Articles: Department of Water and Agricultural Resources Management

Permanent URI for this collectionhttp://repository.embuni.ac.ke/handle/123456789/70

Browse

Now showing 1 - 20 of 209

Surface runoff and soil erosion from Nitisols and Ferralsols as influenced by different soil organic carbon levels under simulated rainfall conditions
(University of Embu, 2023-06-30) Rugendo Mercy K.; Gichimu Bernard M.; Mugwe Jayne N.; Muna Monicah Mucheru; Mugendi Daniel N.
Soil erosion poses a challenge to the environment and the sustainable use of natural resources, particularly in relation to agricultural production. The study aimed to assess the influence of different soil organic carbon (SOC) levels on runoff and soil erosion under varying levels of rainfall intensity. The study was conducted in pre-selected farmers' fields representing low, moderate and adequate SOC levels in Nitisols and Ferralsols. Two parallel experiments were set up in each type of soil using a split-plot layout arranged in Randomized Complete Block Design. The main plots were the different soil organic carbon levels while the sub-plots were the different simulated rainfall intensities. Rainfall simulation was then conducted to determine runoff and sediment losses on each soil type. The simulation was done using a land type sprinkler nozzle rainfall simulator (460 788 type) in an experimental plot of 1 m2, fenced with corrugated iron sheets with a small opening left for runoff collection. Runoff and sediment losses were determined from the volume collected in the jar. The data was subjected to analysis of variance and significant mean differences were determined using Tukey’s Honest Test at a 95% confidence level. Pearson correlation was applied to assess the relationship between runoff volume and sediment loss. The results showed that Ferralsols recorded significantly higher runoff and sediment losses compared to Nitisols, by 60.27% and 53.14% respectively. However, adequate SOC level portrayed a significant effect in reducing erosion in both soil types, where it reduced runoff and sediment loss by 45.30% and 48.38% in Ferralsols and by 65.31% and 48.22% in Nitisols, respectively. In both soil types, runoff yield was positively correlated to rainfall intensity while sediment yield was inversely correlated with SOC levels. Therefore, the study recommends incorporation of organic matter to adequate levels in both soils, for reduced soil erosion.
QTL mapping for pod quality and yield traits in snap bean (Phaseolus vulgaris L.).
(University of Embu, 2024-12) Njau, Serah Nyawira; Parker, Travis A.; Duitama, Jorge; Gepts, Paul; Arunga, Edith Esther
Pod quality and yield traits in snap bean (Phaseolus vulgaris L.) influence consumer preferences, crop adoption by farmers, and the ability of the product to be commercially competitive locally and globally. The objective of the study was to identify the quantitative trait loci (QTL) for pod quality and yield traits in a snap × dry bean recombinant inbred line (RIL) population. A total of 184 F6 RILs derived from a cross between Vanilla (snap bean) and MCM5001 (dry bean) were grown in three field sites in Kenya and one greenhouse environment in Davis, CA, USA. They were genotyped at 5,951 single nucleotide polymorphisms (SNPs), and composite interval mapping was conducted to identify QTL for 16 pod quality and yield traits, including pod wall fiber, pod string, pod size, and harvest metrics. A combined total of 44 QTL were identified in field and greenhouse trials. The QTL for pod quality were identified on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv07, and for pod yield were identified on Pv08. Co-localization of QTL was observedfor podquality andyield traits. Some identified QTL overlapped with previously mapped QTL for pod quality and yield traits, with several others identified as novel. The identified QTL can be used in future marker-assisted selection in snap bean.
A DIALLEL CROSS-BASED ANALYSIS OF THE GENETIC BASIS OF POD QUALITY AND POD YIELD IN SNAP BEAN
(University of Embu, 2024-07) Njau SN.; Arunga EE.; R. Otsyula
Snap bean (Phaseolus vulgaris L.) is among the leading vegetables in Kenya that is mainly grown for export with the potential to increase household income. There are few programs in Kenya that focus on breeding new cultivars for increased production. The development of snap bean varieties that are resilient to the changing climate is crucial for sustainable agriculture in Kenya. To achieve this, knowledge of gene action, trait expression, and heritability is vital in effective breeding for quantitative traits like pod quality and yield. A study was conducted to investigate the inheritance of pod quality and yield traits in snap beans, which can inform the breeding of snap beans. A half diallel cross involving two indeterminate dry beans (G2333 and MCM 5001) and five determinate snap beans (Amy, Moonstone, Seagull, Serengeti and Vanilla) varieties was conducted. Data on pod traits (pod weight per plant, pod number per plant, pod length, pod diameter, pod wall fiber and pod suture string) were collected from 21 F1s and 7 parents grown in two locations (Embu and Kirinyaga Counties) in Kenya. The results showed significant genotypic and environmental effects (P < 0.001) for all traits, with significant genotype by environment (G × E) interactions for most traits. Additionally, general combining abilities (GCA) and specific combining abilities (SCA) were significant for all traits evaluated. The significance of GCA and SCA indicated the importance of both additive and non-additive gene effects in controlling the traits, although the additive gene effects were predominant. The study revealed that Vanilla and Serengeti had the highest GCA estimate for pod quality traits, while G2333 and MCM5001 had the highest GCA estimate for pod yield traits. Snap bean pod yield and quality are quantitative traits controlled by multiple genes and influenced by the environment. Therefore, the predominance of additive gene effects suggests that selection for these traits in segregating generations could yield satisfactory gains. The results of this study could impact the development of snap bean varieties that are more resilient to the effects of climate change. Thus, improving the sustainability and productivity of the agriculture sector in Kenya.
INTROGRESSING sd-1 GENE INTO BASMATI 370 RICE
(University of Embu, 2025-01-29) Gatere FW; Njiruh PN; Kanya JI; Arunga EE
Rice (Oryza sativa) is depended upon by over half of the world's population as a primary staple food. Basmati 370 rice (BS 370) is popularly grown in many parts of the world for its good aroma and long, slender grains with excellent cooking and eating quality. However, its tallness nature and weak stem structure render it susceptible to lodging, particularly when subjected to high doses of nitrogenous fertilizer which leads to grain loss. Lodging reduces the efficiency of mechanized harvesting which is commonly used for large scale rice production, and further aggravates pre-harvest losses. A transformation of BS 370 to a short stature plant was needed to address this challenge. This research initiated a breeding program to develop a semi-dwarf rice line of Basmati 370 origin while being keen to retain the aromatic qualities. To realize this, Basmati 370 being the female parent, was crossed with a semi-dwarf variety IR64, the male parent using the emasculation and dusting method. This was followed by using unique anthocyanin pigmentation for hybrid identification to distinguish successful crosses from non-successful cross breeds. Molecular marker-assisted selection was performed to confirm whether the distinctive aroma associated with Basmati rice was present. The F1s were advanced to F2s. The F2 segregation was analyzed for performance against the parental lines. The findings demonstrate the successful development of a semi-dwarf BS 370 rice line with reduced height, shortened culm length, fairly shorter leaf lengths and, anthocyanin pigmentation on the leaves, stems and tips of seeds which are a good indicator of a semi-dwarf line that will ultimately address the lodging issue once stabilized in advanced filial generations. This breakthrough offers promising prospects for reduced grain loss, and improved efficiency in mechanized harvesting. This will ultimately benefit Kenyan Basmati rice farmers and the rice industry as a whole.
A Modified Climate-Smart Push-Pull Technology for the Management of Fall Armyworm (Spodoptera frugiperda) in the Semiarid Lands of Kenya
(University of Embu, 2024-08-17) Mumo, Catherine Kuthea; Muturi, Phyllis W.; Gichimu, Bernard M.
Successful use of push-pull technology in the control of fall armyworm (Spodoptera frugiperda Smith) in maize has been limited to areas that receive optimal rainfall as opposed to the semiarid areas. This study sought to determine the viability of a modified push-pull technology designed for drier areas. The technology involved the use of the drought-tolerant Brachiaria grass as a potential replacer of Napier grass as a pull crop, alongside drought-tolerant green-leaf Desmodium (Desmodium intortum) and edible legumes as push crops. The study was conducted in Mbeere South Subcounty in Embu County, Kenya. The experiments were laid out in split plots arranged in a randomized complete block design with three replications. The main plots contained Napier and Brachiaria grasses as comparative pull crops while the subplots tested the performance of the drought-tolerant green-leaf Desmodium and edible legumes (cowpea, pigeon pea, and green gram) as push crops. A maize monocrop was used as the negative control. The pest dynamics were determined using the area under damage/pest curve (AUDPC). The highest pest incidence was observed in the maize monocrop treatments with AUDPC range of 64–65.5 as compared to the intercrop treatments with AUDPC range of 45–56. The AUDPC for damage severity ranged from 24 to 24.5 in the maize monocrop treatments and 15.5 to 18.7 in the intercrop treatments. These findings implied that the drought-tolerant green-leaf Desmodium and the edible legumes can be adopted as effective push crops in the modified push-pull technology. Brachiaria and Napier grasses portrayed similar suitability as pull crops implying that the two can be used interchangeably as pull crops based on farmers’ preference. This study confirmed the viability of the modified climate-smart push-pull technology in the management of fall armyworm in dryland areas.
Introgressing photoperiod/thermo-sensitive genic male sterile gene into Basmati 370 rice
(University of Embu, 2024-11-29) Nyankemba, Beatrice Nyarangi; Arunga, Edith Esther; Nthakanio, Paul Njiruh
The emasculation of male gametes in pollen-recipient parents among self-pollinated crops (rice) is key to producing quality hybrid rice seeds. One of the emasculation tools in rice breeding is the photoperiod-thermo sensitive genic male sterility (P/TGMS) method, which ultimately requires long daylight length and high-temperature growth conditions to induce male gametes sterility. Using the P/TGMS method to produce hybrid Basmati rice seeds has been slow because no commercial line has been developed. Crossing the Basmati rice line with a non-aromatic rice line produces F1 with non-basmati quality traits. This study aimed to introgress the p/tgms12-1 gene into Basmati 370 by treating P/TGMS lines (IR-7327-2376-157S and IR-75589-31-27833S) with daytime temperatures (>33ºC) under a polythene greenhouse to emasculate pollen and cross-pollinating them with Basmati 370. Marker-assisted backcrossing was used to develop the BC1F2 Basmati breeding lines evaluated for pollen sterility and agro-morphological traits. Pollen sterility was tested by staining with 1% iodine potassium-iodide solution (I2KI), in which fertile and sterile pollen grains were stained with blue-black and yellow-pink dyes, respectively. The acquisition of near-complete pollen sterility among female parents is a manifestation of the greenhouse temperatures effectively emasculating pollen in P/TGMS parents and BC1F2. Analysis of variance on agro-morphological data showed significantly better agro-morphological traits in BC1F2 than the parents and significantly higher pollen sterility in P/TGMS lines than Basmati 370 (P≤0.05). The presence of the fgr gene in BC1F2 lines was confirmed using SSR markers, and the hybrids had both homozygous aromatic and heterozygous non-aromatic traits, the successful development of BC1F2 with p/tgms12-1 and fgr genes. The results obtained from this study are a major milestone towards improving Basmati rice yields in Kenya using hybrid seeds.
Limited effect of organic matter addition on stabilised organic carbon in four tropical arable soils
(UoEm, 2025-05-30) Mugendi, Daniel
Arable soils are generally characterised by a low soil organic carbon (SOC) content, with negative consequences for soil health, crop yield and global climate. Thus, over the past decades, there has been a focus on how agricultural management practices, such as organic resource addition, can increase the amount of SOC. To sustainably increase SOC stocks, a portion of 5 the organic amendments added to the soil has to be stabilised in persistent fractions such as mineral-associated organic carbon (MAOC). However, there is a lack of research on the magnitude of changes in MAOC in tropical agroecosystems in response to organic resource additions. Here, we show for four long-term field trials in Kenya that the addition of large amounts of organic amendments (farmyard manure or Tithonia diversifolia biomass at 4 t C ha-1 yr-1 for 16 to 19 years) to maize monocropping systems had variable effects on topsoil MAOC stocks (0–15 cm depth), and no significant effect on subsoil MAOC stocks 10 (15–50 cm depth) compared to a control treatment. The addition of mineral N fertiliser did not affect MAOC stocks at any site. Using stable carbon isotopes (δ 13C), we found that the portion of topsoil MAOC originating from Tithonia biomass was larger in the sandy (25 - 40 %) compared to the clayey soils (0.5 - 12 %), while the portion of total added Tithonia biomass that was stabilised over a time period of 16 - 19 years was below 7 % across all sites, or a SOC stabilisation rate of 0.8–27 g C m-2 yr-1 . Using these results, we conclude that while in sandy soils the stabilisation of added OC contributed substantially to limiting 15 SOC losses upon cultivation, this was not the case for clayey soils. These differences were due to the much lower SOC stocks in the sandy soils, compared to the clayey soils. Our results underline the challenges associated with improving soil health in sub-Saharan Africa and stress the need for more research to reliably assess if and how additional SOC can be stabilised over decadal time scales in highly weathered tropical soils.
Depth effects of long-term organic residue application on soil organic carbon stocks in central Kenya
(UoEm, 2025-06-17) Müller, Claude Raoul; Six, Johan; Njiru, Daniel Mugendi; Vanlauwe, Bernard; Broek, Marijn Van de;
In arable soils, a substantial portion of soil organic carbon (SOC) is stored below the plough layer. To develop sustainable soil management strategies, it is important to assess how they affect the quantity of SOC stored in the subsoil. Therefore, we investigated the impact of organic and inorganic nutrient inputs on SOC stocks down to 70 cm depth in a long-term field trial in Embu, Kenya. There were three organic input treatments (manure, Tithonia diversifolia residues, and maize stover) and a control treatment, each with and without the application of mineral nitrogen. These different treatments were applied to a maize monoculture over 38 growing seasons (19 years). Our results show that manure application had the largest positive impact on SOC stocks compared to the control; this effect was observed down to 60 cm depth. In contrast, Tithonia diversifolia and maize stover application led to significantly larger SOC stocks compared to the control, although this was only within the top 20 cm and 40 cm, respectively. Among the three organic residue treatments, only the application of manure had a significant effect on the SOC stock of the subsoil (i.e. the 30–70 cm depth layer). However, when considering the whole measured profile (i.e. 0–70 cm), all treatments led to significantly higher SOC stocks compared to the 91 ± 12 t C ha−1 of the control: manure had the highest stocks (120 ± 24 t C ha−1), followed by maize stover (112 ± 17 t C ha−1) and Tithonia diversifolia (105 ± 11 t C ha−1). Mineral nitrogen application did not have a significant impact on SOC stocks down to 70 cm depth. Our findings demonstrate that SOC in the subsoil comprised 48.5 % ± 1.7 % of the total SOC stocks across the 0–70 cm soil profile; however, only manure application affected subsoil OC levels, whereas other organic amendments solely increased SOC in the surface layer. Our results imply that gathering knowledge on the soil below the typically studied 0–30 cm depth layer will improve the overall assessment of agroecosystem properties, which is necessary to optimize soil system resilience, limit organic matter losses, and improve crop productivity.
Physicochemical and Heavy Metal Characterization of River Kapingazi in Embu County, Kenya
(UoEm, 2025-07-04) Yego, Naomy Chepkirui; Nyambane, Charles Onyari; Yegon, Rebbecca; Kiprotich, Shadrack
Surface water provides crucial support to the aquatic ecosystem and humans in numerous ways. However, its quality is paramount in determining its impact on the health of the aquatic ecosystem and humans. Currently, the malady of pollution arising from anthropogenic activities poses a significant threat to the quality of most rivers. The quality of water in the Kapingazi river in Embu County has received limited attention which is a concern that needs to be addressed. This study therefore, sought to investigate the status of water quality in river Kapingazi. The study analyzed 96 samples from four locations in a span of eight months which combined the dry and wet seasons of the year. Parameters measured in-situ included turbidity, pH, total dissolved solids (TDS), temperature, dissolved oxygen (DO) and electrical conductivity (EC) while ex-situ parameters were phosphates, nitrates and concentrations of heavy metals: iron and manganese. Results showed that Water Quality Index (WQI) during the drought period was74.05, suggesting that the water quality is only recommended for agricultural and industrial applications. During wet season, the water quality index was 89.67, reflecting a poor status, as more contaminants were likely introduced through surface runoff. Overall, the WQI averaged to 88.02. This study concludes that water in River Kapingazi is not suitable for human consumption; therefore, appropriate treatment is essential prior to its use. Similarly, the findings indicate that both rainy and drought periods significantly affect water quality, presenting challenges for its use for various purposes. It is recommended that the allocation of resources towards water treatment facilities and regulation of pollution sources should be enforced to ensure the safety of river water for diverse applications
Diversity analysis and genome‑wide association studies of seed weight trait in Bambara groundnut (Vigna subterranea (L.) Verdc.) using diversity array technology sequence derived single nucleotide polymorphism markers
(UoEm, 2025-02-22) Muturi, Phyllis; Kyallo, Martina; Gasura, Edmore; Yao, Nasser
Bambara groundnut is an indigenous drought tolerant legume cultivated in Africa. In Kenya, the crop is grown by women and the diver- sity of the accessions grown is unknown. Lack of information on the crop’s diversity and population structure make genetic improvement of the crop dif- fcult. The objectives of this study were to: (i) deter- mine the genetic diversity and population structure of 86 Bambara groundnut accessions from Kenya using 4,399 SNP markers and, (ii) identify SNPs associated with the seed weight of the Bambara groundnut col- lection. The DArT complexity reduction approach in combination with Illumina short-read sequencing (HiSeq 2000) was applied. Population structure anal- ysis suggested three genetic clusters. Accessions from the same county grouped into diferent clusters with exception of accessions from Kilif that distinctly fell into the same cluster. Analysis of molecular vari- ance indicated that 0.16% of the variance was due to genetic diferentiation among the populations, 19% of the variance was as a result of diferentiation among individuals within populations, and 81% variation was within individuals in a population. The study suggested signifcant DArTseq derived SNP mark- ers (p<0.05) distributed across Bambara groundnut contigs 1, 2, 3, and 5 associated with hundred seed weight, though the identifed SNPs were not vali- dated. This study provided an important foundation by ofering valuable insights into the genetic diversity of Bambara groundnut in traditional cultivation areas in Kenya. These fndings can serve as a starting point for further validation and application in Bambara groundnut breeding programs.
Introgressing Photoperiod/Thermo-sensitive Genic Male Sterile Gene into Basmati 370 Rice
(UoEm, 2025-01-08) Nyankemba, Beatrice Nyarangi; Arunga, Edith Esther; Nthakanio, Paul Njiruh
The emasculation of male gametes in pollen-recipient parents among self-pollinated crops (rice) is key to producing quality hybrid rice seeds. One of the emasculation tools in rice breeding is the photoperiodthermo sensitive genic male sterility (P/TGMS) method, which ultimately requires long daylight length and high-temperature growth conditions to induce male gametes sterility. Using the P/TGMS method to produce hybrid Basmati rice seeds has been slow because no commercial line has been developed. Crossing the Basmati rice line with a non-aromatic rice line produces F1 with non-basmati quality traits. This study aimed to introgress the p/tgms12-1 gene into Basmati 370 by treating P/TGMS lines (IR7327-2376-157S and IR-75589-31-27833S) with daytime temperatures (>33ºC) under a polythene greenhouse to emasculate pollen and cross-pollinating them with Basmati 370. Marker-assisted backcrossing was used to develop the BC1F2 Basmati breeding lines evaluated for pollen sterility and agro-morphological traits. Pollen sterility was tested by staining with 1% iodine potassium-iodide solution (I2KI), in which fertile and sterile pollen grains were stained with blue-black and yellow-pink dyes, respectively. The acquisition of near-complete pollen sterility among female parents is a manifestation of the greenhouse temperatures effectively emasculating pollen in P/TGMS parents and BC1F2. Analysis of variance on agro-morphological data showed significantly better agro-morphological traits in BC1F2 than the parents and significantly higher pollen sterility in P/TGMS lines than Basmati 370 (P≤0.05). The presence of the fgr gene in BC1F2 lines was confirmed using SSR markers, and the hybrids had both homozygous aromatic and heterozygous non-aromatic traits, the successful development of BC1F2 with p/tgms12-1 and fgr genes. The results obtained from this study are a major milestone towards improving Basmati rice yields in Kenya using hybrid seeds
Exploring Socio-Economic Characteristics on Adoption Intensity of Biochar Among Farming Households in Sub-Humid Regions of Western Kenya
(UoEm, 2025-01-08) Kyalo, Annastacia Maitha; Mogaka, Hezron; Kirimi, Florence Kaumi; Kizito, Kwena; Ndirangu, Samuel Njiri; Onyari, Charles Nyambane; Muriithi, Lydia; Elvin, Otara Nyaboe; Mutungi, Scholastica Katava; Kiprotich, Shadrack; Njiru, Moses Muchangi; Kamau, Ezekiel Areri;
Agriculture is a cornerstone of Kenya's economy, yet declining soil fertility and low adoption of sustainable agricultural technologies, such as biochar, have hindered productivity among smallholder farmers. Biochar is perceived to be a costeffective technology especially among resource constraint farming households. Despite many smallholder farmers acknowledging the importance of biochar as a soil amendment, most farmers face socio-economic barriers that hinder its adoption at scale. This study focused on how socio-economic factors influence adoption intensity of biochar, with a focus on the farming households in the sub-humid regions of Western Kenya. Employing a multistage stratified sampling procedure and Heckman selection model, the study reveals that awareness of biochar, access to credits, total land used in farming and education level positively and significantly influences adoption of biochar while total land owned in acres negatively and significantly influences adoption of biochar. Similarly, awareness of biochar, access to credits, and education level positively and significantly influences adoption intensity of biochar while terms of land ownership negatively and significantly influence adoption intensity of biochar. The study identifies awareness of biochar, education, credit access, and land ownership as key factors influencing its adoption by smallholder farmers. Promoting biochar as a soil amendment and carbon sequestration technique for farmers should be the main goal of the government, non-governmental organizations, and development organizations. Promoting the advantages of biochar for crop yields and soil fertility should be spearheaded by the Ministry of Agriculture's Extension Department. While development organizations offer financial assistance and training to promote adoption, policymakers should push farmer cooperatives to reduce the cost of biochar production and implementation
Modeling integrated soil fertility management for maize production in Kenya using a Bayesian calibration of the DayCent model.
(UoEm, 2024-07-04) Laub, Moritz; Wanjiku Mucheru-Muna, Monicah; Necpalova, Magdalena; Broek, Marijn Van de; Corbeels, Marc; Mathu Ndungu, Samuel; Mugendi, Daniel; Yegon, Rebecca; Waswa, Wycliffe; Vanlauwe, Bernard; Six, Johan
Sustainable intensification schemes such as integrated soil fertility management (ISFM) are a proposed strategy to close yield gaps, increase soil fertility, and achieve food security in sub-Saharan Africa. Biogeochemical models such as DayCent can assess their potential at larger scales, but these models need to be calibrated to new environments and rigorously tested for accuracy. Here, we present a Bayesian calibration of DayCent, using data from four long-term field experiments in Kenya in a leave-one-site-out cross-validation approach. The experimental treatments consisted of the addition of low- to high-quality organic resources, with and without mineral nitrogen fertilizer. We assessed the potential of DayCent to accurately simulate the key elements of sustainable intensification, including (1) yield, (2) the changes in soil organic carbon (SOC), and (3) the greenhouse gas (GHG) balance of CO2 and N2O combined. Compared to the initial parameters, the cross-validation showed improved DayCent simulations of maize grain yield (with the Nash–Sutcliffe model efficiency (EF) increasing from 0.36 to 0.50) and of SOC stock changes (with EF increasing from 0.36 to 0.55). The simulations of maize yield and those of SOC stock changes also improved by site (with site-specific EF ranging between 0.15 and 0.38 for maize yield and between −0.9 and 0.58 for SOC stock changes). The four cross-validation-derived posterior parameter distributions (leaving out one site each) were similar in all but one parameter. Together with the model performance for the different sites in cross-validation, this indicated the robustness of the DayCent model parameterization and its reliability for the conditions in Kenya. While DayCent poorly reproduced daily N2O emissions (with EF ranging between −0.44 and −0.03 by site), cumulative seasonal N2O emissions were simulated more accurately (EF ranging between 0.06 and 0.69 by site). The simulated yield-scaled GHG balance was highest in control treatments without N addition (between 0.8 and 1.8 kg CO2 equivalent per kg grain yield across sites) and was about 30 % to 40 % lower in the treatment that combined the application of mineral N and of manure at a rate of 1.2 t C ha−1 yr−1. In conclusion, our results indicate that DayCent is well suited for estimating the impact of ISFM on maize yield and SOC changes. They also indicate that the trade-off between maize yield and GHG balance is stronger in low-fertility sites and that preventing SOC losses, while difficult to achieve through the addition of external organic resources, is a priority for the sustainable intensification of maize production in Kenya.
QTL mapping for pod quality and yield traits in snap bean (Phaseolus vulgaris L.)
(UoEm, 2024-08-12) Njau, Serah Nyawira; Gepts, Paul; Parker, Travis A.; Duitama, Jorge; Arunga, Edith Esther
Pod quality and yield traits in snap bean (Phaseolus vulgaris L.) inﬂuence consumer preferences, crop adoption by farmers, and the ability of the product to be commercially competitive locally and globally. The objective of the study was to identify the quantitative trait loci (QTL) for pod quality and yield traits in a snap × dry bean recombinant inbred line (RIL) population. A total of 184 F6 RILs derived from a cross between Vanilla (snap bean) and MCM5001 (dry bean) were grown in three ﬁeld sites in Kenya and one greenhouse environment in Davis, CA, USA. They were genotyped at 5,951 single nucleotide polymorphisms (SNPs), and composite interval mapping was conducted to identify QTL for 16 pod quality and yield traits, including pod wall ﬁber, pod string, pod size, and harvest metrics. A combined total of 44 QTL were identiﬁed in ﬁeld and greenhouse trials. The QTL for pod quality were identiﬁed on chromosomes Pv01, Pv02, Pv03, Pv04, Pv06, and Pv07, and for pod yield were identiﬁed on Pv08. Co-localization of QTL was observed for pod quality and yield traits. Some identiﬁed QTL overlapped with previously mapped QTL for pod quality and yield traits, with several others identiﬁed as novel. The identiﬁed QTL can be used in future marker-assisted selection in snap bean.
A Diallel Cross-Based Analysis of the Genetic Basis of Pod Quality and Pod Yield in Snap Bean
(UoEm, 2024-07-27) Njau, Serah N.; Arunga, Esther; Otsyula, R
Snap bean (Phaseolus vulgaris L.) is among the leading vegetables in Kenya that is mainly grown for export with the potential to increase household income. There are few programs in Kenya that focus on breeding new cultivars for increased production. The development of snap bean varieties that are resilient to the changing climate is crucial for sustainable agriculture in Kenya. To achieve this, knowledge of gene action, trait expression, and heritability is vital in effective breeding for quantitative traits like pod quality and yield. A study was conducted to investigate the inheritance of pod quality and yield traits in snap beans, which can inform the breeding of snap beans. A half diallel cross involving two indeterminate dry beans (G2333 and MCM 5001) and five determinate snap beans (Amy, Moonstone, Seagull, Serengeti and Vanilla) varieties was conducted. Data on pod traits (pod weight per plant, pod number per plant, pod length, pod diameter, pod wall fiber and pod suture string) were collected from 21 F1s and 7 parents grown in two locations (Embu and Kirinyaga Counties) in Kenya. The results showed significant genotypic and environmental effects (P < 0.001) for all traits, with significant genotype by environment (G × E) interactions for most traits. Additionally, general combining abilities (GCA) and specific combining abilities (SCA) were significant for all traits evaluated. The significance of GCA and SCA indicated the importance of both additive and non-additive gene effects in controlling the traits, although the additive gene effects were predominant. The study revealed that Vanilla and Serengeti had the highest GCA estimate for pod quality traits, while G2333 and MCM5001 had the highest GCA estimate for pod yield traits. Snap bean pod yield and quality are quantitative traits controlled by multiple genes and influenced by the environment. Therefore, the predominance of additive gene effects suggests that selection for these traits in segregating generations could yield satisfactory gains. The results of this study could impact the development of snap bean varieties that are more resilient to the effects of climate change. Thus, improving the sustainability and productivity of the agriculture sector in Kenya.
Inoculum sources and management of bean scab caused by Elsinoë phaseoli
(UoEm, 2024-06-24) Masheti, Yona; Muthomi, James W.; Muiru, William M; Arunga, Esther E.; Gepts, Paul
Bean scab caused by Elsinoë phaseoli is a major challenge to common bean cultivationin Kenya. However, knowledge about its epidemiology and management is limited.This study conducted three experiments in Kakamega, Kenya, evaluating scab inocu-lum sources and control options. The first experiment evaluated three different inoc-ulum sources over two seasons; bean crop residue caused the highest scab incidencein both the 2021 (62.1%) and 2022 (81.1%) seasons. The second experiment assessedthe effect of rotation history on scab over three seasons. Scab incidence consist-ently surpassed 90% within the first 30 days after planting in half-yearly rotated fieldsacross all seasons, while the disease was absent after planting in fields with no recenthistory of legumes. Fields rotated out of legumes consistently had the highest grainyield, averaging 1.5 t ha−1 over the seasons. Additionally, the rotation land treatmentdisplayed significantly more pods per plant during the 2021 (9.7), 2022a (9.8), and2022b (12.5) seasons. In the third experiment, the impact of five fungicides and fourcropping systems on bean scab was investigated over two seasons. Neither fungicidetreatments nor cropping systems had an effect on bean scab incidence even whenonly severe symptoms were considered. Carbendazim had the highest yield (1.9 t ha−1)outperforming the unsprayed control only in the 2022 season while none of the otherfungicides outperformed the control treatment in yield parameters in either season.This study emphasizes the challenge of managing bean scab without proper crop rota-tion and underscores the role of crop residue as a critical inoculum source.
Efficacy of Metarhizium anisopliae against the Greater Pumpkin Fly Dacus bivitattus
(UoEm, 2023-07-01) Dubois, Thomas; Onsongo, Susan K.; Omuse, Evanson R.; Odhiambo, Joseph A.; Akutse, Komivi S.; Mohamed, Samira A.
The greater pumpkin fly Dacus bivittatus (Bigot) is a fruit fly indigenous to Africa, which causes extensive damage to Cucurbitaceae. To control this pest, farmers rely on synthetic chemicals, often organophosphates, which have negative effects on human health and the environment. However, the sustainable management of D. bivittatus may be obtained through integrated pest management (IPM) practices, with the use of biopesticides as a key component. In this study, the effect of nine isolates of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin (ICIPE 18, ICIPE 20, ICIPE 30, ICIPE 48, ICIPE 62, ICIPE 69, ICIPE 84, ICIPE 91 and ICIPE 94) was directly evaluated on adult D. bivittatus mortality. Adult flies were allowed to walk for 5 min on 0.3 g of dry conidia of each isolate and monitored daily for 10 days. We also evaluated the effect of sand inoculated with M. anisopliae on larval and pupal mortality and adult eclosion and mortality in three replicated experiments. Larvae were exposed to the same isolates at a concentration of 1 × 107 conidia/mL in sterile sand, and adult eclosion and mortality were monitored for 15 days. The median lethal time (LT50) of adults after direct exposure was shortest for ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 (3.11–3.52 days). In infested sand, larval mortality was highest for ICIPE 18 and ICIPE 20 (≥42.50%), while pupal mortality was highest for ICIPE 30 (≥41.25%). The lowest eclosion was observed for ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 (≤40.00%). The LT50 of adults eclosed from infested sand was shortest for ICIPE 18, ICIPE 20 and ICIPE 30 (4.48–6.95 days). ICIPE 18, ICIPE 20, ICIPE 30 and ICIPE 69 are, therefore, potential isolates for subsequent field testing on D. bivittatus populations.
A Guide for Soil Health and Fertility for Maize production in Kenya
(UoEm, 2023) Nyaga, Patrick; Yegon, Rebecca; Laub, Moritz; Six, Johan
The health of your soil is a fundamental aspect of successful farming. However, many arable soils in Kenya have degraded and lost fertility over recent decades1. This is expected because many soils were recently transformed from more permanent land uses, which always leads to soil fertility losses2. However, this soil fertility loss is largely avoidable with best management practices that replenish soil organic matter and soil nutrient resources3,4.
Identification of Elsinoë phaseoli causing bean scab in Kenya and evaluation of sporulation using five adapted techniques
(UoEm, 2024-06-07) Masheti, Y. O.; Muthom, J. W.; Muiru, W. M.; Arunga, E. E.; Gepts, P.
This research addresses the presence of Elsinoë phaseoli in Kenya, where information on the biology of this pathogen remains scarce. Employing a multifaceted approach, the study demonstrates the steps taken to isolate, identify, and characterize E. phaseoli as the pathogen responsible for scab on common bean. Field observations confirmed scab symptoms, particularly the prominent pod lesions. Elsinoë phaseoli was isolated from common bean using a targeted streaking method on older acervulus-bearing lesions. Morphological examinations revealed a notable diversity within E. phaseoli colonies, consistent with the characteristics of the genus. Molecular identification through ITS-rDNA sequencing confirmed isolate AscoSK1 obtained in this study as belonging to E. phaseoli, offering a robust species differentiation method. Assessing conidium production required the implementation of five different culture methods. An adaptation of the Scheper et al. (2013) method yielded the highest quantity of conidia from 25 colonies spaced at 1 cm apart, with a conidial yield of 5.0 × 106 conidia per 9-cm-diameter Petri dish. A higher conidial yield was attained after the colonies were pre-incubated on potato dextrose agar in the dark at room temperature for 28 days, followed by a transfer to corn meal agar for an additional 2 days at 20°C. This emphasizes the pivotal influence of incubation duration and pre-culture conditions on the process. This research provides insights into the biology of E. phaseoli and introduces an improved method for enhancing in vitro sporulation of the pathogen, setting groundwork for future research and handling.
Determinants for rainwater harvesting adoption: a case study of smallholder farmers in Murang’a County, Kenya
(UoEm, 2024-05-17) Itemo Irungu, Francis; Yegon, Rebecca; Milkah Muniale, Faith
Rainwater harvesting has been practiced among smallholder farmers for centuries in many parts of the world. Recently, it has gained more attention due to the reported increasing water demand and the need for sustainable water management. Drawing on data from a cross sectional survey of 384 household heads (HH), the research study explored the determinants for rainwater harvesting among smallholder farmers in Murang’a County, Kenya. Multistage random sampling technique was employed during the survey using KOBO collect software for data collection. The fndings revealed that socio-economic, socio-demographic and institutional factors signifcantly infuenced the adoption of rooftop RWH, mulching, terraces, infltration pits, retention ditches, water bunds, water pans, dams, furrows, negarims and deep ploughing among HH in Murang’a County. The multivariate probit model results showed that household head’s access to credit facilities, land ownership, age, level of income, education level, gender, family size, source of income, membership to farmers’ groups and access to training services positively infuenced rainwater harvesting (RWH) adoption. Similarly, HH membership to farmers group(s) had merits including: social ties, source of information and source of credit which were also key determinants to RWH adoption in the area. The fndings of the present study recommends the relevant stakeholders to carry out training to HH on RWHTs, creation of awareness among youths on merits for RWH adoption, encourage HH to join farmers’ groups and encourage partnership with credit facilities in RWHTs adoption among HH in the region. Results of the present study provide valuable insights into the determinants for rainwater harvesting among smallholder farmers in Murang’a County which can be used to inform policy and practice for widespread adoption.

Browse

Recent Submissions