]E[subscript]T, whereas PM[subscript]E[subscript]T, AT[subscript]E[subscript]T, and COND[subscript]T, increasingly underestimated LYS[subscript]E[subscript]T. Differences exist among ET measurement techniques and one should employ the technique that best fits their situation. An atmometer is an inexpensive tool that can be used to measure turfgrass ET within microclimates, such as those typically found in an urban home lawn. An investigation was conducted to compare AT[subscript]E[subscript]T estimates with PM[subscript]E[subscript]T estimates within a number of lawn microclimates. Home lawns in Manhattan and Wichita, KS, were selected for study during the growing seasons of 2010 and 2011. Open sward AT[subscript]E[subscript]T was 4.73 mm d[superscript]-[superscript]1, whereas PM[subscript]E[subscript]T was 5.48 mm d[superscript]-[superscript]1. Within microclimates, AT[subscript]E[subscript]T was 3.94 mm d[superscript]-[superscript]1 and PM[subscript]E[subscript]T 3.23 mm d[superscript]-[superscript]1. Atmometers can provide practitioners with reliable estimates of PM[subscript]E[subscript]T within microclimates. Zoysiagrass (Zoysia spp.) is a common turfgrass used on home lawns and golf courses. However, poor shade tolerance and cold hardiness have limited its use in the transition zone. A study was conducted to determine changes and differences in growth and physiology among selected Zoysia over a three-year period (2010-2012) in the transition zone. The genotypes were 'Emerald' [Z. japonica × Z. pacifica], 'Zorro' [Z. matrella], 'Meyer' and Chinese Common [Z. japonica], and experimental progeny Exp1 [Z. matrella × Z. japonica], and Exp2 and Exp3 [(Z. japonica × Z. pacifica) × Z. japonica]. 'Zorro' and 'Emerald' experienced winter injury. 'Meyer', Chinese Common, and Exp1 showed poor performance over the three-years. The Exp2 and Exp3 progeny, maintained high percent cover, visual quality, and tiller density, and may provide practitioners more shade-tolerant cultivar choices in the transition zone.

Doctor of Philosophy / Department of Agronomy / Ganga M. Hettiarachchi / Urban gardens have been a popular re-use option in the transformation of brownfields—located in older industrialized cities and near peri-urban developments. They provide accessible, available, and affordable supplies of fresh fruits and vegetables, effectively reducing the enigma of “food deserts” across U.S. cities. However, direct (soil ingestion, inhalation) and indirect (soil-plant-human) human exposure concerns about real or perceived trace element contamination in urban soils persist due to previous use. Elevated lead (Pb) and/or arsenic (As) concentrations were found at two (Tacoma and Seattle, WA) urban gardens. The Tacoma site was contaminated with Pb (51 to 312 mg kg-1) and As (39 to 146 mg kg-1), whereas soil Pb at the Seattle site ranged from 506 to 2,022 mg kg-1, and As concentrations were < 20 mg kg-1. Experimental design at both sites was a randomized complete block with a split-plot arrangement (main plots: biosolids/compost vs. non-amended control; sub-plot: plant type). Tacoma site treatment included a Class A biosolids mix (TAGRO) with dolomite. The Seattle site was amended with Cedar-Grove Compost (CGC) plus dolomite. Efficacy of biosolids/compost amendment in reducing Pb and As concentrations was evaluated using root, leafy, and fruit vegetables. Soil Pb and As bioaccessibility were also evaluated. Food chain transfer of Pb and As in vegetables due to surface contamination of produce samples were evaluated on the basis of cleaning procedures. A laboratory incubation study and a controlled greenhouse experiment were conducted on soils collected from the Tacoma site. Effectiveness of addition of laboratory synthesized ferrihydrite (Fh: iron oxyhydroxide) and TAGRO mix, each alone or in combination were screened and tested on the Pb and As co-contaminated Tacoma soil. Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy studies of Pb and As were conducted on incubation study samples to understand treatment-induced Pb- and As-speciation changes. Dilution of soil Pb (10 to 23%) and As (12 to 25%) were observed for biosolids amendment at the Tacoma site, while CGC amendment resulted in 20 to 50% dilution in soil Pb at the Seattle site. Biosolids and CGC amendments reduced Pb concentrations in the vegetables by 50% to 71%. At both sites, Pb concentrations of root vegetables exceeded the MLs established by the Food and Agriculture Organization (FAO) and the World Health Organization (WHO). Arsenic concentrations in vegetables were below an estimated ML and were reduced by 46% to 80% when grown on biosolids amended soils. Laboratory cleaning further reduced Pb and As food-chain transfer in vegetables grown in contaminated urban soils. Laboratory incubation and greenhouse studies showed dissolution of Pb in TAGRO plus Fh, and Pb concentrations in Fh amendments were significantly lower than the other amendments. Bioaccessible Pb and As were low. Significant reductions in bioaccessible As were observed when soils were amended with both TAGRO and Fh. X-ray absorption spectroscopy results indicated that chloropyromorphite-like (stable Pb phosphates) phases were the most dominant Pb species. Arsenic existed mainly as As5+, scorodite (FeAsO4•2H2O)-like species in all the treatments ranging from about 60% (control) to about 70% (TAGRO plus ferrihydrite). Amendments utilizing both biosolids and Fh significantly reduce human exposure risks present in urban soils contaminated with Pb and As.

Doctor of Philosophy / Department of Agronomy / Allan K. Fritz / Heat stress is one of the major environmental constraints for wheat production worldwide. High temperature during grain filling in wheat leads to a significant reduction in yield. In this research, three different projects were completed. The first project was to study cytoplasmic effects on heat tolerance in wheat, where ten different alloplasmic lines of wheat were backcrossed with four different wheat varieties: „Karl 92‟, „Ventnor‟, „U1275‟ and „Jagger‟. The nuclear genome of the alloplasmic lines was substituted by backcrossing six times using the recurrent parents as males. During the fifth and/or fourth backcross, reciprocal crosses were made to develop NILs (Near Isogenic Lines) for cytoplasm. Sixty-eight NILs and their parents were evaluated in growth chambers for post-anthesis heat tolerance. Plants were grown in the greenhouse and placed under heat stress for 14 days starting at 10 days after anthesis. Growth chambers were maintained at 35°/30°C for heat stress and the greenhouse was maintained at 20°/15°C as the optimum temperature. Effects of high temperature on chlorophyll content and Fv/Fm (a chlorophyll fluorescence measuring parameter) were found to be significant. Cytoplasms 1, 4, 5, 8, 9 and10 provided greater tolerance in one or more nuclear backgrounds. These results indicated that cytoplasmic effects can contribute to heat tolerance of wheat. The second project focused on identification of quantitative trait loci (QTL) for thylakoid membrane damage (TMD), SPAD chlorophyll content (SCC) and plasma membrane damage (PMD), as these traits are found to be associated with resistance to heat stress and contributes to relatively stable yield under high temperature. A RIL (Recombinant Inbred line) population of a cross between winter wheat cultivars „Ventnor‟ and „Karl 92‟ was evaluated using two different temperature regimes (20°/15°C, 36°/30°C) imposed at ten days after anthesis. The aforementioned traits were evaluated and associated with various molecular markers (SSR, AFLP and SNP). The putative QTL associated are localized on chromosomes 6A, 7A, 1B, 2B and 1D and have the potential to be used in marker assisted selection for improving heat tolerance in wheat. In the third project, a transgenic approach to increase grain fill during high temperatures was investigated. Grain fill is reduced at temperatures above 25°C in wheat partly due to the inactivity of soluble starch synthase. We isolated a soluble starch synthase gene from rice that has the potential to overcome this deficiency during high temperatures and placed it behind both a constitutive promoter and an endosperm-specific promoter. Transgene expression and the effects of the transgene expression on grain yield-related traits for four generations (T0, T1, T2 and T3) were monitored. The results demonstrated that even after four generations, the transgene was still expressed at high levels, and transgenic plants produced grains of greater seed weight than Bobwhite control plants under the same environmental conditions. Thousand-seed weight under high temperatures increased 21-34% in T2 and T3 transgenic plants when compared to the non-transgenic control plants. In addition, the duration of photosynthesis was longer in transgenic wheat than in non-transgenic controls. Our study demonstrated that expression of rice soluble starch synthase gene in wheat can improve wheat yield under heat stress conditions.

Master of Science / Department of Agronomy / William T. Schapaugh / Remote sensing technologies might serve as indirect selection tools to improve phenotyping to differentiate genotypes for yield in soybean breeding program as well as the assessment of soybean cyst nematode (SCN), Heterodera glycines. The objective of these studies were to: i) investigate potential use of spectral reflectance indices (SRIs) and canopy temperature (CT) as screening tools for soybean grain yield in an elite, segregating population; ii) determine the most appropriate growth stage(s) to measure SRI’s for predicting grain yield; and iii) estimate SCN population density among and within soybean cultivars utilizing canopy spectral reflectance and canopy temperature. Experiment 1 was conducted at four environments (three irrigated and one rain-fed) in Manhattan, KS in 2012 and 2013. Each environment evaluated 48 F4- derived lines. In experiment 2, two SCN resistant cultivars and two susceptible cultivars were grown in three SCN infested field in Northeast KS, in 2012 and 2013. Initial (Pi) and final SCN soil population (Pf) densities were obtained. Analyses of covariance (ANCOVA) revealed that the green normalized vegetation index (GNDVI) was the best predictive index for yield compared to other SRI’s and differentiated genotype performance across a range of reproductive growth stages. CT did not differentiate genotypes across environments. In experiment 2, relationships between GNDVI, reflectance at single wavelengths (675 and 810 nm) and CT with Pf were not consistent across cultivars or environments. Sudden death syndrome (SDS) may have confounded the relationships between remote sensing data and Pf. Therefore, it would be difficult to assess SCN populations using remote sensing based on these results.