richard onyango | KCA University Kenya (original) (raw)

Papers by richard onyango

Maize is a cereal crop that is grown widely throughout the world in a range of agro-ecological en... more Maize is a cereal crop that is grown widely throughout the world in a range of agro-ecological environments. Maize is ranked third after wheat and rice in terms of production and is a staple food in many regions of the world. However, maize yields in the sub Saharan Africa, will decrease due to drought as majority of farmers in this region depend on rain-fed farming. As such, the future of maize production and livelihoods of a great population of smallholder farmers in this region of climate vulnerability, are based to a great extent on access to climate resilient cultivars. Researchers are working on the development of maize that can tolerate the effects of drought. Conventional breeding has been used in the development of drought tolerant crops but often brings along undesirable agronomic characteristics from the donor parents hence, genetic engineering by identifying and inserting genes only involved in stress tolerance in plants is being explored to complement efforts of this cl...

Asian Journal of Agriculture, 2017

Nawiri SO, Oduor RO, Jalemba AM. 2017. Genetic engineering of sweet potatoes (Ipomoea batatas) us... more Nawiri SO, Oduor RO, Jalemba AM. 2017. Genetic engineering of sweet potatoes (Ipomoea batatas) using isopentenyl transferase gene for enhanced drought tolerance. Asian J Agric 1: 85-99. Approximately 70% of yield crop reduction worldwide is caused by drought. Due to severe drought which happened many times as a result of climate change, substantial yield deprivation is usual among the major cereals such as maize, wheat, and barley.. Therefore, drought tolerant crops that still yield amidst erratic climatic phenomenon are greatly needed. Due to its capability to produce high yield in a short period, sweet potato is suitable for cultivation in regions with limited or erratic rain water supply where other food crops cannot grow easily. Nevertheless, its sensitivity to water deficit may lead to the adverse crop growth and yield. By conventional hybridization method, sweet potato is tried to be improved, but it gives unsatisfied results due to its high male sterility, sexual incompatibil...

Advances in Agriculture, 2022

Groundnut (Arachis hypogaea L.) is an important crop in terms of income and nutrition. Despite it... more Groundnut (Arachis hypogaea L.) is an important crop in terms of income and nutrition. Despite its importance, groundnut yield is limited by environmental factors such as drought. This work reports the genetic transformability of Kenyan groundnut (Arachis hypogaea L.) genotypes with isopentenyl transferase (IPT) gene towards drought tolerance. The cotyledonary nodes of six Kenyan adapted groundnuts genotypes (ICGV 12991, CG 7, Red Valencia, ICGV 90704, Chalimbana, and JL 24) were transformed using Agrobacterium tumefaciens strain EHA 101 carrying PNOV-IPT binary vector containing an IPT gene, which was driven by SARK promoter and terminated by TNOS terminator. The vector also contained the phosphomannose isomerase (PMI) gene for the selection of transformed tissues. Putative transformants were tested for the presence of the transgene by PCR designed to amplify the IPT gene sequence. Gene expression was confirmed by RT-PCR. Transformation frequency was calculated as a percentage of t...

International Journal of Molecular Sciences, 2020

Insect pests pose a serious threat to global food production. Pod borer (Helicoverpa armigera (Hü... more Insect pests pose a serious threat to global food production. Pod borer (Helicoverpa armigera (Hübner)) is one of the most destructive pests of leguminous crops. The use of host resistance has been an effective, environmentally friendly and sustainable approach for controlling several agricultural pests. The exploitation of natural variations in crop wild relatives could yield pest-resistant crop varieties. In this study, we used a high-throughput transcriptome profiling approach to investigate the defense mechanisms of susceptible cultivated and tolerant wild pigeonpea genotypes against H. armigera infestation. The wild genotype displayed elevated pest-induced gene expression, including the enhanced induction of phytohormone and calcium/calmodulin signaling, transcription factors, plant volatiles and secondary metabolite genes compared to the cultivated control. The biosynthetic and regulatory processes associated with flavonoids, terpenes and glucosinolate secondary metabolites sh...

International Journal of Microbiology and Biotechnology, 2021

In-vitro regeneration of banana (Musa spp) is a crucial technique in banana improvement via moder... more In-vitro regeneration of banana (Musa spp) is a crucial technique in banana improvement via modern biotechnology like virus indexing, genetic transformation, and genome editing. However, in-vitro banana plants are prone to microbial contamination from the environment, leading to the loss of important lines and germplasm. Protocols for disinfecting banana plants before their in-vitro culture have been reported; however, there is limited information on strategies for disinfecting in-vitro contaminated banana plants, which are more sensitive to most disinfectants. Thus, this study aimed to establish an efficient disinfection protocol that is effective against contaminants and safe on in-vitro plants. Contaminated in-vitro banana plants (cv. Grand naine) were subjected to commercial bleach (Jik ® ; 3.85% w/v NaClO) at different exposure times (2, 4, 6, and 8 min) with or without rinsing then reinitiated in-vitro. Jik ® exposure time of 2 min with or without rinsing preserved the plant viability by 100% but led to >75% fungal contamination. At 4 min of Jik ® exposure, the viability of the plants remained at 100%, but >33% fungal contamination was observed. No contamination was observed at 8 min of Jik ® exposure, but the plants' viability was reduced to below 85%. Notably, 6 min of Jik ® exposure preserved the viability of the plants by 100% while destroying all the contaminants and is, therefore, recommended as the most efficient treatment. This protocol can save time and other resources and should be applied in banana genetic transformation laboratories.

African Journal of Biotechnology, 2019

Cassava (Manihot esculenta Crantz) is a tropical root crop that serves as a food staple and a vit... more Cassava (Manihot esculenta Crantz) is a tropical root crop that serves as a food staple and a vital income source to resource deprived farmers in the tropics. Despite its importance, cassava production and consumption is faced by a myriad of biotic/abiotic constraints. Genetic transformation which can be applied to mitigate these challenges however has as a prerequisite the availability of robust regeneration systems. This study evaluated the effect of explant type and hormone regime on somatic embryogenesis and regeneration of Kenyan cassava cultivars. The embryogenic competence of immature leaf lobe and stem explants of three cassava cultivars was determined by culturing them in MS medium supplemented with picloram (4, 6, 8 and 10 mg/l). The optimum media composition for embryo maturation, germination and plant recovery was assessed by culturing embryos in media supplemented with varying concentrations of 6-Benzylaminopurine (BAP), α–Naphthalene acetic acid (NAA) and Gibberellic ...

Aquaculture production has been expanding in recent years through Governement support via financi... more Aquaculture production has been expanding in recent years through Governement support via financial and input subsidies in small scale farmers. However, fish farming just like other productive sectors face challenges which include fish diseases that constitute the largest cause of economic loss in aquaculture. The fish bacterial infections are caused by Aeromonas, Edwardsiella, Flavobacterium, Francisella, Photobacterium, Piscirickettsia, Pseudomonas, Tenacibaculum, Vibrio, Yersinia, Lactococcus, Renibacterium, Streptococcus, Nocardia, Staphylococcus, Vagococcus and Weisella species. This study focused on characterizing pathogenic bacteria present in aquaculture systems in Bungoma County. The sampled fish were transferred to a microbiology laboratory in Nairobi where they were subjected to bacterial analysis including microscopy, culture methods and biochemical tests. The study showed that temperature and pH were outside the recommended levels of fish culture production. Further, pa...

African Journal of Biotechnology, 2016

Transformation of a tropical maize inbred genotype (CML144) with the Xerophyta viscosa peroxired... more Transformation of a tropical maize inbred genotype (CML144) with the Xerophyta viscosa peroxiredoxin2 ( XvPrx2 ) gene was reported. The protective role of peroxiredoxin2 against the damage resulting from reactive oxygen species (ROS) under dehydration stress was further determined. Successful integration of XvPrx2 gene into maize we achieved and recovered 10 independent transgenic events. Transformation and regeneration frequencies were 12.9 and 31.3%, respectively. Reverse transcription polymerase chain reaction (PCR) revealed the expression of the XvPrx2 gene in transformed plants under dehydration. Stressed transgenic plants had higher relative water content (RWC) as compared to the conventional plants. Recovery irrigation showed higher RWC in transgenics than in conventional plants. Unlike in conventional plants, rapid morphogenic recovery was observed in transgenics within 24 h. Chlorophyll contents decreased faster in conventional plants than in transgenics with prolonged dr...

PLANTS, PEOPLE, PLANET, 2021

is currently infested with dodders-highly invasive vines that threaten agriculture and biodiversi... more is currently infested with dodders-highly invasive vines that threaten agriculture and biodiversity. We describe historical and ecological factors that have potentially shaped dodder invasion in this region. Our results reveal high levels of genetic diversity within dodder populations, which could enhance their ability to colonize new niches. Further, we identify two main population clusters in eastern and western Kenya, a pattern that is mirrored in an established invader (Cuscuta campestris) and a recent introduction (C. reflexa). Immediate control strategies are needed to limit deliberate or inadvertent seed/vine dispersal, eradicate existing populations, and monitor influx of propagules. Summary • Invasion by dodder (Cuscuta spp.), holo-parasitic plants of the Convolvulaceae family, has recently surged in Eastern Africa. Particularly, colonization by two species, Cuscuta campestris and Cuscuta reflexa that have a broad host range and rapid invasiveness, has escalated. We examined the first assessment of genetic diversity of these invasive species in Kenya to inform subsequent management practices. • A comparative phylogeographic analysis, based on chloroplast and nuclear ribosomal DNA, was performed to determine genetic diversities, population structure, and isolation of C. campestris and C. reflexa in Kenya. • Results reveal high genetic variation in both species within populations across localities. C. campestris had more haplotypes and higher gene diversity (P = .0001) and heterozygosity (P = .004) than C. reflexa. Both species were geographically separated, evidenced by two distinct lineages that mostly corresponded to localities east and west of Kenya. Correlation between genetic and geographic distances revealed evidence of isolation by distance (IBD). • We attribute these genetic variation patterns to establishment via similar invasion routes for the studied Cuscuta spp. and suggest that Cuscuta invasion in Kenya is in the early stages of establishment. Rapid eradication is urgently needed to prevent shifts to economically important hosts, which would have devastating

The International Journal of Science & Technoledge, 2020

Evaluation of Quality Characteristics of Biodiesel Produced From Jatropha Curcas in Kenya 1. Intr... more Evaluation of Quality Characteristics of Biodiesel Produced From Jatropha Curcas in Kenya 1. Introduction The increasing industrialization and modernization of the world has led to a steep rise for the demand of petroleum products. Economic development in developing countries has led to huge increase in energy demand. In Kenya, economic growth has put the country's energy and electricity supply in particular under increasing pressure. Between 2004 and 2013 power demand Kenya rose by 18.9 % annually with the existing capacity barely able to keep up with demand (Netherlands Enterprise Agency, 2018). At the national level, wood fuel and other biomass accounted for about 68 % of the total primary energy consumption, followed by petroleum at 22 % and electricity at 9 %. The country's total value of imports grew by 38.9 percent from Kshs 947.4 billion in 2010 to Kshs 1.3 trillion (1USD = ~100 Kshs) in 2011 accounting for over 40 % of its foreign exchange earnings (Institute of Economic Affairs, 2013). Globally, petroleum-based fuels are limited, with the finite reserves concentrated in certain regions of the world. Countries lacking in fossil fuel reserves are facing foreign exchange crises, mainly due to the import of crude oil. This scenario has increased the focus towards alternative fuels, including generation of bio-based oil and its products using renewable feedstock. Biodiesel, an eco-friendly and renewable fuel substitute for diesel has been getting worldwide attention from media, policy makers, researchers and scientists (Mofijur, et al., 2016). Biodiesel is a non-toxic, biodegradable and carbon neutral renewable fuel that can be produced from a range of organic feedstock including fresh or waste vegetable oils, animal fats, and oilseed plants. Biodiesel has significantly lower emissions than petroleum-based diesel when it is burned, whether used in its pure form or blended with petroleum diesel.

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Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten Africa’s ecosystems, due to ... more Invasive holoparasitic plants of the genus Cuscuta (dodder) threaten Africa’s ecosystems, due to their rapid spread and attack on various host plant species. Most Cuscuta species cannot photosynthesize, hence rely on host plants for nourishment. After attachment through a peg-like organ called a haustorium, the parasites deprive hosts of water and nutrients leading to their death. Despite their rapid spread in Africa, dodders have attracted limited research attention, although data on their taxonomy, host range and epidemiology are critical for their management. Here, we combine taxonomy and phylogenetics to reveal presence of field dodder (Cuscuta campestris) and C. kilimanjari (both either naturalized or endemic to East Africa), and for the first time in continental Africa, presence of the giant dodder (C. reflexa) a south Asian species. These parasites have a wide host range, parasitizing species across 13 angiosperm orders. Evaluating the possibility of C. reflexa to expand this...

International Journal of Agronomy, 2020

Passion fruit (Passiflora edulis(Sims)) is currently ranked third among fruit exports from Kenya ... more Passion fruit (Passiflora edulis(Sims)) is currently ranked third among fruit exports from Kenya and has great potential since the demand for both fresh fruit and processed juice is on a continuous increase. Passion fruit production in Kenya is constrained by a lack of healthy, clean planting material, poor seed viability, and low germination rates. To address this, the present study reports anin vitroplant regeneration protocol for passion fruit using leaf disc and nodal explants and genetic fidelity analysis of the regenerated plants. The highest number of shoot regeneration was obtained on Murashige and Skoog (MS) medium supplemented with 2 mg·L−16-Benzyl amino purine (BAP) (shoot induction medium). The multiplication of shoots was optimum in MS medium supplemented with 3 mg·L−1BAP. To eliminate the requirement of an additional step ofin vitrorooting, exogenous application of putrescine induced the formation and development of roots on nodal explants. Genetic fidelity analysis of...

Drought is the most perilous abiotic stress that affects finger millet growth and productivity wo... more Drought is the most perilous abiotic stress that affects finger millet growth and productivity worldwide. For the successful production of finger millet, selection of drought tolerant varieties is necessary and critical stages under drought stress, germination and early seedling growth, ought to be fully understood. This study investigated the physiological and biochemical responses of six finger millet varieties (GBK043137, GBK043128, GBK043124, GBK043122, GBK043094 and GBK043050) under mannitol-induced drought stress. Seeds were germinated on sterile soil and irrigated with various concentrations of mannitol (200, 400 and 600 mM) for two weeks. Comparative analysis in terms of relative water content (RWC), chlorophyll, proline, and malondialdehyde (MDA) contents were measured the physiological and biochemical characteristics of drought stress. The results showed that increased level of drought stress seriously decreased germination and early seedling growth of finger millet variet...

Journal of Plant Biochemistry & Physiology, 2019

A reproducible regeneration protocol for ICGV 12991, CG 7 and Red Valencia groundnut genotypes us... more A reproducible regeneration protocol for ICGV 12991, CG 7 and Red Valencia groundnut genotypes using Cotyledonary Node explants has been optimized. The effect of different BAP concentrations combined with either 2,4-D or TDZ was tested to determine optimum conditions for high shoot induction. Different BAP concentrations were tested to determine an optimum concentration for shoot elongation. Different NAA concentrations were similarly evaluated to determine the best concentration for rooting. Media containing combination of 5 mg/L BAP and 1 mg/L TDZ was the best concentration for shoot induction while media containing BAP at 5 mg/L was the best for elongation of shoots. NAA concentration of 1 mg/L gave the highest number of plants with roots. This works provides a very good protocol which will be beneficial during groundnut tissue culture as well as genetic transformation of groundnuts.

Journal of Tissue Science & Engineering, 2016

Sweetpotato is an important food crop in the world as well as in Kenya. Various fungal and viral ... more Sweetpotato is an important food crop in the world as well as in Kenya. Various fungal and viral diseases are major constraints in its production and are currently threatening the sweetpotato production in sub-Saharan Africa. Genetic engineering offers significant potential for the crop's genetic improvement. However, this is limited by the low efficiency and strong genotype dependency in tissue culture. This study aimed to establish an efficient somatic embryogenesis and plant regeneration system using shoot apical meristem explants of sweetpotato. Three sweetpotato cultivars that are widely grown in Kenya; KSP36, Kemb36 and Mweu mutheke along with an exotic model cultivar Jewel were evaluated. The maximum somatic embryogenic induction, at 96.72%, was obtained from explants cultured on Linsmaier and Skoog salts and vitamins medium supplemented with 0.5 mg/l dichlorophenoxyacetic acid and 0.2 mg/l zeatin riboside. The highest number of shoot induction (33) was observed after transfer of embryonic callus to embryo maturation medium supplemented with 2 mg/l abscisic acid. Significant differences were observed between cultivars for somatic embryogenesis and plant regeneration. Jewel showed the best response, while Mweu mutheke was the least responsive under the culture conditions tested in this study. Regenerated plants were successfully rooted and grown to maturity after hardening in soil in the greenhouse. Such a robust, successful and efficient system possesses the potential to become an important tool for crop improvement and functional studies of genes in sweetpotato.

Frontiers in Plant Science, 2015

Banana (Musa spp.) is an important staple food as well as cash crop in tropical and subtropical c... more Banana (Musa spp.) is an important staple food as well as cash crop in tropical and subtropical countries. Various bacterial, fungal, and viral diseases and pests such as nematodes are major constraints in its production and are currently destabilizing the banana production in sub-Saharan Africa. Genetic engineering is a complementary option used for incorporating useful traits in banana to bypass the long generation time, polyploidy, and sterility of most of the cultivated varieties. A robust transformation protocol for farmer preferred varieties is crucial for banana genomics and improvement. A robust and reproducible system for genetic transformation of banana using embryogenic cell suspensions (ECS) has been developed in this study. Two different types of explants (immature male flowers and multiple buds) were tested for their ability to develop ECS in several varieties of banana locally grown in Africa. ECS of banana varieties "Cavendish Williams" and "Gros Michel" were developed using multiple buds, whereas ECS of "Sukali Ndiizi" was developed using immature male flowers. Regeneration efficiency of ECS was about 20,000-50,000 plantlets per ml of settled cell volume (SCV) depending on variety. ECS of three different varieties were transformed through Agrobacterium-mediated transformation using gusA reporter gene and 20-70 independent transgenic events per ml SCV of ECS were regenerated on selective medium. The presence and integration of gusA gene in transgenic plants was confirmed by PCR, dot blot, and Southern blot analysis and expression by histochemical GUS assays. The robust transformation platform was successfully used to generate hundreds of transgenic lines with disease resistance. Such a platform will facilitate the transfer of technologies to national agricultural research systems (NARS) in Africa.

Journal of biological research (Thessalonikē, Greece), 2016

Bananas and plantains (Musa spp.) provide 25 % of the food energy requirements for more than 100 ... more Bananas and plantains (Musa spp.) provide 25 % of the food energy requirements for more than 100 million people in Africa. Plant parasitic nematodes cause severe losses to the crop due to lack of control options. The sterile nature of Musa spp. hampers conventional breeding but makes the crop suitable for genetic engineering. A constitutively expressed synthetic peptide in transgenic plantain has provided resistance against nematodes. Previous work with the peptide in potato plants indicates that targeting expression to the root tip improves the efficacy of the defence mechanism. However, a promoter that will provide root tip specific expression of transgenes in a monocot plant, such as plantain, is not currently available. Here, we report the cloning and evaluation of the maize root cap-specific protein-1 (ZmRCP-1) promoter for root tip targeted expression of transgenes that provide a defence against plant parasitic nematodes in transgenic plantain. Our findings indicate that the m...

International Journal of Life Sciences, 2015

In response to increased public concern on antibiotic or herbicide resistance genes usage in gene... more In response to increased public concern on antibiotic or herbicide resistance genes usage in genetically modified plants, mannose was evaluated as selectable agent for the genetic transformation of sweetpotato. Nontransformed sweetpotato stem explants of cv. KSP36 were cultured on media containing various combinations and concentrations sucrose and mannose ranging from 0 to 30 g/l. Likewise, efficacy of hygromycin and kanamycin as selection agents for transformation of sweetpotato was evaluated on media containing varying concentrations of antibiotics ranging 0 to 100 mg/l. Selection agent effectiveness was determined by detecting the minimal concentration of the selection agent required to fully inhibit sweetpotato calli growth. Hygromycin was the most effective selection agent as it inhibited cell growth at concentrations above 20 mg/l. Kanamycin was moderately effective as it inhibited cell growth at 60 mg/l. Sweetpotato calli were able to grow and even produce embryos even when ...

Challenges and Opportunities for Agricultural Intensification of the Humid Highland Systems of Sub-Saharan Africa, 2014

ABSTRACT al. (eds.), Challenges and Opportunities for Agricultural Intensification of the Humid H... more ABSTRACT al. (eds.), Challenges and Opportunities for Agricultural Intensification of the Humid Highland Systems of Sub-Saharan Africa, DOI 10.1007/978-3-319-07662-1_8, © Springer International Publishing Switzerland 2014 97 Abstract The Association for Strengthening Agricultural Research in Eastern and Central Africa (ASARECA) through its Agrobiodiversity and Biotechnology Programme is enhancing the utilization of biotechnology research and development innovations in Eastern and Central Africa (ECA). We present successes in the application of biotechnology to enhance the productivity of cassava, sweet potato, banana, maize and sorghum in ECA. These products—drought tolerant maize, sorghum resistant to striga, as well as the technology for producing and distributing disease free planting materials of cassava, sweet potato and banana to farmers—are central for the agro-ecological intensification of farming systems in the central African highlands.