Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.

Rice is the leading staple for half the world’s population. Climate change, expanding populations and loss of agricultural land are projected to reduce rice yields by upwards of 30%. Significantly, rice yields decline by 10% for every 1°C increase in temperature. Temperatures ≥ 32°C can cause failure in male reproductive development and eliminate yields in some cultivars. This dissertation determined the developmental features and mechanisms associated with failure in male reproduction at temperatures of 32 °C and 36 °C in temperature tolerant and sensitive cultivars of O. sativa and O. glaberrima. Temperatures of 32 °C impaired anther dehiscence in the temperature sensitive cultivar of O. sativa by preventing septum cell wall degradation, which is essential for pollen dispersal. Temperatures of 36 °C induced abortion in pollen development either during meiosis primarily in O. sativa or at the uninucleate stage in O. glaberrima. Abortion during meiosis was associated with autophagic programmed cell death, whereas failure at the uninucleate stage of pollen development was associated with features of necrosis such as cytoplasmic shrinkage and cell wall collapse. Increased hydrogen peroxide production was detected in aborting meiocytes and uninucleate microspores at 36 °C, indicating that this reactive oxygen species may contribute to the failure of male reproductive development in rice during high temperature stress. Identification of the timing of failure in male reproductive development, and the cellular features associated with these processes in rice, form the basis for the identification of molecular mechanisms that control yield responses to high temperature stress.

Anaerobiosis results in low ATP levels and cytoplasmic acidosis. Pyrophosphate (PPi) may play an important role in anaerobiosis as an energy source replacing ATP, as suggested by the hypoxic induction of PPi:fructose 6-phosphate 1-phosphotransferase and sucrose synthase in preference to phosphofructokinase and invertase. Here we show that vacuolar H$ sp+$-translocating pyrophosphatase (PPase) is also strongly induced by anoxia in rice seedlings. The PPase transcript abundance is increased within the first hours of anoxia, and decreases within 2 days after the return of seedlings to air, similarly to alcohol dehydrogenase-1 (Adh1). However, tissue studies show that the highest transcript induction for PPase is in the root whereas the highest induction of Adh1 is in the shoot. Assays of enzyme specific activity indicate a 75-fold increase in PPase activity over 6 days of anoxia, while the vacuolar ATPase changes only slightly. Return of seedlings to air results in rapid disappearance of enzyme activity. Chilling stress in rice seedlings also gives rise to an increase in immunoreactive PPase enzyme, and a progressive 20-fold increase in enzyme specific activity within 6 days. Upon return to room temperature both enzyme level and specific activity decrease. In corn, hypoxic stress results in a small induction in the PPase transcript, and no increase in PPase specific activity, which, however, is constitutively high in this material. It is suggested that in both species, H$ sp+$-PPase may play an important role in hypoxia and chilling stress, not only in conserving ATP, but also in limiting cytoplasmic acidosis.

Wild rice is recognized as a whole grain by U.S. FDA and it is rich in polyphenol compounds. This study aimed to investigate the potential cardiovascular benefits of wild rice in LDLr-KO mice. Seventy-two male and female mice were randomly assigned to 3 different diet groups, control diet (a), white diet (b), and wild diet (c) for 24 weeks. Dietary cholesterol 0.06 % (w/w) was added in all diets, and digestible carbohydrate source was replaced with: (a) commercial carbohydrate source (sucrose and corn starch); (b) white rice; (c) wild rice. Incorporation of wild rice in the diet distinctly increases total phenolic content of the diet. Plasma total cholesterol, VLDL, and LDL cholesterol levels declined significantly in wild diet group. The hypocholesterolemic properties of wild rice were mainly attributed to the increased excretion of fecal cholesterol. Our data suggest that substituting refined grains with wild rice may potentially lower cardiovascular risks.

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Atherosclerosis is the primary underlying pathology of CVD. Dietary treatment may be considered as one of the initial steps in the prevention of atherosclerosis. Replacing refined carbohydrate source of a cholesterol- enriched diet with antioxidant rich whole grain and inclusion of phytonutrition in the diet such as wild rice and phytosterols may reduce cardiovascular risk factors. The wild rice (Zizania palustris L.), an annual plant native to aquatic areas of the northern America, receives much attention by researchers because of its potent nutritional and phytochemical contents. Furthermore, another dietary component with cardiovascular benefits is the inclusion of plant sterols in our daily diet. The aim of this study was to investigate the antiatherogenic activity of wild rice in combination with phytosterols in LDL-r-KO mice. Male LDL-r-KO mice were divided into 4 groups receiving one of the following experimental diets for 20 weeks: 1. Atherogenic diet, 2.Wild rice (as the main source of dietary carbohydrates) diet, 3. 2% Phytosterols-enriched diet and 4. Diet containing both wild rice and 2 % phytosterols. Blood samples were collected through jugular vein during study, and at sacrifice through cardiac puncture; the heart and fecal materials were collected and used for biochemical and histological examinations. The supplementation of wild rice in combination with phytosterols to an atherogenic diet for up to 20 weeks significantly reduced the total plasma concentrations of cholesterol (TC) in LDLr-KO mice. However, there was no significant difference in triglyceride (TG) in wild rice in combination with phytosterols after 20 week exposure of diet. Further, wild rice in combination with phytosterols resulted in increased fecal excretion of cholesterol. Also, there was reduction in the development of atherosclerotic lesion in the group of mice supplemented with wild rice in combination with 2% phytosterols (w/w). Our data support that combination of plant sterols and wild rice does not have additive effect in lowering cardiovascular risk.

Wild rice is recognized as a whole grain by U.S. FDA and it is rich in polyphenol compounds. This study aimed to investigate the potential cardiovascular benefits of wild rice in LDLr-KO mice. Seventy-two male and female mice were randomly assigned to 3 different diet groups, control diet (a), white diet (b), and wild diet (c) for 24 weeks. Dietary cholesterol 0.06 % (w/w) was added in all diets, and digestible carbohydrate source was replaced with: (a) commercial carbohydrate source (sucrose and corn starch); (b) white rice; (c) wild rice. Incorporation of wild rice in the diet distinctly increases total phenolic content of the diet. Plasma total cholesterol, VLDL, and LDL cholesterol levels declined significantly in wild diet group. The hypocholesterolemic properties of wild rice were mainly attributed to the increased excretion of fecal cholesterol. Our data suggest that substituting refined grains with wild rice may potentially lower cardiovascular risks.

Despite substantial public expenditure from domestic and international sources on free-to-user agricultural extension services in Bangladesh, there is a lag between the availability and application of seed technologies.  Besides the slow pace of diffusion of newly generated modern varieties (MVs), there exist wide gaps between potential and achieved yields at the farm level.  This study aims to assess the performance of Bangladeshi research and extension (R&E) institutions in disseminating new rice MVs to end-users, and to identify factors affecting farm-level diffusion of the disseminated MVs.  The study also examines the relationship between users’ technological knowledge and yields in the case of a new T. <i>Aman</i> season rice MV, BR32. The results suggest that the efficiency of the extension services was associated with the allocation of project funds between farm-level dissemination activities and overheads costs, and with the timing of project implementation.  The presence of many divisions and administrative levels in the technology transfer system appears to be responsible for high overheads, while farm-level diffusion of BR32 was delayed for 4 years after its release due to the late start of project-funded dissemination activities.  The rate of MV diffusion was restricted by seed scarcity, deficiencies in technical knowledge transfer, and some undesirable technology attributes.  The reasons for the seed crisis were:  i) the low amounts supplied by the public parastatal agency whose capacity was found to be under-utilized, ii) the lack of effective distributional channels for farmer-produced seeds, iii) the lack of farmer access to information about seed sources and demonstration sites, and iv) the low involvement of NGOs and the private sector.  The average and marginal costs of BR32 dissemination would have been much lower if seed and technical knowledge could have been delivered more according to farmers’ demand.

Agriculture remains a dominant economic sector in many developing countries. Rice constitutes a staple food for more than half of the world's population and is the main meal of all Lao people (FAO, 2005). However, rice production faces many problems, including the effects of floods, drought and poor soil quality. These challenges combine to reduce rice productivity below what might be possible. However, before new agricultural policies are put in place, it is important to identify the factors associated with rice production efficiency. This thesis analyses technical and socio-economic factors that influence rice production and estimates the level of technical efficiency of individual rice farmers in Ban Home, Laos. / Survey data were collected in the region in 2003, for both wet season and dry season rice production. Using these data, a Cobb-Douglas frontier production function was estimated for each season using two approaches, deterministic and stochastic. During the wet season, several factors were statistically significant and positive in their effect on rice yield: area in rice production, level of fertilizer use, total labour, the use of a modern variety, sandy soil and contact with a professional agricultural advisor. During the dry season, only area in rice production and fertilizer were significant. Based on the frontier production functions, it is possible to conclude that the average technical efficiency of farmers is higher during the dry season than the wet season, for both the deterministic and stochastic approaches. / However, socio-economic factors were unable to explain the level of technical efficiency among farmers, when evaluated using a standard regression approach. By using a simple t-test to compare the mean level of efficiency of different groups of farmers, some significant differences emerged. Farmers who used credit were found to be more efficient than those who did not. Moreover, experienced farmers were more efficient than less experienced farmers. Also, farmers with less than 7 years of education were more efficient than more educated farmers.

Graduation date: 1981