Analysis of genetic structure in Melia volkensii (Gurke.) populations using random amplified polymorphic DNA

Melia volkensii (Gurke.) is a popular fast growing agroforestry tree species in the East Africa's arid and semi arid lands (ASALs). The species is valued for its high quality termite resistant timber. In addition, its fruits are eaten by livestock thus making it the species of choice by small-scale farmers. However, the species has been overexploited and information on its existing gene pool is currently lacking. The present work was therefore carried out using random amplified polymorphic DNA (RAPD) markers to assess genetic diversity within and between populations in order to suggest appropriate conservation and management strategies. Eight RAPD primers generated 38 scorable polymorphic bands which were used to estimate genetic distances between populations and for construction of neighbour-joining phenograms. Analysis of Molecular Variance (AMOVA) indicated significant genetic differentiation between populations in the eastern and the coastal regions with 21.1%, (P < 0.0002) of the total variation attributed to differences between these regions. There was a clear split between populations from Eastern and Coastal populations of Kenya. These differences may be due to ecogeographical association with genetic variation and should be conserved to retain the full breadth of genetic variation of the species. Key Words: Melia volkensii, random amplified polymorphic DNA, genetic variation, agroforestry species. African Journal of Biotechnology Vol.3(8) 2004: 421-42

Estimation of out-crossing rate in a natural breeding population of Warburgia ugandensis using AFLP marker

Warburgia ugandensis Sprague (Canellaceae) occurs in East and Central Africa, and the species is of great medicinal importance to the local communities where it occurs. As the wild populations diminish,planted stands will in future be used as the source of medicinal products as well as germplasm. This study investigated the levels of out-crossing rates to provide knowledge for proper planning in futurecultivation programmes. The mating parameters estimated using the mixed mating model (software MLTR) showed the species to be predominantly out-crossing (89%) with significant levels of selfing.The multi-locus population out-crossing rate was higher than the single-locus population out-crossing rate (tm- ts= 0.023; SE = 0.010), implying that there was less likelihood of mating between relatives (biparental inbreeding). Low values were also obtained for the correlation of paternity, rp(s) = 0.028 (SE = 0.040) and correlation of selfing among family, rs = 0.016 (SE = 0.015). For most loci, allele frequencies of pollen and ovule contributions to the progeny genotypes were significantly different (

Estimates of outcrossing rates in Moringa oleifera using Amplified fragment length polymorphism (AFLP)

The mating system in plant populations is influenced by genetic and environmental factors. Proper estimates of the outcrosing rates are often required for planning breeding programmes, conservation and management of tropical trees. However, although Moringa oleifera is adapted to a mixed mating system, the proportion of selfing has not been previously estimated. The current work therefore, shows the use of AFLP markers in a mating system study of M. oleifera seed orchard. Data revealed a mixed mating system with a multilocus outcrossing rate (tm) of 0.74. It further demonstrated that AFLP markers, though dominant with a lower information content than co-dominant markers are adequate for the study of the mating system in plant populations. The 26% selfing observed in M. oleifera can lead to overestimation of the proportion of additive genetic variance and appropriate adjustments are therefore required. However, the presence of selfing as well as early sexual maturity (6 months to 1 year) in M. oleifera provides an opportunity for developing inbred lines and hybridisation. Additionally, in designing M. oleifera seed orchards, randomisation and minimum distance between related individuals need to be worked out to maximise cross-fertilisation among unrelated clones and minimise selfing or mating among related ramets. Key words: Moringa oleifera, mating system, outcrossing rates, amplified fragment length polymorphism. African Journal of Biotechnology Vol.3(2) 2004: 146-15

Analysis of genetic diversity in Eucalyptus grandis (Hill ex Maiden) seed sources using inter simple sequence repeats (ISSR) molecular markers

Eucalyptus grandis is an economically important tree species that is native to the Australian continent and its northern neighbours, where it is grown primarily for its hard wood timber and pulp for paperindustries. It is widely grown in tropical countries such as South Africa, Kenya, Angola, Ghana, and Zimbabwe. Five ISSR primers generated 41 scorable polymorphic bands which were used to analyse genetic diversity between and within the seed sources and for construction of neighbour-joining phenogram. Mean Genetic Diversity per each primer loci based on Nei (1987) statistics indicated significant genetic variation between seed sources with 26.4%, (Gst = 0.264) of the total variation attributed to differences between seed sources. The variation between populations could be due to ecological, geographical association and gene flow rates and hence they should be conserved to retain the full breadth of genetic variation of the species. Thus, ISSR-PCR technology is a reliable, rapid (high throughput) and cost effective marker system that can be used to study genetic variation and genetic relationships among E. grandis seed sources

Antibiotic resistant Salmonella and Escherichia coli isolated from indiginous Gallus domesticus in Nairobi, Kenya

Objective: To characterise and investigate antimicrobial resistance of Esherichia coli and salmonella strains isolated from indigenous Gallus gallus in a leading slaughterhouse/market outlet in Nairobi-Kenya.Design: A repeated cross sectional study and based on random sampling was used.Setting: The study was carried out in a leading market outlet in Nairobi, Kenya.Results: A hundred and four indigenous chicken rectal swabs were analysed, of which 67.3% were contaminated with Escherichia coli and 12.5% with Salmonella typhimurium. Seventy Escherichia coli isolates showed resistance phenotypes to one, two or more antibiotics. The most common antimicrobial resistance pattern was the single resistance to Tet (21.43%), followed by Amp Cot Tet (14%), Aug Amp Cot Tet (4.29%), Aug Amp Cot Tet Kan Chl (2.86%), Amp Cot Tet Chl, Cot Tet (2.86%) and Crx Amp Cot Tet Chl, Crx Amp Cot Chi, Amp Cot, Aug Amp, (1.43%) respectively. The highest rate of resistance was against Tet (55.7%), followed by Cot (40%). Third in line of resistance was Amp 32.86%, followed by Aug (11.43%), low or moderate resistance was against Chl (8.57%), Kan (4.29%), and Crx (2.86%) (