Acetobacter diazotrophicus, a nitrogen-fixing bacterial endophyte, is believed to be responsible for biological nitrogen fixation (BNF) in sugarcane. However, no monocot has yet been unequivocally shown to receive fixed N through BNF. The main question addressed in this dissertation is whether A. diazotrophicus promotes plant growth, and if so, whether growth promotion is via BNF. Another question is whether the growth benefits can be extended to other grasses. To answer these questions, the nifHDK genes encoding the protein subunits of the nitrogenase enzyme were first isolated and sequenced. Secondly, Nif⁻ mutant strains were constructed by inserting a gene cassette in nifD. The growth of sugarcane plants inoculated with A. diazotrophicus wild type and Nif⁻ mutant strains were compared in growth chamber, greenhouse, and field experiments. A. diazotrophicus was also tagged with marker genes to investigate the colonization process in sugarcane and other grasses. The effect of A. diazotrophicus on the growth of other grasses was also determined. Analysis of the A. diazotrophicus NifHDK sequence revealed features typical of proteobacterial nifHDK genes and gene products. Phylogenetic analysis established the close relationship of A. diazotrophicus with the α-proteobacteria and the β-proteobacterium, Herbaspirillum seropedicae, another sugarcane endophyte. Nif⁻ mutant strains established endophytically in sugarcane plants equally well as wild type strains. ¹⁵N₂ incorporation experiments demonstrated that wild type strains but not the Nif⁻ mutants fixed N inside sugarcane plants with decreased fixation when plants were grown in medium with fixed N. In N-deficient conditions, sugarcane inoculated with wild type strains grew better and had higher total N content than either uninoculated or plants inoculated with Nif⁻ mutants. When N was not limiting, growth enhancement was observed in plants inoculated with either wild type or the Nif⁻ mutants. These results suggest that depending on the nitrogen condition, A. diazotrophicus promotes sugarcane growth via nitrogen fixation and other growth promoting factor. The results also indicated a possible strain-cultivar specificity in growth promotion. A. diazotrophicus colonized other grasses through different entry sites but was limited in the root. Under N-deficient conditions, wild type strain but not the Nif-- mutant promoted rice seedling growth indicating the beneficial effects of A. diazotrophicus to other grasses.

This educational ethnography describes and examines the training process of the World Bank's sponsored "Train and Visit" agricultural extension method which was introduced to the Peruvian jungle department of San Martin in 1980. The T&V training service attempts to transfer new crop growing technologies to a group of 46 small-scale subsistence and commercial farmers who make up the network of T&V's "contact farmers" in the Bellohorizonte sector of Tarapoto's Agricultural Extension Agency. Farmers who participated in this study live in remote high-jungle valleys of the San Martin province located in Peru's northeastern Amazon region. They also play an important "contact" role in transmitting agricultural information to neighboring farmers who are the beneficiaries in the "modernization" process observed. / Using ethnographic field research methods, this case study tries to reveal the intended and unintended socio-cultural effects produced by the local T&V farmer extension training methodology on some of the "marginalized" farmers of this jungle milieu. Farmers of this area are said to be "marginalized" because they lack access to education, health, arable land, water, credit, and other necessary life-supporting services. / A closer exmination of the interaction of cultural, socio-economic and political factors on the local farmer training process identified important cultural and technical factors which could be included in the redesign of a more appropriate farmer education model for the Peruvian high Amazon. / A major finding of this study is that considerable unplanned learning (informal learning) has already taken place through long-established culturally defined channels, like "reciprocal labor groups" and "father-to-son apprenticeships," and that these may be playing a role in the small-scale farmer development process. As part of this thesis, efforts were made to make "visible" these traditional learning activities and show how they may relate to formal education and contextual factors like each farmer's previous work experience, work style, geographic origin and the availability of important agricultural inputs like land, water, and credit. / Source: Dissertation Abstracts International, Volume: 49-07, Section: A, page: 1671. / Major Professor: George J. Papagiannis. / Thesis (Ph.D.)--The Florida State University, 1987.

<p>Type 2 diabetes is characterized by insufficient insulin secretion to maintain euglycemia in the setting of peripheral insulin resistance. The majority of insulin-resistant diabetics are obese, yet not all insulin-resistant obese individuals develop diabetes. This obesity/diabetes dichotomy suggests that genetic factors play a pivotal role in disease pathogenesis.</p><p>Gene mapping has identified genetic quantitative trait loci (QTL) influencing disease-related phenotypes. To uncover molecular pathways leading from genotype to clinical trait, we classify phenotypes in greater depth and identify QTL that influence combinations of physiological traits, mRNA levels, and metabolite abundance. A major challenge then becomes deciphering the causal interrelationships among correlated phenotypes. </p><p>In this dissertation, we develop methods for building causal direction into an undirected network by including QTLs for each phenotype. We then apply and validate these methods in an F2 intercross between the diabetes-resistant C57BL/6 leptinob/ob (B6ob/ob) and the diabetes-susceptible BTBR leptinob/ob (BTBRob/ob) mouse strains. We show that genomic analysis can be integrated with liver transcriptional and metabolite profiling data to construct causal networks for specific metabolic processes in liver. This causal network construction led to the discovery of a pathway by which glutamine induces Phosphoenolpyruvate carboxykinase (Pck1) expression.</p><p>To investigate glutamine induction of Pck1 in the context of diabetes, we perform mRNA expression analysis and metabolic profiling in liver of the parental strains. We find glutamine is decreased with obesity in both strains; in the diabetes-resistant B6 strain, liver Pck1 expression parallels glutamine abundance, but in the diabetes-susceptible BTBR strain, Pck1 is elevated with obesity. Follow-up in vitro studies indicate that α-ketoglutarate, which is elevated nearly two fold in the livers of BTBR relative to B6 mice in vivo, may mediate the glutamine effect. We hypothesize that hepatic Pck1 is regulated by glutamine abundance in the liver of B6 animals, but in the presence of high α-ketoglutarate, Pck1 becomes uncoupled from glutamine regulation in the livers of diabetes-susceptible BTBR mice.</p><p>Our method of causal network construction led to the discovery of glutamine induction of a key hepatic gluconeogenic enzyme, a pathway potentially disrupted in the diabetes-susceptible BTBR mouse. Future studies will include identifying hepatic mediators of the glutamine effect, and applying QTL-directed networks to multiple organs to ultimately define causal relationships between tissues involved in diabetes progression.</p> / Dissertation

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3229. Adviser: John B. Masiunas. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

This research describes one approach to commercializing new horticultural crops for the natural products industry. The use of aeroponic technology proved to be feasible for the production of difficult-to-harvest, high-value root crops. Using Arctium lappa Asteraceae ("burdock") as a model crop in a modified A-frame aeroponic growing unit, the biomass and phytochemical yields of roots grown in aeroponics were compared to controls grown in a typical greenhouse soilless peat/perlite/sand mixture. No significant differences were seen in the yields of root biomass, measured as dry weights. No significant differences were seen in the phytochemical quality of the roots, as measured by the concentration of chlorogenic acid. Variability in the concentration of chlorogenic acid appeared to be lower in roots from the aeroponically-grown plants, indicating the possibility of improving phytochemical consistency using this horticultural technology. The feasibility of producing raw materials for the herbal dietary supplement industry in Native American communities and on reservations was also examined. Research exploring the use of a matched savings program called Individual Development Accounts indicated that low- and moderate-income Native American families are interested in becoming producers of herbal crops, using aeroponic and conventional horticultural technologies. This model of economic development for rural Native American populations may provide an example for integrating various tribal and federal programs with private enterprises to provide entrepreneurial opportunities for supplemental farm-based and home-based income. Finally, the feasibility of introducing a line of Native American branded products into the herbal dietary supplement market was tested. The results of this research indicate that this industry is an appropriate venue for adding value to agricultural products through the imagery and association of Native American culture, providing the consumer is convinced of the authenticity of the products. This multi-pronged, interdisciplinary approach to the commercialization of new agricultural crops, particularly those targeting niche consumer groups, could be transferred to other agricultural products.

Remote sensing is a tool that is increasingly used in agriculture for crop management purposes. A ground-based remote sensing data acquisition system was designed, constructed, and implemented to collect high spatial and temporal resolution data in irrigated agriculture. The system was composed of a rail that mounts on a linear move irrigation machine, and a small cart that runs back and forth on the rail. The cart was equipped with a sensors package that measured reflectance in four discrete wavelengths (550 nm, 660 nm, 720 nm, and 810 nm, all 10 nm bandwidth) and an infrared thermometer. A global positioning system and triggers on the rail indicated cart position. The data was postprocessed in order to generate vegetation maps, N and water status maps and other indices relevant for site-specific crop management. A geographic information system (GIS) was used to generate images of the field on any desired day. The system was named AgIIS (A̲gricultural I̲rrigation I̲maging S̲ystem). This ground based remote sensing acquisition system was developed at the Agricultural and Biosystems Engineering Department at the University of Arizona in conjunction with the U.S. Water Conservation Laboratory in Phoenix, as part of a cooperative study primarily funded by the Idaho National Environmental and Engineering Laboratory. A second phase of the study utilized data acquired with AgIIS during the 1999 cotton growing season to model petiole nitrate (PNO₃⁻) and total leaf N. A latin square experimental design with optimal and low water and optimal and low N was used to evaluate N status under water and no water stress conditions. Multivariable models were generated with neural networks (NN) and multilinear regression (MLR). Single variable models were generated from chlorophyll meter readings (SPAD) and from the Canopy Chlorophyll Content Index (CCCI). All models were evaluated against observed PNO₃⁻ and total leaf N levels. The NN models showed the highest correlation with PNO₃⁻ and total leaf N. AgIIS was a reliable and efficient data acquisition system for research and also showed potential for use in commercial farming systems.

A data acquisition system to collect soil moisture readings at 60 field locations was developed. The system predicted a resistance value from a measured counts per time. An error was associated with the measured counts and time, however, this error was minimized by increasing the time for resistance measurement. The effect of temperature was minimized by an automatic calibration of the system before collecting readings. The Watermark electrical resistance moisture sensor was used to sense water content. The system, including eight sensors, was tested in the field. The data collected was difficult to explain. An evaluation of the Watermark sensors indicated a large variation from sensor to sensor, and also indicated a marked influence of soil texture on sensor resistance.

Guayule (Parthenium argentatum Gray), a semidesert shrub was evaluated as a potential rubber crop. Since polyploid guayule reproduces by apomixis, progeny of individual plants should duplicate the characteristics of their parent. This study was conducted to estimate variations within and among progeny families from single-plant selections. Ten progeny per family were individually evaluated for plant height, width, fresh and dry weight of clipped branches, rubber and resin content, and yield. Leaves of selected plants were analyzed by gradient polyacrylamide gel electrophoresis for esterase and peroxidase to estimate genetic relatedness between parents and progenies. Negative correlation was between parents and progenies for most characters, but none were statistically significant from zero. This suggests a low heritability for the characters measured. Esterase and peroxidase detected variation in banding between parents and progenies and among progenies. This study suggested that out-crossing and meiotic reduction have occurred among apomictic guayule lines.

Subsurface drip irrigation was compared to sprinkler irrigation on bermudagrass turf during three consecutive years using tertiary treated wastewater. Irrigation amount required by each treatment, visual appearance of the grass, shoot biomass production, and soil salinity were measured, and potential management problems were identified. The amount of irrigation water applied via subsurface irrigation was similar or higher than that applied via sprinkler irrigation for a turf of similar quality. Shoot biomass production did not differ between both irrigation methods when similar amounts of water were applied. Soil salinity, measured as electrical conductivity, was monitored at the beginning and end of each season. The changes in electrical conductivity at the end of every irrigation season did not negatively affect the appearance of the turf in any of the years. Emitter clogging by root intrusion was identified as a potential problem in the subsurface drip irrigation system. A series of greenhouse experiments were conducted to evaluate the effect of different herbicides and acids at several concentrations on root intrusion into subsurface drip emitters. The first greenhouse experiment was a study intended to identify chemical concentrations that could inhibit bermudagrass root growth in soil without negatively affecting the visual appearance of the grass. As a result, two herbicides, trifluralin and thiazopyr, and one acid, phosphoric acid, were selected for a second greenhouse experiment. The second greenhouse experiment focused on the effects of the two herbicides and the acid on root intrusion into subsurface drip emitters. Only the emitters treated with thiazopyr at the highest dose were completely clean, root-free emitters.

Since the mid-1970's, there has been active research on the development of Vernonia galamensis (Cass.) Less. as a potential new oilseed crop. Vernolic acid (cis-12:13-epoxy-cis-9-octadecenoic acid) comprises 70--75% of vernonia oil and is chemically reactive, affording it a variety of industrial applications. A concern in the domestication of an oilseed crop is to establish a breeding program to improve oil quality traits. The objectives of this research were to (1) develop a rapid procedure for seed analyses; (2) determine the development of vernonia oil; and (3) estimate the narrow-sense heritability (h 2) of oil quality traits. Successful separation of free fatty acids (FFA) and acylglycerides from small vernonia seed samples was achieved using aminopropyl solid phase extraction columns. Acylglycerides were eluted with a mixture of chloroform and isopropanol, while FFA were eluted with a mixture of acetone and trifluoroacetic acid. Four breeding lines from a collection of Vernonia galamensis held at the US Water Conservation Laboratory in Phoenix, AZ were used for the oil development study and grown in field trails in Phoenix and Tucson, Arizona. Seeds were collected on nine different days after flowering over the course of seed maturation. Seed samples were analyzed for FFA, acylglyceride constituent fatty acids, total acylglycerides, and total oil. In each breeding line, FFA content changed significantly throughout the course of the measurement period, and synthesis of acylglycerides constituent fatty acids followed a previously described pathway proceeding from C16:0 to C18:0 to C18:1 to C18:2 to C18:1 epoxy. Vernolic acid increased late in the measurement period, while total acylglycerides and total oil increased steadily over the period. Mature vernonia seed exhibited substantial variation in the amount of FFA, acylglyceride constituent fatty acids, total acylglycerides, and total oil. Sixty-nine half-sib families were created to study the heritability of FFA, vernolic acid, acylglycerides, and total oil production. Mature capitula were collected and analyzed individually for oil constituents. Narrow sense heritability estimates for these four oil quality traits were: FFA = 33%, vernolic acid = 65%, acylglycerides = 47%, and total oil = 50%. The results indicate potential for progress in selection for these traits.