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Search Results: 1 - 10 of 29 matches for " Geofrey Soka "
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Arbuscular mycorrhizal symbiosis and ecosystem processes: Prospects for future research in tropical soils  [PDF]
Geofrey Soka, Mark Ritchie
Open Journal of Ecology (OJE) , 2014, DOI: 10.4236/oje.2014.41002
Abstract:

Arbuscular mycorrhizal fungi (AMF) are more widely distributed and can associate with a wide range of plant species. AMF are keystone organisms that form an interface between soils and plant roots. They are also sensitive to environmental changes. AMF are important microbial symbioses for plants under conditions of P-limitation. The AMF are crucial for the functioning of terrestrial ecosystems as they form symbiotic interactions with plants. Mycorrhizal fungi are known to influence plant diversity patterns in a variety of ecosystems globally. AMF hyphae form an extensive network in the soil. The length is a common parameter used to quantifying fungal hyphae. The mycelial network of AM fungi extends into the soil volume and greatly increases the surface area for the uptake of immobile nutrients. Also, AM symbioses improve plants tolerance to drought and enhance plants’ tolerance of or resistance to root pathogens. Also, the networks of AM hyphae play a crucial role in the formation of stable soil aggregates and in the building up of a macroporous structure of soil that allows penetration of water and air and thereby prevents erosion. The functioning of AMF symbiosis is mediated by direct and indirect effects of biotic and abiotic factors of the surrounding rhizosphere, the community, and the ecosystem. AMF have great potential in the restoration of disturbed land and low fertility soil. However, despite the importance of AMF to terrestrial ecosystems, little is known about the effects of environmental changes on AMF abundance, activity and the impact of these changes on the ecosystem services. Therefore, it is important to gain a clearer understanding of the effects of environmental changes on the AM fungal species to guide conservation and restoration efforts.

Application of Remote Sensing and Developed Allometric Models for Estimating Wood Carbon Stocks in a North-Western Miombo Woodland Landscape of Tanzania
Geofrey Soka,Nanjiva Nzunda
Journal of Ecosystems , 2014, DOI: 10.1155/2014/714734
Abstract: Quantifying ecosystem carbon stocks is vital for understanding the relationship between changes in land use and cover (LULC) and carbon emissions; however, few studies have documented the impacts of carbon cycling on Miombo ecosystems. Here, we estimate the amounts of wood carbon which is stored and lost as a result of LULC changes in Kagoma Forest Reserve (KFR) for the periods between 1988 and 2010 using GIS data, Landsat imagery, and field observations. The land cover was captured on the basis of Landsat 5?TM and Landsat 7?ETM. The amounts of wood carbon stored and lost were estimated based on four previously developed allometric models. Spatial analysis of the Landsat images shows that in the year 1988, woodlands dominated the area by covering 32.66% whereas in the year 2010 the woodlands covered only 7.34% of the total area. The findings of the current study reveal that KFR had undergone notable changes in terms of LULC for the period of 1988–2010. It was estimated that the woodlands in the KFR lost an average of 4409.79?t . In this study, the amount of carbon stocks stored was estimated to be 21457.02 tonnes in tree stem biomass based on the area (1226.12?ha) that was covered by woodlands. We estimated that an average of 17.79?t was stored in the Miombo woodlands based on the four models. The efforts to ensure sustainable management of the Miombo ecosystem can contribute to the creation of a considerable carbon sink. 1. Introduction Miombo woodlands are widespread in the tropics, covering over 2.7 × 103?km2 in east, central, and southern Africa [1]. It occurs on poor soils derived from acid crystalline bedrock occurring under a hot, seasonally wet climate [2]. Its woody vegetation is mainly dominated by Brachystegia spp., Julbernardia spp., and Isoberlinia spp. [1]. Miombo woodlands ecosystems are considered to directly support the livelihood of an estimated 39 million people, particularly in low income rural communities in central African countries [1, 2]. The woodlands supply charcoal, firewood, fruits, building poles, and timber to over 15 million people living in the urban areas in the region [1]. Woody biomass consumption from Miombo woodland is said to amount to about 48?Tg?yr?1, releasing almost 22?Tg of Carbon to the atmosphere [2]. For example in Tanzania, forests and woodlands cover more than 40% of the total land surface and directly support the livelihood of over 85% of the rural poor [3]. Cultivation and deforestation mainly for charcoal production have been reported to be the major factors that contribute to the decline of Miombo
Genetic Diversity of Yeasts from Fermented Orange Juice Based on PCR-RFLP and Sequence Analysis of the Internal Transcribed Spacer Regions
SUSAN SOKA,ANASTASIA SUSANTO
Microbiology Indonesia , 2010, DOI: 10.5454/mi.4.1.1
Abstract: Orange is one of the most valuable and common fruits in Indonesia. High glucose level in orange juice provides good growth conditions for yeasts. In this study, yeasts were isolated from fermented orange juice and subjected to diversity analysis. The analysis was conducted using restriction fragment length polymorphism on the internal transcribed spacer (ITS) region (including ITS1, 5.8S rRNA gene and ITS2), which was amplified using PCR with ITS1 and ITS4 primers.Restriction enzymes used in this research were HhaI, HinfI and HaeIII. A total of 24 yeast isolates were obtained from three different kinds of fermented orange juices (Indonesian Medan orange, Sunkist orange and Indonesian Pontianak orange). RFLP analysis of ITS regions revealed different amplified PCR fragment sizes and restriction profiles for each type of orange juice. However, all yeasts isolated from the same type of orange juice showed identical restriction patterns. Sequencing of ITS regions showed that three different yeast species were detected from each type of orange, e.g. Pichia veronae from Indonesian Pontianak orange, Cryptococcus albidosimilis from Sunkist orange and Issatchenkia orientalis from Indonesian Medan orange.
Constraints to Fertilizer Use in Uganda: Insights from Uganda Census of Agriculture 2008/9
Geofrey Okoboi,Mildred Barungi
Journal of Sustainable Development , 2012, DOI: 10.5539/jsd.v5n10p99
Abstract: Uganda’s agriculture faces numerous challenges, including low productivity due to declining soil fertility. Yet, the majority agricultural households in the country do not use organic and inorganic fertilizers due to not well-known constraints. Using data from the Uganda Census of Agriculture 2008/9, this paper provides insights into these constraints. Results show that most of the farm-households that use inorganic fertilizers also apply organic fertilizers. With regard to factors influencing adoption of fertilizer, lack of knowledge on use of and market information on fertilizer due to limited access to fertilizer-specific extension services is found to be perhaps the most limiting factor irrespective of fertilizer type. Low access to credit and constrained access to input and output markets due to distance are also key constraints to fertilizer use. Household characteristics including education level, household size, share of adults in the household, and ownership of livestock/poultry also stand-out as influencing factors on fertilizer adoption decisions. Results suggest that targeted interventions including extensive and intensive extension training and visits, and access to affordable credit and will be pertinent in the promotion fertilizer use in the country.
Prevalence, Awareness and Control of Hypertension in Uganda
Geofrey Musinguzi, Fred Nuwaha
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0062236
Abstract: Background Prevention and control of hypertension are critical in reducing morbidity and mortality attributable to cardiovascular diseases. Awareness of hypertension is a pre-condition for control and prevention. This study estimated the proportion of adults who were hypertensive, were aware of their hypertension and those that achieved adequate control. Methods We conducted a community based cross sectional survey among people≥15 years in Buikwe and Mukono districts of Uganda. People had their blood pressure measured and were interviewed about their social-demographic characteristics. Hypertension was defined as systolic blood pressure ≥140 mmHg, or diastolic blood pressure ≥90 mmHg, or previous diagnosis of hypertension. Participants were classified as hypertensive aware if they reported that they had previously been informed by a health professional that they had hypertension. Control of hypertension among those aware was if systolic blood pressure was <140 mmHg and diastolic blood pressure was <90 mmHg. Results The age standardized prevalence of hypertension was 27.2% (95% CI 25.9–28.5) similar among females (27.7%) and males (26.4%). Prevalence increased linearly with age, and age effect was more marked among females. Among the hypertensive participants, awareness was 28.2% (95% CI 25.4–31.0) higher among females (37.0%) compared to males (12.4%). Only 9.4% (95% CI 7.5–11.1) of all hypertensive participants were controlled. Control was higher among females (13.2%) compared to males (2.5%). Conclusion More than a quarter of the adult population had hypertension but awareness and control was very low. Measures are needed to enhance control, awareness and prevention of hypertension.
Factors Affecting Tree Husbandry and Woodlots Establishment in Kilimanjaro Region, Tanzania  [PDF]
Revocatus Petro, Francis Laswai, Mohammed Mijai, Geofrey Nyaradani, Chelestino Balama
Open Journal of Soil Science (OJSS) , 2015, DOI: 10.4236/ojss.2015.58017
Abstract: The study on assessment of factors affecting tree husbandry and woodlots establishment was carried out between September and November 2014 in all seven districts of Kilimanjaro region, namely Hai, Siha Rombo, Mwanga, Same, Moshi Rural and Moshi Municipal Council (MMC). A purposive sampling design was employed whereby two wards per district were selected for the study. Household questionnaire survey was used in data collection. Results show that, factors affecting tree husbandry and woodlots establishment in Kilimanjaro region are gender, livelihood activities, access and ownership/land tenure, cultural factors, legal issues and by-laws insisting people to plant trees. About 32.4%, 32.4% and 30% of all respondents own land with size of 1.0 acre and below, 1.1 - 2.0 and 2.1 - 5.0 acres respectively. Respondents from Hai (55.3%), Same (26.3%), Rombo (11%) and MMC (8%) agreed that cultural issues affect tree husbandry. About 1%, 23%, 30% and 40.8% of respondents in Siha, Same, Hai and Rombo districts respectively agreed that some of by-laws insist people to plant trees on their environments. None of the respondents from any district reported labour availability to be one of the factors affecting tree husbandry. Other factors reported to affect tree husbandry in Kilimanjaro region were capacity building in tree planting and tending, insect pests, diseases and climate change. Formulation of by-laws which insist on tree planting and limit land degradation is recommended at village level. Every piece of land should be planned and used sustainably including area for tree planting. Custom and norms which inhibit women to plant trees should be prohibited through capacity building.
The Genetic Diversity of Endophytic and Phyllosphere Bacteria from Several Indonesian Herbal Plants
Yogiara, Susan Soka,Stella Magdalena,Devi Rachelia
Makara Seri Sains , 2012,
Abstract: Herbal plants have been believed by Indonesians to be an alternative medicine to treat illnesses. The bioactivecompounds in the plant can be derived from secondary metabolites or from endophytic and phyllosphere bacteria whichcoexist within medicinal plants. A total of 18 endophytic bacteria and 32 phyllosphere bacteria were isolated from theherbal plants of Citrus sp., Pluchea indica, Curcuma longa, Nothopanax scuttelarium, Piper crocatum, andAndrographis paniculata. About 72% of endophytic bacteria isolates have proteolytic activity and about 11% havelipolytic activity. On the other hand, about 59% of phyllosphere bacteria isolates have proteolytic activity and about19% have lipolytic activity. Phylogenetic diversity analysis was conducted by using the amplified ribosomal DNArestriction analysis (ARDRA) method and the sequence of 16S rDNA was digested with endonuclease restrictionenzymes: MspI, RsaI, and Sau961. The diversity of endophytic and phyllosphere bacterium from the samples of herbalplants was high. Bacteria isolated from the same herbal plant does not always have a close genetic relationship exceptfor the bacteria isolated from the P. indica plant which showed a close genetic relationship with each other.
Scientific basis for banana cultivar proportions on-farm in East Africa
G Nantale, EK Kakudidi, DA Karamura, G Soka
African Crop Science Journal , 2008,
Abstract: Banana (Musa spp.) production and diversity in the East African region, has been on the decline for the last 20 years due to both a biotic and biotic problems. There has been an ecological and socio-economic imbalance in the East African Highland banana (Musa AAA-EA) growing systems due to this decline. However, farmers have been growing these bananas in cultivar mixtures, a practice which ensures the continuous sustainability of the system. Cultivar mixtures, however, seem to be in specific proportions based on the strength and weakness of each cultivar and so affecting the clone sets to which cultivars belong, as well as providing predictions on the conservation status of each clone set. The primary objective of the study was to account for the farmers’ perceptions behind cultivar proportions and to understand the scientific basis of these proportions in selected sites in East Africa. The study was carried out in Karagwe, Bushenyi and Masaka districts in East Africa, a region considered to be a secondary centre of diversity for bananas. Thirty farms were sampled in one selected parish/ward in the three sites for ecological data. The quadrat method was used to record abundances of identified cultivars in order to determine the cultivar proportions. Ethno-botanical data collected on traditional knowledge was analysed for twenty-three identified traditional cultivar-selection criteria used in the participatory rural appraisal (PRA), as well as interviews from 15 key informants of each study area. A total of 105 cultivars were identified, 76% of which were the East African Highland bananas. Although fourteen cultivars were common to the three sites, Masaka had the highest proportion with Nfuuka cultivar leading the five clone sets. Cultivar diversity indices explained the proportions in terms of richness and evenness and Nfuuka was the richest clone set. Although all clone sets were represented at each site, they were not evenly distributed; a factor which is disadvantageous in the conservation status of the crop. While results indicated that the agro-ecological and traditional utilisation criteria formed the basis for cultivar proportions on farm for both Karagwe and Masaka, farmers were found to do so because of the high traditional values attached to the crop. However, knowing cultivar proportions in terms of richness and evenness can assist in predicting the stability or change in diversity of banana growing sites.
Population Dynamic of Dendronephthya sp.-Associated Bacteria in Natural and Artificial Habitats
SUSAN SOKA,RORY ANTHONY HUTAGALUNG,YOGIARA,CLARA ASSISI
HAYATI Journal of Biosciences , 2011,
Abstract: Dendronephthya sp. is a soft coral that has huge distribution starting from Indopacific, Tonga, Solomon Islands to Great Barrier Reef in Australia. However, this soft corals survive only in short period after cultivation in artificial habitat (aquarium). Recent study showed that the soft coral Dendronephtya sp. has an association or symbiotic relationship with several bacteria, commonly known as coral associated bacteria (CAB). In this study, we compared the population dynamic of Dendronephthya sp.-associated bacteria in natural and artificial habitat, resulting different bacterial community profiles using terminal restriction fragment length polymorphism (T-RFLP) analysis of bacterial community DNA. There were 15 main classes of bacterial population identified along with uncultured microorganism, uncultured organism, uncultured bacteria and unidentified organism. Members of Actinobacteria, Arthrobacteria, Chlorobia, Caldilineae, -proteobacteria and Proteobacteria were predicted to give contributions in the survival ability of both Dendronephthya sp. The cultivation of soft corals after 2 weeks in artificial habitat increases bacterial population similarity on 2 different samples by 10%. Bacterial population similarity in artificial habitat would increase along with the longer cultivation time of soft corals.
Isolation of Active Substances from the Seeds of the Milk Thistle Plant (Silybum marianum) and Determination of Antioxidant Activity
Ga?o-Soka, D.,Kova?, S.,Bu?i?, V.
Kemija u Industriji , 2011,
Abstract: Isolation of silymarin, a mixture of well-defined flavonolignans, from the seeds of milk thistle (Silybum marianum) was achieved. Silymarin was extracted from defatted seed with acetone without heating; the yield was Y=4.1 %. The antioxidant activity of silymarin was determined at ambient temperature by means of a 2,2-diphenyl-1-picrylhydrazyl (DPPH) colorimetry with a detection scheme at Λ= 515 nm. The activity was evaluated by the decrease in absorbance as the result of a DPPH radical color change from purple to yellow. The results obtained showed that ascorbic acid was a substantially more powerful antioxidant than silymarin, but silymarin was a significantly stronger quencher of DPPH radical than the standard silibinin.
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