Department of Agricultural Sciences
Permanent URI for this collectionhttp://localhost:4000/handle/20.500.12092/3079
Browse
7 results
Search Results
Item Assessment of genetic diversity of Kenyan dolichos bean (Lablab purpureus L. sweet) using simple sequence repeat (SSR) markers.(2016-01) Kamotho, Grace N.; Kinyua, iriam G.; Muasya, Reuben M.; Gichuki, Simon T.; Wanjala, Bramwel W.; Kimani, Esther N.; Kamau, Eliezah N.The level of genetic relatedness or dissimilarity of Lablab genotypes used by growers in different regions in Kenya has not been determined. In this study, ninety six (96) Lablab accessions collected from various parts of Kenya were characterized based on simple sequence repeat (SSR) molecular markers. Ten SSR primers were used and detected a mean of 4.3 alleles per primer. Expected heterozygosity was on average 0.38. The average polymorphic information content (PIC) was 0.63. Analysis of molecular variance (AMOVA) revealed 15% genetic variation among populations and 85% variation within populations. Highest Nei’s genetic distance of 0.998 was found between Western and Mwingi populations while lowest genetic distance of 0.092 was found between Embu and Meru populations. Lablab purpureus populations exhibited a high level of relatedness as revealed by cluster analysis and dendrogram based unweighted pair group method with arithmetic averages (UPGMA)Item Assessment of phenotypic diversity of Kenyan dolichos bean (Lablab purpureus L. sweet) germplasm based on morphological markers(2017) Kamotho, Grace N.; Muasya, Reuben M.; Kinyua, Miriam G.In Kenya, lack of phenotypic diversity assessment of Lablab has hindered its improvement. It is common to find that morphologically similar cultivars do not bear the same name while cultivars bearing the same name may not be identical morphologically. The aim of this study was to clear the ambiguity that exists in differentiating between the various phenotypes of Lablab. The morphological method is the oldest and considered the first step in description and classification of germplasms. Forty five accessions of Lablab collected from farmers’ fields in Rift Valley, Eastern, Coast and Central regions of Kenya were planted at Kenya Agricultural and Livestock Research Organization, Njoro farm. A descriptor from Asian Vegetable Research Development Center was used as a guide. Results on means separation showed a high level of variability in quantitative traits and a low level of variability in qualitative traits. Eigen vectors derived from principal component analysis indicated that seed yield per plant, number of pods per plant, plant height and days to 90% mature pods contributed highly to total diversity in Lablab. In conclusion, Lablab germplasm grown in Kenya is morphologically diverse in quantitative traits where different genotypes are distinctly dissimilar.Item Effects of induced mutagenesis and single backcrossing on agronomic traits of wheat (Triticum L.).(2014-07-12) Obare, I. J.; Kinyua, M. G.; Kiplagat, O. K.Induced mutagenesis has been extensively used to improve main crop species, particularly cereals including barley (Hordeum vulgare L).The main strategy in mutation-based breeding is to upgrade the well adapted plant varieties by improving a few desirable major traits such as yield component, tolerance to biotic and abiotic stress for consumer preferences. The present experiment was set out to determine the effects of induced mutagenesis on agronomic traits in mutant barley. The experiment was carried out in University of Eldoret research field in May –August 2012. One hundred and eighty three mutant lines were selected and used in the experiment with the parent (Nguzo) as a check. They were laid in a randomized complete block design with three replicates. The following parameters were used for the study; Number of tillers, plant height, a thousand seeds weight, spike length and days to 50% heading. The data obtained were analysed by Genstat software and mean separated by Duncan Multiple Range test. It was found that muta had a significant effect on number of tillers, plant height, weight of 1000 seeds, spike length and days to 50% heading at P<.001. From the results it is evident that mutagenesis had effects on agronomic traits in mutant barley lines hence can be used in creation of the much needed variation in breeding strategies in barley. The barley mutant lines that had superior characteristics in terms of the agronomic traits could be advanced and used in breeding programme or released as varieties.Item Evaluation of drought tolerance in mutant Kenyan bread wheat (Triticum aestivum L.) using in vitro techniques(INNSPUB, 2016-08-31) Githinji, Gerald Gikonyo; Kinyua, Miriam; Kiplagat, Oliver; Birithia, RaelWheat (Triticum aestivum L) is widely cultivated as a small-grain cereal. In Kenya, it is ranked second after maize in its contribution towards food security. Biotic stress conditions such as drought cause extensive losses to agricultural production worldwide. In Kenya, arid and semiarid lands represent 83% of total land area, which experience frequent crop failure due to drought stress. Developing drought-tolerant wheat genotypes has been the focus of many wheat improvement programs. Few drought tolerant varieties are available for commercial production in Kenya. Hence, there is need to develop more drought tolerant wheat varieties. The objective of this study was to screen for drought resistance in two mutant wheat lines in vitro using Polyethylene Glycol (PEG). Four wheat germplasm were tested for drought tolerance using -3.0, -9.0 and -15.0 PEG-6000 concentrations and the data was recorded on various seedling parameters including root length, shoot length and root length /shoot length ratio. The experiment was carried out in three replicates using completely randomized design. Data was subjected to analysis of variance (ANOVA) using GENSTAT 12th edition. Correlation was done by Pearson Correlation Coefficients to determine significant associations among the different variables. Results indicated that there was a significant difference (p=0.05) between Mutant 1 and Mutant 2 having longer roots, shoots and a root to shoot ratio compared to Chozi and Duma in the different PEG concentrations used. Hence, the two mutant lines are possible candidates for varieties that can be grown in ASALs regions in Kenya.Item Effects of entomopathogenic fungus and spider plant intercrop in control of onion thrips and iris yellow spot virus(INNSPUB, 2018-06-30) Birithia, Rael Kayume; Subramanian, Sevgan; Muthomi, James Wanjohi; Narla, Rama D.Iris yellow spot virus (IYSV) is a major constraint to bulb onions production in Kenya. In search for alternative to synthetic insecticide, field experiments were conducted for two cropping seasons to evaluate the effectiveness of spider plant intercrop, Metarhizium anisopliae and carbonsulfan insecticide in the management of onion thrips and IYSV. Two onion varieties; Bombay red and Red creole were used. Randomized complete block design in a split plot arrangements was adopted. Results showed both varieties treated with entomopathogenic fungus recorded the least number of adult thrips while insecticide treated plots recorded the least larvae thrips. Insecticide, entomopathogenic fungus and intercrop significantly reduced IYSV incidence as compared to the control plots. Bombay red variety treated with fungus recorded the lowest severity and virus titer levels in the two cropping seasons. Adult thrips positively correlated with IYSV incidence in season one (r = 0.575; P <0.001) and two (r = 0.580; P <0.001). Red Creole treated with insecticide recorded the highest bulb onion total yield (10782.8 T/ha) and marketable yield yield (8314.8 T/ha) in the first cropping season. Entomopathogenic fungus treated plots outweighed other treatments in the second cropping season and recorded total bulb yield of 8503.7 T/ha and marketable yield of 7611.1 T/ha. Although, spider plant intercrop reduced bulb yield in both seasons, it contributed significantly in reducing onion adult thrips and increased food productivity. Metarhizium anisopliae and spider plant intercrops were found to be effective bio-pesticide and we suggest their inclusion in the integrated management strategies of vector thrips and IYSV.Item SEASONAL DYNAMICS AND ALTERNATE HOSTS OF THRIPS TRANSMITTED Iris yellow spot virus IN KENYA(African Crop Science Society, 2018) BIRITHIA, R.K.; Subramanian, S.; Muthomi, J. W.; Narla, R. D.Thrips-transmitted Iris yellow spot virus (IYSV) (Family Tospoviridae, Genus Orthotospovirus) is a major constraint to onion (Allium cepa L.) production in Kenya. Determining seasonal patterns of the vector and alternate hosts of the virus could help onion farmers plan Integrated Pest Management strategies; while allowing them to move away from calendar-based applications of insecticides. The objective of this study was to determine the distribution, seasonal variations and alternate hosts of vector and IYSV. For distribution, a survey was carried out on a network of farms in all onion growing areas in Kenya; while for seasonality, surveys were done in two areas; Loitoktok and Naivasha. Data were collected on IYSV incidence, thrips population and alternate hosts. Results showed IYSV was widely distributed in all onion growing areas; with incidence varying from 26 to 72%. Highest IYSV incidence was recorded during the cool-dry season, and varied from 56.5 to 71%; while lowest IYSV incidence in onions was observed during the cool and wet season (29.9 to 32.2%). Iris yellow spot disease incidence positively correlated with the number of onion thrips in Loitokitok (r = 0.659; P<0.0001) and Naivasha (r = 0.623; P<0.0001). Identified alternate hosts for IYSV were leeks, chives, shallots, lambsquarters, redroot pigweed, Chinese lantern and black nightshade.Occurrence of thrips on onions, which is grown all year round calls for urgent integrated pest management strategies that includes host plant resistance, field sanitation, forecasting and use of beneficial insects and parasitoids to reduce impact of the pest and disease. Plant health adherence through removal of alternate weeds hosts around the cultivated fields, would be useful in minimising IYSV incidence.Item Evaluation of drought tolerance in some Kenyan bread wheat (Triticum Aestivum L.) at seedling stage(2019-11-02) Githinji, Gerald G.; Kinyua, Miriam; Kiplagat, Oliver; Birithia, Rael K.Wheat (Triticum aestivum L) is the second largest contributor to food security in Kenya. However, water deficiency retards plant growth and productivity significantly. With few drought tolerant varieties available, there is need to develop more drought tolerant wheat varieties. Objective of this study was to screen for drought tolerance in the mutant wheat lines at seedling stage. Seeds of two wheat varieties were subjected to gamma radiation at an irradiation dose of 300 gy (gray). The mutants and two local varieties – Chozi and Duma (controls) were sown in polythene bags in a complete randomized design and screened for various seedling traits. Data were analysed using ANOVA and Pearson correlation. Results indicated that Mutant 1 and Mutant 2 had high emergence percentage, emergence index, energy emergence and per cent seedling recovery compared to local varieties Chozi and Duma. Emergency percentage showed a positive correlation with the following parameters; emergence index (r = 0.965); Energy of emergency (r = 0.990) and Percentage seedling recovery (r = 0.941). It was recommended that the mutant wheat be screened for other biotic and abiotic stresses that affect wheat production in Kenya.