Browsing by Author "Kimani, J.M."
Now showing 1 - 3 of 3
- Results Per Page
- Sort Options
Item Association of Phenotypic Traits and Variations in SSR Markers for Rice Grain Fragrance and Metric Traits Under Different Soil Fertility Regimes(2013) Kimani, J.M.; Githiri, S.M.; Tongoona, P.; Derera, J.; Nyende, A.B.; Jedidah, W.D.; Kenya Agricultural Research Institute- Mwea TebereFragrance in rice (Oryza sativa L.) is an important quality trait. This study was conducted to determine the association between variations in fragrance and in SSR markers, and to establish gene action for fragrance. Nine parents and 72 F2 populations generated by full diallel mating design, planted in a nine by nine alpha lattice design at KARI-Mwea Tebere Research Centre, were used for the study. DNA analysis was done using SSR markers RM223 and RM284. The results indicated that RM223 was polymorphic among the parents, while RM 284 gave monomorphic results. Four alleles of RM223 (146, 155, 161, and 163) were detected. Test for independence using Chi-square indicated that there was no association between fragrance phenotype and RM223 marker. The additive gene action was greater for the fragrance score. The general combining ability was about one and halftimes higher than interactions specific combining ability (SCA). The performance of the fragrant lines was generally lower than that of non-fragrant ones, indicating that aroma genes have negative interaction for yield. There was generally negative effect between fragrant score and other agronomic traits such as grain yield across the three soil N and P fertility conditions. The NERlCAl was found to be a good donor for fragrant based on phenotypic (sensory) tests and is a potential genotype for improvement of rice.Item Farmers Demonstrate Rationality and Transitivity in Variety Choice: Empirical Evidence from Two Rice Growing Niches in Coastal Kenya(International Journal of Agriculture, 2022) Kengo, D.M.; Kimani, J.M.; Sang-Bok, L.; Kenya Agricultural and Livestock Research Organization ; Africa Rice Training CenterPurpose: A cross-sectional survey was designed to study farmers’ preference and choice framework for rice varieties in Kwale and Taita-Taveta counties of coastal lowland Kenya. Methodology: The survey used a multi-stage sampling technique; systematic selection for the study counties niches, a purposive sampling approach for the study population (rice growers only) and a systematic random sampling for the respondents on an nth occurrence. Data was collected with the aid of a semi-structured questionnaire and key informant interviews from key rice value chain actors; including farmers as producers as well as consumers and agricultural extension service providers (AESPs) and other stakeholders. A total of 137 individual respondents were interviewed using the semi-structured questionnaire while the key informant interviews engaged a total of 29 AESPs. Data analysis focused on exploring on the varieties that farmers grew and whether they had a criteria or pattern for choosing the varieties to grow and seed source. Findings: Results confirmed that the Kwale rice growing niche had a higher rice variety diversity (more than 12 varieties) while Taita-Taveta had only around seven (7) common varieties. Rice was more traditionally grown in Kwale with low acreage and low yields compared to Taita-Taveta. Common varieties grown were Pachanga, Supa, Kitumbo, Makonde and Kibawa in Kwale while in Taita-Taveta, Japan, Supa and Hybrid 6444 rice varieties were common (with prevalence rating of 44.8%, 25.4%, 22.4%, 20.9 and 17.9% in Kwale respectively and 55.7%, 54.3% and 18.6% in Taita-Taveta respectively). Varieties grown by farmers in Kwale had a long history of seed recycling and were characterized by low productivity (less than 6, 90-kg bags per acre) and subsistent in nature than in Taita-Taveta. The general picture for variety prevalence in both (Kwale and Taita) growing niches was that farmers mostly relied on traditional (own-preserved, farmer-to-farmer exchange or market) seed systems for the recycled rice varieties. Variety choice by farmers who are both producers and consumers demonstrated a rational and transitive behavior with land resource allocation. Contribution to theory, practice and policy: The study provided evidence of an urgent need for strategic interventions towards improving the production system through on-farm researcher-led demonstrations for superior rice varieties, agronomic practices as well as an input subsidy and sustainable market linkages. Formation of farmer producer groups and strategic facilitation of the groups with rice certified seed and mills are proposed as positive drivers to improving rice marketing and increased productivity.Item Foliar Diseases and the Associated Fungi in Rice Cultivated in Kenya(MDPI, 2022-05-07) Nganga, E.M.; Kyallo, M.; Orwa, P.; Rotich, F.; Gichuhi, E.; Kimani, J.M.; Mwongera, D.; Waweru, B.; Sikuku, P.; Musyimi, D.M.; Mutiga, S.K.; Ziyomo, C.; Murori, R.; Wasilwa, L.; Correll, J.C.; Talbot, N.J.; Maseno University ; -International Livestock Research Institute ; University of Embu ; Kenya Agricultural and Livestock Research Organization ; International Rice Research Institute ; The University of Arkansas System ; University of East AngliaWe conducted a survey to assess the occurrence and severity of rice blast and brown spot diseases on popular cultivars grown in the Busia, Kirinyaga, and Kisumu counties of Kenya in 2019. Working with agricultural extension workers within rice production areas, we interviewed farmers (n = 89) regarding their preferred cultivars and their awareness of blast disease, as this was the major focus of our research. We scored the symptoms of blast and brown spot and assessed the lodging, plant height, and maturity of the crops (days after planting). Furthermore, we collected leaf and neck tissues for the assessment of the prevailing fungal populations. We used specific DNA primers to screen for the prevalence of the causal pathogens of blast, Magnaporthe oryzae, and brown spot, Cochliobolus miyabeanus, on asymptomatic and symptomatic leaf samples. We also conducted fungal isolations and PCR-sequencing to identify the fungal species in these tissues. Busia and Kisumu had a higher diversity of cultivars compared to Kirinyaga. The aromatic Pishori (NIBAM 11) was preferred and widely grown for commercial purposes in Kirinyaga, where 86% of Kenyan rice is produced. NIBAM108 (IR2793-80-1) and BW196 (NIBAM 109) were moderately resistant to blast, while NIBAM110 (ITA310) and Vietnam were susceptible. All the cultivars were susceptible to brown spot except for KEH10005 (Arize Tej Gold), a commercial hybrid cultivar. We also identified diverse pathogenic and non-pathogenic fungi, with a high incidence of Nigrospora oryzae, in the rice fields of Kirinyaga. There was a marginal correlation between disease severity/incidence and the occurrence of causal pathogens. This study provides evidence of the need to strengthen pathogen surveillance through retraining agricultural extension agents and to breed for blast and brown spot resistance in popular rice cultivars in Kenya.
