Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2008. / Source: Dissertation Abstracts International, Volume: 69-05, Section: B, page: 2789. Adviser: Schuyler S. Korban. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

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 / Kimberly A. Williams / Ivy geranium (Pelargonium peltatum L’Herr ex. Ait.) and tomato (Solanum lycopersicum L.) are two economically important greenhouse crops known to be affected by non-pathogenic lesions on leaf tissues. These physiological disorders are often termed edema (oedema) or intumescences, but several other names have been used including enations, non-pathogenic galls or tumors, and neoplasms. These lesions, characterized by small protrusions on leaf tissues that become necrotic over time, are considered to be the result of environmental factors. Our research focused on determining what environmental factors affect these disorders on ivy geranium and tomato. The physiological disorder of ivy geranium is thought to be the result of water uptake exceeding transpiration, resulting in a build-up of water and solutes in leaf tissue that results in the blister-like protrusions in the epidermal layer. Current convention suggests that susceptible plants be grown in an environment that promotes transpiration with low humidity and infrequent watering. Over four experiments, we evaluated the effects of four root medium water contents, five rates of supplemental calcium application and two vapor pressure deficit (VPD) environments on three cultivars of ivy geranium. Our results indicate that high root medium water contents do not increase the incidence of edema on ivy geranium, but increase overall plant growth. Supplemental calcium had no affect on edema or growth, while our VPD results were inconclusive. These results suggest that current convention regarding cultural practices that abate the disorder be revisited. In tomato var. hirsutum ‘Maxifort’, the physiological disorder is characterized by individual epidermal cells swelling, which is unlike the disorder in ivy geranium where solutes build up across a group of epidermal cells. The environmental factors we focused on were two root medium water contents and supplemental UVB light. Our results suggest that root medium water content may play a role in development of tomato intumescences based on visual observation, and UVB light supplementation helps prevent the lesions from forming.

<p>Topography, vegetation, nutrient dynamics, soil features and hydroclimatic forcing are inherently coupled, with feedbacks occurring over a wide range of temporal and spatial scales. Vegetation growth may be limited by soil moisture, nutrient or solar radiation availability, and in turn influences both soil moisture and nutrient balances at a point. These dynamics are further complicated in a complex terrain, through a series of spatial interactions. A number of experiments has characterized the feedbacks between soil moisture and vegetation dynamics, but a theoretical framework linking short-term leaf-level to interannual plot-scale dynamics has not been fully developed yet. Such theory is needed for optimal management of water resources in natural ecosystems and for agricultural, municipal and industrial uses. Also, it complements the current knowledge on ecosystem response to the predicted climate change.</p><p>In this dissertation, the response of vegetation dynamics to unpredictable environmental fluctuations at multiple space-time scales is explored in a modeling framework from sub-daily to interannual time scales. At the hourly time scale, a simultaneous analysis of photosynthesis, transpiration and soil moisture dynamics is carried out to explore the impact of water stress on different photosynthesis processes at the leaf level, and the overall plant activity. Daily soil moisture and vegetation dynamics are then scaled up to the growing season using a stochastic model accounting for daily to interannual hydroclimatic variability. Such stochastic framework is employed to explore the impact of rainfall patterns and different irrigation schemes on crop productivity, along with their implications in terms of sustainability and profitability. To scale up from point to landscape, a probabilistic representation of local landscape features (i.e., slope and aspect) is developed, and applied to assess the effects of topography on solar radiation. Finally, a minimalistic ecosystem model, including soil moisture, vegetation and nutrient dynamics at the year time scale, is outlined; when coupled to the proposed probabilistic topographic description, the latter model can serve to assess the relevance of spatial interactions and to single out the main biophysical controls responsible for ecohydrological variability at the landscape scale.</p> / Dissertation

No description available.

No description available.

No description available.

Master of Science / Genetics Interdepartmental Program / Bikram S. Gill / TILLING (Targeting Induced Local Lesions IN Genomes) is a high-throughput, reverse genetics strategy for scanning mutagenized populations for point mutations in loci of interest. Originally, TILLING was used to investigate gene function in Arabidopsis and has since been similarly applied for gene functional analysis in other organisms. TILLING also allows the generation of novel genetic variation in specific genotypes and, thus, has been implemented as a tool for crop improvement. Ethyl methanesulfonate (EMS) is a widely used mutagen to induce point mutations in most TILLING protocols. M1 plants are then self-pollinated and M2 seed harvested. A single seed is grown from each M2 progeny and tissue taken for DNA isolation. M3 seed is cataloged. DNA is pooled to increase the efficiency and aid in mutation detection. Polymerase chain reaction (PCR) is used to amplify a locus of interest using the M2 DNA pools as a template. The PCR products are digested with an endonuclease that cleaves mismatched, mutant DNA, and the digested products are visualized. The pools for which PCR products are positive for a mutation are deconvoluted to determine which individual plant of the pool was responsible for the mutation. DNA from the positive individual is sequenced to determine the type of mutation (missense, nonsense, synonymous). Individuals with mutations that are more likely to disrupt gene function (nonsense and certain missense) are studied further by growing the corresponding M3 generation. In bread wheat, Triticum aestivum, TILLING is complicated by polyploidy: genes that have homoeologs require that the functionality of each be studied. If functional homoeologs are present for all three genomes, mutants must be identified for each homoeolog, followed by successive intercrossing to produce a triple mutant plant. As a model for wheat genetics, we propose TILLING in diploid wheat. EMS mutant populations were created in diploid wheat (Triticum monococcum ssp. monococcum) and the hexaploid bread wheat cultivar ‘Jagger’. The diploid and hexaploid wheat populations were screened for mutations at the waxy locus, GBSS1, as a validation of our population and for comparative analysis of mutation rates in 2x and 6x wheat. For diploid wheat, GBSSI was screened in 716 M2 plants, and one mutant was found for 1.9 Mb screened. 3 For hexaploid wheat, GBSSI was screened in 518 M2 plants, and 30 mutants were identified within a total of 657 Kb screened, giving a mutation frequency of one mutation per 22 Kb. The reasons for this vast difference in mutation frequency between diploid and hexaploid wheat are discussed. The diploid wheat population was further examined by screening for mutations within four lignin biosynthesis candidate genes, for a total of 2 Mb screened. A single mutant was discovered for both of the lignin genes PAL6 and HCT, giving a mutation frequency of one mutation per 1 Mb screened.