Browsing by Author "Njeru, Ezekiel Mugendi"
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Item Agrobiodiversity conservation enhances food security in subsistence‑based farming systems of Eastern Kenya(BioMed Central, 2016) Mburu, Simon Wambui; Koskey, Gilbert; Kimiti, Jacinta Malia; Ombori, Omwoyo; Maingi, John M.; Njeru, Ezekiel MugendiBackground: Globally, there is great concern about expanding agricultural activities due to their impact in the conservation of agrobiodiversity. African continent is known for its richness in biodiversity. In Kenya, there is a continuous unabated expansion of agriculture into natural habitats due to demographic and economic pressures posing a significant threat to biodiversity. Therefore, there is a need to study biodiversity loss and its regain through practices in agricultural landscapes. In this study, we assessed the status of agrobiodiversity and its contribution to food security in four agroecological zones of Eastern Kenya. Sixty households were sampled from two selected agroecological zones (upper and lower midland zones) in Embu and Tharaka-Nithi counties. Structured questionnaires and checklists were used to collect the data. Results: Thirty-nine crop species were identified dominated by vegetables, fruits, legumes and cereals with relative densities of 28.8, 20.5, 18.3 and 8.3 %, respectively. Embu Lower Midland and Tharaka-Nithi Lower Midland zones had relatively higher crop species richness of 243 and 240, respectively, and Shannon–Wiener diversity indices (H′) of 3.403 and 3.377, respectively, compared with Embu Upper Midland and Tharaka-Nithi Upper Midland zones with species richness of 229 and 207, respectively, and H′ of 3.298 and 3.204, respectively. Conclusions: Households from lower midland zones with high crop diversity and richness were more food secure compared with those from the Upper Midland zones with low crop diversity and richness. These findings suggest that farm production systems with high agrobiodiversity contributed more toward food security among smallholder farmers in the selected sites. Keywords: Agrobiodiversity, Food security, Biodiversity loss, Smallholder farmers, KenyaItem Arbuscular Mycorrhizal Fungi and Trichoderma spp Influence on Nutrient Uptake and Water Stress Tolerance in Cowpea (Vigna unguiculata L. Walp)(AJHS, 2023-09) Wanjala, Daniel; Mutune, Adelaide; Njeru, Ezekiel MugendiDrought and nutrient un-availability are amongst the major environmental stresses that hinder plants productivity. The use of synthetic fertilizers in drought-stricken lands is unaffordable to most small-holder farmers and contributes to environmental pollution. This study was conducted to determine the influence of Arbuscular Mycorrhizal fungi and Trichoderma spp on nutrient uptake in cowpea at different soil water levels under greenhouse conditions. The experiment was conducted using a 3 × 2 × 8 factorial arranged on a completely randomized block design with the three water levels treatment of90 % (no stress), 60 % (mild stress), and 30 % (severe stress) of field capacity (FC). Two cowpea varieties (KVU 27-1 and K80) were used in each water level and each was subjected to eight fungal inoculation treatments: Funneliformis mosseae, Rhisophagus irregularis, Trichoderma harzianum, Trichoderma asperellum, Funneliformis mosseae + Rhisophagus irregularis, Trichoderma harzianum + Trichoderma asperellum, T. harzianum + Funneliformis mosseae + Rhisophagus irregularis, and control (un-inoculated) that were in the replicates of four. The shoot tissue analysis was done to determine the nitrogen (N), phosphorous (P) and potassium (K) contents. The data were subjected to a Two-Way ANOVAto determine the influence of the two fungi on nutrient uptake.Means were separated using Bonferroni at p < 0.05. Results showed that all the shoot nutrient contents were significant at (p<0.05) with soil water level treatment in both varieties. Water stress negatively influenced shoot nutrient contents. The combined inoculation of HarS and HBB greatly influenced shoot nutrient levels for both cowpea varieties than the controls. The highest N and P shoot content were 3.7 % (in KVU 27-1) and 0.12 % (in K80) inoculated with HBB and HarS respectively. The highest K content was 2.7 % in both varieties inoculated with HarS. Therefore, co-inoculation of HarS and HBB was the most appropriate to nutrient uptake in the cowpea varieties.Item Changes in the composition of native root arbuscular mycorrhizal fungal communities during a short-term cover crop-maize succession(Springer Verlag, 2016) Turrini, Alessandra; Sbrana, Cristiana; Avio, Luciano; Njeru, Ezekiel Mugendi; Bocci, Gionata; Giovannetti, ManuelaArbuscular mycorrhizal fungi (AMF) establish mutualistic associations with the most important agricultural food and feed crops, sustaining plant growth, nutrient uptake and tolerance of biotic and abiotic stresses. Scanty information is available on the role played by crop identity and diversity as a driving force shaping AMF species communities in the field, in particular in low-input and organic farming, where crop rotation and the use of cover crops are common practices. Here, using a molecular approach, we investigated whether plant communities established in low and high diversity cover crop treatments affect the composition of native AMF root communities of subsequent maize in a Mediterranean organic agroecosystem. A total of 16 AMF sequence types were detected, with Acaulospora cavernata as the most abundant phylotype, accounting for 37.4 % of the sequences, followed by Funneliformis mosseae, Claroideoglomus lamellosum and Rhizoglomus intraradices. Sequences matching to Funneliformis caledonium, Diversispora aurantia, Diversispora epigaea and Archaeospora schenckii corresponded to less than 2.0 % of the total. The most abundant sequences retrieved in plants from cover crop treatments were represented by A. cavernata, while sequences in maize roots were related to F. mosseae, R. intraradices and Glomus sp. Such data show for the first time a change in the composition of native AMF communities colonizing maize roots, which was independent of the identity and diversity of the preceding crop. Our findings suggest that host preference may represent a strong driver of AMF community dynamics in agroecosystems, differentially boosting or depressing AMF species, possibly in relation to their functional significance.Item Differential Response of Promiscuous Soybean to Local Diversity of Indigenous and Commercial Bradyrhizobium Inoculation under Contrasting Agroclimatic Sones(Springer Nature, 2020) Mburu, Simon Wambui; Koskey, Gilbert; Njeru, Ezekiel Mugendi; Ombori, Omwoyo; Maingi, John M.; Kimiti, Jacinta MaliaPromiscuous soybeans are grain legumes that nodulate with diverse strains of indigenous Bradyrhizobium and play a significant role in biological nitrogen fixation through symbiosis. However, experiments on the potential use of promiscuous soybean varieties have recorded very low nodulation and poor nitrogen fixation probably due to ineffective native Bradyrhizobium isolates. Experiments were designed to investigate symbiotic nitrogen fixation of two promiscuous soybean varieties (SB8 and SB126) with indigenous Bradyrhizobium isolates in contrasting agroclimatic zones through greenhouse and field experiments. Inoculation of soybeans in the greenhouse had a significant (p < 0.001) effect on shoot and nodule dry weight. The best performing indigenous isolates RI9 and RI4 from the greenhouse study outperformed the commercial inoculant (Biofix) in symbiotic effectiveness with 119.17%, 142.35% and 101.01%, respectively. Inoculation in the field experiments showed a significant (p < 0.0001) increase in shoot dry weight and grain yield of promiscuous soybean. Agroclimatic zones showed significant (p < 0.0001) variability in above ground biomass of soybean due to inoculation. Despite the apparent promiscuity of the soybean varieties used, the response in nodulation suggests the cultivars grown under contrasting agroclimatic zones have a preference to specific Bradyrhizobium isolates.Item Elucidating the potential of native rhizobial isolates to Improve biological nitrogen fixation and growth of common bean and soybean in smallholder farming systems of Kenya(Hindawi Publishing Corporation, 2016) Ouma, Ernest Wandera; Asango, Anne Mercy; Maingi, John; Njeru, Ezekiel MugendiIdentification of effective indigenous rhizobia isolates would lead to development of efficient and affordable rhizobia inoculants. These can promote nitrogen fixation in smallholder farming systems of Kenya. To realize this purpose, two experiments were conducted under greenhouse conditions using two common bean cultivars; Mwezi moja (bush type) and Mwitemania (climbing type) along with soybean cultivar SB 8. In the first experiment, the common bean cultivars were treated with rhizobia inoculants including a consortium of native isolates, commercial isolate (CIAT 899), a mixture of native isolates and CIAT 899, and a control with no inoculation. After 30 days, the crop was assessed for nodulation, shoot and root dry weights, and morphological features. In the second experiment, soybean was inoculated with a consortium of native isolates, commercial inoculant (USDA 110), and a mixture of commercial and native isolates. Remarkably, the native isolates significantly (𝑝 < 0.001) increased nodulation and shoot dry weight across the two common bean varieties compared to the commercial inoculant, CIAT 899.Mixing of the native rhizobia species and commercial inoculant did not show any further increase in nodulation and shoot performance in both crops. Further field studies will ascertain the effectiveness and efficiency of the tested indigenous isolatesItem Exploiting diversity to promote arbuscular mycorrhizal symbiosis and crop productivity in organic farming systems(AIMS Press, 2018) Njeru, Ezekiel MugendiBeneficial soil microbiota especially arbuscular mycorrhizal fungi (AMF) deliver essential agroecosystem services in organic farming systems, where the application externalities is often limited. Undoubtedly, organic farming provides optimal conditions for agroecological functioning due to minimal soil disturbance and limited use of agrochemicals. In this context, beneficial soil microbiota are expected to deliver optimal ecosystem services. Nevertheless, the composition, diversity and function of beneficial rhizospheric microorganisms including AMF communities vary upon agronomic practices and soil conditions. Moreover, it is well known that some modern crop cultivars are less responsive to AMF, since they are bred for high intensive agricultural systems where there is sufficient supply of nutrients especially P. Until now, the establishment and function of AMF in organic cropping systems is still poorly understood. Such information is a prerequisite for the implementation of efficient cropping systems that capitalize on biological processes, a key step towards agricultural sustainability. The overall aim of this review is to provide insights on increasing mycorrhizal symbiosis and crop productivity in organic agroecosystems through innovative, temporal and spatial manipulation of species and genetic diversity at the crop cultivar, AMF species and cover crop management levels. The bulk of this review underscores the importance of examining different levels of diversification in organic farming systems, considering functional identity (single species), composition (mixed species) and diversity (heterogeneity within species) and how such components contribute to delivery of multiple agroecosystem servicesItem Functional identity has a stronger effect than diversity on mycorrhizal symbiosis and productivity of field grown organic tomato(Elsevier, 2017) Njeru, Ezekiel Mugendi; Bocci, Gionata; Avio, Luciano; Sbrana, Cristiana; Turrini, Alessandra; Giovannetti, Manuela; Bàrberi, PaoloBeneficial soil biota, and in particular, arbuscular mycorrhizal fungi (AMF) are increasingly being recognized as key elements of organic and low-input agriculture where agrobiodiversity is central to enhanced crop production. However, the role of AMF in diversified organic systems, especially in field crops, is still poorly understood. A 3-year field experiment was carried out in Central Italy to investigate whether organic cropping systems that promote species and genetic diversity are more prone to mycorrhizal symbiosis increasing tomato growth, production and yield quality. Three tomato cultivars with varying genetic diversity were grown following four cover treatments: Indian mustard (Brassica juncea L. Czern.), hairy vetch (Vicia villosaRoth), a commercial mixture of seven cover crop species (Mix 7) and no-till fallow. Plants were either inoculated or not in nursery, with the two AMF isolates Funneliformis mosseae (IMA1) and Rhizoglomus intraradices (IMA6) used alone or mixed in a 1:1 volume ratio. On average, Mix 7 produced higher shoot dry matter (5.0 t ha−1) than V. villosa (3.5 t ha−1) or B. juncea (2.5 t ha−1). Pre-transplant inoculation increased tomato root colonization at flowering and harvest compared to the non inoculated plants (31.8 vs 23.6%) and cv. Rio Grande was on average the best colonized. The mean fresh weight of marketable fruits was 18.4, 28.0 and 28.6 t ha−1 for cvs. Rio Grande, Roma and Perfect Peel, respectively. Cover crops inconsistently affected tomato marketable fruit production in year 1, while in years 2 and 3, Vicia villosa and Mix 7 showed the best effect respectively. In year 3, among the pre-inoculated plants those treated with isolate IMA6 showed a higher production of marketable fruit number m−2 (56.7) than those inoculated either with IMA1 (51.5) or the mixed inocula (52.1). Most fruit quality parameters were affected by tomato genotype. This study shows that while increased agrobiodiversity is important to increase agroecosystem resilience, AMF, crop and cover crop functional identity may be more important than diversity per se to promote mycorrhizal symbiosis and productivity of field grown organic tomato.Item Leveraging the Complex Interplay between Arbuscular Mycorrhizal Fungi, Seasonal Dynamics, and Genotypic Diversity to Optimize Maize Productivity in Semi-Arid Agroecosystems(Heliyon, 2024-09) Kipkorir, Koech; Koskey, Gilbert; Njeru, Ezekiel Mugendi; Maingi, JohnMaize production under low-input agricultural systems in semi-arid areas of Sub-Saharan Africa faces significant challenges, primarily stemming from the synergistic impacts of climate vari ability and suboptimal agronomic practices. Harnessing soil microbiota, particularly arbuscular mycorrhizal fungi (AMF), represents a pivotal strategy for bolstering low-input systems. However, their functional utility is contingent upon their compatibility with the prevailing environmental conditions and biotic interactions. This study examines the influence of two distinct AMF in oculants on the growth and yield attributes of diverse maize genotypes across varying seasons within semi-arid regions of Kenya. We hypothesized that AMF inoculants exhibit differential adaptability to varying environmental sites and seasons, and their interaction will enhance the provision of key ecosystem services important for maize production. Field experiments were conducted in three semi-arid Counties (Tharaka-Nithi, Embu, and Kitui) during the 2019/2020 cropping seasons. A randomized complete block design with three replications and three treat ments was adopted. Treatments consisted of Rhizatech (a commercial AMF inoculant), a con sortium of AMF isolates (Rhizophagus irregularis and Funneliformis mosseae), and a non-inoculated control. In season one, notable interaction effects were observed for both site × maize genotype (p = 0.0007) and site × AMF inoculation (p < 0.0001), whereby Duma 43 genotype had the highest yield in Embu (11.93 t ha− 1 ) and Kitui (11.76 t ha− 1 ) counties, and Rhizatech and con sortium inoculation consistently led to elevated grain yields across all three genotypes in Kitui, surpassing non-inoculated controls. AMF inoculation notably augmented phosphorus (P) uptake, with Rhizatech demonstrating a 79.7 % increase and consortium showing a 38.7 % increase in shoot P content compared to control plants in season 1. These findings highlight the complex interplay between AMF effectiveness, seasonal variations, and maize diversity. Further research is needed to elucidate the underlying mechanisms driving these seasonal shifts, allowing for opti mized AMF inoculation strategies for improved maize performance under diverse conditions.Item Response of a wild-type and modern cowpea cultivars to arbuscular mycorrhizal inoculation in sterilized and non-sterilized soil(Taylor & Francis, 2018) Oruru, Marjorie Bonareri; Njeru, Ezekiel Mugendi; Pasquet, Remy; Runo, SteveCowpea is an important crop that serves as a legume and vegetable source to many smallholder farmers in sub-Saharan Africa. Soil fertility is a significant limitation to its production thus; inoculation with beneficial soil biota such as arbuscular mycorrhizal fungi (AMF) could improve its performance. However, plant–AMF interaction could vary based on crop cultivar hence affecting overall crop production. The present study aimed at determining the effect of AMF inoculation and soil sterilization on root colonization and growth of a wild-type and three modern cowpea cultivars grown by smallholder farmers in Kenya. Potted cowpea plants were inoculated with a commercial AMF inoculum comprising of Rhizophagus irregularis, Funneliformis mosseae, Glomus aggregatum and Glomus etunicatum and maintained in a greenhouse for 40 days. After harvesting, mycorrhizal colonization, nodule number and dry weight, root and shoot dry weights, nitrogen (N,) phosphorus (P) and potassium (K) content were determined. Interestingly, the modern cultivars showed significantly (p < 0.001) higher root colonization, nodulation, shoot P and N compared to the wild-type cultivar. Moreover, a strong positive correlation between AMF root colonization and shoot P (r2 D 0.73, 0.90, p < 0.001), AMF root colonization and shoot N (r2 D 0.78; 0.89, p < 0.001) was observed in both sterilized and non-sterilized soil, respectively. Soil sterilization affected root colonization and growth parameters with plants grown in non-sterilized soil performing better than those grown in sterilized soil. This study provides major evidence that modern cowpea cultivars are still responsive to mycorrhizal inoculation suggesting that modern breeding programs are not deleterious AMF symbiosis.Item Soil management practices affect arbuscular mycorrhizal fungi propagules, root colonization and growth of rainfed maize(AIMS Press, 2018-06) Nyamwange, Methuselah Mang’erere; Njeru, Ezekiel Mugendi; Mucheru-Muna, Monicah; Ngetich, FelixAgronomic management practices influence beneficial soil biota, especially arbuscular mycorrhizal fungi (AMF). AMF colonizes about eighty percent of land plants, promoting absorption of essential nutrients and crop growth. Here, a 5-year field experiment was carried out in Central Kenyan Highlands to determine the effect of tillage, mulching and inorganic fertilizers on the number of infective AMF propagules in the soil, mycorrhizal root colonization of maize and uptake of P and N from the soil. The study involved conventional and minimum tillage systems, mulching using dried maize stovers and inorganic fertilizers (120 kg N/ha). The experiment was set up in randomized complete block design and replicated thrice. The number of infective AMF propagules decreased in the following order; V4 stage (p < 0.0001), V6 stage (p < 0.0001), maize harvest (p = 0.0076) and before maize planting (p = 0.0061). Minimum tillage + mulch + no NP fertilizer (ZRO) treatment recorded the highest number of infective AMF propagules with an average of 90 propagules g-1 of soil whereas conventional tillage + mulch + NP fertilizer (CRF) and conventional tillage + no mulch + NP fertilizer (CWF) treatments recorded the lowest number of AMF propagules with an average of 1.33 propagules g-1 of soil. Besides, AMF colonization of maize roots at V4, V6 and harvest stages was significantly affected by tillage (p < 0.0001), mulch (p = 0.0001) and fertilizer (p < 0.0001). Results at juvenile stage showed a strong positive correlation between AMF colonization and shoot P (r = 0.933, p < 0.0001) and N (r = 0.928, p < 0.0001). These findings demonstrate a strong effect of agronomic management practices on soil AMF propagules which subsequently affected root colonization and uptake of essential nutrients such as P and N.