The weed red rice is a major problem in rice producing areas world wide. All of the red rice in commercial rice fields in the United States has traditionally been considered to be the same species as commercial rice, Oryza sativa. However, using DNA markers it was found that most of the red rice with black hulls was sufficiently divergent to be considered a separate species. This includes TX4, a red rice ecotype that has been reported to have considerable natural tolerance to the herbicide glufosinate. TX4 is closely related to samples that have been classified as Oryza rufipogon. However, it was shown that both the TX4-like red rice from commercial fields and most of the Oryza rufipogon accessions in the US National Small Grains Collection are more accurately classified as Oryza nivara. This is significant since Oryza rufipogon is regulated under the Federal Noxious Weed Act, while Oryza nivara is not. Oryza nivara closely related to TX4 was found to be widely distributed across the rice production areas of Texas and was also found in Arkansas, Louisiana, and Mississippi. Of 240 samples from across Texas, 23 samples from six different counties were identical with TX4 with all 18 DNA markers tested. The reported glufosinate tolerance of TX4 is a potential problem since this same herbicide would be used in conjunction with genetically modified (GM) that is being developed as a method of red rice control. Thus, field, greenhouse and tissue culture studies were conducted to evaluate the degree of glufosinate tolerance in TX4. TX4 typically was severely damaged by glufosinate, but not efficiently controlled. Even with the maximum number of herbicide applications at the proposed maximum label rate, TX4 often re-sprouted and produced viable seed. Herbicide tolerance was found to be variable, but appears to be sufficient to present a problem with the use of the GM glufosinate resistant varieties currently under development, particularly when combined with variation in the response of ??sensitive?? varieties.

In this work, 80% lime-treated rice straw and 20% lime-treated chicken manure were used as substrates in rotary fermentors. Countercurrent fermentation was performed at various volatile solid loading rates (VSLR) and liquid residence times (LRT). The highest acid productivity of 1.69 g/(L·d) was at a total acid concentration of 32.4 g/L. The highest conversion and yield were 0.692 g VS digested/g VS fed and 0.29 g total acids/g VS fed, respectively. The continuum particle distribution model (CPDM) was used to predict product concentrations at various VSLR and LRT. CPDM predicted the experimental total acid concentration and conversion at an average error of 6.41% and 6.55%, respectively. A fixed-bed fermentation system was designed to perform pretreatment and fermentation in the same unit. High product concentrations (~48 g/L) as well as high conversions (0.741 g VS digested/g VS fed, F4, Train B) were obtained from the same fermentor. CPDM was extended to predict product concentrations in the fixed-bed fermentation system. The model gave a good estimate of the product concentrations and retention time. After biomass fermentation, the residue can be combusted to generate heat. For pretreatment purposes, the use of ash can replace lime. A study was performed using ash as a potential pretreatment agent. Ash from raw poplar wood was effective in pretreating poplar wood; however, ash from bagasse fermentation residues was not useful in pretreating bagasse. Previous modeling studies indicate that a conversion of 95% could be achieved with bagasse using countercurrent fermentation. Because lignin constitutes 13% of the dry weight of bagasse, this means lignin would have to be digested to obtain a conversion of 95%. Experiments on the fermentation of enzymatically liberated lignin from both poplar wood and bagasse do not show that solubilized lignin was fermented to organic acids by using a mixed culture of marine microorganisms. Two buffer systems (ammonium bicarbonate and calcium carbonate) were used to compare product concentrations of carboxylic acid fermentations using office paper and chicken manure. It has been demonstrated that the total product concentration using ammonium bicarbonate is almost double the product concentration using calcium carbonate.

¡@Recently, with the speedy pace of upcoming WTO negotiation, import tariff imposed on rice become inevitable. Thus, agriculture in Taiwan has been trapped by the depression atmosphere caused by WTO negotiation. How to make rice industry in Taiwan enjoy a clear business climate and bring with revival development opportunities under globalization is really a critical issue worthy of our concern. ¡@¡@This research is not only aimed to insightfully understand the impact on rice industries in Taiwan after WTO entry but also intended to explore whether the promoted agriculture policies can reach profit goals set by farmers, enhance the competence of local rice and establish marketing outlets under open rice markets. Thus, this research is designed with questionnaires based on SWOT analysis structures. Also, through questionnaire surveys and in-depth interview on farmers and personnel from farmers' association, it is aimed to delineate what impact and challenge (menace) will affect local rice industries after Taiwan's WTO entry. Also, the possible breakthrough opportunities and development to improve the competence of local rice products, together with insightful knowledge on the advantages of natural environment and human culture conditions on Kaohsiung and Pingtung regions are also explored. ¡@¡@Research results indicate that aging farmers show less cognition to advantages, disadvantages and opportunities than that of younger farmers. The employees' cognition to advantages and disadvantages from farmers' associations is stronger than that of amateur or professional farmers. The respondents in Pingtung regions show stronger cognition to advantages and disadvantages to that of respondents on Kaohsiung regions. Higher-educated farmers show stronger cognition to opportunities. Families with higher income show stronger cognition to disadvantages. Finally, based on results from questionnaire surveys and in-depth interview, the suggestion is proposed to solve the possible influential issues on rice industries after Taiwan's WTO entry. It is expected through this research; the issues from the stakeholders in rice industries can be clearly highlighted with beneficial reference for governmental agencies, farmers and scholars to put forward production and marketing strategies in rice industries under WTO.

Texte remanié de: Thesis Ph. D.--Michigan state university, 2004. / Notes bibliogr. Index.

Thesis (Ph. D.)--Yale University, 1979. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 522-527).

Thesis (Ph. D.)--York University, 2000. Graduate Programme in English. / Typescript. Includes bibliographical references (leaves 276-306). Also available on the Internet. MODE OF ACCESS via web browser by entering the following URL: http://wwwlib.umi.com/cr/yorku/fullcit?pNQ56254.

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Agrichemicals have been misused by rice farmers in Vietnam for a long time. This thesis has studied the rice farmers’ knowledge, risk awareness and risk perception to get an understanding of the rice farmers’ agrichemical management. 15 rice farmers in An Giang province in the Mekong Delta, Vietnam were interviewed in 2015 when the winter-spring rice was cultivated. Field method Contextual Inquiry was used to observe and interview the rice farmers. The rice farmers in Mekong Delta, Vietnam think that they are exposed to a medium risk when handling pesticides. They think that pesticides are the most effective pest controlling method. They do not use any protective gear because the weather is to hot which makes the protective gear uncomfortable to wear, even though the majority of the farmers have experienced health effects. The farmers overuse agrichemicals. The rice farmers can increase their gross income if they start using agrichemical more responsible. The majority of the farmers do not follow recommendations established in research. The Vietnamese government have a big responsibility to implement new laws to create a healthier and more environmentally sound agriculture.

Three isolates of Curvularia belonging to Curvularia tuberculata (isolates 93-020 and 93-022) and Curvularia oryzae (isolate 93-061) were obtained from diseased Cyperus difformis, Cyperus iria, and Fimbristylis miliacea, respectively, in the Philippines in 1993. Under greenhouse conditions, these fungal isolates caused high mortality and significant plant dry weight reduction in C. difformis, C. iria, and F. miliacea when sprayed at the rate of 1 x 108 spores/m3. Cross-pathogenicity of the isolates was demonstrated in three other sedge weed species. C. difformis, C. iria, and F. miliacea were killed but C. rotundus was resistant. Most of the thirteen rice varieties tested were resistant to the fungal isolates. The order of decreasing pathogenicity to rice was C. oryzae (93-061), C. tuberculata (93-020), and C. tuberculata (93-022). The infection process of C. tuberculata and C. oryzae was similar. Spore germination was polar for C. tuberculata and bipolar for C. oryzae. Germ tube growth was random and branching. Appressoria were formed preferentially over epidermal cell wall junctions on sedge hosts and over stomatal apertures in rice. Complex infection cushions were observed only on sedge hosts. Infection hyphae developed inter- and intracellularly, causing epidermal cell walls to separate and mesophyll cells to shrink and collapse. The vascular bundles were not invaded. Colonization of susceptible weeds was rapid and conidiophores emerged from the stomatal aperture between 96 to 120 hours post inoculation (HPI). Resistance to C. tuberculata and C. oryzae in C. rotundus and rice was expressed as a delay in appressorial formation, inhibition of fungal growth after penetration, and lack of sporulation.

Transposons, also known as transposable elements (TEs), are genetic elements capable of changing their location in the genome and amplifying in number. Because of their ability to cause mutations in the host genome, often with detrimental consequences to the host, yet avoid being eliminated by natural selection, transposons have been labeled selfish elements or genomic parasites. However, the advent of genomics has allowed the identification of numerous instances where transposons have played a crucial role in host genome evolution. In this thesis, I evaluate the extent to which transposons have influenced the genomes of their hosts, with an emphasis on plant genomes. I review the present knowledge of different mechanisms by which this is achieved and provide examples to illustrate them. Next, I tackle the problem of annotating transposons in the completed genomic sequence of domestic rice by comparing RepeatMasker, the standard approach used in transposon annotation, with an alternative approach employing hidden Markov models. In addition, I perform a genome-wide analysis of gene fragment capture by rice Mutator-like transposons. I conclude that, while this is a widespread phenomenon in rice, it is unlikely to represent a major force in generating novel protein-coding genes. Nevertheless, the duplicated gene fragments that are transcribed may playa role in the regulation of host genes they arose from via an RNAi-like mechanism. Finally, I conduct an in silico analysis of a gene family derived from a domesticated Mutator-like transposase, called MUSTANG (MUG), in conjunction with an experimental characterization of the MUG family in Arabidopsis. The results of the study indicate that the MUG family arose in a common ancestor of flowering plants and that the Arabidopsis genes AtMUG1 and/or AtMUG2 may act as global regulators of mitochondrial function. I conclude that our appreciation of the role of transposons in host function and evolution will undoubtedly continue to grow as our understanding of these processes deepens.