Zones In Kenya Research Articles

English

  This study investigates the patterns of land use change, the reasons for those changes and the vulnerability of forests in Nandi North forest zone in Kenya between the years 1986 to 1995 and 1995 to 2006. Landsat TM images of 1986, 1995 and ETM+ of 2006 were used to create single image depicting the sequence of land use change for the period between 1986 and 2006. The spatial relationship between forest cover change and the causes was determined based on the ground truthing and additional literature from the zonal forest officer and the zone management plan where a total of seven classes including dense natural forest, sparse forest, grassland, agricultural land, plantation forest, tea plantation and built up area was used for classification. Both unsupervised and supervised classifications were carried out using a false colour composite image for interpretation. Out of the seven classes, the results indicate an increase in agriculture over the study period while natural forests were reducing. Extreme poverty, planned deforestation for development needs, and unsustainable forest practices such as illegal logging, charcoal burning and encroachment were seen as key drivers of land use change as indicated by the information from the officer. Accessibility to the forest was a key threat to the existence of the forest. This is seen in the result where forest zones with gentle slopes and flat areas, lower elevation, close to roads and settlement had higher probability for conversion to other land uses due to easier access to them compared to steep slopes, with high elevation and which are from roads and settlement. The resulting vulnerability map categorized the forest into four degrees of varying vulnerability namely: highly vulnerable, moderately vulnerable, vulnerable and least vulnerable starting from the easily accessible to least accessible. The resultant map is important in forest conservation by the forest department as areas highly vulnerable can be put into high consideration at the same time involving the community adjacent to be involved in the management process.   Key words: Forest cover, LULC, change detection, vulnerability, GIS.

Yield Selection within Coffea arabica cv. Ruiru 11

Aims: This study was aimed at identifying high yielding Ruiru 11 sibs in varying growing conditions. The study also intended to measure the extent to which cherry yields of Ruiru 11 are affected by the environment. Study Design: Randomized Complete Block Design with three replications. Place and Duration of Study: The study was conducted in three different agro-ecological zones in Kenya namely Mariene in Meru County, Kisii near Kisii town in Kisii county and Koru in Kericho County between November 2008 and September 2011. Methodology: Thirty four (34) Ruiru 11 sibs, all of which are resistant to Coffee Berry Disease and Coffee Leaf Rust, were evaluated in this study alongside two entries of SL28, a cultivar susceptible to the two diseases. One entry of SL28 was sprayed with copper fungicides to control, while the other SL28 entry was not sprayed with any fungicides. Planted at a spacing of 2m by 2m, each entry had 12 trees per plot per rep, giving a total of 1296 plants per experiment per site. Cherry yield recording was done during the peak harvesting period of May to July at Mariene and July to September at Koru and Kisii. The data was subjected to Analysis of Variance (ANOVA) using XLSTAT version 2012 statistical software and effects declared significant at 5% level. Results: Significant (P = .05) yield differences among Ruiru 11 sibs were obtained in all Research Article American Journal of Experimental Agriculture, 3(1): 76-88, 2013 77 years of evaluation at Koru but only in 2011 at Kisii and Mariene. There was a greater discrimination between sibs at Koru, followed by Kisii and then Mariene. Year effect was highly significant (P < .001) and equally distinguished in all sites but year x sib interactions were significant (P = .05) only at Kisii. Combined analysis for all environmental combinations showed highly significant (P < .001) differences between sibs, environments and their interaction. Environments made a greater contribution (42.6%) to the variation compared to sibs (7%). The interaction term also made a significant contribution (18.7%). The best sibs per site and those adapted to contrasting environments were identified. Conclusion: The expression of high yield variation among Ruiru 11 sibs is a sign of high potential of intra-selection within the cultivar for yield improvement. Identified sibs can be recommended to farmers and also exploited in future breeding programmes for improvement of Ruiru 11 productivity and agronomic adaptability. The occurrence of significant sib by environment (G x E) interactions was an indication that the best improvement strategy should be a multi-site selection.

Adapting agriculture to climate change in Kenya: Household strategies and determinants

Countries in Sub-Saharan Africa are particularly vulnerable to climate change, given dependence on agricultural production and limited adaptive capacity. Based on farm household and Participatory Rural Appraisal data collected from districts in various agroecological zones in Kenya, this paper examines farmers' perceptions of climate change, ongoing adaptation measures, and factors influencing farmers' decisions to adapt. The results show that households face considerable challenges in adapting to climate change. While many households have made small adjustments to their farming practices in response to climate change (in particular, changing planting decisions), few households are able to make more costly investments, for example in agroforestry or irrigation, although there is a desire to invest in such measures. This emphasizes the need for greater investments in rural and agricultural development to support the ability of households to make strategic, long-term decisions that affect their future well-being.

Toxigenic potential of Aspergillus species occurring on maize kernels from two agro-ecological zones in Kenya.

Two agro-ecological zones in Kenya were selected to compare the distribution in maize of Aspergillus spp. and their toxigenicity. These were Nandi County, which is the main maize growing region in the country but where no human aflatoxicoses have been reported, and Makueni County where most of the aflatoxicosis cases have occurred. Two hundred and fifty-five households were sampled in Nandi and 258 in Makueni, and Aspergillus was isolated from maize. Aspergillus flavus and A. parasiticus isolates were tested for the presence of aflD and aflQ genes. Positive strains were induced to produce aflatoxins on yeast extract sucrose and quantified using liquid chromatography-tandem mass spectrometry (LCMSMS). Aspergillus flavus was the most common contaminant, and the incidence of occurrence in Nandi and Makueni was not significantly different (82.33% and 73.26%, respectively). Toxigenic strains were more prevalent than non-toxigenic strains. All the toxigenic strains from Makueni were of the S-type while those from Nandi belonged to the L-type. Quantitative differences in aflatoxin production in vitro between isolates and between strains were detected with S strains producing relatively larger amounts of total aflatoxins, B toxins and lower values for G toxins. This was in accord with the frequent aflatoxicosis outbreaks in Makueni. However some L strains produced considerable amounts of B toxins. Given the widespread distribution of toxigenic strains in both regions, the risk of aflatoxin poisoning is high when favorable conditions for toxin production occur.

Socio-economic constraints to adoption of yield improving tea farming technologies: A study of small holder tea farmers affiliated to estates in Nandi Hills, Kenya

Tea farming technical packages tailored to improve productivity have been developed by the Tea Research Foundation of Kenya and availed to farmers for adoption where the estate subsector has demonstrated that these packages can double the current small holder tea production of 1,800 kg made tea per hectare. Despite this potential, there exists an alarmingly low uptake of these technologies by small holder tea farmers which points to significant gaps in the current tea sector policies and technology transfer worth exploring in the small holder tea sector. Lack of knowledge on socio-economic factors that constrain the adoption of these packages by smallholder tea farmers could be the cause of the wide gap that exist on the rate of adoption within the estate and small holder tea sub sectors. This is clearly demonstrated by low productivity in the latter over the years. Understanding these factors may provide explanations to the low adoption rates, which in turn could be used to formulate policies and offer research recommendations. This study is aimed at estimating how socio economic factors influence smallholder farmers’ decision to adopt the available tea farming technologies. Descriptive statistics and logistic regression were employed with socio-economic factors as independent variables being regressed against the dependent variable of recommended yield improving tea farming technology in the Logistic Regression Model. The study was carried out among smallholder tea farmers affiliated to estates in the Nandi hills tea growing zone in Kenya. A questionnaire was randomly administered to 190 smallholder tea farmers who supplied green leaf to estate factories. The results generally showed that although, 99% of small holders grow potentially high yielding TN14/3 and C12 tea varieties, they do not apply the recommended practices needed to maximize the potential of these varieties. Only 45.8% of the small holder farmers were found to use the technologies. The logistic model analysis of the survey data showed that head gender, benefits awareness, costs awareness, and extension services significantly affected adoption. The implied significance on extension contact could be explained by lack of information on these packages among smallholder farmers who may be willing to adopt the technology. Policies that focus on transfer of information and reduction in cost of production based on these packages to smallholder farmers may help to boost the adoption. The evidence from the study also suggests that management skills seem to be lacking among the tea farmers in Nandi hills and calls for its inclusion in the training package. An organization to specifically represent the interests of estate smallholders would also be welcomed and useful.

Parasitism of Lepidopterous Stem Borers in Cultivated and Natural Habitats

Plant infestation, stem borer density, parasitism, and parasitoid abundance were assessed during two years in two host plants, Zea mays (L.) (Cyperales: Poaceae) and Sorghum bicolor (L.) (Cyperales: Poaceae), in cultivated habitats. The four major host plants (Cyperus spp., Panicum spp., Pennisetum spp., and Sorghum spp.) found in natural habitats were also assessed, and both the cultivated and natural habitat species occurred in four agroecological zones in Kenya. Across habitats, plant infestation (23.2%), stem borer density (2.2 per plant), and larval parasitism (15.0%) were highest in maize in cultivated habitats. Pupal parasitism was not higher than 4.7% in both habitats, and did not vary with locality during each season or with host plant between each season. Cotesia sesamiae (Cameron) and C. flavipes Cameron (Hymenoptera: Braconidae) were the key parasitoids in cultivated habitats (both species accounted for 76.4% of parasitized stem borers in cereal crops), but not in natural habitats (the two Cotesia species accounted for 14.5% of parasitized stem borers in wild host plants). No single parasitoid species exerted high parasitism rates on stem borer populations in wild host plants. Low stem borer densities across seasons in natural habitats indicate that cereal stem borer pests do not necessarily survive the non-cropping season feeding actively in wild host plants. Although natural habitats provided refuges for some parasitoid species, stem borer parasitism was generally low in wild host plants. Overall, because parasitoids contribute little in reducing cereal stem borer pest populations in cultivated habitats, there is need to further enhance their effectiveness in the field to regulate these pests.

Cattle Farmers’ Preferences for Disease‐Free Zones in Kenya: An application of the Choice Experiment Method

AbstractManagement of livestock diseases is important in ensuring food safety to consumers in both domestic and export markets. Various measures are prescribed under the Sanitary and Phytosanitary Standards (SPS) agreement of the World Trade Organization. In order to prevent the spread of trans‐boundary cattle diseases, the SPS agreement recommends the establishment of Disease‐Free Zones (DFZs). These have been implemented successfully in some major beef‐exporting countries, but in Kenya are still at a pilot stage. To understand Kenyan farmers’ preferences on the type of DFZ that would be readily acceptable to them, a choice experiment was conducted using a D‐optimal design. Results show that farmers would be willing to pay to participate in a DFZ where: adequate training is provided on pasture development, record keeping and disease monitoring; market information is provided and sales contract opportunities are guaranteed; cattle are properly labelled for ease of identification; and some monetary compensation is provided in the event that cattle die due to severe disease outbreaks. Preferences for the DFZ attributes are shown to be heterogeneous across three cattle production systems. We also derive farmers’ preferences for various DFZ policy scenarios. The findings have important implications for policy on the design of DFZ programmes in Kenya and other countries that face similar cattle disease challenges.

Factors Affecting Stem Borer Parasitoid Species Diversity and Parasitism in Cultivated and Natural Habitats

The effects of biotic and abiotic factors on stem borer parasitoid diversity, abundance, and parasitism were studied in cultivated and natural habitats in four agroecological zones in Kenya. Comparing habitat types, we found partial support for the "natural enemy" hypothesis, whereby, across all localities, parasitoid diversity was higher in more diverse host plant communities in natural habitats, whereas parasitoid abundance was higher in cultivated habitats. For both habitats, parasitoid richness was mainly influenced by stem borer density and/or its interaction with stem borer richness, whereas parasitoid abundance was mainly affected by stem borer abundance. Parasitoid richness was higher in localities (with bimodal rainfall distribution) with increased spatial and temporal availability of host plants that harbored the borers. Across seasons, parasitoid richness was lower in both cultivated and natural habitats in the driest locality, Mtito Andei. Overall, parasitoid diversity was low in Suam and Mtito Andei, where maize cultivation was practiced on a commercial scale and intense grazing activities persist across seasons, respectively. Across localities, habitats, and seasons, stem borer parasitism was positively correlated with parasitoid richness and abundance. Furthermore, the interaction of rainfall and altitude influenced the presence and absence of parasitoids, and consequently, stem borer parasitism. Parasitism was positively and negatively correlated with temperature in cultivated and natural habitats, respectively. Overall, natural habitats seem to serve as important refugia for sustaining parasitoid diversity, which in turn can affect stem borer parasitism in the cereal cropping system.

Similarities In Periods Of Meteorological Variables Over Kenya And Solar Activity Periods

Using the fast Fourier transform (FFT) method, we determined the spectral characteristics of some meteorological variables over Kenya and identified the prominent periodicities associated with the variables. The meteorological variables studied are the maximum temperature, mini-mum temperature, average temperature, wind speed, precipitation, relative humidity, solar radia-tion intensity, evaporation and sunshine duration. Data from five terrestrial stations, represent-ing the regional climatic zones in Kenya, were employed in the study. The result reveals periods that are associated with solar activity. It is established that solar forcing is very significant over the Kenyan climate. The Sun-Climate relations were influenced at some locations by local ef-fects such as orography and vegetation. Keywords: periodicity, solar activity, Sun-climate relations

Species diversity of lepidopteran stem borer parasitoids in cultivated and natural habitats in Kenya

AbstractField surveys were conducted during 2005 to 2007 to assess the species diversity of stem borer parasitoids in cultivated and natural habitats in four agroecological zones in Kenya. In total, 33 parasitoid species were recovered, of which 18 parasitized six stem borer species feeding on cereal crops, while 27 parasitized 21 stem borer species feeding on 19 wild host plant species. The most common parasitoids in cultivated habitats were Cotesia flavipes Cameron, Cotesia sesamiae (Cameron), Pediobius furvus Gahan and the tachinid Siphona sp., whereas in natural habitats, Siphona sp. was the most common. The majority of parasitoids were stenophagous species; only five species –Cotesia sp., Enicospilus ruscus Gauld and Mitchell, Pristomerus nr. bullis, Sturmiopsis parasitica (Curran) and Syzeuctus ruberrimus Benoit – were monophagous. In both cultivated and natural habitats, parasitoid species diversity was highest on the most dominant stem borers Busseola spp. and Chilo spp. On cereal crops, parasitoid diversity was highest on maize and among wild host plants, it was highest on Setaria spp. The ingress‐and‐sting attack method was the most common strategy used by parasitoids in both habitats. In all agroecological zones, parasitoid species diversity was significantly higher in natural than in cultivated habitats. Furthermore, the majority of parasitoid species were common to both cultivated and natural habitats. It was concluded that natural habitats surrounding cereal crops serve as refugia for sustaining the diversity of stem borer parasitoids from adjacent cereal fields.

Molecular characterization of Candidatus Liberibacter species/strains causing huanglongbing disease of citrus in Kenya

This study was undertaken to characterize the alpha subgroup of the proteobacteria causing the huanglongbing (HLB) disease of citrus from three different ecological zones of Kenya namely the Lower highlands (LH2, LH3, 1800-1900 m above sea level); Upper midlands (UM3, UM4, 1390-1475m), Lower midlands (LM5, LM4, LM3 of 1290-1340-1390m), by isolation and sequencing DNA encoding the L10 and L12 ribosomal proteins and the intergenic region. A 7I6-basepair DNA fragment was amplified and sequenced and consisted of 536 basepairs of DNA encoding the L10 protein, 44 basepairs of DNA intergenic region and 136 basepairs of DNA that partially encodes the L12 protein. Sequences of rpL10/L12 protein genes from Kenyan strains were 98% and 81% similar to the South African ‘Candidatus Liberibacter africanus strain Nelspruit' and the Asian ‘Candidatus Liberibacter asiaticus' strains, respectively. The intergenic rDNA sequence of Kenyan strain from UM and LM showed 84% similarity with ‘Candidatus L. africanus strain Nelspruit' and 50% similarity with ‘Candidatus L. asiaticus' strain. However, the LH strain had an 11- basepairs deletion, while the LM4 had a 5- basepair deletion in the intergenic region compared to ‘Candidatus L. africanus strain Nelspruit'. The L10 amino acid sequence was 100% homologous among HLB bacteria obtained from the agro-ecological zones in Kenya and the L10 protein sequence was also homologus to ‘Candidatus L. africanus strain Nelspruit'. Nevertheless, the L10 amino acid sequence of ‘Candidatus L. asiaticus' and the ‘Candidatus L. africanus subsp. capensis' differed from the Kenyan strains by 18.36% and 11.82%, respectively. Phylogenetic analysis of both the L10/L12 rDNA sequences and the L10 amino acid sequences clustered the Kenyan strains of the ‘Candidatus Liberibacter' species with members of alpha subdivision of proteobacteria

Host–parasitoid community model and its potential application in biological control of cereal stemborers in Kenya

AbstractA two‐host–two‐parasitoid model was constructed to assess the effects of the introduced larval parasitoid, the braconid Cotesia flavipes, on its primary target host, the invasive crambid Chilo partellus, and on secondary host species, in inter‐specific competition with Cotesia sesamiae, the main native parasitoid species of stemborers in Kenya. The model assumed that: (1) there was no host discrimination by either parasitoid species; (2) Cotesia flavipes was the superior competitor that out‐competed Cotesia sesamiae when the host was suitable; and (3) Cotesia flavipes could only develop in an unsuitable host if it had been previously parasitized by Cotesia sesamiae. Model parameters were estimated from surveys conducted in Kenya and from laboratory experiments. Different scenarios of host and parasitoid species composition and host suitability occurring in the different ecological zones in Kenya were analyzed. Results indicated that: (1) the coexistence of stemborer host populations are determined by their population growth rates, the degree of aggregation of the parasitoids and their searching efficiency; (2) in the regions where both the invasive and the predominant native host species were suitable to either parasitoid species, stemborer densities would be reduced to and controlled at low densities, and Cotesia flavipes would become the dominant parasitoid species. However, the extinction or predominance of the native stemborer species depends on the ratio of the growth rates of exotic and native stemborers and their relative searching efficiencies; and (3) if the native host species was acceptable but unsuitable to Cotesia flavipes, the parasite would not become established.

Diversity and abundance of wild host plants of lepidopteran stem borers in two agro-ecological zones of Kenya

A survey was carried out between 2005 and 2006 in two ecologically different localities, Suam and Mtito Andei, to assess diversity and abundance of wild host plants of lepidopteran stem borers during the cropping and non-cropping seasons. Suam in western Kenya is situated in the moist high tropics and is characterised by an Afromontane vegetation mosaic, while Mtito Andei is located in the dry mid-altitudes characterised by a Somalia Masai vegetation mosaic. In Suam, wild host plants and maize covered 11 and 50%, respectively, of the surveyed area. In Mtito Andei, 27% of the surveyed area was under maize during the cropping season, while wild host plant species covered 13% and 8% during the cropping and non-cropping seasons, respectively. There was no significant variation in the relative abundance and diversity of the wild grasses between the two seasons in either location. The abundance of host plants of B. fusca and C. partellus is low in natural habitats surrounding cereal crops. The abundance of C. partellus was low in its wild host plants and B. fusca was absent. Therefore, the role of wild vegetation surrounding cultivated areas in the carry-over of these pests during the non-cropping season is limited.

Quality of Honey Harvested and Processed Using Traditional Methods in Rural Areas of Kenya

The honey consumed in most of Africa is harvested from traditional hives and processed using traditional methods. This work presents the quality characteristics of honey samples (n = 72) processed using traditional methods and on sale in various important beekeeping zones in Kenya: West Pokot, Baringo, Mwingi, Tana, North Kinangop, Mbeere, Nandi Hills, Mida Creek, Kakamega and Taita. The quality of the honey was compared to international standards as proposed in the Codex Alimentarius. The quality markers analyzed were moisture, hydromethylfurfural (HMF), sugar content, diastase, proline content, and free acidity. Moisture was determined using a honey refractometer, HMF and Diastase content were determined through spectrophotometry, sugars were determined by High Performance Liquid Chromatography (HPLC), proline was determined through spectrophotometry and free acidity quantified by volumetry - titration technique. Average constituent values were at 16.00 - 21.20% (moisture); 3.70 - 389.36 mg/kg (HMF); 20.83 - 300.6 mg/kg (proline); 8.03 - 56.98 Schade units (diastase); 57.03 - 102.66% (fructose and glucose levels) and 18.00 - 71.85 50 mg/kg (free acidity). Most of the samples had constituent levels within the limits set in the Codex Alimentarius. Traditional honey harvesting and processing methods seem not to have negative effects on the major honey constituents. However, excessive smoking during harvesting had compromised the aroma and flavour of some samples. In an effort to promote beekeeping as an eco-friendly, sustainable alternate source of livelihoods, training in best apiculture practices, improved extension services and establishment of honey marketplaces is being done to improve honey quality in Kenya.

Diversity and abundance of wild host plants of lepidopteran stem borers in two different agroecological zones of Kenya

A survey was carried out between 2004 and 2005 in two ecologically different locations, Kakamega and Muhaka to assess diversity and abundance of wild host plants of lepidopteran stem borers as compared to maize plots during the cropping and non-cropping seasons. Kakamega in Western Kenya is characterized by a Guineo-Congolian rain forest mosaic and Muhaka at the Kenyan coast by a Zanzibar Inhambane mosaic with secondary grassy and woody vegetation. In Kakamega, wild host plants and maize covered 2 and 43% of the surveyed area. No variation in diversity and relative abundance of wild host plants was observed between both the cropping and non-cropping seasons. In Muhaka, the diversity and relative abundance of wild host plant species differed between seasons, with the Shannon Weaver Index (H) of 1.67 and 0.95 for cropping and non-cropping seasons, respectively. Similarly in this location, wild host plant cover varied between cropping (23%) and noncropping (17.9%). During both seasons, this was higher than the maize cover, with 10.7% and 0% for the cropping and non-cropping seasons, respectively. For both localities, the implication of the differences found in the abundance and diversity between the cropping and non-cropping seasons is discussed.

Biological control of cereal stem borers in Kenya: A cost benefit approach

Lepidopteran stem borers are the key pests of maize in Sub-Saharan Africa. In the lowland tropics, dry mid-altitude, dry transitional and the moist mid-altitude zones of Kenya, the invasive crambid Chilo partellus (Swinhoe) (Lepidoptera: Crambidae) causes up to 73% yield loss. The International Centre of Insect Physiology and Ecology (ICIPE) started a biological control (BC) program in 1991 to control stem borers in subsistence agriculture in Africa with emphasis on classical BC of C. partellus. The project released the braconid larval parasitoid Cotesia flavipes Cameron (Hymenoptera: Braconidae) in 1993 in coastal Kenya, where it got established and spread to other regions. This study assesses the economic impact of the introduced parasitoid. Temporal data on percentage parasitism by the introduced parasitoid and on stem borer density were collected between 1995 and 2004. Socio-economic data was collected through administration of questionnaires to 300 farmers. Economic impact of the project was calculated as the value of the yield loss abated by the parasitoid based on a model of expected stem borer density and parasitism level. Average annual parasitism increased linearly from the time of introduction to reach 20% parasitism by 2004. The net reduction in total stem borer density over the last 10 years was 33.7%, thus abating 47.3% of yield loss. The region will accumulate a net present value of US $ 183 million in economic benefits in 20 years since release of the parasitoid. Introduction of other parasitoid species targeting the egg and pupal stages of the stem borer life cycle stages would be required for biological control to push yield loss by stem borers to an insignificant level.

Understanding Low Rates of Technology Adoption by Women Farmers: A Case Study of the Determinants of Adoption of Improved Sorghum Varieties by Women Farmers in Mbeere District, Kenya

The paper acknowledges the increasing recognition of women's contribution in agricultural and food production, both in terms of provision of labour and in the day-to-day management of farm households and farm activities. However, despite women's increased contribution in farming, not much is understood about their decisions on whether or not to adopt available agricultural technologies. Instead, majority of women farmers in Sub-Saharan Africa tend to be involved in subsistence farming with little use of improved technologies, which in turn translates into sub-optimal yields and low productivity. This paper identifies and analyses the factors that influence smallholder women farmers' decisions to adopt improved sorghum varieties in a marginal agricultural ecological zone in Kenya. A total of 81 farm households of whom 41 were female managed in Mbeere District were interviewed with the aid of a structured questionnaire. The data on various institutional, infrastructural, farm/farmer characteristics as well as technology attributes was analysed using a logit regression model. The analysis revealed that non-yield attributes of improved varieties do affect the probability of adoption. Such attributes in the case of sorghum include taste, ease or difficulty of processing the grain and proneness to attack by birds. Since women play a major role in agricultural and food production in much of Sub-Saharan Africa, the implications of these results are that more and more women should be encouraged to participate in later stages of technology development and evaluation. This would ensure that their views with regard to other important attributes besides yield were incorporated, which in turn would make improved technologies more appealing to farmers. Journal of Agriculture, Science and Technology Vol.3(1) 2001: 30-40

Genetic Diversity of Phaeoisariopsis griseola in Kenya as Revealed by AFLP and Group‐specific Primers

AbstractGenetic diversity of 50 Phaeoisariopsis griseola isolates collected from different agroecological zones in Kenya was studied using group‐specific primers and amplified fragment length polymorphism (AFLP) markers. Group‐specific primers differentiated the isolates into Andean and Mesoamerican groups, corresponding to the two common‐bean gene pools. Significant polymorphisms were observed with all the AFLP primer combinations used, reflecting a wide genetic diversity in the P. griseola population. A total of 207 fingerprints was generated, of which 178 were polymorphic. Cluster analysis of the polymorphic bands also separated the isolates into the two groups defined by group‐specific primers. All the isolates examined were grouped into three virulence populations; Andean, Afro‐Andean and Mesoamerican, and their genetic diversity measured. On average, greater diversity (91%) was detected within populations than between populations (9%). The genetic distance between Andean and Mesoamerican populations was higher (D = 0.0269) than between Andean and Afro‐Andean (D = 0.0095). The wide genetic diversity reported here has significant implications in breeding for resistance to angular leaf spot and should be taken into consideration when screening and deploying resistant bean genotypes.

Etiology, effect of soil pH and sweetpotato varietal reaction to Alternaria leaf petiole and stem blight in Kenya

Leaf petiole and stem blight disease is commonly encountered on sweetpotato in Kenya. A study was carried out to confirm the causal agent of the disease in different agro-ecological zones of Kenya and determine the importance of soil pH as well as field conditions on disease development. Diseased leaf and vine tissues were collected and pathogen isolated. The Kabete, Kakamega, Busia (Alupe), and Kabondo isolates were identified as Alternaria bataticola while the Kisii isolate was identified as Alternaria alternata. Pathogenicity and virulence of different isolates of A. bataticola and A. alternata were investigated under greenhouse conditions. Within 4 - 6 days following artificial inoculation, and depending on sweetpotato cultivar, the fungus produced characteristic symptoms typical of Alternaria leaf petiole and stem blight. All the isolates were pathogenic and differences in virulence depended on isolate source and conidial concentration. The Kabete isolate was more virulent than Kakamega, Kabondo and Alupe isolates, whose virulence did not differ significantly from each other (P Key Words: Alternaria bataticola, A. alternata, virulence, Ipomoea batatus, Kenya (African Crop Science Journal 2001 9(1): 287-292)

Availability of Haemonchus contortus L 3 larvae on pasture at Kiboko: a semi-arid warm agro-climatic zone in Kenya

A study was carried out to determine the availability of Haemonchus contortus L 3 larvae on pasture in a semi-arid warm agro-climatic zone of Kenya. By means of tracer sheep, it was shown that no H. contortus L 3 larvae were available on pasture during the dry periods of the year (July–October and February). They were only available on pasture during the rainy season (November–January and March–June). Sheep permanently grazed on the same pasture however, harboured adult H. contortus in their abomasa throughout the year indicating that the perpetuation of haemonchosis in livestock in this agro-climatic zone was greatly dependent on the ability of the parasite to survive in the host throughout all seasons.