Browsing by Author "Nyakinywa, Ruth"

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AGRICULTURAL SIGNIFICANCE OF RHIZOBIUM SPECIES FROM DIFFERENT SOURCES
(Chuka University, 2022) Nyakinywa, Ruth; Atieno, Margaret Faith; Ogolla, O. Fredrick
Strong demand for food necessitates efforts by researchers to create methods for sufficient production. Agricultural challenges include soil fertility loss, climate change, and increased pest infestations. Environmentally friendly practices such as the use of bio pesticides, bio fertilizers, and the return of crop residues are used to produce sufficient quantities in a healthy and sustainable farming system. The wide range of beneficial impacts of soil microorganisms, notably plant growth stimulation, emphasizes the need for more research and application in modern agriculture. Legumes are an important part of many people traditional diets around the world because they provide a slew of benefits to a soil and other crops produced alongside or after them in a variety of cropping systems. Legumes ability to fix atmospheric nitrogen in conjunction with rhizobia allows them to thrive in severely deteriorated soils. Is it, nevertheless, necessary to inoculate legumes on a regular basis? Rhizobia are extremely valuable agriculturally and economically since they are the primary supplier of nitrogen in agricultural soils. Aside from nitrogen fixation, several rhizobia strains have plant-growth-promoting features such phytohormone synthesis, siderophores, and 1-aminocyclopropane-1-carboxylic acid deaminase, as well as inorganic phosphate solubilization. Rhizobia have become important for both legumes and non-legumes as a result of these factors. Plant growth has been improved by screening and using effective rhizobial strains as inoculants. Plant growth has been improved by screening and using effective rhizobial strains as inoculant. The use of rhizobia as a bio fertilizer ensures crop yield while also reducing the demand for expensive and environmentally harmful artificial fertilizers. Rhizobia and other plant-growth-promoting rhizobacteria inoculated together resulted in increase in plant-growth promotion. Bioremediation properties of certain rhizobial strains have also been found.
In-vitro Evaluation of Fungicide Sensitivity of Tomato Leaf Blight Pathogens
(Jurnal Pertanian Tropik (JPT), 2021) Ogolla, Fredrick O.; Nyakinywa, Ruth; Chabari, Samson K.; Onyango, B.; ; ;
Tomato early and late blight diseases caused by Alternaria solani and Phytophthora infestans respectively, are constraints to tomato production globally. Conventional use of commercial synthetic fungicides in management of tomato blight disease has become a key input for tomato production among farmers in Tharaka Nithi County, Kenya. Indiscriminate use and application of sub-lethal doses of fungicides negate disease management efforts, and may lead to gradual fungicide resistance. Yet, local tomato farmers have continued to use the fungicides without periodic evaluation of their effectiveness. This study was carried out in-vitro to evaluate the efficacy of six synthetic commercial fungicides used by farmers around River Ruguti, against two tomato leaf blight pathogens; Alternaria solani and Phytophthora infestans. The poison food method was used to evaluate fungicides known by trade names and application levels; Mancozeb (640 g kg-1) + Metalaxyl (40 g kg-1), Mancozeb 640 g/kg + Metalaxyl 80 g/kg, Mancozeb, Propineb700 g/kg + Cymoxanil 60 g/kg, Carbendazim and Triticonazole at different concentration (25%, 50% and 75%). The in-vitro plate experiment was laid out in a Complete Randomized Design with 3 replicates, and data on mycelia growth inhibition analyzed through General Linear Model (α=.05) and significant means separated using Least significant difference (LSD) using Scientific Analysis System version 9.4. All the tested fungicides significantly (p≤ 0.05) inhibited mycelial growth of tested pathogen. Percentage inhibition for early blight pathogen (Alternaria solani) was 80.42% compared to late blight pathogen Phytophthora infestans at 69.51%. Mancozeb (640 g kg-1) + Metalaxyl (40 g kg-1) and Propineb700 g/kg + Cymoxanil 60 g/kg recorded higher per cent inhibition of mycelia growth of 92.4% and 89.71% respectively. Carbendazim recorded lower per cent inhibition of 39.15%. Mycelia growth inhibition increased with an increase in fungicide concentration. Lower inhibition of 71.78% was observed at 25% concentration as compared to 50% and 75% with 76.77% and 76.36% respectively. Fungicides screened varied in mycelia inhibition against P. infestans and A. solani isolates with Mancozeb (640 g kg-1) + Metalaxyl (40 g kg-1) and Propineb700g/kg +Cymoxanil 60g/kg giving significantly (p≤ 0.05) better inhibition while Carbendazim had the lowest inhibition effect. Increased fungicide concentration effectively inhibited mycelia growth. Thus higher concentration of fungicide application is recommended in cases where there is low efficacy of fungicides.
IN-VITROEVALUATION OF FUNGICIDES SENSITIVITY OF TOMATO LEAF BLIGHT PATHOGENS ISOLATES Alternariasolani and Phytophthorainfestans
(Chuka University, 2021) Nyakinywa, Ruth; Ogolla, Fredrick O.; Chabari, Kithaka Samson
Tomato early and late blight diseases caused by Alternaria solani(Ellis & Martin) Sorauer and Phytophthora infestansrespectively hinder tomato production globally. Use of fungicides in management of blight diseases has become a priority among farmers. However, indiscriminate or use of sub lethal doses negate disease management efforts. Despites the knowledge of possible occurrence of fungicide insensitive phyto-pathogens, farmers has continued using fungicides without periodic evaluation of their effectiveness. This study was carried out to evaluate an in-vitro sensitivity of tomato leaf blight pathogens (Alternaria solaniand Phytophthora infestans) against selected fungicides mostly used by tomato farmers along River Ruguti in Tharaka Nithi County in Kenya.Fungicides evaluated included, Mancozeb (640 g kg-1 ) + Metalaxyl (40 g kg-1 ), mancozeb 640 g/kg + metalaxyl 80 g/kg, Mancozeb, Propineb700 g/kg + Cymoxanil 60g/kg, Carbendazim and Triticonazole at different concentration (25%, 50% and 75%). Poison food method was used for evaluation. Complete Randomise design was used for the experiment. Per cent data on mycelia growth inhibition by various fungicides at different concentration were analysed using General Linear Model (α=.05) and significant means separated using Least significant difference (LSD) in Scientific Analysis System version 9.4. All the tested fungicides significantly (P≤ 0.05) inhibited the mycelial growth of tested pathogen. However, among tested fungicides, Carbendazim (89.83%) and Propineb700g/kg +Cymoxanil 60g/kg were superior over other fungicides with Carbendazim being the least. Mycelia growth inhibition increased with an increase in fungicide concentration. Mycelia growth inhibition of Alternaria solaniwas 81.78% as compared to Phytophthora infestans at 69.78%.