33 Records out of 22207 Records

Pollination of strawberry in Kenya, by stingless bees (Hymenoptera : meliponini) and honey bee (hymenoptera : apini) for improved fruit quality

Author: Asiko, Grace Adala

Awarding University: University of Nairobi, Kenya

Level : PhD

Year: 2012

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Strawberries ; Plant reproduction ; Bees ; Hypotrigona sp. ; Meliponula sp. ; Plebeina sp. ; Apis mellifera ; Agricultural production ;

Abstract:

The essence of pollination in crop and fruit production, for increased food production, in quantity and quality, is undisputed. A wide range of agricultural crops rely on pollinators, particularly bees for their pollination requirement. Strawberry, for instance, is self-pollinated, wind and bee-pollinated. The production of strawberry fruits is heavily dependant on efficient and effective pollination, such that when properly pollinated, the fruits become heart-shaped, suitable for market at premium prices. Besides pollination by honey bees, stingless bees and solidary bees are suitable alternative pollinators, in the wake of declining honey bee colonies, due to anthropogenic factors, hence declines in food production. Pollination studies in Africa have, in the past been initiated but abandoned due to prioritization challenges. The study aimed at testing the pollination efficiency of three stingless bee species? Hypotrigona sp., Meliponula sp. Plebeina sp.) and the honey bee, Apis mellifera scutellata, on two strawberry varieties, rotunda and chandler, in enclosures, in order to recommend their utilization by commercial farmers to increase horticultural production and for improved fruit quality. Specific objectives were: a) To determine the pollination efficiency of the selected stingless bee species and the honey bee, Apis mellifera scutellata, on strawberry plants in net enclosures, cages. b) To determine the quality and quantity of strawberry fruit production through stingless and honey bee pollination. c) To establish strawberry fruit variation due to: ecological zone, stem age, season, bee species, strawberry variety and crop husbandry. Experiments were set up in three ecological zones of Kenya, with differing Agricultural land productivity: Kakamega, high potential; Nairobi, medium potential and Kima, low potential. Using a randomized split block design, five stingless bee species, Hypotrigona gribodoi, Hypotrigona ruspo/ii, Meliponula ferruginea, M bocandei, Plebe ina hildebrandti and the honey bee, Apis mellifera scutellata, were tested for their suitability in the pollination of two strawberry varieties, rotunda and chandler. This was done on 6 x 11 Metre split plots. The study incorporated two control strategies: In the first control, strawberry cultivars were planted in the open with free pollination and could therefore be pollinated by self, wind or any other pollinator in the viscinity. In the second control, the study plots were enclosed by an insect net, to keep off would be pollinators, hence, no external pollinator was used such that only self pollination occurred. The total number of fruits harvested per day, their weight, size and quality classification, were used as the response variables, whereas bee species, strawberry variety and location, were the main explanatory variables. Rainfall and daily temperature data were recorded. Regression analysis revealed significant association between rotunda strawberry variety and bee species (d.f=6; P<O.OOI, 505). Similarly, between chandler variety and bee species (d.f =9; P<O.OOI, 2055). A chisquare test to establish association between fruit quality and stingless bee species, and fruit quality and strawberry variety, were both highly significant (d.f=21; X2 =62.95; P<O.OOI and d.f=7; X2 =2909; P<O.OOI respectively). Pearson chi-square test for association between strawberry variety and bee species was highly signi!icant (d.f=7; X2=2909; p<O.OOI). The mean number of fruits picked per day for chandler strawberry variety was 4, whereas that of rotunda was 2 (d.f 424; P<O.OOI). The study showed that strawberry variety and quality of fruits for, Kima and Nairobi sites were significant (d.f 3; P=0.05). There was high significant association between strawberry variety and quality of fruits for, Kakamega and Nairobi sites (d.f=3, X2=46.79, P<O.OOI). The honey bee pollination improved fruit yield and quality. The Pearson Chi-square test showed significant association

Impacts of crop irrigation on rangeland soil biodiversity and insect pollinators at Isinya, Kenya

Author: Uduogu, Austin O Denis

Awarding University: University of Nairobi, Kenya

Level : MA

Year: 2012

Holding Libraries: University of Nairobi Jomo Kenyatta Memorial Library ;

Subject Terms: Tillage/Rangelands/Soils/Plant reproduction/Insects/Isinya District/ ;

Abstract:

Anthropogenic perturbations have varying short and long terms effects on structure and function of an ecosystem. How and the extent to which irrigated tillage and crop rotation affect agricultural beneficial belowground microorganisms as well as above ground structure in cultivated tropical rangelands are not adequately understood. This knowledge is key to efficient ecosystem management through land reclamation or restoration, in addition to providing understanding for affordable and environmentally benign means for soil fertility replenishment. The study explored how the introduction of irrigated legumebased rotational cropping system impacts on soil assemblages of rhizobia, insect species richness and abundance, as well as soil seed bank density and composition in a managed rangeland. The study involved three independent but related experiments comprising field activities and laboratory procedures carried out between January and December 2011. The fieldwork was carried out at three agro-pastoral farms and their adjacent natural grasslands located within the range unit of Isinya District, Kajiado County. The location is about 70 km south of the Kenya capital, Nairobi. Soil samples were systematically taken from experimental blocks to assess rhizobia assemblage and seed bank composition. The Most Probable Number plant infection method (MPN) was used to compare rhizobia assemblages between the natural range and cultivated plots under different crop rotation regimes. Seed bank assessment was carried out using the seedling germination method. Sweep nets and water traps were used to sample insets population during the dry and wet seasons. Multiple diversity indices were calculated to understand the effects of cover type on insect visitation. Rhizobia population was found to vary between disturbed and undisturbed range sites, and the degree of differences significantly depended on cover crops and rotation regimes. This suggested that in soils containing significant amounts of rhizobia, the necessity of inoculating legumes seeds with the bacteria innoculum prior to planting diminishes with repeated precropping of compatible grain legumes. Secondly, with respect to the insect assessment, higher taxonomic diversity of pollinators was found in the French bean plots compared to the natural grasslands. The dominant pollinators were of the Apidae family (bees). However, majority of the pollinators found in the unmanaged range were absent in the cultivated areas including the French bean plot. Many other arthropods found in the adjacent grassland were absent in the cultivated plots. This showed that although monocrops of nectar rich legumes provided habitat resources for some pollinators, the cultivation of the range was detrimental to many others insects that dot not derive direct benefit from agricultural crops. The study also found that tillage was both a sink and a pool of seed bank. Tillage was detrimental to natural seeds because it entailed soil turning, which brought deep buried propaules closer to the surface where condition was favorable for their germination, only for germinants to be destroyed and wasted as weed. At the same time it caused seeds of agriculture associated plants to be buried in the soil thereby changing the seed bank composition over time. The most resilient natural seeds included those of Crotalaria sp and Trifolium sp, which belong to the pea family known for their affinity for pollinators and ability to colonize rhizobia. Tillage is likely to engineer structural composition of abandoned agricultural fields within East African rangelands.

Agrobacterium tumefaciens-mediated transformation of three groundnut (Arachis hypogae L.) genotypes from Southern and Eastern Africa

Author: Kahariri, Esther Wanja

Awarding University: Kenyatta University, Kenya

Level : MSc

Year: 2011

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Agrobacterium tumefaciens/Arachis hypogea/Groundnuts/Plant reproduction ;

Abstract:

Groundnut or peanut (Arachis hypogae L.) is one of the principal economic oilseed legumes and 'is largely cultivated in tropical, subtropical and warm temperate regions of the world. It is an . upright or prostrate annual plant. Groundnut contributes significantly to household food security and cash income through the sale of the seeds and also provides a valuable source of proteins, .. fats, energy and minerals. Developing countries account for nearly 9S% of the world production .Groundnut production in African countries has been fluctuating greatly over the last decade. This has been attributed to biotic and abiotic constraints. Pests and diseases that are major biotic factors can lead to yield losses as high as 100% resulting in total crop failure. Traditional plant breeding methods used to improve the crop are time consuming, expensive and involve transfer of unwanted traits along with the desired ones. Besides they are limited to the existing narrow gene pool within compatible groundnut genotypes. Recent advances in biotechnology offer alternative tools such as genetic engineering through which genes that confer some of these traits can be isolated, cloned and introduced into important crops. Genetic transformation protocols are both genotype and species dependent and specific protocols need to be developed for every plant species and sometimes even each genotype. Development of a good transformation protocol for African groundnuts will provide a platform for further genetic improvement for traits such as drought, pest and disease resistance and biofortification. Transformability of three groundnut genotypes; ICGV90704, ICGV12991 and JL24 was assessed using cotyledon explants from mature seeds infected with four Agrobacterium tumefaciens strains AGLO, EHA lOS, CS8 and LBA 4404 containing a standard binary vector with a GUS reporter gene. The transformation efficiency (TE) expressed as a % of PCR positive shoots out of the total number of shoots infected, of groundnut variety ICGV90704 was 1.33% with strain EHAI0S, 0.81% with strain AGLO and 0.39% with strain LBA4404. Variety ICGV12991 recorded a TE of 1.11% with strain AGLO, 0.S9% with strain CS8 and 0.53% with strain LBA4404. Variety JL24 had a TE of 1.03% with strain AGLO and 0.99% with strain CS8. ANOV A between and within the three varieties at the explant producing shoots, total shoots in S 1, total shoots in S2 and total shoots in RIM showed strain LBA4404to be more efficient followed by AGLO and EHAI0S. The least efficient strain wasCS8. Groundnut variety ICGV 90704 was found to be the most amenable to transformation. It is concluded that cotyledons can be used as explants in the transformation of African groundnuts.

Pollination of Coffea Arabica L. and associated awareness of pollination significance among farmers in selected farms in Kiambu District , Kenya

Author: Karanja, Rebecca Hugiru Ngumburu

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : PhD

Year: 2010

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: Farmers/Coffee/Coffea arabica/Plant reproduction/Bees/Andrena/Patella pis/Lasioglossum/Apis mellifera/Agricultural extension work/ ;

Abstract:

Kenyan coffee (Coffea arabica L.) is rated among the best quality coffee produced worldwide. Unfortunately, there has been a decline of coffee production and inadequate pollination is suspected to be among the contributing factors. This was the first study in Kenya to investigate on the pollinators of coffee, the role of natural floral resources as alternative floral resources, importance of pollination in improving coffee yield and cup quality, efficiency of some key pollinators of coffee and pollination knowledge among coffee farmers. Two farms were selected for the study based on management practices; in one farm organic farming was practiced while in the other conventional practices were carried out. Two transects each 1.5 km were selected per farm and plots of 100m2 laid within the two transects. Bees that visited coffee and other plant flowers were sampled. Observation of bee foraging behavior and the resources collected was recorded. Investigations on the effects of pollination levels on fruit set and retention was analysed. Pollination knowledge of coffee farmers was assessed using a semi- structured questionnaire and a knowledge index assigned. In total, bees from 63 families were recorded as pollinators of coffee with a record of 60 species in the organic farm and 24 species in the conventional farm. Bee abundance and diversity were significantly higher in the organic than in the conventional farm (P<0.05). During the study period, Andrena spp. a rare bee species not previously described in Kenya was collected from the organic farm. A total of 42 plant species represented in 19 plant families formed natural floral resources in coffee fanns and the surrounding areas. The organic farm recorded all the 19 plant families and 40 species. The conventional farm had 25 plant species from 14 families. A highly significant relationship (P<O.OOOl) existed between natural vegetation richness and the bee richness. This study provided evidence that coffee requires pollination for enhanced yields, heavy berries and high cup quality. Significant differences (P<O.OOI) existed between the percentage fruit set, fiuit retention (t= 49.258, P<O.OOl), berry weight (P< 0.001) and the average cup quality (p<O.OOI) between autogamy and different pollination levels. Open pollination which encompassed pollinators, wind and autogamy produced the best quality coffee while the lowest quality was recorded from autogamy. Peak foraging time of bees coincided with the time of high nectar volume and average nectar sugar concentration. There was a positive significant correlation (P<O. 01) between the average time taken on a flower and the number of flowers of the same plant foraged on and a negative significant relationship (P<O.05) between percentage flowering and the number of flowers foraged on per plant. Among the sampled bee species solitary bees Patella pis (Zonalictus spp.) and Lasiog!ossum spp. deposited higher numbers of coffee pollen grains while Apis mellifora L. had the highest number of non coffee pollen hence the former could be more efficient pollinators of C. arabica. Significant differences in both the pollen deposited and pollen purity occurred between A. mellifera and Patella pis zonalictus (p<O.OOl) and A. mellifera and Lasioglossum spp. (P<O.OOI). This finding calls for enhancement of diverse populations of solitary bees for more efficient pollination. Coffee farming was dominated by males (84%) with only 16% female farmers. Male farmers had a higher pollination knowledge index than female farmers but the differences were not significant (p>O.OOI). The differences in pollination knowledge between education level groups were not significant (P>O. 00 I). This indicates that education on pollination issues should be done across all education levels and both genders. This study concludes that biotic pollination is important in enhancing yields and the quality of coffee without additional farm inputs. Further, other relatively unkno

Mass propagation of bamboo and its adaptability to waste water gardens

Author: Murage, Hunja

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : PhD

Year: 2009

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: Bamboo ; Plant reproduction ; Water treatment ;

Abstract:

Mass Propagation of Bamboo, and its Adaptability to Waste Water Gardens Unregulated and inappropriate disposal of wastewater poses serious pollution problems in many parts ofthe developing World. However, reuse of wastewater may help to ameliorate global water shortages, especially in developing nations where facilities for safe disposal of wastewater do not exist. Some bamboo species grow more rapidly than timber species and have numerous actual and potential applications for environmental conservation and income generation. In view of these attributes, bamboo was chosen for use in the present study of the potential utilisation of wastewater to improve water and nutrient supplies, while providing an environmentally compatible method for wastewater disposal and a fast-growing, non-timber source of woody material for subsistence farmers As the extremely long vegetative period before flowering occurs in many species limits seed supplies, it is vital to develop effective methods for mass propagation of bamboo to enable its widespread adoption by subsistence farmers in East Africa. Seven potentially important species were used in studies intended to develop suitable micropropagation procedures: these were Dendrocalamus membranaceus, Dendrocalamus yunnanicus, Dendrocalamus strictus, Phyllostachys heterociada, Oxytenanthera abyssinica, Phyllostachys pubescene and Dendrocalamus giganteus. Multiplication rates differed between species (P<O.OOI) and these difference became apparent within five months of establishing the cultures. D. yunnanicus was the most promising in terms of multiplication rate, easily outperforming all other species (P<O.OO 1), by increasing to 3,500 plantlets within eight months. species (Dendrocalamus giganteus, Bambusa vulgaris and B. nutans) were grown in 100 tanks in a factorial experiment under field conditions. Sewage effluent or clean water was applied daily according to the treatment involved. A second experiment contained 339 younger plants irrigated with three sources of water, including industrial wastewater. Subsequent analysis revealed that the wastewater did not contain toxic concentrations of nutrients or trace metals. Weekly and diurnal measurements of net photosynthesis, transpiration rate and stomatal conductance were made over a nine month period, while non-destructive measurements of plant height, collar diameter, number of leaves and leaf area were made over a 15 month period. Destructive harvests after 0, 9 and 15 months of treatment were used to determine leaf and stem fresh and dry weights. When averaged over all species, irrigation with wastewater increased stem fresh and dry weight plant' by 30-40 % relative to plants receiving clean water (P<0.05), with B. vulgaris and B. nutans performing better than D. giganteus. A significant water*time interaction was apparent for plant height, branch number, leaf area plant' and biomass production for all species; values were greater for plants irrigated with wastewater than in those receiving clean water. Volumetric soil moisture content did not differ significantly between the clean and wastewater treatments between March and November 2006, but differed between the two measurement depths (20 and 60 em; P<O.OO 1). The gas exchange and SPAD values (an indirect measure of chlorophyll concentration) revealed several significant effects. SP AD values varied with time (P<O.OO 1), but not between species, and were greater in plants irrigated with wastewater than in those receiving clean water (P<O.OO 1). Stomatal conductance, transpiration and net photosynthesis all showed significant effects of species, irrigation treatment, time and leaf position in the canopy (P<0.05). Instantaneous transpiration efficiency (ITE) was greater in plants irrigated with wastewater than in those receiving clean water (P<0.05). Elemental analysis showed that the concentrations of trace metal nutrients in the wastewater supplies used in both experiments were not sufficiently

Collection, morphological characterization and in vitro propagation of the Kenyan yam (dioscorea spp)

Author: Mwirigi, Peter

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : MSc

Year: 2009

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: Food crops ; Tuber crops ; Kenyan yam ; Dioscorea ; Plant reproduction ;

Abstract:

Yam tuber is used as food where it provides cheap starch-rich staple food of the hot, humid tropics. In Kenya the yam is mainly boiled, fried or roasted although a minority of consumers also processes it into flour for use in some baked products. A majority of the farmers grow yams both for commercial and subsistence purposes. A set of three investigations were carried out in the period of August 2007 to August 2008 with the overall objective of collecting and documenting, morphologically characterizing and eventually optimizing an in vitro protocol for mass propagation of the Kenyan yam (Dioscorea spp). The first objective was achieved by carrying out a survey on 84 farm households in 6 selected administrative districts (Meru, Nyeri North, Nyeri South, Teso, Hamisi and Bungoma West) in the yam growing regions of Kenya. Data collection was carried out through individual interviews using structured and semi-structured questionnaires. 43 named landraces were recorded on farm where it was established that 38 landraces had limited distribution and abundance and only 5 dominant landraces were widely grown within the respective regions. However further studies are required to determine the actual extent of distribution and diversity of these named landraces. The second objective was to characterize the yam cultivars based on their morphological characters as recorded on farm. This involved subjecting data of seventeen morphological variables that were measured from the accessions to multivariate analysis using principal components and cluster analyses. A Dendogram generated through agglomerative hierarchical clustering based on a similarity matrix revealed that the 43 landraces belonged to four main groups of the Dioscorea genus. However, further confirmatory research through genetic analysis is required. The final objective was to optimize an efficient in vitro mass propagation protocol of this particular species. This experiment involved establishment of the best sterilization procedure for the explants that were initially grown in pots in a screen house at Jomo Kenyatta University of Agriculture and Technology then culturing the nodal cuttings in MS media supplemented with different levels of growth regulators. The two step-wise sterilization procedure using commercial bleach was found to be the best and hence recommended for future work. There were also significant differences among the treatments with the combination of BAP and IAA at levels of O.5mgll of BAP + O.02mgll of IAA giving the best results for plantlet regeneration. In vitro rooting was achieved without the use of hormones and the most vigorously growing plantlets acclimatized in the green house. In conclusion, the study found out that there is morphological diversity among the 43 cultivars grown in Kenya and that a new yam cultivar, 'nkone' was documented. Nevertheless, further confirmatory work based on molecular characterization is required. In addition with the development of an efficient in vitro protocol for micro-shoots growth, increased rates of multiplication can be achieved. This technique can then be exploited to generate clean, disease free material both for mass propagation and experimental work.

Diversity and abundance of bee pollinators visiting hedgerow plants in the farmlands bordering Kakamega forest

Author: Mwangi, David Kamande

Awarding University: University of Nairobi, Kenya

Level : MSc

Year: 2009

Holding Libraries: University of Nairobi Upper Kabete Library ;

Subject Terms: Kakamega District ; Kakamega Forest, Kenya ; Bees ; Apis mellifera ; Pollination USE Plant reproduction ; Plant reproduction ;

Abstract:

The study was carried out in Kakamega farmland, north of the Kakamega forest, from October 2008 to March 2009, in order to determine the diversity and abundance of bee pollinators that forage on flowers in the hedgerows, and the major bee plant species. Fourty hedgerow transects measuring 50m each were selected and marked in the farmland. Five land use categories i.e, forest, roads, sugarcane, grazing and maize/beans production were used as a criteria for transect selection, hedgerow plant composition was also considered. Each of the transect was sampled twice a month for the bees visiting the flowers from October 2008 to March 2009. During sampling all the bees foraging on the flowers of the plants in the hedgerow were recorded, together with the plant species visited. Each sampling took 40 minutes. All the bees that could not be identified on site were captured using standard sweepnets, kept in killing jars and labelled with a code. Later the bees were pined in the insect pinning boxes for identification at the NMK. Similarly, specimen of the plants that could not be identified were collected and labelled with similar codes for further identification. The results indicate a significant variation both in bee diversity and abundance across the five land uses. A total of 82 bee species belonging to three families, i.e. Apidae, Megachilidae and Halictidae were recorded on hedgerow flowers. Apidae was the most diverse family having 42 bee species with Apis mellifera being the most frequent visitor. The megachilidae and halictidae families had 20 species each. Xylocopa species mostly visited Justicia flava, Caesalpinia decapetala and Solanum incanum plants while most Meliponula species visited Tithonia diversifolia flowers. The plant species/family in the hedges had significant variation both in the number of bee species (diversity) and individuals (abundance) for all the bees except Megachilidae. The most important bee resource plants in the hedgerows based on the number of indviduals that visited the flowers are in the Acanthaceae family represented by Justicia flava, Asystasia gangtica and Acanthus pubescens, Asteraceae family represented by the species Tithonia diversifolia, Craessocephallum vuellinum and Aspillia mossambicensis and the species Caesalpinia decapetala in the Fabaceae family. From the results obtained from this study it can be concluded that hedgerow plants play an important role in providing food resources (nectar and pollen) for various species of bee pollinators, and can be used for their conservation in the farmland.

Regeneration of two tropical maize genotypes (Zea mays L.) from mature embryos through callus initiation using split seed technique

Author: Demissie, Zerihum Abebe Demissie

Awarding University: Kenyatta University, Kenya

Level : MSc

Year: 2007

Holding Libraries: Kenyatta University Moi Library ;

Subject Terms: Maize ; Plant reproduction ; Seeds ; Agricultural research ;

Abstract:

Plant regeneration from single or few cells is a prerequisite for effective selection of transformed cells and to minimize the event of chimeras during transformation. This can only be achieved if plants are regenerated through callus initiation. To date immature embryos have been widely used as explants for maize (Zea mays L.) plant regeneration through callus initiation and transformation work. However, the utilization of immature embryos has been hampered by their strictly limited suitable stage for culture, 12-17 days after pollination. In contrast mature seeds are ubiquitous. Therefore, use of mature embryos as an explant can significantly reduce the time required to generate immature embryos and hence the overall time required to regenerate maize plant. However, tropical maize genotypes and mature embryos have been considered as the most recalcitrant for tissue culture work. Consequently tropical maize line regeneration using mature embryos has not been reported so far. The purpose of this study was to regenerate two tropical maize lines, CML 216 and Katumani, from mature embryo. Splitting maize seeds longitudinally exposes three different tissues of the embryo simultaneously: scutellum, coleoptile-ring and shoot apical meristem. In the present study up to 92.6% germination and 0% contamination rate was attained for mature embryos harvested directly from open field or screen house by soaking sterilized seeds in 1% NaOCI solution for 2-3 hours. Seeds were germinated on MS media supplemented with 2 mg 1-1 2,4-D. Both the amount and frequency of callus produced by splitting mature seeds early (one day after germination) was found to be low, 43.3 % and 57.4 % for Katumani and CML 216 genotypes respectively, as compared to 66.3 % and 75.7% for Katumani and CML 216 respectively when splitting was done late (3-5 days after germination). The maximum average callus induction recorded was 90% for CML 216, 80% for Katumani and 34.3% for A188. When 2,4-D was combined with lower levels of Kinetin ( cytokinin) both the amount and frequency of callus induction was reduced to 52.5% for CML 216 and Katumani and to 34.3% for A188. The media used was LS salts and B5 vitamins supplemented with 900 mg 1-1, 250 mg 1-1 and 3-4 mg 1-1 of 2,4-D. The average production of Type II and Type I callus was 75.6% and 62.3% respectively. The media used was LS salts and B5 vitamins supplemented with 900 mg 1-1, 250 mg 1-1 and 2 mg 1-1 of 2,4-D. The frequency of regenerable calli produced was 21.14% for CML 216 and 16.51% for Katumani. The number of shoots regenerated per callus induced from single split seed ranged from 1-5. The media used was LS salts and B5 vitamins supplemented with 900 mg 1-1 , 250 mg 1-1 and 4 mg 1-1 of BAP and 2 mg 1-1 of Kinetin. Plants were acclimatized in pots contained pit moss. This regeneration protocol gives an alternative explant source for maize researchers of the tropics in transgenic maize production to tackle different production constraints.

Multi-species pollination interactions in a Kenyan savannah ecosystem.

Author: Baldock, K C R

Awarding University: University of Edinburgh, Scotland

Level : PhD

Year: 2007

Holding Libraries: Index To Theses ;

Subject Terms: Biological sciences ; Ecosystems ; Plant reproduction ; Grasslands ;

Abstract:

Co-flowering plant species (species that flower together in space and seasonal time) that share pollinators could compete for pollination. This can result in a negative effect on reproductive success for one or more species. Such plant species could compete for one or both of pollinator visits or pollen load quality. Plant species could minimise competition for pollinators (i) by using different pollinators, (ii) through spatial separation, (iii) by flowering at different seasonal times, (iv) by placing pollen on different parts of the same pollinator and (v) by segregating shared pollinators in daily time. In this thesis I investigate pollination interactions between plant species in (i) a guild of ten acacia species and (ii) an entire flowering plant community in Laikipia, Kenya. I examined the acacia species? flowering phonologies to identify species that regularly co-flower. I compared daily patterns of dehiscence between co-flowering acacia species for evidence of character displacement on a daily timescale and assessed the extent to which (i) acacia species shared pollinators and (ii) shared pollinators are partitioned in daily time in response to patterns of pollen availability. A number of pollinator species were shared among acacia species making competition for pollination possible. Although up to five species of acacia regularly co-flowered, there was no consistent evidence to suggest that character displacement of dehiscence time had occurred among these species. Previous analyses have only considered the dynamics of co-flowering within guilds of related species. In this thesis I examined evidence for the daily partitioning of shared pollinators in a savannah plant community using a null model approach to analyse plant-pollinator interaction networks.

Investigation into low cost tissue culture media for micropropagation of potato (solanum tuberosum L.)

Author: Kuria, Paul Kimemia

Awarding University: Jomo Kenyatta University of Agriculture and Technology, Kenya

Level : MSc

Year: 2007

Holding Libraries: Jomo Kenyatta University of Agriculture and Technology Library ;

Subject Terms: Solanum tuberosum/Plant reproduction/ ;

Abstract:

Conventional propagation of potato gives very low multiplication and can easily transmit diseases over generations. Tissue culture which is an alternative to this method is rapid and is performed under aseptic conditions to produce in vitro plantlets from which mini-tubers are produced generally in screen-house for field multiplication. Agar and analytical grade sucrose are two components of the culture medium that increase significantly the cost of tissue culture, accounting for 57% and 34%, respectively in total cost of the propagation medium. Experiments were carried out in National Potato Research Centre - Kenya Agricultural Research Centre, Tigoni to evaluate alternative cheap sources of carbon and gelling agent in culture media. A randomized complete block design was used to compare grade sucrose with two types of commercial sugar (white sugar and brown sugar) in full strength Murashige and Skoog (MS) medium at 3% (w/v) using three potato cultivars (Tigoni, Asante and Kenya Sifa). The explants regenerated shoots and roots at 5-7 days after culturing (DAC) and 100% plantlet survival was recorded during the four generations of subculturing. The mean number of nodes per plantlet was significantly higher in brown sugar for 'Kenya Sifa' and 'Asante'. At 35 DAC the mean number of nodes per plantlet on media with brown sugar, grade sucrose and white sugar were respectively 9.8, 10.1, and 8.8 for 'Tigoni' 8.7, 8.8 and 8.1 for 'Kenya Sifa' and 10.0, 8.8 and 8.9 for 'Asante'. The number of roots ranged from 5-8 per plantlet, with brown sugar enhancing significantly higher mean number of roots at the end of the four generations. For cultivar Kenya Sifa, plantlets were significantly taller in brown sugar compared to those in grade sucrose and white sugar. The percentage of plantlets survived after transplanting to a glasshouse was not significant for 'Asante' and 'Kenya Sifa' but media with grade sucrose had significantly lower survival for 'Tigoni'. Commercial sugar not only enhanced micropropagation but also significantly brought down production cost by 34%. Cassava starch at 10% (w/v) gave adequate support of potato explants, although the medium had low viscosity and softened at 42 DAC. Composite media (8% cassava starch and 0.25% agar) provided the same firmness as 0.8% agar and maintained gel strength to the end of the culture period. liquid medium enhanced better performance of plantlets; however, majority of shoots developed hyperhydric structures resulting to low survival after transplanting. Cassava starch boosted plantlets growth better than agar. This was attributed to absence of inhibitory factors as reported in agar, additional carbon sources and beneficial compounds which act as ionic supplements. The study revealed that cassava starch at 10% can bring down the cost of media by 42.5% without compromise on quality of plantlets. The stability of cassava starch can be improved by mixing it with 0.25% agar. This research recommends the use of commercial sugar at 0.3% as a source of carbon and cassava starch at 10% as an alternative low cost gelling agent in micropropagation potatoes.