Browsing by Author "Tibazarwa, Flora I."
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Item Cross Compatibility of Cultivars of Gossypium Hirsutum L. and Feral Gossypium Barbadense L. in the Southern Highlands of Tanzania(2012-12) Shilla, O.; Hauser, T. P.; Tibazarwa, Flora I.Cotton is the second most important cash crop contributing about 15% to the annual foreign earning in Tanzania and is purely from Gossypium hirsutum L. cultivars. Gossypium barbadense L., a textile source in other parts of the world occurs as a feral perennial of ornamental and medicinal value in home gardens. G. barbadense L. is a natural host of the red bollworm, a destructive pest to cotton. The Southern Highlands (SH) of Tanzania have been quarantined from cotton production to control spread of the red bollworm to other growing areas. Transgenic cotton expressing the delta-endotoxin genes from Bacillus thuringiensis (Bt) offers an alternative control to the pest and reduced dependence on insecticide. Gene flow between wild or valued feral relatives and transgenic crops is a biosafety concern should transgene escape result in resistance development and contamination of germplasm. Potential gene flow between feral G. barbadense (including accessions Gb1 and Gb2) from the SH and G. hirsutum cultivars was assessed using controlled hybridization. The crosses produced fertile F1 but intraspecific seeds from G. barbadense did not germinate. G. barbadense is more likely to receive than donate genes implying development of pest resistance if introgressed filial generations express the Bt product.Item Distribution and Potential Impact of Feral Cotton on the Reintroduction of Cotton in the Southern Highlands, Tanzania(2012) Shilla, O.; Hauser, T. P.; Tibazarwa, Flora I.Cotton (Gossypium hirsutum) production is limited by bollworms that cause declining yields and poor lint quality. Generally, farmers manage pests by employing Integrated Pest Management (IPM) strategies, which include biological, cultural, physical and chemical approaches. Pest management by quarantine and pesticide sprays reduce production area and lead to resistance build-up. The Red bollworm, Dipsaropsis castanea is an important cotton pest of significant economical importance to Tanzania. The pest invaded the Southern Highlands (SH) of Tanzania in 1960’s from southern neighbour countries causing the Government to quarantine cotton production from 1968 as measure to limit the spread of the red bollworm. Transgenic Bt cotton with insecticidal properties presents a potential solution to the bollworm infestation in Tanzania. However, concerns associated with transgenic crops viz.; transgene flow to wild and feral relatives, increased potential for resistance evolution, need to be addressed prior to adoption of any transgenic crop. Information from national herbaria, research stations and a field survey established sparse distribution and diversity of feral cotton species G. barbadense, an exotic ornamental from Brazil though as isolated garden plants. Informal interviews revealed medicinal and fibre value of the ornamental. Diploid wild cotton relatives such as G. longicalyx and Gossypoides kirkii were also recorded but are incompatible to G. hirsutum. Field observations indicate continued red bollworm presence in the SH on feral cotton, but low in number as plants are few and isolated. Cluster analysis indicates presence of hybrid remnants of G. hirsutum and G. barbadense suggesting potential for gene flow.Item Expression of Genes for The Biosynthesis of Compatible Solutes During Pollen Development Under Heat Stress in Tomato (Solanum Lycopersicum)(Elsevier, 2015-02) Sangu, Emmanuel; Tibazarwa, Flora I.; Nyomora, Agnes; Symonds, RachaelAccumulation of compatible solutes is considered a key adaptation mechanism in many plants in response to abiotic stress. The expression of four genes, involved in sucrose metabolism (SPS and SuSy), biosynthesis of galactinol (GoLS1) and proline accumulation (P5CS) was compared: at meiosis (MM), vacuolated and mature stages of pollen development in heat tolerant and heat sensitive tomato genotypes. The results showed differences in gene expression across tomato genotypes and stages of pollen development. Three genes (P5CS, SPS and SuSy) were up regulated in heat tolerant genotype CLN1621L at the mature stage and one gene (P5CS) in genotype CLN5915-93D at the MM stage. Two genes (SPS and GoLS1) were down regulated in heat sensitive genotype CA4 and one gene (GoLS1) in genotype CLN2498E at the MM stage. Additionally, the continuous exposure of tomato genotypes to temperatures of 35°C/28°C day/night completely impaired flower development in genotypes CA4 and CLN2498E but not in genotypes CLN1621L and CLN5915-93D. Tomato genotypes CLN1621L and CLN5915-93D produced fully developed flowers containing mixture of non viable pollens and very few viable pollens grains. Membrane permeability was affected at all stages of development under heat stress with heat tolerant genotypes CL5915-93D4, CLN2498E and CLN1621L showing varying degrees of heat acclimation. Significant increases in total chlorophyll were seen in all genotypes in response to heat stress. The expression of compatible solute genes at MM is more critical than at mature stage for the development of viable pollen grain. Copyright © 2015 Elsevier GmbH. All rights reserved.Item Levels of ABA, its Precursors and Dehydrin-like Proteins During Mangrove Leaf Development and Senescence(2009) Tibazarwa, Flora I.; Masoud, M; Derksen, J. W. M.; Mariani, C.Abstract—Abscisic acid (ABA) and dehydrin proteins are thought to confer tolerance to plant tissue under physiological stress and drought. Rhizophora mucronata, a true mangrove species, is subjected to physiological drought from fluctuating high saline conditions where leaf loss or senescence is considered a possible regulation mechanism to combat stress. Levels of ABA and proteins that cross reacted with an anti – dehydrin antibody were assessed through development with the aim of correlating these factors to physiological water stress or salinity stress in R. mucronata leaves. Younger leaves showed lower levels of ABA than mature and senescing leaves. In situ production and translocation from mature to younger leaves may contribute to these observations. The presence of ABA in senescing leaves is thought to be due to the presence of low levels of physiological activity. Proteins detected by anti–dehydrin antibody require cDNA confirmation, but the visibly increasing intensity of a band at ~64kDa through development suggests potential correlation to drought or salinity stress which is expected to be maximal in maturing leaves. The absence of the dehydrin–like proteins in senescing leaves is postulated to be due to the lack of energy investment to synthesise these proteins in dying leaves.Item Semi-viviparous Embryo Development and Dehydrin Expression in the Mangrove Rhizophora Mucronata Lam.(2010) Tibazarwa, Flora I.; Nitsch, L. M. C.; Wolters-Arts, M. M. C.; Mariani, Celestina; Derksen, J. W. M.Rhizophora mucronata Lam. is a tropical mangrove with semi-viviparous (cotyledon body protrusion before shedding), non-quiescent and non-desiccating (recalcitrant) seeds. As recalcitrance has been thought to relate to the absence of desiccation-related proteins such as dehydrins, we for the first time systematically described and classified embryogenesis in R. mucronata and assessed the presence of dehydrin-like proteins. Embryogenesis largely follows the classic pattern till stage eight, the torpedo stage, with the formation of a cotyledonary body. Ovule and embryo express radical adaptations to semi-vivipary in the saline environment: (1) A large, highly vacuolated and persistent endosperm without noticeable food reserves that envelopes the developing embryo. (2) Absence of vascular tissue connections between embryo and maternal tissue, but, instead, transfer layers in between endosperm and integument and endosperm and embryo. Dehydrin-like proteins (55–65 kDa) were detected by the Western analysis, in the ovules till stage 10 when the integuments are dehisced. An additional 50 kDa band was detected at stages 6–8. Together these results suggest a continuous flow of water with nutrients from the integument via the endosperm to the embryo, circumventing the vascular route and probably suppressing the initially induced dehydrin expression.Item Shades of Green: Conservation in the Developing Environment of Tanzania(2013) Tibazarwa, Flora I.; Gereau, Roy E.; Raven, Peter H.; Sodhi, Navjot S.; Gibson, LukeIn this chapter, two conservation areas, Lake Natron and Kitulo Plateau, are used to exemplify the challenges and delineate best practices, with Kitulo presenting a notable example of conservation to be emulated. The chapter demonstrates the challenges to and opportunities for achieving sustainable development in Tanzania, based on two development projects. One is a soda ash extraction project and the other a dairy farm converted to a national park. In particular, the chapter focuses on the gray areas where benefits are considered losses and vice versa and the realities of striving towards a balance between development and conservation. Lake Natron and Kitulo National Park are protected for their biodiversity and conservation value under Tanzanian policies and legislation for natural resource management.Item Uterine Contraction Induced by Tanzanian Plants Used to Induce Abortion(2011-05) Nikolajsen, Tine; Nielsen, Frank; Rasch, Vibeke; Sørensen, Pernille H.; Tibazarwa, Flora I.; Kristiansen, Uffe; Jägera, Anna K.Ethnopharmacological relevance Women in Tanzania use plants to induce abortion. It is not known whether the plants have an effect. Aims of study Collect data on plant use in relation to induced abortion and test the effect of plant extracts on uterine contraction. Materials and methods During interviews with traditional birth attendants and nurses, plants were identified. Cumulative doses of plant extracts were added to rat uterine tissue in an organ bath, and the force and frequency of contractions recorded. Acetylcholine was used as positive control.