PHD-Department of Plant and Microbial Sciences
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Item Introgressing Genes for Maize Lethal Necrosis Disease Tolerance to Maize Inbred Lines and Awareness Evaluation in Selected Counties in Kenya(Kenyatta University, 2023) Peterson, Muchemi Kariuki; Joseph Wainaina Kamau; Mathew Piero NgugiMaize lethal necrotic disease remain a major biotic challenge facing maize production in Kenya and the entire Sub-Saharan region. The disease is caused by the synergistic co-infections of any member of potyviridae family and maize chlorotic mottle virus (MCMV). Improving maize cultivars through hybridization of single crosses and screening in a multiple agro ecological locations, is a fundamental stage in understanding projeny performance and disease reaction across the varying ecologies/locations.The identifications of the best parental combinations are important stages towards identification of MLND resistance maize cultivars in Kenya. The current study aimed at introgressing genes for maize lethal necrosis disease that is tolerance to maize inbred lines and determination of the level of awareness at Bomet and Nyandarua counties. Bomet County is the hot spot area for Maize lethal Necrotic Disease in Kenya, while Nyandarua county have a variation of agroecological zones imprptant for maize breeding. Structured questionnaire were used to collect data on farmers awareness and MLND managements among Bomet and Nyandarua Subcounties. A total of twenty-four inbred maize lines were collected at Kenya Agriculture Research and Livestock Organization Muguga Centre. In addition four commercial checks were also collected as positive and negative control for Maize Letahl Necrotic Diseases evaluation. The selected inbreds lines and control maize lines were evaluated in a green house environment at Kenyatta University. Field evaluation for MLND was also done at Bomet County. Ten inbred lines, six susceptible and four tolerant, were selected for hybridization. This was followed by identification of inbred lines and their hybrids with high combining ability for MLND resistance, yield, and other morpho-agronomic traits under natural MLND hotspot conditions. Twenty-four single cross hybrids were evaluated in MLND hotspot areas (Longisa and Itembe) Bomet county. The varieties of maize grown by the farmers differed significantly (P < 0.05) across all the five Sub counties in Bomet County. Majority of the farmers in Bomet County preferred genotype DK777 (23.91 %), SC DUMA 43 (8.26 %). Genotype DK777 was mostly prereferred by farmers due to MLND tolearant ability compared to other commercial hybrid. On the contrary, maize farmers in Nyandarua County preffered genotypes H614, H629 and H628 (26.27 %, 18.63 %, 16.87 % and 13.28 %), across all the Sub-counties (P < 0.05). The preference of H614 was due to high yielding compared to other maize varieties. Farmer’s knowledge, awareness and management varied significantly among sub counties evaluated. The screened inbred lines both at controlled environment and natural field, indicated several symptoms like mottling, dwarf maize plants, sterile tassels, short cob, and development of silk on ear position. Maize genotypes KUBT 2, KUBT 6 and KUBT 7 recorded tolerance in both green house and natural environment at Bomet County. Inbred lines KUBT6, KUBT7 and KUBT2 recorded the lowest severity levels after screening using natural conditions at Bomet County. Maize Hybrids KUBT2×KUBT9, KUBT6×KUBT9 and KUBT7×KUBT17 recorded negative Specific Combining Ability effect for severity scores which is an indicator of desirable genes tolerance to MLND. These single crosses hybrids are therefore, recommended for further evaluations to validate the stability for resistance to MLND in Kenya and Sub-saharan region towards food sustainability. The awareness evaluation of MLND among maize farmer, should be given first priorities toward management of MLND in Kenya.Item Application of Taxonomic and Dna Barcoding Techniques in Identifying Commonly Traded Herbal Plant Species in Selected Counties, Kenya(Kenyatta University, 2022) Mwaura, Ann; Joseph Kamau; Omwoyo Ombori; Barbara GravendeelOver eighty percent of the world’s population depends on herbal products for their basic health care needs. However, this widespread popularity is counterbalanced with the lack of relevant research to authenticate the source and purity of the traditional herbal products. There exists an extensive history on use of herbal products but lately there are concerns on authenticity and safety of these products. The objectives of the study were: determine plant species commonly traded as herbal products, assess the products using taxonomic and DNA barcoding techniques, application of DNA barcoding technology in reference barcodes generation, and determine if the plant herbal products are accurately labeled. The study was carried out in selected markets in three counties in Kenya (Kajiado, Narok and Nairobi). Data collection involved use of structured questionnaires, species observation, taxonomic and DNA barcoding techniques. Structured questionnaires were administered to individual herbalists and complementary interviews with key herbalists to enrich the data collected. The local and common names were recorded and later translated to scientific names using para-taxonomists and previously published data. Scientific names listed on labels of packaged plants products were as well recorded. The generated species list guided the collection of voucher specimens and creation of a reference library of DNA barcodes. DNA barcoding technology was used to authenticate the herbal product samples. The common single species samples were analyzed using Internal Transcribed Spacer (ITS) and ribulose -1,5-bisphosphate carboxylase Large subunit (rbcL) DNA barcoding markers while metabarcoding was applied in multi-species samples using nrITS2 marker. The study revealed that 86 plant species belonging to 43 families were traded as herbal products in the regions. Most of these plants were shrubs (66 %) traded as stem and bark. Majority of herbal plant species belong to Fabaceae, Apocynaceae and Rhamnaceae families. The DNA technology successfully generated barcode sequences that were used as reference for herbal products identification. Single species samples were found to be more authentic compared to the mixed species samples as most species were identified to species level as listed on the label. Adulteration in single species samples was mainly by substitution with closely related and/or looks alike species, which raises concern on value and quality of the herbal products sold in the studied counties. Kajiado County had more authentic samples in comparison to Narok and Nairobi. DNA metabarcoding technology was successful in identification of mixed species sample at 92 % to species level and 4 % each to genus and family level. This study has made the first attempt to identify herbal plant species traded in selected markets in Kenya using DNA barcoding technology in combination with morphological and literature methods. Authentication using DNAbarcoding provided a more reliable and accurate results compared to morphological identification. DNA barcoding should therefore be applied in identification and verification of herbal products. DNA barcodes successfully generated and deposited in National Centre for Biotechnology Information (NCBI) Genbank form crucial reference data for future studies and can be used as a baseline library for useful medicinal plants of Kenya.Item Phenotypic, Physiological Characters and Quantitative Trait Loci in F2 Generation of Phaseolus Vulgaris under Drought Stress in Machakos County, Kenya(Kenyatta University, 2022) Langat, Charles Kipkoech; Omwoyo Ombori; Richard C. Cheruiyot; Moses P.H. GathaaraCurrently, yield of common bean (Phaseolus vulgaris L.) in smallholder systems in Kenya is comparatively low; standing at 400 kg ha-1 against global average of 960 kg ha-1. The low yield is attributed to drought which has become a major constraint affecting more than 60% of common bean production across the world. The most effective measure to mitigate effects of drought on common bean production is development of drought tolerant genotypes. Hence, there is need to select for drought tolerant genotypes from the local germplasm of common bean for hybridization. The current conventional method used in screening for drought tolerant bean genotypes involve long duration of field testing. Therefore, there is need to use other alternative method like, marker assisted selection (MAS) using DNA markers linked to quantitative trait loci (QTL) that could quicken the selection process and subsequent development of drought tolerant genotypes. The objectives were to; i) assess phenotypic and physiological characters associated with drought tolerance, ii) characterize F2 (KAT B1 × GLP2) population for drought tolerance using phenotypic and physiological characters, iii) determine QTLs associated with drought tolerance in an F2 (KAT B1 × GLP2) population of common bean. A series of experiments were carried out to elucidate the phenotypic and physiological characters and map quantitative trait loci (QTL) for drought tolerance in common bean. Six genotypes; KAT B1, GLP2, Nyota, Angaza, Faida and Metameta were assessed in a rain-out shelter under water stress for phenotypic and physiological characters related to drought tolerance. Characterization of phenotypic and physiological characters was also carried out in F2 population consisting 116 individuals previously developed from KAT B1 × GLP2 cross. The F2 population comprising of 120 lines derived from KAT B1 and GLP2 were mapped for quantitative trait loci (QTL) linked with drought tolerance. The experiments were laid out in a randomized complete block design replicated three times. Stomatal conductance and stem biomass showed greatest variation among genotypes and had significant positive correlations with yield per plant under water stress. Estimates of expected genetic advance indicated that high gains and progress are attainable on genotypic selection for characters such as days to maturity, pod number plant-1, stomatal conductance and leaf water potential at 34.97 %, 22.32 %, 22.87 % and 25.46 % respectively. High estimate values for heritability in broad sense were also obtained for these characters. A genetic linkage map with a total length spanning 634 cM of the common bean genome at an average distance of 2.02 cM between adjacent markers was generated using 229 single nucleotide polymorphism (SNP) markers. A total of twenty three QTLs were detected for the branch numbers, pod numbers, grain number per pod, stem biomass, leaf biomass, pod biomass, days to flowering and maturity, 100-seed weight, seed yield, stomatal conductance and leaf water potential. Two putative QTLs involved in drought adaptation mechanisms were detected; SCO4.1KG associated with stomatal conductance on chromosome Pv04 and LWP1.1KG associated with leaf water potential chromosome Pv01. Overall, this research provided insight into the genomic regions (QTLs) controlling traits related to drought tolerance in common bean. Given the long duration taken in developing improved common bean cultivars using conventional phenotypic selection, the identified QTLs should be incorporated in marker assisted selection in screening and selection of high yielding and drought tolerant genotypes hence, hastening common bean improvement efforts.Item Passion Fruit Woodiness Disease in Coastal Lowlands of Kenya and Genetic Transformation System of Farmer Preferred Passion Fruit (Passiflora Edulis Sims)(Kenyatta University, 2021) Kwamboka, Asande Lydia; Omwoyo Ombori; Richard Okoth Oduor; Evans NyabogaPassion fruit (Passiflora edulis [Sims]) is an important economic crop grown for both export and domestic market world-wide. In Kenya, passion fruit productivity is low due to both biotic and abiotic constraints. Passion fruit woodiness disease (PWD) complex is the most damaging viral disease causing yield losses of up to 100%. The most effective way to manage PWD is by using resistant cultivars. Conventional breeding of passion fruit for resistance against PWD is hampered by sexual barriers, narrow genetic variability, high ploidy levels and long generation cycles. Thus there is need to incorporate alternative approaches such as genetic transformation in passion fruit improvement. The objectives of this study were to determine the occurrence of passion fruit woodiness disease in selected Counties at the Coastal lowlands of Kenya and develop regeneration and transformation systems for farmer preferred passion fruit genotypes. A survey of PWD was undertaken in major passion fruit growing areas in Kwale and Kilifi Counties. Evaluation of five passion fruit genotypes for resistance to PWD was carried out under greenhouse and field conditions. For shoot induction and multiplication from leaf and nodal explants, respectively, Murashige and skoog (MS) medium supplemented with benzylamino purine (BAP) ranging from 1.0 - 3.0 mg L-1 as well as 2.0 mg L-1 BAP in combination with 0.5 mg L-1 kinetin were tested. The effect of putrescine on root induction was tested. The genetic fidelity of both in vitro regenerated and putrescine treated plants was established using sequence-related amplified polymorphism markers. Callus induction and somatic embryogenesis was carried out using leaf explants and immature seeds on MS supplemented with 0.5 – 16.0 mg L-1 2, 4- dichlorophenoxyacetic acid (2, 4-D) and 1.0 mg L-1 thidiazuron (TDZ). Data on disease severity was used to compute area under disease progress curve (AUDPC). The data was subjected to analysis of variance and means were separated according to Tukey‟s Honest Significant Difference test at 5% confidence level. The highest disease incidence of 59.16% and 51.43% was observed at Kilifi and Kwale Counties, respectively. A significant difference (p < 0.05) in symptom severity was observed within the tested genotypes with purple and banana passion fruits presenting the highest and lowest AUDPC values, respectively, both under greenhouse and field conditions. Efficient induction and multiplication of shoots was achieved on MS supplemented with 2 mg L-1 and 3 mg L-1 BAP, respectively. The homogenous banding pattern based on SRAP analysis confirmed genetic uniformity of in vitro regenerated and macropropagated plants. Exogenous application of putrescine induced root formation on nodal explants. The conditions for optimum gus expression in the histochemical assays were optical bacterial density of 0.5, 30 min infection time, 200 μM acetosyringone and 3 days co-cultivation period. The regenerated putative transgenic lines showed presence of transgene by PCR. The in vitro regeneration system developed can be utilized for mass clonal propagation of passion fruit. The Agrobacterium mediated transformation system can be used to introduce genes which encode beneficial traits such as resistance to PWD and other agronomically important traits into KPF4 variety.Item Spatial-Temporal Variation in Forage Resource Production in Richtersveld National Park, South Africa(kenyatta University, 2021) Konje, Martha Muthoni; Paul K. Muoria; Emily Wabuyele; Susanne VetterForage production and distribution in rangelands is not uniform but varies with seasons and between landscapes. In arid ecosystems such as Richtersveld National Park (RNP), biotic and abiotic factors affects forage production. production.biotic factors affects forage production. The aim of the study was to assess the effects of biotic and abiotic factors on plant biomass production, species composition and diversity of annual-dominated vegetation in RNP; to assess the spatial and temporal variation in forage production by shrubs and factors that influence forage production and variability in RNP; and to quantify spatial and temporal variation in browse production by seven tree species along the riparian zone and determine the factors that influence browse production in RNP. Stratified sampling of vegetation and soil was done in the five vegetation types found in RNP. Mobile exclosures were placed at 100 m, 500 m and 1000 m from the stock posts to exclude grazing. Soil samples were collected at the same sample plots. Harvest method of clipping vegetation of the current year’s growth was used to calibrate Fraction of Photosynthetic Active Radiation (fPAR) values from remotely sensed MODIS imageries. To determine variation in browse production by trees, plants of the seven most abundant tree species were sampled in three study sites along the river. Biomass production and species diversity of annual plants differed significantly (P<0.05) with distances from the stock posts. Biomass production, species richness and diversity of annual plants were positively correlated to rainfall and soil nutrients. Biomass production by shrubs was significantly higher (P<0.05) in Succulent Karoo than in Desert biome. There was a strong relationship between biomass production and fpar values. Ziziphus mucronata (Willd.), Rhus pendulina (Dr.J.P. Roux) and Acacia karoo (Hayne) were found to be the most browsed tree species by goats. Browse production differed significantly (P<0.05) between the tree species but did not differ between the study sites. Leaves and twigs contributed the highest components of litter. Knowledge spatial-temporal variation in forage production is beneficial in the development of adaptive management policies that would support pastoralism and conservation of plant species in arid ecosystems worldwide. An Integrated Ecological Modelling of biotic, abiotic and social economic factors is recommended for clear understanding of various dynamics found in arid ecosystems. Further studies on the nutritive value of browse forage found in RNP are recommended as well as mapping and identification of landscapes with threatened plant species in RNP.Item Metagenomic Analysis of Bacterial Communities in Drinking Water Distribution Systems in Mombasa County (Kenya)(Kenyatta University, 2016) Jeophita, Mwajuma JuneHygienic problems in drinking water distribution systems may originate from contamination by external microorganisms or growth of indigenous biomass. Among all water related disease outbreaks, 33% waterborne diseases were caused by-contaminated source water, 39% by inadequate or interrupted treatment processes and 18% by distribution systems and premise --plumbing deficiencies (Craun et 'al., 2010). The Mombasa County water distribution systems have since inception undergone a sanitary survey and there has been no information on the bacterial community composition therein . .The primary focus of this study therefore was to generate detailed information on the genome information stored within the water distribution system, microbiome. This was achieved through an analysis of the 16S rRNA phylotypes of the microbes present within the microbial community of21 water and biofilm samples collected from Mzima and Baricho water lines, which have been operational for more than 50 years, making them excellent sources of mature distribution system biofilms. Physicochemical characteristics of the water were determined by a portable Palin Photometer and Atomic Absorption Spectrophotometer; while bacterial taxonomic affiliations were analyzed using 16S rRNA based 454-FLX Titanium pyrosequencing. Water from both water lines registered pH, nitrates, phosphates and residual chlorine levels that were within the limits stipulated for drinking water by the Kenya Bureau of Standards (KEBS). All Baricho line samples had iron and lead levels way above the maximum allowable limit of 0.05 mg L-1• Nitrates, iron and temperature correlated positively with bacterial community composition and diversity in all samples as shown by Canonical correspondence analysis (Mantel test: r = 0.27, P = 0.001). Pyrosequencing yielded 27,937 sequences, which were denovo clustered into 2,294 unique operational taxonomic units (OTUs) based on their sequence similarity (3%). A total of 20 bacterial phyla and 6 candidate phyla were identified from pooled samples and were dominated by the Proteobacteria (73.2%), Firmicutes (13.4%), Bacteriodetes (5.9%) and Candidate divisions at 0.9% of the total phylotypes. Renyi diversity profiles t' demonstrated that all sampled sites regardless of source or type have larger species richness, but lower species evenness. Shannon-Wiener diversity (H) index of each sampling site ranged from 0.00 to 1.725. The highest bacterial diversity was found in Baricho water (1.725) and Mzima biofilms (1.391). Biofilms featured characteristically higher bacterial diversity, richness and abundance than bulk water. Bulk water was predominated by Nitrospirae (20.2%), Betaproteobacteria (15.9%) and Alphaproteobacteria (6.4%), while Favobacteria (8.6%), Deltaproteobcteria (3.2%), bacteria NP L. UPA2 and Candidate division OD! were characteristic of biofilms. Redundancy analysis indicated substantial comparative differences in water and biofilms bacterial community composition among the two water lines. Nitrospirae, Elusimicrobia, Cyanobacteria, Gemmatimonadetes, NP-UPA2, and Candidate Divisions TM7, OP11 and OD1 were present only at source but not at endpoints. Differences in community structure and abundance were noted between Baricho water line source and endpoint water and biofilms bacterial composition (p= 0.013). A total of 140 phylotypes of potentially pathogenic species including; Pseudomonas, Escherichia, Shigella, Aeromonas, Enterobacter and Bdelovibrio were identified. Metagenome analyses also confirmed the ubiquity of mycobacteria in drinking water distribution systems. Maintainance of the integrity of water systems, periodic monitoring and effective treatment techniques should take precedence in water delivery services to reduce the risk of contaminating the drinking water with pathogenic microorganisms.Item Diversity and Molecular Phylogenetic Analyses of Parmelioid Lichens (Parmeliaceae, Ascomycota) In Kenya(Kenyatta University, 2017-11) Muigai, Kirika PaulLichens are symbiotic associations of fungi and algae or cyanobacteria.They are ecologically important as bioindicators for air pollution, forest age and health, and as sources of food, shelter and nesting materials for animals. Man has historically used them for dyes, medicines, poisons and in the manufacture of perfumes and antibiotics. Globally there are an estimated 28,000 species of lichens. Parmeliaceae is the largest family with over 2800 species in about 80 genera. Parmelioid clade is the largest group comprising 75% of the total number of species in the family. About 180 species of parmelioid lichens distributed in 19 genera are known for Kenya. The advent of molecular tools has shown that, the morphological and chemical characters traditionally used to delimit taxa in lichens underestimate diversity. Application of molecular data has therefore become a prerequisite while making taxonomic evaluations in this group. Molecular DNA sequence data were used to evaluate the phylogenetic relationships and to re-asses traditional phenotype-based taxon delimitation in Bulborrhizina, Bulbothrix, Canoparmelia, Hypotrachyna, Parmelinella, Relicina and Relicinopsis. Seventy seven samples were collected from 5 floral regions in Kenya and duplicates deposited in EA, F and MAF herbaria. Genomic DNA were extracted from newly collected samples and the ITS, nuLSU and mtSSU regions of rDNA sequenced using Sanger sequencing approach. To infer phylogenetic relationships, 6 datasets of concatenated ITS, nuLSU and mtSSU comprising 746 DNA sequences were analyzed using ML and BI methods. Three species, Bulbothrix kenyana, Hypotrachyna himalayana and Parmelinella schimperiana were described as new to science, and taxonomic re-evaluation of 22 taxa carried out. Eight new combinations were proposed: Bulbothrix sublaevigatoides, Parmotrema epileucum, P. zimbabwense, Relicina dahlii, R. intertexta, R. malaccensis, R. rahengensis and R. stevensiae. The monotypic genus Bulborrhizina had not been studied previously using molecular data and its phylogenetic position hitherto unknown. DNA sequences of Bulborrhizina africana were analyzed with 95 other samples of parmelioid lichens. In the resultant phylogenetic tree, B. africana clustered with Bulbothrix, in the Parmelina clade. Species boundaries in Bulbothrix isidiza and B. tabacina, two pantropical and asexually reproducing species were re-examined using mutilocus dataset of Bulbothrix specimens from E. Africa, Asia and S. America. Five species-level lineages in Bulbothrix isidiza s.lat. and three in B. tabacina s.lat were recovered. Alternative hypothesis testing using SH and ELW tests significantly rejected monophyly of B. isidiza and B. tabacina, respectively. In the phylogenetic analysis of Canoparmelia s.lat. the genus was recovered as polyphyletic with three divergent lineages, two formed a sister group relationship with Parmotrema. Consequently they were included in Parmotrema and recognized at subgeneric level as Parmotrema subgenus Africanae and Crespoa, the former described as new. Genetic diversity of the pantropical sorediate species Hypotrachyna sorocheila was assessed with the resultant phylogeny forming two distinct species-level lineages.The pantropical species Parmelinella wallichiana s.lat. was assessed, samples of P. wallichiana were recovered in four well-supported clades. Evolutionary relationships of Relicina and Relicinopsis were elucidated; Relicina was recovered nested with Relicinopsis. However, based on differences in conidia, Relicinopsis is accepted at a subgenus rank as Relicina subgen. Relicinopsis. The use of DNA sequence data in understanding true diversity and biogeography in Parmeliaceae is underscored. A wider taxon sampling is recommended for the lineages that remain undescribed in this study.Item Characterisation of Colletotrichum Gloeosporioides and Effectiveness of Management Strategies of Anthracnose Disease of Avocado in Murang’a County, Kenya(Kenyatta University, 2018) Kimaru, Stanley KirugoAvocado (Persea americana Mill) is a fruit commercially grown worldwide. Its production is affected by anthracnose disease which causes huge loss of avocado fruits both at farm level and in storage. Management of anthracnose disease worldwide has been mainly through use of fungicides. In Kenya, farmers use fungicides such as bayleton, milraz and Copper oxychloride which are not registered for controlling anthracnose in avocado. Despite this, the disease has continued to cause significant fruit losses of up to 40% as a post-harvest disease. This study was conducted to evaluate avocado production and anthracnose disease management practice; determine the incidences of anthracnose disease in avocado in Murang‘a County; determine the morphological and genetic characteristics of the Colletotrichum gloeosporioides; determine the pathogenicity of the representative isolates of the fungus on avocado varieties (Fuerte and Hass) and determine the inhibitory effect of selected fungicides on C. gloeosporioides isolates in vitro. A completely randomized block design was used in the laboratory tests while questionnaires were used during surveillance. The data on incidence, latent and surveillance was analysed descriptively into histograms and percentages using IBM SPSS version 21 software. Cultural and morphological data was analysed through ANOVA and Fisher's LSD to compare means using Genstart version 6 while molecular data was analyzed through PCR, sequencing (sanger sequencing), alignment (Bio edit software version 7.2.1 and phylogentics relationship of sequences using MEGA 7.0.18. Surveillance on anthracnose disease incidence and the control strategies adopted by farmers was done in the three agro-ecological zones upper midland (UM) 2, 3 and 4 where avocado is grown. The survey revealed that agro- ecological zone 2 had the highest disease incidence of 24.3% followed by zone 3 with 15% and lastly zone 4 with 9.6%. Farmers controlled the disease by pruning, sanitation and use of fungicides not registered for use in avocado. Eight percent of the farmers used fungicides while 30.2% used pruning strategy. Morphological and molecular studies identified C. gloeosporioides, C. boninense and Pestalotiopsis microspora as the causal agents of anthracnose. Further studies on C. gloeosporiodes showed a signicant difference (P≤0.05) among isolates in mycelia diameter and size of conidia. Both Hass and Fuerte fruit varieties were susceptible to all C. gloeosporioides isolates. Diameter of lesions on unripe Fuerte varieties four days after inoculation were not significantly different (P≥ 0.05) ranged from 7.33 -10.00 cm while in unripe Hass it was 6.33-7.33cm. However, lesions on ripe, Fuerte variety 2 days after inoculation ranged 10-17cm while ripe Hass was 9.67cm - 12.33cm. Hass variety was more tolerant to the disease as compared to Fuerte variety. The fungicides Bayleton, Milraz and Copper oxychloride significantly (P≤0.05) inhibited mycelial growth and sporulation of C. gloeosporioides invitro. Farmers should be encouraged to use cultural methods and field sanitation as management strategies to reduce loses and should be trained on strategies in handling, harvesting and storage. They should also be encouraged to grow Hass variety which is tolerant to anthracnose as compared to Fuerte variety. Field studies on the effectiveness of fungicides Bayleton, Milraz and copper oxychloride on anthracnose disease of avocado is recommendedItem Rapid Bioconversion of Rice Straw Using Cellulolytic Cultures for Improved and Sustainable Crop Productivity and Soil Fertility in Mwea, Kenya(Kenyatta University, 2018) Karanja, Anncarol W.Proper management strategies for huge amounts of crop residue generated from agricultural farms need to be obtained. Composting is a good strategy in rice straw management. Traditional methods of composting rice straw are limited in timely production of good quality compost due to its recalcitrant nature. There is need to develop and formulate microbial starter cultures that are adapted to local climatic conditions to ensure efficiency in using microorganisms in composting. This study aimed at assessing and presenting appropriate starter cultures for bioconverting rice straw into bioorganic fertilizer for use in crop production. Bacteria and fungi with lignocellulolytic potential were isolated and used alongside other starter cultures to enhance bioconversion of recalcitrant and abundant rice straw in Mwea, the main rice producing area in Kenya. The microbial isolates were selected through screening procedures and then characterized morphologically, biochemically and genetically. Rice straw was composted by treating it with the selected microorganisms, chicken droppings, commercial effective microorganisms and donkey dung in separate setups. The resultant compost types were characterized in respect to their maturity, heavy metal content and nutrient concentrations. Changes in microbial population densities and diversity during a natural composting process were also studied. The lignocellulolytic microorganisms selected for use in composting the rice straw in this study included 20 bacterial and 11 fungal isolates. Results from various identification techniques used showed that most of the bacterial isolates belonged to Genus Bacillus while most of the fungi were mainly in Genus Trichoderma. Mean values for temperature, pH and electrical conductivity (EC) among the five treatments of the study revealed significant differences at 5 % level of confidence. Using the starter cultures of the study, composting the rice straw was successfully completed within 62 days. The five compost types produced by the composting experiments were physicochemically different as demonstrated by the significant differences revealed by analysis of variance (ANOVA) of their cation exchange capacity, phosphorus, nitrogen and carbon content. The composts were observed to have attained biological maturity as revealed by the germination index, plant growth index and C: N ratio values recorded. Microbial analysis of compost samples taken from the natural composting experiment indicated notable variations in the number of bacterial cells at different phases of composting ranging from 8.7 x 105 to 2.1 x 106 CFU/ g. It was observed that fungi were less prevalent in the compost during the thermophilic phase with a lower overall prevalence compared to bacteria. Bacteria were most predominant in the compost having 28 different bacterial isolates against 17 fungal isolates. Results indicated that addition of the selected lignocellulolytic bacteria and fungi and various starter cultures significantly improved the composting process and the quality of the resultant composts. The experiment on natural composting process showed that variations in microbial population densities and diversity correspond to fluctuations in temperature within the composting materials. From the findings of this study, it is recommended that the obtained lignocelluloytic microorganisms be formulated and used for composting plant residue and other organic wastes to enhance the composting process and improve the quality of resultant bioorganic fertilizers.Item Genetic transformation of select African sweet potato (ipomoea halalas l. Lain.)Cultivars with Weevil resistance genes and evaluation of phytoalexin levels from infected roots(Kenyatta University, 2015) Wamalwa, Lydia NanjalaAbstract Sweetpotato is an important root and tuber crop in Sub-Saharan Africa (SSA) used as food and feed but weevil infestation remains a major concern. Weevils account for production losses between 28 and 100% but no resistance genes are available in the natural gene pool. When weevils attack, they create avenues for secondary infection, which in turn elicit phytoalexin production, toxic to farm animals. Since genetic transformation has been widely used to introduce genes into germplasm that may not be available in the natural gene pool, it was used in this study. Objectives of this study included (i) to develop a regeneration protocol of 32 SSA cultivars through indirect organogenesis, (ii) to develop a transformation protocol for the best cultivars using uidA gene and the double gene construct (cry7AaJ and ET33-34), and (iii) to isolate a fungus that infects sweetpotato after weevil infestation and subsequent analysis of the furanoterpenoid elicited from infected roots. Regeneration and transformation were conducted via indirect organogenesis. Four gene constructs were used in this study: pCIPlOO, pCIP87, pCIP88 and pCIP85. Phytoalexin levels were evaluated on four consumer-preferred sweetpotato cultivars using coupled gas chromatography mass spectrophotometry (GC-MS), thin layer chromatography (TLC), high performance liquid chromatography (HPLC) and Nuclear Magnetic Resonance (NMR). Results showed 6 SSA cultivars with RE above 40% while TE of 5 SSA cultivars revealed GUS-stained calli between 6 and 98%. Six transgenic events were produced using the double gene construct as confirmed by southern blot but they had low protein levels. For phytoalexins, levels between 0.3 and 2,900 mg/kg were recorded. The results suggested that pre-screening for high RE and TE was important in identification of the best cultivars. Low protein concentration levels obtained could be due to post transcription or/and post-translational factors. Such high variations in furanoterpenoid levels have previously been reported, and could be an indicator of a potential health concern to both animals and humans on consumption.Item Efficacy of Selected Medicinal Plants Used by the Ogiek Communities against Microbial related Infections(2014-02-24) Amuka, Omari; Okemo, P. O.; Mbugua, P. K.Ethnobotany and traditional medicines have been used for bioprospection for modern pharmaceutical in all the world continents. In Kenya the ethnobotanical of several communities has revealed that plants are important source of medicinal products that require further research to establish their validity, efficacy and quality of health services. The Ogiek communities who currently live in harmony with nature and have minimal with modern cultural practices exhibit high potentials for discovery of new pharmaceutical products through ethnobotanical, phytochemical, and microbial strategic studies. Furthermore, such studies have been necessited by newly emerging and reemerging diseases and the development of resistance of diseases to the drugs that are currently in use. The Ogiek community, who has lived in Mau forest for over six centuries, is fast being assimilated into other culturally stronger communities. However, their life is shrouded in secrecy and their rich cultural practices including ethnomedicine are being lost. Ethnobotanical field surveys revealed that over 80% of the Ogiek community has constructive knowledge of the forests and forest products. They have clear knowledge of medicine plants, their pharmaceutical procedures and pharmacological manifestations. It was evident that majority of the human health complaints were parasitic, bacterial, and fungal in nature. Symptomatic areas were the abdomen, chest, and the head. A total of 49 plant species in 33 families were collected. Bioassay of the extracts showed that some of the plant species possessed promising antimicrobial activities. In order to verify the efficacy of the drugs, selected pathogens were selected and in vitro studies carried out on individual crude extracts and essential oils. It emerged that 16 plant species showed reasonable biological activities on the selected human pathogens. Further studies to confirm the efficacies of the drugs were successfully done to establish the susceptibility (MIC, MBC and MFC) individually. Several metabolites known for their efficacy were identified. There is need to further document the Ogiek culture, in situ and ex-situ conservation of the Mau forest complex so as to conserve the biodiversity for the future generations. Further elucidation of the extracts may lead to discovery of new pharmaceutical compounds that could be used in the synthesis of new drugs for the currently challenging medical conditions.Item Distribution, Behavioural Biology, Rearing and Pollination Efficiency of Five Stingless Bee Species (Apidae: Meliponinae) in Kakamega Forest, Kenya.(2013-08-01) Kiatoko, NkobaThe study on distribution, behavioral biology, rearing and pollination efficiency of five stingless bee species (Apidae: Meliponinae) in Kakamega forest, Kenya showed that; species diversity was higher at Ivihiga compared to Isiekuti sites. Within habitats, species diversity varied and the indigenous and the mixed indigenous forests had more species diversity than the other habitats. The number of nesting habitats and also the chance of getting a nest of a particular species within nesting habitats varied among the stingless bee species. The nest pattern was under-dispersed for almost all the species nesting in the indigenous forest; mixed indigenous forest and grassland with the indigenous tree species. The nesting pattern for M. ferruginea (reddish brown) and H. gribodoi changed from an under-dispersed and over-dispersed pattern, respectively, to a clumped nest pattern when nesting in the homesteads. Within interspecific species nesting in the same habitat and within the nesting habitats of conspecific species; a difference was observed in the average nearest neighbour distance separating their nest entrances. Three different nesting sites were identified overall species (tree, underground, residential houses). Nest aggregation was observed within four bee species (except M. lendliana) and the average less minimum nearest neighbour distance between nests aggregated on a single substrate varied within conspecific and interspecific aggregation. Daily temperature and humidity influenced the bee flight activities out for foraging or grooming; with temperatures below 22oC and relative humidity above 70% being not ideal for the five bee species to start or maintain their out going flight activity. M. ferruginea (reddish brown) and H. gribodoi were the only species which bite to defend their nests from intruders. M. ferruginea (reddish brown) and M. lendliana were the only species which completely seal the open entrance of their nests at night. Acceptance of the designed hive types varied across bee species. All types of hives designed for M. ferruginea (reddish brown) were accepted at a probability of 0.63 and above. M. ferruginea (black) showed preferences for the two non compartmented hive designs and OATH hive type at a probability of 0,63 and above. H. gribodoi accepted only the icipe 1 hive model compared to the two designs of compartmented hives. M. lendliana preferred nesting only in the hives made out of clay as opposed to wooden hives. Three colonies of M. bocandei were succefully reared in the icipe 1M hive design. The average annual honey production under domestication varied among the five bee species and was higher in the M. bocandei species (3.13 ± 0.21 litres). The hive splitting method was more successful in propagation of colonies of three Meliponula species. Natural enemies recorded in this study included mainly parasites, predators and disturbers. Lastly, flowers of green pepper pollinated by H. gribodoi produced heavier fruits with superior number of seeds and the seeds were bigger compared to those produced by self-pollinated flowers or flowers pollinated by feral insects.Item Nitrogen fixation in faidherbia albida (chev) Del(2012-06-07) Gitonga, Nkanata MburuguNodulation and arbuscular mycorrhizal infection was assessed in soils obtained from two habitats of Faidherbia albida in different ecoclimatic zones. A third site in a semi arid area but without F. albida was also assessed. All three sites had Bradyrhizobium spp, Rhizobium spp and arbuscular mycorrhizas. Soils from the two sites with F. albida differed in soil mineral content, nodulation and mycorrhizal infection of F. albida and Acacia senegal. In laboratory experiments it was observed that F. albida took about 21 days to nodulate. Inoculated seedlings suffered an early period of nitrogen stress. Application of combined nitrogen alleviated early nitrogen stress but reduced nodulation and nitrogen fixation. Combined nitrogen in form of NG4+ had less severe effects on nodulation than NO3- at the three levels of N (0.5, 2.5 and 5.0 mol m-3) tested. In an experiment using 5.0 mol m-3 N provided as 15NO3- (5 atom %) or as 15NH4+ (5 atom %) it was established that preference for nitrogen form was pH dependent. Nitrate was preferred at low pH (5.5) and ammonium at high pH (6.5). The N form/pH combination resulting in good plant growth had also less severe effects on nodulation and nitrogen fixation. Improvised glass fronted gutter containers, made from open gutter pipes were used for monitoring taproot elongation. Effect of N2, NO3-, and NH4+ at mol m-3 was assessed. The taproots elongated very quickly but independently of nitrogen for at least the first 70 days. There were also no statistical differences between taproot elongations in three provenances of F. albida tested. In an experiment to find out the effects of phosphorus and nitrogen form of F. albida, phosphorus was found to increase nodulation and nitrogen fixation. High levels (above 3.0 mol m-3) of phosphorus reduced plant growth, nodulation and nitrogen fixation. A statistically significant interaction was observed between nitrogen form and phosphorus levels. The contribution of arbuscular mycorrhizas to growth, nodulation and nutrient uptake in F. albida seedlings at 0.2, 0.5 and 1.0 mol m-3 was not statistically significant. There were no statistically significant differences between F. albida seedlings grown at 0.5, 50.0 and 75.0 mol m-3 NaCl. Percent nitrogen and nitrogen content were statistically lower in plants grown at 75.0 mol m-3. However the ratio of carbon to nitrogen was significantly higher in plants grown at 75.0 mol m-3 compared to 0.5 and 50.0 mol m-3 NaCl. It has been shown in this study that nodulation, nitrogen fixation and growth of F. albida is influenced by nitrogen form and levels, phosphorus levels, pH and salinity. It is also evident from the results that agronomic protocils can be designed to militate against conditions adverse to growth and nitrogen fixation of the tree. It is envisaged that change of agronomic practices in the growth of F. albida coupled with selection of both macro and micro-symbiont for the field conditions will improve growth and nitrogen fixation of the tree.Item Fungal parasitism of root-knot nematode eggs and effects of organic matter, selected agrochemicals and intercropping on the biological control of meloidogyne javanica on tomato(2012-06-05) Owino, P. O.Root-knot nematodes are serious pests all over the world. Over 50% Pyrethrum losses have been associated with these pests in Kenya. Chemical management of these organisms is effective but difficult to sustain for long-term benefits, and alternative control measures must be sought. The use of fungal antagonists may provide an alternative but factors affecting their efficacy are not known. Therefore, in vitro, in vivo and greenhouse tests were conducted at Kenyatta University, Nairobi, Kenya, to compare efficacy of the fungi Paecilomyces lilacinus Thom(sam), Fusarium oxysporum Schlecht isolates 1, 2 and 3, and Phoma herbarum against root-knot nematode eggs, egg masses and females, and (2) assess whether aldicarb (10% Temik), captafol (orthodifolatan 80% wp), organic matter and intercropping with the nematicidal plants Tagetes minuta L, Datura stramonium L,. and Ricinus commnis L., could stimulate , inhibit or have no effect on the biocontrol potential of P. lilacinus, tomato (Lycopersicon esculentum (Mill) shoot heights and weights, nematode population in soil, gall index and number of galls per gram root weight were assessed using standard methods. Gall index was based on a subjective scale of 0-4, where 0=no gall and 4=76 - 100% of the root system galled. To obtain the P. lilacinus isolate and other fungi for this study, 120 fungal isolates were isolated from nematode eggs extracted from soils collected from fields in Kakamega, Kiambu, Nyeri, Mombasa, Baringo, Kisumu, and Kisii districts. Isolates that parasitized 30-95% of eggs on agar were selected for further tests. Paecilomyces lilacinus and F. oxysporum isolate 1 parasitized significantly (P<0.05) more M. javanica eggs and females on agar than F. oxysporum isolates 2 and 3, and P. herbarum,. P. lilacinus F. oxysporum isolates 1,2 and 3, and P. herbarum parasitized up to 91.9% eggs and 87.3% females, 82.4% eggs and 79.1% females, 25.9% eggs and 44.7% females 9.4% eggs and 19.2% females and 29.5% eggs and 60.6% females, respectively, on water agar. Levels of egg parasitism, however, were lower in sterile field soil. P. lilacinus and F. oxysporum isolate 1, the most aggressive isolates on agar, parasitized only 22.2% and 19.6% of the eggs in sterile soil, respectively. Besides egg parasitism, the five fungi influenced egg hatch differently. Up to 22.2%, 24%, 24.1%, 55.8%, and 74.4% of egg hatched on WA plates inoculated with F. oxysporum isolate 1, P. lilacinus, P. herbarum, F. oxysporum isolate 2, and F. oxysporum isolate 3, respectively. Chicken manure, and the nematicidal plants T. minuta, D. stramonium and R. communis significantly increased egg parasitism by up to 112, 72, 54.9 and 106.3% respectively, when compared to controls. The nematicidal plants also stimulated parasitism of M. javanica eggs were parasitized in soils planted with R communis T. minuta and D. stramonium, respectively 50 days after inoculation, compared to 23.2% in controls. Levels of egg parasitism were however, lower, 17.6, 16.4 and 15.1% respectively, 98 days after inoculation compared to 10.3% in controls. In both cases, percentages of egg parasitism were higher than those obtained in non-amended soils, but lower than those obtained on water agar. R. communis, T. minuta and D. stramonium increased egg parasitism by 3.2, 28.4 and 22% respectively, 50 days after noculation. The treatments, chicken manure, R. communis, D. stramonium and T. minuta also suppressed nematode population and gall development significantly than controls. Galling indices were decreased by up to 76.5%, 35.3, 47% where chicken manure, R. communis, D. stramonium and T. minuta were used, respectively. These treatments enhanced shoot weights by up to 159, 106, 100, and 64.7% respectively when used in combination with P. lilacinus. Delaying the time of planting tomato in soil amended with chicken manure and infested with P. lilacinus from 0 to 8 weeks increased egg parasitism significantly (b=1.9;) and significantly reduced gall development (b=-0.5; r=-0.9). Tomatoes planted in chicken manure-amended soil 8 weeks after incorporation of chicken manure and P. lilacinus were significantly heavier than those planted 0 - 6 weeks after soil amendment. The number of juveniles increased with time of planting in soil not amended with chicken manure (b=+2.1; r=0.44) but the increase was not significant. Significant decrease in galling index with time of planting (r=-0.95) was observed in pots treated chicken manure alone or in combination with P. lilacinus. In general, aldicarb and chicken manure were effective in suppressing gall development and nematode population build up, whether used alone or in combination with P. lilacinus. Among the nematicidal plants, R. communis enhanced egg parasitism more significantly than T. minuta or D. stramonium. However, the maximum levels of egg parasitism achieved in all tests were less than 40%, an indication that the treatments used may not enhance egg parasitism to levels that can reduce nematode populations significantly in the field.Item A study of the determinants of diversity and biosystematics of agromyzidae associated with leguminosae(2012-05-25) Tengecho, C. B.Leafmining Agromyzidae has been reported to cause damage a wide variety of crops. Spencer (1973) Compiled a comprehensive review of the damage caused by the family and listed 156 pest species. He also provided summarized information on the morphological identification, biology, distibution and control of agromyzid pest species. This study is concerned with the identification of eleven agromyzid species that could be collected easily from legumes in Kenya. Although Kenya has approximately 602 species of leguminous plants only a total of 14 agromyzid species were reported to be associated with them. These were 3 species in the genera Tropicomyia, 3 in Ophiomyia, 2 in Liriomyza, 1 in Chromatomyia and 5 in elanagromyza. First and foremost major determinants of diversity of Agromyzidae associated with leguminous plants were analysed using multiple regression.The theory that geographically ubiquitous species of plants have more species of insects feeding on them than similar but less widespread species was shown to hold true for the Kenya leguminous plants so area alone can explain most species richness in any region. Similarly the logarithmic plot of species-area relationship indicated that variations not accounted for was possibly due to the leaf-form, different number of habitats, altitude and taxonomic isolation. The drawback was inadequate botanical collecting of leguminous plants in Kenya, which possibly limited the species-area effects to only 16%. Gel electrophoresis was also used to score enzyme mobilities of ten different species first using polyacrylamide gel then isoelectic points of the different proteins examined. All were diagnostic in separating the ten species of Agromyzidae.Starch gel electrophoresis was also carried out and an account of the species variation was provided, based on the data obtained. It can be suggested that enzymic data should be used as taxonomic characters in parallel with morphological, anatomical and multivariate characters. However from using the enzyme profile of mostly wild individuals all the ten species studied could be placed into distinctly separate genera. Out of four genera occurring in Kenya that were revised the species O. spencerella, O. phaseoli, M. chalcosoma, M. vignalism. T. flacourtiae, Melanagromyza spp. and C. horticila were found to be distinct. However overlap or relatedness existed between them the enzymes that distinctly separated these species were non-specific esterase enzyme, Malic dehydrogenase, Malic enzyme, Glucose-6-phosphate dehydrogenase, Hexokinase and phospho gluvose isomerase. An attempt was also made to see whether the populations from different host plants could be separated statistically bymeasurements calculated for both male and female using wilk's Lambada stepwise discriminant method, The measurements taken were ten morphological characters of Chromatomyia horticola,sixteen Morphological characters of Ophiomyia spencerella populations collected from different localities in Burundi and one locality in Kenya, sixteen morphological characters for O. phaseoli from Sri Lanka and Kenya and seventeen morphological characters for seven species associated with legumes. The proportion of the proximal to the distal part of the wing vein M3+4 was shown to be the best character that separated the five populations of C. horticola into two clusters. The first cluster consisted of Galinsoga parviflora, Bidens pilosa and Sonchus oleraceus while the second cluster consisted of Solanum spp. and Solanum nigrum. Moreover the other nine characters were similar for the five populations studied. This suggests the possible variation for populations of of agromyzid species on different host plants. the populations of O. spencerella from different areas in Burundi and one locality in Kenya were shown to be easily separated by seven different characers shoeing differences in the populations from the different areas. All the seven species of Agromyzidae associated with legumes showed distinctness but overlap existed in male O. spencerella, O. phaseoli and C. horticola. Similarly overlap existed in female O. phaseoli, T. vigneae, L. trifolii and C. horticola. Using genitalia preparation, multivariate analysis and gel electrophoresis, it was shown that the species of agromyzidae on legumes were no coherent and diverse. This confirms their placement into different genera in most existing keys.Item Phytoplankton and nutrient dynamics at Turkwel Gorge Reservoir, a new man-made lake in northern Kenya(2012-04-17) Kotut, KiplagatSpatio-temporal variation in some physicochemical and phytoplankton parameters were investigated at Turkwel Gorge Reservoir and its inflowing and outflowing rivers between 1994 and 1995. Seasonal variation in inflow volume had the most impact on the reservoir conditions investigated. A wide difference between wet and dry season inflow volume had the most impact on the reservoir conditions investigated. A wide difference between wet and dry season inflow volume combined with a regulated outflow independent of season resulted in a drawdown of over 10m in each year. Reservoir Secchi depth ranged from 0.09m (wet season) to 2.80 m (dry season). Low levels resulted from turbid flood inflows. Electrical conductivity (EC, S cm-1) varied from 140-200 (reservoir), 107-210 (inflowing river) and 155-200 (outflowing river). Total alkalinity (TA, as mg1-1 CaCO3) ranged from 80-111 (reservoir), 62-125 (inflowing river) and 80-113 (outflowing river). Low levels of EC and TA were observed during the wet season. A functional relation between EC and TA (TA = 0.529 EC: R2 = 0.876) was established suggesting a predominance of carbonates among the anions. Variations in pH were from 6.7-8.9 (reservoir), 1.8 - 8.2 (inflowing river) and 0.4 - 6.4 (outflowing river). High pH and DO levels at the reservoir were observed during the wet season and were the result of higher phytoplankton photosynthesis. Floodwater inflow and hypolimnetic oxygen depletion possibly brought about low levels of pH and DO at the beginning of the wet season in the inflowing and outflowing river sections respectively. Detectable levels of nitrite nitrogen (NO2-N) were noted at all study sites during the wet season. Nitrate nitrogen (NO3-N, g1-1) varied from 6.7-111.1 (reservoir), 53.3-482.2 (inflowing river) and 8.9-111.1 (outflowing river). Total nitrogen (TN, g1-1) ranged from 119-526 (reservoir), 205-3354 (inflowing river) and 82-624 (outflowing river). Phosphate phosphorus was mostly undertectable. Total phosphorus (TP, g1-1 ranged from 8.9 -71.6 (reservoir), 101.8-1259.4 (inflowing river) and 8.6-31.3 (outflowing river). Variation in NO3-N was mostly irregular except for a wet season increase at the inflowing river. In general, TN and TP showed a wet season increase explicable by an increase at the inflowing river loading. Dissolved reactive silica (DRS, mg1-1) varied from 0.41 to 9.77 (reservoir), 9.01-19.93 (inflowing river) and 5.07-9.77 (inflowing river). Reservoir DRS showed a wet season decline that had an inverse correlation to total diatom biomass (P=0.001, n=12). Estimates of input and output balance of NO3-N, TN, PO4-P, TP and DRS in 1994 revealed a reservoir areal loading rates of 5.98, o.75, 10.90 and 408.5 mg m-2 with a reservoir retention of 78, 74, 94, 95, and 46 percent respectively. Reservoir chlorophyll a (g1-1) ranged from 4.8 to 36.9 (1994) and 4.9 to 11.4 (1995) with coefficients of variation of 42% and 8% respectively. Greater variation in 1994 resulted from higher inflow volume. Outflowing river chlorophyll a ranged from 1.07 to 8.31 g 1-1 with low levels resulting from reduced DO concentration. Positive correlation between mean reservoir chlorophyll a (n=13) and inflow volume (P=0.007), NO3-N (P=0.04), TN (P<0.001), and TP (P<0.001) was observed in 1994. A positive correlation with inflow volume (P=0.005) and TN (P<0.001) was observed in 1995. Phytoplankton diversity (bits based on natural log) at the reservoir varied from 0.18 to 2.43 bits with an inverse correlation to total counts (P<001). Total counts ranged from 2.52 - 77.60 (1994) and 4.57-23.90 (1995) million units 1-1. Species density change varied from a distinct seasonality, through a wax and wane character to a nearly uniform density throughout the annual cycle. Throughout the study period, Achnanthes exhibited a distinct seasonality, characterized by a very high cell count during the wet season and very low counts during the dry season. However, the reservoir peak density in 1994 (75.6x106 cells 1-1) was much higher than in 1995 (3.7x106 cells 1-1). The majority of the other species exhibited a wax and wane pattern with greater amplitude in 1994. Dominance in unit counts varied throughout the study period. In 1994, while the dry season was characterized by a quick succession in dominance, Achnanthes dominated the wet season. Coccoid Cyanophyceae dominated most of 1995. Phytoplankton density changes at the outflowing river followed a pattern close to that of the reservoir with lower unit counts. Total phytoplankton biomass (mg1-1) at the reservoir ranged from 0.44-11.17 (1994) and .49-1.35 (1995). Positive correlation between phytoplankton biomass and the loading rates of NO3-N (P=0.009), TN (P=0.040), TP (P=0.011) and DRS (P=0.033) was established in 1994 suggesting the reliance of biomass increase on inflow nutrient recharge. Among the phytoplankton divisions represented, only the Bacillariophyceae showed a regular wet season peak biomass that can be explained by their dependence on the nutrient rich turbulent inflows of this season. Variation in the other divisions was less regular with peak biomass levels at different times of the intervening period. The Bacillariophyceae contributed biomass in both 1994 (88%) and 1995 (40%). Outflowing river phytoplankton biomass changes (range, 0.27-6.72 mg1-1) showed a positive correlation to reservoir phytoplankton biomass (P<0.001) suggesting that the reservoir is the source of downstream flora. Reservoir primary production ranged from 1.85-9.67 (1994) and 3.00-5.41 (1995) g O2m-2 day-1. High rates were characteristic of the wet season while low rates occurred during the dry season especially following an overturn. High inflow volumes therefore transform the reservoir that is on average mesotrophic to a hypereutrophic state while low inflow volumes or mixing reduce the reservoir that is on average mesotrophic to a hypereutrophic state while low inflow volumes or mixing reduce the reservoir to an oligotrophic state.Item The influence of drip irrigation on ecophysiology and yield of arabica coffee hybrid Ruiru 11(2012-04-11) Gathaara, M. P. H.The influence of drip irrigation on Coffee arabica L. cultivar Ruiru 11 was studied in a field experiment. Drip irrigation was applied when a soil moisture deficit (SMD) of 100 mm was recorded. FOur drip irrigation rates (25, 50, 75 and 100 mm of water) were applied to offset the SMD by 25%, 75% and 100%. These were applied at intervals of 21, 28 and 42 days. The control treatment was unirrigated. Primary (first order) branch extension growth, stomatal conductance, CO2 assimilation, leaf water potential, biomass accumulation, root distribution, yield and quality were measured. The drip irrigated coffee plants had a significantly higher primary branch extension growth rate (8.1 mm wk-1), stomatal conductance (0.605 mol m-2 s-1) and leaf water potential at 14.00 h (-1.98 MPa) than the unirrigated plants. The corresponding growth rate, stomatal conductance and leaf water potential in the unirrigated plants were 1.2 mm wk-1, 0.368-mol m-2 s-1 and -2.67 MPa. Irrigated plants had higher CO2 assimilation rates in the upper levels of the plant canopy when compared to the unirrigated ones. Root distribution was not significantly influenced by irrigation. However the mean vertical distribution (125 cm) was about half the horizontal distribution (232 cm). The unirrigated coffee had a total coffee yield of 6142 kg per ha. The 25 mm, 50 mm, 75 mm and 100 mm irrigation rates resulted in yields of 9373 kg, 10531 kg, 10307 kg and 8726 kg per ha respectively. Theses represented increases of 52.6, 71.5, 67.8 and 42.1% respectively. The results showed that the 50 mm irrigation rate may be optimal. Evidence that dry season water requirements for the cultivar may be met by low irrigation rates at short intervals is presented. The practical implications of the results are discussed.Item Interaction between arbuscular mycorrhiza fungi (AMF) and meloidogyne hapla on pyrethrun in Kenya(2012-04-05) Wanjohi, Waceke J.In this study, mycorrhizal status of pyrethrum in Kenya was determined. Fungal isolates obtained from pyrethrum fields were screened for efficacy against M. hapla and in improving pyrethrum growth. Effect of inorganic P fertilizers and intercropping on Glomus sp. (isolate KS14), one of the effective isolate against M. halpa was dertermined. To determined mycorrhizal status of pyrethrum, spores were extracted from soil samples obtained from 30 different study sites and their abundance (numbers) and composition (types) determined. In addition, percent growing ecozones; Kisii, Limuru study and Molo representing low, mid and high altitude ecozones, respectively. In general, Limuru study sites revealed lower percentage of root colonization, higher spore were characterized and placed into various AMF genera. Except for Sclerocytis spp. five of the six known AMF genera were encountered in the study sites. Glomus was the most commonly encountered genus (10 isolates) followed by Acaulospora (5 isolates). Only one isolate of Entrophospora was present. In the screening tests, arbuscular mycorrhiza fungal (AMF) isolates; KS14 (Glomus sp.3); KS 18 (Glomus etunicatum), KS74 (Scutellospora sp.3), ML34 (Glomus sp.6), ML35 (Glomus sp.7, LM61(Glomus sp.4) and LM83 (Gigaspora sp.3) were screened . Fungal mixed inoculum (20g) was incorporated into sterized sand-soil mixture before planting with 6-week-old pyrethrum seedlings. The inoculum consisted of spores, hypla, infected root fragments and soils in which the plants for inoculum production were growing. The plants were inoculation with 6000 M. hapla second stage juvenile (J-2) 3 months after fungal inoculation. Dry shoot weights, fresh root weights, percent root colonization by the fungi, nematode gall indices, number of eggs, females and J-2 were determined at the end of the experiment 2 months after nematode inoculation. Root length was also determined where possible. Isolates KS14, LM61, KS18 and KS74 significantly improved top biomasses of fungus-treated and fungus-nematode-treated plants. Isolate KS14 was the most effective (47% top biomass increase) followed by isolates LM61 and KS18 (33%). Isolates ML34, ML35 and LM83 improved top biomasses of fungus-nematode-treated plants. Fungal isolates KS74 and ML34 significantly increased fresh root weights of pyrethrum by 45% and 50%, respectively. Isolate KS18 reduced pyrethrum by 45% and 50%, respectively. Isolate KS18 reduced pyrethrum root length by 18%. Except fungal isolates ML34 and ML35, all the other isolates suppressed M. hapla disease severity and egg production. Isolate LM61 (86%) was the most effective followed by KS14 (75%). Isolates KS18, KS74 and LM83 suppressed disease severity and egg production by up to 75%, 32% and 37%, respectively. All the fungal isolates screened significantly reduced the number of females in the root system and J-2 in the soil. The presence of nematodes in fungus-treated plants did not affect root colonization by the fungus except in KS18, ML34 and ML 35-treated plants. In testing for effects of inorganic P fertilizers on efficacy of KS14, Triple super phosphate (TSP) and Single super phosphate (SSP) were used. The fertilizers were applied at two rates (1 and 2g/g soil) at the time of fungus inoculation. Two months after, plants were inoculated with the nematodes. The plant growth and nematode disease parameters were determined at the end of the experiment, 2 months after nematode inoculation. The fertilizers at both levels improved plant growth of non-mycorrhized, mycorrhized, non-mycorrhized-nematode and of mycorrhized-nematode-treated plants. The fungus in general improved plant growth on its own or in the presence of nematodes but not in the presence of fertilizers. The fungus, however, improved plant growth by a lesser percentage than both fertilizers at both levels. The fungus unlike the fertilizers, suppressed nematode's disease severity. The suppressive effects of the fungus were, in most cases reduced by the fertilizers. In addition, the fertilizers significantly reduced root colonization of pyrethrum by the fungus. The nematodes, on the other hand, did not have any significant effects on root colonization by the fungus or on its ability to improve pyrethrum growth. The presence of nematodes in fertilizer or fertilizer-fungus-treated plants, however, significantly reduced pyrethrum growth. Efficacy of isolate KS14 to improve pyrethrum growth was tested in presence of maize and/or bean intercrops. Pyrethrum plants inoculated with 20g of KS14 and left to grow for 3 months were intercropped with maize and/or beans. Two months after planting the intercrops, pyrethrum dry shoot and fresh root weights were determined. Percent root colonization on the three crops by the fungus was also determined. In general, maize significantly reduced shoot and root weights of mycorrhized and non-mycorrhized plants. In addition, maize significantly reduced root colonization of pyrethrum. Beans on the other hand, significantly reduced shoot and root growth of mycorrhized plants but not of non-mycorrhized plants. Beans did not have any significant effects on root colonization of pyrethrum by the fungus. A combination of both intercrops had no significant effects on shoot weights of mycorrhized pyrethrum but reduced that of non-mycorrhized pyrethrum. Pyrethrum root colonization by the fungus was not affected by the presence of the two intercrops. Both maize and beans are hosts of the fungus.Item Cultural management of banana weevil cosmopolites sordidus germar (coleoptera: curculionidae) for improved banana field in Western Kenya(2012-04-04) Ngode, LucasStudies on the effects of planting materials, weevil trapping, and intercropping on the banana weevil cosmopolites sordidus Germar. and crop yields were conducted in western Kenya from 1994 to 1997. The objectives of the investigations were to explore the efficacy of non-pesticidal options for the management of the banana weevil. Field experiments were undertaken using clean planting materials, pseudostum traps for the weevil management and intercropping banana with groundnuts Arachis hypogaea L. different banana plant densities. Results indicate that paring and hot water treatment is effective in cleaning infested banana planting material. It did not affect the banana growth and yield performance. The infested planting material resulted into significantly high weevil damage and yield losses within two crop cycles compared to the infested but pared and hot water treated material. The lowest damage of 12.6% was recorded under furadan protection while the highest damage of 66% was in the infested suckers. The infested, pared and hot water treated material suffered 17.6% damage while in the healthy material it was 16.3% during the three crop cycles. The banana bunch yield under insecticide protection was 14.5 kg and in the healthy plant it was 15.3 kg whereas the infested, pared and hot water treated material yielded 13.3 kg. These weights were not significantly different from each other but differed significantly different from each other but differed significantly from the infested materials yield of 6.8 kg. The associated yield losses were 53.1% in the infested materials, 16.6% under paring and hot water treatment and 8.3% under insecticide protection. The use of split pseudostem traps for weevil management at low weevil population density significantly reduces the number of adult weevils and larval damage caused. However, trapping where the infestation and resulting damage is already high may not result into significant population decrease and yield responses. Intercropping banana with groundnut did not affect weevil colonizing the banana but influenced their distribution during the early stage of the banana establishment. The banana crop planted at 3x3m and 5x5m spacing did not affect the growth of the groundnut during the first one year. Thereafter, the banana canopy significantly reduced the growth and yield of the groundnuts in the 3x3x banana spacing. Nevertheless, spacing significantly influenced the banana yield per unit area with the 3x3m banana spacing yielding more than double that of the 5x5m spacing. The number of flower thrips and aphids were reduced in the banana intercrop compared to those in the groundnut monocrop. Incorporation of organic mature improves the banana performance. Nevertheless, with increased bunch weight snapping of the banana became significant due to the weakened corms. Thus, the use of clean planting materials, weevil trapping and application of organic manure are essential components of banana weevil integrated management.Item Neem seed for the management of the banana weevil, cosmopolotes sordidus germar (coleoptera: curculionidae)and banana parasitic nematode complex(2012-04-04) Musabyimana, ThaddéeThe study was conducted in Western Kenya, a prime banana growing area during the period of May 1996 to February 1999. The objectives were to control the banana weevil and parasitic nematodes with neem materials, thereby reducing yield losses and contributing to sustainable banana production. The repellent, antifeedant, ovipositional deterrent, and growth inhibitory effects of powdered neem seed (NSP), Kernel (NKP), cake (NC) and neem oil (NO) on Cosmopolites sordidus and its population build-up were studied in the laboratory and outdoors tests at ICIPE's Mbita point field station (MPFS). In choice tests, 48h after release, less than 30% of weevils settled under neem-treated banana corms while more than 75% settled under untreated corms. In a feeding test, weevil larvae did not feed or fed little on neem-treated corms. Larvae caused little damage to neem-treated corms, but untreated corms were heavily damaged, indicating a strong repellent and antifeedant effect of neem seed derivatives on C. sordidus. Compared with the untreated control, 3-10 times fewer eggs were laid by female in neem-treated corms. Egg hatchability was less than 25% in neem- treated corms and more than 50% in the control. Neem treatments also inhibited larval growth and development. Forty to 60% of 2nd-instar larvae died in 14 day when confined to neem-treated banana pseudostems, the survivors were small in body size and weighed 4 to 6 times less than those in the control where less than 20% larvae died and adults were recovered. The higher the concentration of neem materials, the higher was the severity of effects. Efficacy of neem materials against the banana weevil and parasitic nematodes was evaluated under controlled pest infestation levels at MPFS. Effective rates, methods and frequency of application of the selected neem materials were determined at MPFS and in Farmers' fields, under different levels of soil fertility and pests infestation. In a pot experiment, four weeks after planting, NSP, NKP, or NC was applied at 5g per plants inoculated with 500 nematodes and 5 pairs (females and Males) of the banana weevil. Compared with control, 1.5 months after the treatment, neem materials application significantly reduced the nematode population and weevil damage on a par with Furadan applied at 5 g/plant. Similar results were obtained with the application of neem materials to pared or unpared banana suckers planted in 100 or 200l drum's capacity and inoculated with 2000 nematodes and 5 pairs (female and males) of the banana weevil per drum. NSP-or NC- treated unpared suckers supported much fewer nematodes than the pared treated suckers with same neem products, obviating the need for paring of suckers. NKP and NO applications were toxic to the banana plant and were excluded from further testing. Soil application of powered NSP or NC against the banana pests was more effective than their application in aqueous forms. Application of NSP or NC at planting time and then at 1, 2, 3, or 4- month intervals to plants grown under controlled pest infestations in drums significantly reduced nematode density and the weevil damage. Similarly, in farmers' fields, soil application of NSP or NC at 60, 80 or 100 g/mat at planting and then at 4 month-interval significantly reduced the weevil and nematode damage. Although the application of NSP or NC at 200 to 400 g/mat at 6 month-intervals significantly reduced the nematode population and weevil damage, they were toxic to the banana plant. Application of NSP or NC at 60, 80 or 100 g/mat at 4-month intervals to a fertile soil with a moderate pest load, increased yields by 27-50% over the control during the 1st crop and by 30-60% during the 2nd crop. Furadan increased the fruit yield by 27% over the control in the 1st crop but dropped down to -2% in the 2nd crop. Under low soil fertility and high pest infestation levels, the neem treatments also controlled the pests and markedly increased the yield 7 to 10 times more than that in the control during the first crop. During the second crop, all plants in the control plots dried up before fruiting, but neem-treated plants continued to produce bunches. Depending on the soil fertility and doses of application, net gain over the control obtained with the application of NSP or NC ranged from US $ 70 and US $ 800 per hectare. However, a loss of US $ 700/ha was observed with the Furadan application. Neem application of doses higher than 100 g/mat was also uneconomical. The beneficial effects of neem seed materials application on the banana plant growth, pest control, and implications of these findings in the banana pest management and further areas of investigation are discussed.