Browsing by Author "Muli, Joshua K."
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Agro-Morphological Characterization of Kenyan Slender Leaf (Crotalaria brevidens and C. ochroleuca) Accessions(Hindawi, 2020-04) Mwakha, Fridah A.; Gichimu, Bernard M.; Neondo, ohnstone O.; Kamau, Peter K.; Odari, Eddy O.; Muli, Joshua K.; Budambula, NancySlender leaf (Crotalaria spp) is among the indigenous and underutilized vegetables in Kenya whose production is limited to the Western and Coastal regions of the country. For a long time, this crop has been neglected in terms of research and genetic improvement. *ere is therefore scanty information on its morphological diversity and agronomic performance, hence the need for this study. Field experiments were carried out for two seasons in October to December 2018 and March to May 2019. *e experiments were laid out in Randomized Complete Block Design with 29 accessions and replicated three times. Both qualitative and quantitative data were recorded from the accessions based on the Crotalaria descriptors. Quantitative data were subjected to analysis of variance using XLSTAT Version 2019, and accession means were separated using Student’s Newman Keuls test at 95% level of confidence. Both qualitative and quantitative data were subjected to multivariate cluster analysis, and a dendrogram was constructed using the unweighted pair-group method with arithmetic average. *e principal component analysis was conducted to obtain information on the importance of the characters. Significant variation in agro-morphological traits was found within and between the two species. Cluster analysis grouped the accessions into seven major classes with a between-classes diversity of 75.13% and a within-classes diversity of 24.87%. *is study sets the basis for genetic improvement of slender leaf in Kenya since the observed diversity can be exploited in selection for intraspecific and interspecific hybridization.Item Competence of Tropical Maize Lines to Agrobacterium-Mediated Transformation and the Expression of Maize Poly (ADP-Ribose) Polymerase (PARP2) Gene under Drought Stress.(Kenyatta University, 2017) Muli, Joshua K.Drought stress affects many maize growing regions in sub-Saharan Africa. As population increases, the gap between maize supply and demand increases. There is, therefore, need to develop maize lines that are tolerant to drought as well as amiable to Agrobacterium-mediated transformation. This study aimed to assess the competence of tropical maize lines after co-cultivation on Yeats Extract Peptone (YEP) media to Agrobacterium-mediated transformation and determine the relative expression of PARP2 gene under drought during development. Tropical inbred maize lines CML 144, CML 216, A04, and E04 as well as Agrobacterium strain EHA101 harboring vector pTF102 containing the GUS reporter gene were used in this study. The ability of immature maize embryos to form embryogenic calli was determined after pre-culturing these embryos on YEP and Murashige and Skoog (MS) media. Transient GUS assay was used to evaluate the competence of the inbred maize lines to Agrobacterium-mediated transformation using YEP as co-cultivation media or YEP that was supplemented with growth regulator 2,4-D (YEP+2,4-D), Cysteine (YEP+CYS), Proline (YEP+PRO) or in combination (YEP+ALL). In all cases, MS media was used as the control. The optimum Agrobacterium concentration for infection of immature maize embryos before co-cultivation was determined. The physiological response of tropical maize lines to drought stress was evaluated and the expression of the PARP2 gene at different drought levels determined by Polymerase chain reaction (PCR). The data collected was analysed using ANOVA at 95% confidence interval with SAS statistical computer software (version 9.1.3). Separation of means was carried out using Tukey’s pairwise comparison at 5% probability level. Callus formation frequency and regeneration were genotype dependent (P= 0.0001). Immature embryos from the four inbred maize lines exhibited high transient GUS expression when co-cultivated with Agrobacterium on YEP (12.31%), YEP+PRO (13.75%) and YEP+ALL (8.68%) media than when cocultivated on MS media (6.76%). Co cultivation in YEP+2,4-D and YEP+CYS, however, resulted in lower transient GUS expression than on MS media. Agrobacterium tumefaciens at a concentration of 0.07 (OD660) gave the highest transient GUS expression (20.90%) while higher concentrations of 0.2 and 0.8 resulted in low transient GUS expression (9.17% and 12.22%), suggesting that YEP media is superior to MS media in enhancing the competence of immature embryos to Agrobacterium-mediated transformation. Thus YEP media is proposed as an alternative media in in Agrobacterium-mediated transformation protocols. Growth rate, fresh weights of seedlings and dry weights of seedlings was low in seedlings subjected to severe drought stress compared to seedlings subjected to moderate drought and unstressed conditions. Severe and moderate drought stresses induced the expression of maize PARP2 gene, suggesting that deregulation of maize PARP2 gene is likely to improve the ability of tropical maize to resist severe drought stress condition.Item Drought Response in Selected Tropical Inbred Maize Lines and Relative Expression of PARP2 Gene under Limited Water Conditions(Science Publishing Group, 2018-04) Muli, Joshua K.; Budambula, Nancy; Mweu, Cecilia; Anami, Sylvester E.Drought is the leading single factor that limits maize production thus inhibiting the crops genetic potential. In response to drought, maize and other plants synthesize Poly ADP-Ribose (PAR) protein. This process is controlled by the Poly ADP-Ribose Polymerase (PARP) genes and consumes cellular energy, leading to plant death. This study evaluated four tropical inbred maize (Zea mays L.) lines; CML 216, CML 144, A04 and E04 for their response to growth limiting water stress and their relative expression of PARP2 gene under drought and non-drought conditions. The leaf lengths and growth rates of the fourth leaf were monitored for 21days post emergence while fresh and dry weights of drought stressed and non-stressed seedlings were recorded a month after emergence of the fourth leaf. The relative expression of PARP2 gene was determined using rtPCR after isolating RNA from drought stressed and non-stressed maize seedlings. There was no significant difference in the mature lengths of the fourth leaf in the four genotypes when the maize seedlings were not subjected to drought and when subjected to severe drought stress. However, subjecting maize seedlings to mild drought resulted in a significant difference in the mature leaf lengths based on the different genotypes (P= 0.0066). The growth rate of maize seedlings based on the fourth leaf was observed to be affected by drought, with a higher mean growth rate (1.74 cm day-1) registered in seedlings which were not subjected to drought and those subjected to moderate drought (1.78 cm day-1). A slower growth rate (1.37 cm day-1) was observed in seedlings subjected to severe drought stress. Fresh and dry weights of maize seedlings were also observed to be significantly different based on the level of drought exerted (P = < 0.0001) and the genotype (P = < 0.0001). The expression of PARP2 gene was found to be directly proportiItem Genetic diversity and population structure of wild and cultivated Crotalaria species based on genotyping-by-sequencing(Plos One, 2022-09) Muli, Joshua K.; Neondo, Johnstone O.; Kamau, Peter K.; Michuki, George N.; Budambula, Nancy L.Crotalaria is a plant genus that is found all over the world, with over 700 species of herbs and shrubs. The species are potential alternative food and industrial crops due to their adaptability to different environments. Currently, information on the genetic diversity and population structure of these species is scanty. Genotyping-by-sequencing (GBS) is a costeffective high-throughput technique in diversity evaluation of plant species that have not been fully sequenced. In the current study, de novo GBS was used to characterize 80 Crotalaria accessions from five geographical regions in Kenya. A total of 9820 single nucleotide polymorphism (SNP) markers were obtained after thinning and filtering, which were then used for the analysis of genetic diversity and population structure in Crotalaria. The proportion of SNPs with a minor allele frequency (maf) > = 0.05 was 45.08%, while the GuanineCytosine (GC) content was 0.45, from an average sequence depth of 455,909 reads per base. The transition vs transversion ratio was 1.81 and Heterozygosity (He) ranged between 0.01–0.07 in all the sites and 0.04 to 0.52 in the segregating sites. The mean Tajima’s D value for the population was -0.094, suggesting an excess of rare alleles. The fixation index (Fst) between the different populations based on the Wright Fst (1943) ranged from 0.0119 to 0.066 for the Eastern-Western and Nairobi-Western populations. Model based techniques of population structure analysis including structure, k-means and cross-entropy depicted eight clusters in the study accessions. Non-model based techniques especially DAPC depicted poor population stratification. Correspondence Analysis (CA), Principal coordinate analyses (PCoA) and phylogenetic analysis identified a moderate level of population stratification. Results from this study will help conservationists and breeders understand the genetic diversity of Crotalaria. The study also provides valuable information for genetic improvement of domesticated species.Item Genetic diversity and use of African indigenous vegetables especially slender leaf(Taylor and Francis, 2020-10) Muli, Joshua K.; Neondo, Johnstone O.; Kamau, Peter K.; Budambula, NancyAfrican indigenous (AIVs), and traditional, vegetables play a role in food security. This review examines distribution, use, diversity, and techniques used to study AIVs with special interest on Crotalaria species. Google scholar, PubMed, and the open web were searched for published articles between 1990 and 2020. The AIVs are distributed in almost all African countries but are mostly consumed in East and West Africa. The distribution and genetic diversity of some common AIVs has been documented. There is a need to create awareness on the use and conservation of AIVs because of their role in food security and livelihoods.Item Genetic Transformation of Sweet Potato for Improved Tolerance to Stress: A Review(2016-10) Imbo, Mary C.; Budambula, Nancy; Mweu, Cecilia M.; Muli, Joshua K.; Anami, Sylvester E.The sweet potato (Ipomoea batatas Lam) is a major staple food in many parts of the world. Sweet potato leaves and tubers are consumed as food and livestock feed. Biotic and abiotic stresses affect yield leading to a reduction in production. This review analyzes factors limiting sweet potato production and the progress made towards stress tolerance using genetic transformation. Genetic transformation could enhance yield, nutritional value and tolerance to stress. Transgenic sweet potatoes tolerant to biotic and abiotic stress, improved nutritional value and higher yields have been developed. Sweet potato expressing the endotoxin cry8Db, cry7A1 and cry3Ca genes showed lower sweet potato weevil infestation than non-transformed lines. Transgenic cultivar ‘Xushu18’ expressing the oryzacystatin-1 (OC1) gene showed enhanced resistance to sweet potato stem nematodes. Sweet potato line ‘Chikei 682-11’ expressing the coat protein (CP) exhibited resistance to the sweet potato feathery mottle virus (SPFMV). Transgenics expressing the rice cysteine inhibitor gene oryzacystatin-1 (OC1) also exhibited resistance to the SPFMV. Transgenic cultivar ‘Kokei’ expressing the spermidine synthetase gene FSPD1 had higher levels of spermine in the leaves and roots, and displayed enhanced tolerance to drought and salt stress. ‘Shangshu’ variety expressing the IbMas has shown enhanced tolerance to salt stress. Transgenic ‘Lixixiang’ expressing IbMIPSI showed an up-regulation of metabolites involved in stress response to drought, salinity and nematode infestation. Transgenic ‘Yulmi’ sweet potato transformed with copper/zinc superoxide dismutase (CuZnSOD) gene showed an enhanced tolerance to methyl viologen induced oxidative and chilling stress. Similarly, transformation of cultivar ‘Sushu-2’ with betaine aldehyde dehydrogenase (BADH) gene resulted in transgenics tolerant to salt, chilling and oxidative stress. Sweet potato varieties ‘Kokei14’ and ‘Yulmi’ transformed with the bar gene were shown to be tolerant to application of the herbicide Basta. The development of stress tolerant varieties will immensely increase the area under sweet potato production and eventually promote the adoption of sweet potato as a commercial crop. Sweet potato research and breeding for stress tolerance still faces technical and socio-political hurdles. Despite these challenges, genetic transformation remains a viable method with immense potential for the improvement of sweet potato.Item A hybridization technique for orphan legumes: development of an artificial interspecific pollination protocol for Crotalaria spp.(Taylor and Francis, 2020-08) Wasonga, Mercy A.; Arunga, Ester E.; Neondo, Johnstone O.; Muli, Joshua K.; Kamau, Peter K.; Budambula, Nancyrotalaria brevidens: and C. ochroleuca commonly grown as vegetables have been extensively studied. However, information on breeding techniques is scanty. This study aimed to develop an artificial interspecific pollination protocol for two genotypes of Crotalaria with contrasting leaf and pod morphological features. The two are landraces that were previously collected from two counties in Kenya. The experimental design was a completely randomized design (CRD) in a greenhouse with C. ochroleuca as the female parent and C. brevidens as the male parent. Six-day-old flower buds of the female parent were emasculated. Pollen from a freshly opened flower was rubbed over the stigma of the emasculated flower. The pollinated stigma was inserted back into the keel petal and covered by the wing and standard petal. Data on success rate, pod, and seed production were subjected to analysis of variance. The developed artificial pollination method showed 75% success rate in the interspecies cross of C. ochroleuca and C. brevidens. Time of crossing did not significantly influence the success rate, pod, and seed production. The study demonstrated artificial interspecific pollination of Crotalaria by keel petal incision rubbing method. This protocol lays the foundation for genetic studies and improvement of Crotalaria spp.Item Plant Hybridization as an Alternative Technique in Plant Breeding Improvement(2019-05) Mwangangi, Immaculate M.; Muli, Joshua K.; Neondo, Johnstone O.For ages, plant breeders have relied on the genetic variability that results from sexually crossing plants within the same species. However, the variability that exists within species populations is inadequate, hence the need to exploit desirable traits of interest in distantly related or even unrelated plants through hybridization techniques. Hybridization can be categorized into two; sexual and somatic. Sexual hybridization, also referred to as wide or distant hybridization involves combining two genomes from different parental taxa through pollination, either naturally or by induction. Somatic hybridization involves the fusion of somatic cells instead of gametes, which highly depends on the ability to obtain viable protoplasts and eventually differentiate them to whole plants in vitro. The impacts of hybrids can either be positive or negative. Among the positive attributes of hybrids that have been exploited is heterosis, which results either from dominance, over-dominance or epistasis. Negative ones include sterility, arrested growth of the pollen tube and embryo abortion. To overcome these problems, chromosome doubling, the use of hormones such as 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and embryo rescue have been employed to overcome sterility, arrested growth of pollen tubes and embryo abortion respectively. After the development of hybrids, different hybrid identification techniques have been used to test them such as the use of molecular and morphological markers, cytogenetic analysis and fluorescent in situ hybridization. The use of hybridization techniques in plant improvement remains a vital tool to cross species barriers and utilization of important attributes in unrelated crop plants which could not have been achieved through conventional techniques of plant breeding.Item Yeast Extract Peptone Based Co-cultivation Media Promotes Transient GUS Expression in Tropical Maize Genotypes(2017) Muli, Joshua K.; Mweu, Cecilia; Budambula, Nancy; Anami, Sylvester E.Background and Objective: Tropical maize is the most cultivated crop in sub-Saharan Africa and is a staple food to over 220 million people. This study, evaluated the competence of four tropical maize (Zea mays L.) inbred lines to callus induction and regeneration through somatic embryogenesis when co-cultivated on yeast extract peptone medium (YEP). Materials and Methods: Transient GUS assay was used to evaluate the competence of the genotypes to Agrobacterium-mediated transformation using YEP as co-cultivation media or when YEP was supplemented with 2,4-D (YEP+2,4-D), cysteine (YEP+CYS), proline (YEP+PRO) or in combination (YEP+ALL). Data on all parameters were analyzed using multivariate ANOVA and SAS. Results: Co-cultivation media based on YEP alone did not impact callus induction and immature embryos exhibited preconscious germination. When YEP was supplemented with 2,4-D at concentrations 1.5 and 3 mg LG1 2,4-D, the formation of embryogenic calli was induced and regeneration initiated. Immature embryos had high transient GUS expression when co-cultivated with Agrobacterium on YEP, YEP+PRO and YEP+ALL media than when co-cultivated on MS media, suggesting that YEP promotes Agrobacterium-mediated integration of transgenes in tropical maize. Agrobacterium tumefaciens at a concentration of 0.07 (OD660) gave the highest transient GUS expression (20.90%) while concentrations of 0.8 and 0.2 resulted in low transient GUS expression (9.17 and 12.22%, respectively). Conclusion: The integration of YEP media in the Agrobacterium-mediated transformation protocols is likely to contribute in the development of a more efficient Agrobacterium-mediated transformation system for tropical maize genotypes.