TCP genes comprise a large family of genes that have been implicated in a diverse range of plant developmental pathways ranging from lateral branching (Doebley et al, 1997) to organ symmetry (Luo et al, 1999) and leaf curvature (Nath et al, 2003; Palatnik et al, 2003). I studied three closely related Arabidopsis TCP genes, one of which was recovered in an enhancer trap screen to identify downstream targets of the regulator of inflorescence architecture, BREVIPEDICELLUS (Douglas and Riggs, 2005). The enhancer trap marker line served as a reporter for TCP15 expression. Data mining has revealed a possible link between TCP15 and the hormone auxin. Using the DR5::GUS molecular reporter for auxin accumulation I found that TCP15 and the related TCP14 genes limit auxin maxima in seedling and reproductive tissues and that auxin transport is necessary for correct TCP15 expression. The closely related TCP8 gene was found to regulate leaf shape as demonstrated by decreased leaf index values. The rounder leaves of tcp8 plants also exhibited increased adaxial trichome and stomatal densities resulting in significantly decreased spacing between adjacent cells. tcp8 leaves showed increased serration density suggesting that TCP8 limits marginal outgrowth. Vein patterning was also perturbed in the mutants. Vein loops were rounder and smaller, and decreased loop subdivision indicated that vein patterning is retarded in the mutant. TCP8 evokes organ-specific effects on vascular patterning as mutant rosette leaves showed increased vascular complexity, whereas mutant cauline leaves showed decreased vein complexity. These results suggest that TCP8 is necessary for correct leaf development. The Arabidopsis genome contains 24 TCP genes, many of which have not been characterized. Studies of these genes will lead to the identification of additional factors necessary to control plant architecture and enable us to optimize plant growth and yield using genetic engineering.

TCP genes comprise a large family of genes that have been implicated in a diverse range of plant developmental pathways ranging from lateral branching (Doebley et al, 1997) to organ symmetry (Luo et al, 1999) and leaf curvature (Nath et al, 2003; Palatnik et al, 2003). I studied three closely related Arabidopsis TCP genes, one of which was recovered in an enhancer trap screen to identify downstream targets of the regulator of inflorescence architecture, BREVIPEDICELLUS (Douglas and Riggs, 2005). The enhancer trap marker line served as a reporter for TCP15 expression. Data mining has revealed a possible link between TCP15 and the hormone auxin. Using the DR5::GUS molecular reporter for auxin accumulation I found that TCP15 and the related TCP14 genes limit auxin maxima in seedling and reproductive tissues and that auxin transport is necessary for correct TCP15 expression. The closely related TCP8 gene was found to regulate leaf shape as demonstrated by decreased leaf index values. The rounder leaves of tcp8 plants also exhibited increased adaxial trichome and stomatal densities resulting in significantly decreased spacing between adjacent cells. tcp8 leaves showed increased serration density suggesting that TCP8 limits marginal outgrowth. Vein patterning was also perturbed in the mutants. Vein loops were rounder and smaller, and decreased loop subdivision indicated that vein patterning is retarded in the mutant. TCP8 evokes organ-specific effects on vascular patterning as mutant rosette leaves showed increased vascular complexity, whereas mutant cauline leaves showed decreased vein complexity. These results suggest that TCP8 is necessary for correct leaf development. The Arabidopsis genome contains 24 TCP genes, many of which have not been characterized. Studies of these genes will lead to the identification of additional factors necessary to control plant architecture and enable us to optimize plant growth and yield using genetic engineering.

Doctor of Philosophy / Department of Agronomy / Allan Fritz / Wheat breeders are constantly working to develop new wheat varieties with improved performance for agronomically important traits such as yield and disease resistance. Identifying better ways of phenotyping germplasm, developing methods for predicting performance based on genetic information, and identifying novel sources of genetic disease resistance can all improve the efficiency of breeding efforts. Three studies relating to these research interests were conducted. Synthetic hexaploid wheat lines were screened for resistance to root-lesion nematodes, an economically important pest of wheat. This resulted in the identification of three lines resistant to the root-lesion nematode species Pratylenchus thornei. Grain yield data from multi-location yield trials and average yields for counties in Kansas were used to identify wheat production areas in Kansas. Knowledge obtained from this study is useful for both interpreting data from yield trials and deciding where to place them in order to identify new higher yielding varieties. These data also aided the final research study, developing a genomic selection (GS) model for yield in the Kansas State University wheat breeding program. This model was used to assess the accuracy of GS in conditions experienced in a breeding project. Available measurements of GS have been constructed using simulations or using conditions not typical of those experienced in a wheat breeding program. The estimate of accuracy determined in this study was less than many of the reported measurements. This measure of accuracy will aid in determining if GS is a cost efficient tool for use in wheat breeding.

Doctor of Philosophy / Division of Biology / Carolyn J. Ferguson / The genus Lappula Moench is a diverse group of herbaceous plants in the large, cosmopolitan family Boraginaceae. Over sixty species are recognized in Eurasia; many are found in cold deserts, steppes, and semi-deserts of Central Asia. Fewer species were described from western North America, and compared with the Asian species they are poorly known. Various North American taxa have been placed into synonomy under Eurasian species, and complex patterns of variation have made species circumscription challenging. The goal of this dissertation was to explore phylogenetic relationships between North American and Eurasian species and to revise the taxonomy of the North American species. A molecular phylogenetic study was initiated in order to infer patterns of relationships among the North American species relative to Eurasian diversity. Samples were collected from throughout the western United States and from Siberia. Additional samples of Eurasian species were taken from herbarium specimens. Sequences were generated for three DNA regions (the ITS region of the nuclear ribosomal DNA, and chloroplast intergenic spacers trnS-trnG and rpl32-trnL) and phylogenies were generated using parsimony and Bayesian analyses. Results were in general agreement among all analyses. The genus Lappula was recovered as a monophyletic group, with the exception of the morphologically anomalous L. sessiliflora (Boiss.) Gürke, which was sister to the genus Rochelia Rchb. The native North American species of Lappula and L. redowskii (Hornem.) Greene formed a clade. Samples of L. squarrosa (Retz.) Dumort., a Eurasian steppe plant with a wide introduced range in North America, grouped with samples from Eurasia. Sampled species of Hackelia Opiz, a genus sometimes treated as part of Lappula, formed a clade separate from the Lappula species sampled here. Herbarium and field studies resulted in a revised taxonomy for the North American Lappula. Nomenclatural problems were resolved; nine native species and four varieties were recognized along with the introduced Eurasian species L. squarrosa.

Using the short-lived radiotracer 13N, we examined the hypothesis that toxic, futile ammonia/ammonium (NH3/NH4+) fluxes at high external concentrations are mediated by ammonia-transporting aquaporins in roots of intact barley (Hordeum vulgare L.) plants. Effects of the aquaporin inhibitors zinc, copper, mercury, gold, silver, hydrogen peroxide, propionic acid, and nitrogen gas supported this hypothesis. Further tests with these inhibitors showed that changes in plant water potential and water content could be linked to NH3/NH4+ fluxes. An increase in external pH, causing an increase of NH3 in the nutrient solution, resulted in large increases of 13N influx, which can only be explained in energetic terms if the transported solute is neutrally charged. Taken together, the evidence here strongly supports the proposed hypothesis.

Using the short-lived radiotracer 13N, we examined the hypothesis that toxic, futile ammonia/ammonium (NH3/NH4+) fluxes at high external concentrations are mediated by ammonia-transporting aquaporins in roots of intact barley (Hordeum vulgare L.) plants. Effects of the aquaporin inhibitors zinc, copper, mercury, gold, silver, hydrogen peroxide, propionic acid, and nitrogen gas supported this hypothesis. Further tests with these inhibitors showed that changes in plant water potential and water content could be linked to NH3/NH4+ fluxes. An increase in external pH, causing an increase of NH3 in the nutrient solution, resulted in large increases of 13N influx, which can only be explained in energetic terms if the transported solute is neutrally charged. Taken together, the evidence here strongly supports the proposed hypothesis.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Dale J. Bremer / Steven J. Keeley / High temperature and drought may reduce quality in cool-season turfgrasses during summer in the transition zone. Texas bluegrass hybrids (HBG) are genetic crosses between native Texas bluegrass (Poa arachnifera Torr.) and Kentucky bluegrass (Poa pratensis L.) (KBG) that resemble KBG but may have greater drought and heat resistance than other cool-season grasses. The objectives of four studies were to evaluate high temperature, drought, and lower mowing height effects on HBG compared with KBG ('Apollo') and tall fescue (Festuca arundincea Schreb.)(TF, 'Dynasty'), compare their rooting characteristics, and investigate their membrane lipid molecular species compositional differences. Under high temperature (35/25°C, 14h light/10h darkness), HBG ('Thermal Blue') had greater quality and gross photosynthesis (Pg), and lower electrolyte leakage than KBG and TF in a growth chamber study. The combination of high temperature and drought (60% ET replacement) caused rapid declines in quality, but HBG generally performed better. In field and greenhouse studies, TF had more roots deeper in the profile than two HBG ('Reveille' and Thermal Blue) and KBG under well-watered conditions. In the field, quality and Pg were greatest in TF among turfgrasses. Performances in quality and Pg generally ranked: TF > Reveille >= Thermal Blue = KBG. In a separate mowing height and drought field study, HBG (Thermal Blue) generally had lower quality and Pg than KBG at both high (7.62 cm) and low (3.81 cm) heights but particularly at the low height. Drought resistance and tolerance to low mowing in Thermal Blue was similar to or poorer than in KBG. Under supra-optimum temperature (35 /25°C and 40 /30°C, 14h light/10h darkness), the ratio of digalactosyldiacylglycerol (DGDG) to monogalactosyldiacylglycerol (MGDG) was highest in HBG (Thermal Blue) and lowest in TF. Heat tolerance was also associated with higher phosphatidylethanolamine (PE) content, higher phosphatidylglycerol (PG) content, and reduced overall unsaturation compared with heat-sensitive. Results suggest that 40 membrane lipid molecules are potential biomarkers for heat tolerance and that compositional changes in lipids in response to heat may contribute to differences in heat tolerance among cool-season grasses. Generally, studies indicated greater heat resistance, but not drought resistance, in HBG than in KBG or TF.

Doctor of Philosophy / Department of Horticulture, Forestry, and Recreation Resources / Jack D. Fry / ‘Meyer’ zoysiagrass (Zoysia japonica Steud.) has been the predominant cultivar in the transition zone of the U.S. since its release in 1952, primarily because of its good freezing tolerance. However, it is slow to establish and recover after sod harvest, and has poor shade tolerance. I evaluated ‘Meyer’, some commonly used cultivars, and 18 progeny from crosses of ‘Emerald’ (Z. japonica × Z. tenuifolia Willd. ex Thiele) × Z. japonica or Z. matrella (L.) Merr. × Z. japonica for stolon growth characteristics; sod tensile strength and recovery after harvest; shade resistance; freezing tolerance and its relationship to autumn color retention; and the potential influence of dehydrin and chitinase gene expression in freezing tolerance. After planting vegetative plugs, rates of stolon initiation (r = 0.66 in 2007, r = 0.94 in 2008) and elongation (r = 0.66 in 2007, r = 0.53 in 2008) were positively correlated (P < 0.05) with zoysiagrass coverage. At 60 days after sod harvest, recovery growth coverage ranged from 17% to 97% and a progeny from Z. matrella × Meyer (97% coverage) demonstrated superior sod recovery growth to Meyer (38% coverage). Under 68% silver maple (Acer saccharinum L.) tree shade, stolon number was reduced 38 to 95% and stolon length 9 to 70% compared to turf in full sun. Several progeny from crosses between Emerald or a Z. matrella x Z. japonica produced more and/or longer stolons than Meyer in the shade, suggesting potential for increased shade tolerance. Autumn color in October and November, 2007 was positively correlated (r = 0.44 and r = 0.58, P < 0.01) with the lethal temperature killing 50% of tillers (LT50) in December, 2007. All grasses except Cavalier and one progeny were equivalent to Meyer in freezing tolerance with LT50s ranging from -0.2 to -12.2 oC. Dehydrin-like (11.9, 23, 44.3, and 66.3 kDa) and chitinase (26.9 kDa) gene expression increased with cold acclimation and was similar among all grasses. In general, some new zoysiagrass progeny exhibited superior growth and/or stress tolerances compared to Meyer, which bodes well for potential release of a new cultivar for use in the transition zone.

Master of Science / Department of Entomology / John C. Reese / The soybean aphid, Aphis glycines Matsumura, arrived first to North America during the midst of 2000. It is a very fast spreading insect and causes a high yield loss of above 50% in most of the soybean growing tracts of United States. Another important economic threat is it’s ability to transmit some viruses to soybean. Studies to control this exotic pest started early during the year of its arrival. But a complete integrated pest management (IPM) approach that includes a combination of different control measures has yet to be completely developed. Host plant resistance is one component of integrated pest management and is more sustainable than any other control methods against this insect. In the first study, more than 80 genotypes were screened with two given aphid biotypes, biotype 1 and biotype 2. It was found that the genotypes that were earlier resistant to biotype 1 (K1639, K1642, K1613 K1621, Dowling and Jackson) were susceptible to the new biotype 2 with large populations developing on these genotypes. But we found three new Kansas genotypes that showed resistance only against biotype 1, but not against biotype 2. However, the two of the Michigan genotypes (E06902 and E07906-2) showed resistance to both biotype 1and biotype 2. In second study, the feeding behavior analyses of aphid biotypes were done using the EPG, Electrical penetration graph, technique for a recorded 9 hrs probing time. The resistant and susceptible genotypes show significant differences in their EPG parameters, especially for the sieve element duration in both biotypes. Most of the aphids reached sieve element phase (> 90%) in susceptible genotypes, but only few (<30%) were reached in resistant genotypes. But, no differences were found in any other probing phases between resistant and susceptible genotypes, except the number of potential drops (PDs) in biotype 2. Thus, it is concluded that resistance is largely associated with phloem tissues and there could be some biochemical, physical or morphological factors that affect the stylet penetration in aphids.

Master of Science / Department of Horticulture, Forestry, and Recreation Resources / Cheryl Boyer / The nursery industry in the United States, particularly in the Great Plains region is growing; however, materials used in creation of artificial substrates used to grow ornamental nursery crops continue to increase in price. Eastern Redcedar (Juniperus virginiana L.) is an indigenous plant throughout much of the United States and, in the Great Plains, it has become a pest. Use of wood-based substrates (primarily composed of pine trees) has been proven effective in both nursery and greenhouse production. Eastern Redcedar chips (JVC) could become a local and sustainable resource for the horticulture industry throughout the Midwest. Experiments were conducted to determine if JVC could be used as a substrate to replace or supplement three major substrate components; pine bark (PB), perlite, or peat moss. Four studies evaluated ornamental crop growth: two focused on comparing nursery crop production in PB and JVC, one focused on greenhouse production in peat moss, and the last on plant propagation in perlite. The first experiment (Chapter 2) involved combining ratios of JVC and PB with two fertilizer rates to grow woody plants. It was shown that while higher levels of fertilizer produced larger plants, that plants grown at either rate of fertilizer showed the same growth trends. As JVC content increased more than 20%, growth measurements such as shoot dry weight and plant height decreased. This decrease in growth can be attributed to the physical properties of JVC, which showed that as JVC content increased so did airspace with a corresponding decrease in container capacity. A follow-up experiment (Chapter 4) evaluated several different particle sizes of JVC and a PB control. It showed that despite the different particle sizes JVC substrate produced less growth than plants grown in PB though plants grown in JVC were all similar to each other. Another experiment (Chapter 3) was conducted to evaluate if JVC as a replacement for peat moss in producing greenhouse-grown annual crops. JVC’s low container capacity hindered plant growth with each increase in JVC content associated with a decrease in growth. Finally a propagation experiment (Chapter 5) used a combination of finely-ground JVC and perlite to grow cuttings of woody and herbaceous plants. It was shown that, in most cases, JVC and perlite were equivocal rooting cuttings. This work demonstrates that JVC can be used as a PB and peat moss supplement, but not a replacement nursery and greenhouse crop production. Use of JVC as a perlite replacement for plant propagation is recommended.