<p>Fusarium ear rot and fumonisin contamination are serious problems for North Carolina maize growers. With the discovery of fumonisin toxicity to animals and humans, and the finding that no maize genotypes are resistant to Fusarium verticillioides infection or fumonisin contamination, management strategies for limiting fungal and toxin contamination of harvested grain are necessary. Maize ears were harvested weekly for 14 or 15 weeks after pollination and assayed for percent kernel infection and fumonisin contamination. Kernel infection and fumonisin contamination occurred before kernel maturity and increased throughout the season, with kernel infection peaking 7 to 10 weeks after pollination. Data from this experiment and data from grower?s fields indicate that early harvest is necessary to limit rotten kernels and fumonisin in harvested grain.Difficulty in identifying resistant genotypes has limited the development of more resistant hybrids. Many inoculation techniques have been employed to reproduce Fusarium ear rot with marginal results, primarily because differentially resistant and susceptible hybrids were not used to identify promising inoculation techniques. In my study, ears were treated with different inoculation techniques to reproduce ear rot and fumonisin contamination in hybrids of known resistance to Fusarium ear rot. Two inoculation techniques, Pinbar and Silk Channel, were able to separate hybrids on visible ear rot and fumonisin contamination. Addition of inoculum to ears appears important for screening hybrids for resistance to Fusarium ear rot and fumonisin contamination.<P>

Thesis (Ph. D.)--University of Washington, 1983. / Vita. Bibliography: leaves [136]-146.

Thesis (Ph. D.)--Oregon State University, 1970. / Typescript (photocopy). Includes bibliographical references (leaves 51-55). Also available on the World Wide Web.

Volatile organic compounds (VOCs) play important roles in plant indirect defense against herbivorous insects by attracting the natural enemies. I first used a tritrophic model system involving rice, rice fall armyworm (Spodoptera frugiperda), and the parasitoid Cotesia marginiventris to discover and characterize the volatile terpenoids and TPS genes involved in the indirect defense of rice against the insect herbivory with integrated functional genomics analyses. Seven rice TPS genes were found to be significantly up-regulated by both microarray and real-time PCR analyses, with one characterized as a linalool synthase and two as sesquiterpene synthases. The products of all three characterized genes covered most of the volatile terpenoids emitted by the fall armyworm-damaged rice. The products of all three characterized genes covered most of the volatile terpenoids emitted by the fall armyworm-damaged rice. In addition to the insect treatment, responses induced by defense hormone jasmonic acid were also examined with volatile analysis, gene expression profiling and enzyme assays. Only one TPS gene in the microarray analysis was up-regulated during the early response to jasmonic acid, and the gene was characterized as OsLMS (rice limonene synthase). Moreover, a homolog gene with similar sequence was characterized with limonene synthase activity and named OsLMS2. Both genes exhibited a time-dependent expression upregulation upon jasmonic acid treatment. The regulation of terpenoid volatile emission was also examined from the perspective of diurnal cycle. Our results showed that the emission of volatile terpenoids was linked to the diurnal cycle; however, the base level emissions were different among the products of three genes. The volatile terpenoid biosynthesis and emission were regulated at both TPS gene expression level and the substrate level. To further understand the molecular evolution of plant indirect defense against herbivorous insects, I also investigated the evolution of the TPS gene family using comparative genome analyses. These analyses revealed both a rapid evolution of the TPS gene family and a conserved group of monoterpene synthase with a deep evolutionary origin. Biochemical analysis of one of the poplar TPS genes in the conserved group showed linalool synthase activity.

The objective of this research was to compare the effects of combinations of a wide range of cropping sequences and soil bio-covers on soil organic carbon (SOC) and Heterodera glycines under no-tillage. The experiment used a split-block design with four replications at the Milan (RECM) and Middle TN (MTREC) Research & Education Centers. The whole-block treatment was cropping sequences of corn (Zea mays), soybean (Glycine max), and cotton (Gossypium hirsutum). The split-block was bio-covers of winter wheat (Triticum aestivum), hairy vetch (Vicia villosa), poultry litter, and fallow. Soil samples were taken over four years of experimentation. A novel technique was developed to measure SOC called near infrared reflectance spectroscopy (NIR). Partial least squares regression was used to predict SOC as measured by NIR. Results were compared to assess the reliability of NIR determination of organic carbon. NIR analysis correlated well (r greater than 0.9) with SOC as determined by combustion. NIR was therefore considered sufficiently accurate for quantifying soil organic carbon. Overall, both sites showed a small but consistent loss in carbon over all treatments. The average losses of SOC at the 0-5 cm depth were 1.06 and 1.40 Mg ha-1 at RECM and MTREC, respectively. In the subsurface, mean SOC loss at RECM was 1.43 Mg ha-1. Conversely, the subsurface SOC at MTREC was 3.14 Mg ha-1 higher than preexperiment levels. Crop sequence had a significant effect on change in SOC (P ≤ 0.05) in both surface and subsurface regions at RECM. Sequences with two or more years of cotton tended to lose significantly more (P ≤ 0.05) SOC than those with two or more years of soybean. The poultry litter bio-cover lost less surface SOC (0.58 Mg ha-1) than those under vetch (1.33 Mg ha-1) or fallow (1.8 Mg ha-1). Soybean cyst nematode (SCN) eggs were found in sequences containing no soybean throughout the experiment, indicating survival of over seven years without soybean. Sequences with two or more years of soybean had significantly higher (P ≤ 0.01) SCN egg density than others, with continuous soybean having the greatest egg population density. One year of rotation with a non-host crop typically reduced SCN egg population density by more than 50%.

Known members of the plant SABATH family of methyltransferases (MTs) have important biological functions by methylating hormones, signaling molecules and other metabolites. This dissertation aims to systematically investigate the biochemical and biological functions and evolution of SABATH genes in plants. The genomes of rice and poplar have been fully sequenced, which provides unprecedented opportunities for cross-species comparison of the SABATH family. Using a comparative genomic approach, 41 and 33 SABATH genes were identified in rice and poplar, respectively. The expression of these genes in different tissue was analyzed using RT-PCR approach and some genes highly expressed in multiple tissues were cloned. The cloned cDNAs were expressed in E. coli to produce enzymes. Recombinant proteins were tested with a large number of compounds for MT activities. In poplar, two proteins were determined to have MT activities with indole-3-acetic acid (IAA) and jasmonic acid (JA), respectively. Biochemical and gene expression evidence suggests that poplar IAMT (PtIAMT1) has an important role in poplar development through IAA methylation. Poplar JMT (PtJBMT1) shows high levels of expression at multiple tissues under normal conditions, and the expression of PtJBMT1 was slightly induced by wounding and methyl jasmonate treatment, suggesting it has a role in poplar development and defense. Two SABATH genes, IAMT (OsIAMT1) and BSMT (OsBSMT1), were identified in rice. The high level of OsIAMT1 transcripts in rice roots and panicles implies that OsIAMT1 is involved in root and panicle development. OsBSMT1 has MT activities with both salicylic acid and benzoic acid. The specific induction of OsBSMT1 by herbivory and enhanced emission of methylsalicylate support that it has a specific role in plant response to insects. The evolution of the SABATH gene family was also investigated based on the identified SABATH genes in plants using comparative genomics analysis. Phylogenetic analysis revealed that IAMTs in Arabidopsis, rice and poplar are highly conserved, suggesting IAMTs are evolutionarily ancient. However, SAMTs in these plant species are divergent, indicating it is possible that SAMTs were evolved after the split of these plant lineages.

This study focused on three aspects of plant improvement for insect resistance including: testing of candidate organisms for their production of insecticidal proteins, testing of transgenic plants expressing insect resistance genes, and testing novel systems for the evaluation of insect resistance genes. In the initial part of this study, the candidate fungus Beauveria bassiana was tested for its production of insecticidal proteins through a series of insect bioassays containing fungal protein extracts. These extracts were shown to be orally toxic to Plutella xylostella (diamondback moth) and Spodoptera frugiperda (fall armyworm). Assays involving protease treatments significantly decreased mortality indicating the presence of a protein based oral toxin. The following research tested transgenic tobacco plants expressing proteinase inhibitors from Brassica oleracea (cabbage) and Manduca sexta (tobacco hornworm) on the insect pests Helicoverpa zea (corn earworm) and Heliothis virescens (tobacco budworm). Insects fed transgenic tobacco were able to adapt to the recombinant proteinase inhibitors to varying degrees and resulted in no major impacts on insect growth and development. The last part of this study tested a novel insect resistance gene screening system. Agroinfiltrated tobacco transiently co-expressing genes encoding GFP with either a known insecticidal protein (Bt Cry1Ac) or a candidate gene (Brassica oleracea proteinase inhibitor, BoPI) were fed to larval H. zea. Insects fed the known insecticidal protein experienced high mortality. Insects fed tobacco expressing GFP and BoPI showed significant decreases in growth compared to those fed GFP only tissue. Insects feeding on GFP only tissue showed unexpected increases in growth and development compared to insects fed control tissue. Agroinfiltration coupled with an insect bioassay constitutes an efficient system for the evaluation of candidate insect resistance genes.

A general overview of family Psychodidae is given. Genus Eurygarka Quate is revised to include three species. Genus Gondwanoscurus Jezek is revised to include seven species. The status of genus Stupkaiella Vaillant is revised. Eight new Nearctic species: Eurygarka cyphostylus sp. nov., E. nelderi sp. nov., Stupkaiella lasiostyla sp. nov., S. robinsoni sp. nov., S. capricorna sp. nov., Trichomyia rostrata sp. nov., Australopericoma delta sp. nov., and Threticus thelyceratus sp. nov., and two new Oriental species: Gondwanoscurus cruciferus sp. nov. and G. ornithostylus sp. nov. are described. Two Nearctic species: Eurygarka helicis (Dyar) and Stupkaiella bipunctata (Kincaid), and four Oriental species: Gondwanoscurus ejundicus (Quate), G. eximius (Quate), G. mcclurei (Quate) and G. praecipuus (Quate) are redescribed. A list of species collected during a survey of the Psychodidae of Great Smoky Mountains National Park is given, and a key to the genera of Psychodidae occurring in GSMNP is provided. A classification of psychodid subfamilies based on morphological and molecular evidence is proposed.

This research focused on understanding genetic responses of plants to explosives, which is necessary to produce plants to detect and clean soil and water contaminated with toxic explosive compounds. The first study used microarray technology to reveal transcriptional changes in the model plant Arabidopsis thaliana exposed to the explosive compounds RDX (hexahydro-1,3,5-trinitro-1,3,5-triazine; Royal Demolition Explosive or Research Department Explosive) and TNT (2,4,6-trinitrotoluene). This study yielded a list of genes up- and downregulated by explosive compounds, which can be potentially used for phytoremediation (remediation using plants) or phytosensing (detection using plants) of explosive compounds. The second study presented biotechnology tools to enhance phytosensing that might have application in not only explosives phytosensing but also sensing of other contaminants or important biological agents. This study addressed the problem of low detectable levels of reporter gene signal from a phytosensor and the results suggest the potential use of a site-specific recombination system to amplify the reporter gene signal. The final study addressed microarray data analysis and best practices for statistical analysis of microarray data. Standard parametric approaches for microarray analysis can be very conservative, indicating no unusable information from expensive microarray experiments. A nonparametric method of analysis on a variety of microarray datasets proved to be effective in providing reliable and useful information, when the standard parametric approach used was too conservative.

Rhinocyllus conicus Fröelich and Trichosirocalus horridus (Panzer) were introduced from Europe into North America as biological control agents of the exotic weed species Carduus nutans L. Concern exists over the feeding of these weevils on at least 25 species of native Cirsium thistles. Research was conducted to 1) estimate phenological synchrony of the eight thistle species in Tennessee with R. conicus and T. horridus, 2) investigate naturally-occurring populations of the five native Cirsium thistle species for non-target activity by R. conicus and T. horridus, 3) quantify the impacts to plants of each thistle species to feeding of R. conicus and T. horridus, and 4) identify potential areas of non-target feeding by the weevils using spatial analysis. Phenologies of two native species, C. carolinianum and C. horridulum, are synchronous with R. conicus reproduction, and all eight thistle species are phenologically synchronous with the reproduction of T. horridus. No non-target activity by R. conicus was observed in naturally-occurring populations of Cirsium thistles, but adults of T. horridus were documented for the first time on the native species C. carolinianum, C. horridulum, and C. muticum. In caged plant studies, larvae of R. conicus completed development in heads of C. carolinianum and C. horridulum and reduced seed numbers of both native species. Basal meristems of all eight thistle species exposed to T. horridus were damaged at varying levels in caged plant studies, but no other impacts to plants were observed. Spatial analyses showed associations between Mahalanobis distance values and plant counts of Carduus nutans and Cirsium carolinianum in predicted habitats, and the occurrence of Carduus nutans was associated with the occurrence of both weevil species in these habitats. About 12% of the total study area consisted of habitats where C. nutans and Cirsium carolinianum overlap. The potential exists for these weevils to utilize native Cirsium species found in Tennessee as plant hosts. The spatial model developed during this study not only allows potential monitoring of populations of C. carolinianum to be more targeted, but also may be modified to apply to other systems involving interactions among introduced and native species.