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Publication The Kenya Cereals Enhancement Programme -Climate-resilient agricultural livelihoods (kcep-cral): Cowpea extension manual(Kenya Agricultural and Livestock Research Organization, 2021-04) Kuruma, R.W.; Macharia D.; Waithaka M.; Otipa M.; Amata, R.; Too A.; Esilaba A. O.; Nyongesa D.; Okoti M.; Mutuma E.; Kathuku-Gitonga A.N.; Mutisya D.; Njunie M.; Muli B.; Karanja J. K.; Wasilwa L.Cowpea Vigna unguiculata (L.) Walp. is an important grain legume in the farming systems of Kenya since it is a major source of dietary protein and income for the people. The crop is usually grown at subsistence level as an intercrop with maize, sorghum, millet and/or cassava. It also play an important role in soil fertility improvement, suppression of weed, supply of vegetables and dry grain after maturity. Cowpea rank second to beans in importance as vegetable protein food crops. It is consumed in the form of whole leaves or dried grains. The mean crude protein levels of leaves, grains and crop residues are 32 -34%, 23 – 35%, and 11 – 12% respectively. Cowpea is mainly grown as a green leafy vegetable in Western Kenya and for grain in the dry lands of Eastern, Coast and Nyanza regions. Cowpea grown as a vegetable requires rich soils and high rainfall. In contrast, cowpea grown for grain requires low rainfall and high temperature. About 85% of total area under cowpea production in the eastern region of Kenya, is under intercropping systems with maize and or cassava. Despite cowpea importance, its yields have remain low, or even declined. Low yields result from low soil fertility, poor agronomic practices, pest, diseases and poor postharvest management. Use improved and good crop management options could greatly reduce losses. The grain is rich in protein, up to around 30% in some varieties. It also has micronutrients such as iron and zinc, which are necessary for healthy living. Women particularly value cowpea, which helps to bridge the “hunger months” prior to the main cereal harvest and also a source of cash to the rural and urban households. Relative to other grain legumes and vegetable crops, cowpea possess multiple advantages for farmers. Cowpea is tolerant to drought and high temperatures as compared to other grain legumes. It is able to capture atmospheric nitrogen, providing symbiotic nitrogen fixation and hence improving soil fertility. Cowpea is cultivated with other crops as it tolerates shade and also covers the ground quickly, preventing erosion. It is thus a valuable component of farming systems in areas where soil fertility is limiting. It is intercropped with cereals in rotation.Publication Nutritional and Technological Characteristics of New Cowpea (Vigna unguiculata) Lines and Varieties Grown in Eastern Kenya(Scientific Research Publishing, 2020-05) Biama Peter K.; Faraj Abdul K.; Mutungi Christopher M.; Osuga Isaac N.; Kuruma Rose W.Protein sources in the diet of people living in semi-arid land of Kenya are lacking and if available it is costly to them. In terms of safe food and a healthy food supply, cowpeas (Vigna unguiculata.) are a significant source of protein, carbohydrates, and minerals especially for poor populations in the Kenya, it is said to be poor man’s meat. The aim of this study was to determine nutritional composition of newly bred ten cowpea lines and five varieties commonly grown in Eastern Kenya of Kitui, Machakos and Makueni counties to understand their potential utilization in curbing rising food and nutrition insecurity in arid and semi-arid lands ASALs and in any other food applications in Kenya. The experiment was arranged in Completely Randomized Design (CRD) whereby proximate composition and minerals were determined using standard AOAC and AACC methods and technological characteristics checked using modified methods used by other researchers. Collected data were subjected to Analysis of Variance (ANOVA) using SAS (2006) version 9.1, mean separation was done using Tukey’s Honestly Significant Difference (HSD) method at 5% level of significance. Cowpeas composition ranged from 12.28% - 13.35% for moisture content, 49.37% - 55.74% for total carbohydrates, 2.99% - 3.34% for crude ash, 0.13% - 0.81% for crude lipids, 23.37% - 29.70% for crude protein and 1.40% - 4.34% for crude fibers. Cowpea samples recorded highest percentage of essential amino acids (60.71%) and non-essential amino acids (39.29%). Minerals ranged from 1.97 - 2.69 mg/100g for calcium, 3.23 - 3.90 mg/100g for magnesium, 205.53 - 223.30 mg/100g for sodium, 0.80 - 1.23 mg/100g for zinc, 1071.15 - 1152.62 mg/100g for potassium and 0.62 - 1.06 mg/100g for phosphorus. For technological properties, lines absorbed water equivalent to their weights and they were comparable to varieties grown in the region. From the results it showed that cowpea line IT97K-1042-3, TEXAN PINKIYE, TX123, IT85F-867-5, IT82D-889-1 and IT82D-889 have desirable attributes such as high crude protein contents, good water absorption capacities and volumetric expansion. They compared well with existing K80 variety. These cowpea lines could possibly be bred and combined into a single cowpea line and further improved by breeders to have other good properties such as higher levels of water absorption during soaking hence reduced cooking times. Therefore, this work has shown that cowpea lines developed can be used as food security crop, industrial food applications and enriching foods of low protein like in complementary foods for healthy food supply in Eastern Kenya.Publication An Economic Analysis of Grain Legumes Profitability in Nandi County, Kenya(Research in Agricultural & Applied Economics, 2016) Onyango Mercy; OtienoDavid Jakinda; Nyikal Rose Adhiambo; Ojiem JohnGrain legumes have great potential for improving smallholder farmers’ productivity in Sub Saharan Africa (SSA) though their potential has not been fully exploited due to critical problems including high insect pests and disease infestation. As part of the process of addressing these challenges, the Collaborative Crop Research Program (CCRP) of the McKnight Foundation in collaboration with Cornell University and Kenya Agricultural and Livestock Research Organization (KALRO) recently introduced crop and soil enhancing strategies in Western Kenya. One of the strategies introduced included use of multipurpose grain legumes species in Nandi County (Koibem, Kapkerer and Kiptaruswo sites). Through this initiative, various legume species including common bean, cowpea, groundnuts, lablab and soybean of different varieties are being promoted at the farm level. However, no empirical study has assessed the economic benefits that farmers are likely to obtain if they adopt the legume species. In order to address the aforementioned knowledge gap, the present study sought to evaluate economic proftitability from the production of grain legumes. Gross margins and profits were computed from farm-level data gathered from a random sample of 163 legume farmers in the above CCRP sites. Results showed that grain legumes species differed in terms of their gross margins; beans, groundnuts, cowpeas and soybean had positive gross margins while lablab had a .negative gross margin. Further, the farm-area under grain legumes, age of the farmer, access to extension services and access to credit had significant influence on the amount of gross margin obtained by a farmer. The results point to the need for recruitment of more extension staff at local levels to enhance extension service delivery. Also, there is need for the county government to promote credit awareness and establish credit associations, which can boost farmers’ access to creditPublication Seed Quality and Variety Preferences Amongst Potato Farmers in North-Western Kenya: Lessons for the Adoption of New Varieties(Springer Link, 2023-06-03) Kwambai, Thomas K.; Griffin, Denis; Struik, Paul C.; Stack, Laura; Rono, Selly; Brophy, Caroline; Nyongesa, Moses; Gorman, MonicaPotato (Solanum tuberosum L.) is an important commercialised food crop in Kenya. Recently, Kenya has realised a huge increase in the number of formally released potato varieties. The performance of these varieties is not clear and their adoption across various growing environments is low. This study explored how availability, access, quality and systems of seed and storability and market demand of potatoes influence farmers’ decisions on choice of varieties they grow and how they select seed for planting in the different seasons. Focus group discussions (83 farmers) and a household survey (225 farmers) were conducted in three major potato growing areas (Lelan, Saboti and Kaptama) in north-western Kenya. Results showed that farmers mainly used farm-saved seed and only 4.9% had used certified seed, while 71% indicated that certified seed was not available locally. Almost all farmers ensured they used healthy seed by visually examining the seed tubers while most farmers also examined the health of the crop in the field before harvest. Farmers renewed their seed depending on the number of cycles used, infection, decline in yield and availability of clean seed. Seed was usually renewed for up to after 5 years of recycling, and generally involved the varieties Shangi, Kabale and Arka. Farmers ranked five variety traits: tuber yield, disease resistance, market demand, early maturity and storability as most important in the choice of a variety. Farmers understood the importance of dormancy and had methods for managing dormancy, but their knowledge was biased to the few varieties they had, particularly Shangi, the predominant variety in the market. Despite agronomic attributes, market demand featured as a primary determinant of variety choice amongst farmers. The findings from this paper can guide use of seed, adoption of new varieties and future breeding of potato varieties for Kenya.Publication Understanding Genotype × Environment Interactions in Potato Production to Guide Variety Adoption and Future Breeding Strategies(Springer Link, 2023) Kwambai, Thomas K.; Struik, Paul C.; Gorman, Monica; Nyongesa, Moses; Rop, Wilfred; Kemboi, Edward; Griffin, DenisPotato (Solanum tuberosum L.) is a versatile crop given its adaptation, production capacity and utilization, and therefore valuable in many different countries. In Kenya, potato is mainly grown by smallholder farmers for food and cash. Access to quality seed of adapted and acceptable varieties was limited. This led to public–private partnerships with European seed companies working independently or with their Kenyan counterparts in introducing high-quality seed of new varieties. Some of these showed improved yield, quality and disease resistance. However, some European varieties were less adapted to the short photoperiods prevailing in Kenya than the late blight-resistant elite clones from South America, introduced by the International Potato Center (CIP). Traits that influence genotype adaptation can aid breeding cultivars or support their recommendation for certain production areas, but such traits have not been studied in detail for Kenya. This study sought to understand the adaptation of 50 contrasting genotypes from Europe, CIP and Kenya and the traits driving adaptation to four seasons and three altitudes. Genotypes showed a wide range of yields in all environments studied. The factor genotype explained most of the variance for total tuber yield (71.2%), plant height (49.3%) and area under the disease progress curve (25.1%) based on the Wald statistic, followed by season and the genotype by altitude interaction. Other traits studied hardly contributed to the understanding of the responses to the twelve testing environments. However, the largest proportions of variances for days to 50% emergence, days to maturity and canopy cover were accounted for by altitude.Publication Development of sequence-based markers for seed protein content in pigeonpea(Springer Link, 2018-09-01) Obala, Jimmy; Saxena, Rachit K.; Singh, Vikas K.; Kumar, C. V. Sameer; Saxena, K. B.; Tongoona, Pangirayi; Sibiya, Julia; Varshney, Rajeev K.Pigeonpea is an important source of dietary protein to over a billion people globally, but genetic enhancement of seed protein content (SPC) in the crop has received limited attention for a long time. Use of genomics-assisted breeding would facilitate accelerating genetic gain for SPC. However, neither genetic markers nor genes associated with this important trait have been identified in this crop. Therefore, the present study exploited whole genome re-sequencing (WGRS) data of four pigeonpea genotypes (~ 12X coverage) to identify sequence-based markers and associated candidate genes for SPC. By combining a common variant filtering strategy on available WGRS data with knowledge of gene functions in relation to SPC, 108 sequence variants from 57 genes were identified. These genes were assigned to 19 GO molecular function categories with 56% belonging to only two categories. Furthermore, Sanger sequencing confirmed presence of 75.4% of the variants in 37 genes. Out of 30 sequence variants converted into CAPS/dCAPS markers, 17 showed high level of polymorphism between low and high SPC genotypes. Assay of 16 of the polymorphic CAPS/dCAPS markers on an F2 population of the cross ICP 5529 (high SPC) × ICP 11605 (low SPC), resulted in four of the CAPS/dCAPS markers significantly (P < 0.05) co-segregated with SPC. In summary, four markers derived from mutations in four genes will be useful for enhancing/regulating SPC in pigeonpea crop improvement programs.Publication Frontiers | Genomics-assisted breeding for boosting crop improvement in pigeonpea (Cajanus cajan)(Frontiers Media, 2015-02-17) Pazhamala, Lekha; Saxena, Rachit K.; Singh, Vikas K.; Sameerkumar, C. V.; Kumar, Vinay; Sinha, Pallavi; Patel, Kishan; Obala, Jimmy; Kaoneka, Seleman R.; Tongoona, P.; Shimelis, Hussein A.; Gangarao, N. V. P. R.; Odeny, Damaris; Rathore, Abhishek; Dharmaraj, P. S.; Yamini, K. N.; Varshney, Rajeev K.Pigeonpea is an important pulse crop grown predominantly in the tropical and sub-tropical regions of the world. Although pigeonpea growing area has considerably increased, yield has remained stagnant for the last six decades mainly due to the exposure of the crop to various biotic and abiotic constraints. In addition, low level of genetic variability and limited genomic resources have been serious impediments to pigeonpea crop improvement through modern breeding approaches. In recent years, however, due to the availability of next generation sequencing and high-throughput genotyping technologies, the scenario has changed tremendously. The reduced sequencing costs resulting in the decoding of the pigeonpea genome has led to the development of various genomic resources including molecular markers, transcript sequences and comprehensive genetic maps. Mapping of some important traits including resistance to Fusarium wilt and sterility mosaic disease, fertility restoration, determinacy with other agronomically important traits have paved the way for applying genomics-assisted breeding (GAB) through marker assisted selection as well as genomic selection (GS). This would accelerate the development and improvement of both varieties and hybrids in pigeonpea. Particularly for hybrid breeding programme, mitochondrial genomes of cytoplasmic male sterile (CMS) lines, maintainers and hybrids have been sequenced to identify genes responsible for cytoplasmic male sterility. Furthermore, several diagnostic molecular markers have been developed to assess the purity of commercial hybrids. In summary, pigeonpea has become a genomic resources-rich crop and efforts have already been initiated to integrate these resources in pigeonpea breeding.Publication Estimation of General and Specific Combining Ability of Maize Inbred Lines Using Single Cross Testers for Earliness(Science and Education Publishing, 2018-03-13) Mbuvi, Benard; Mwimali, Murenga; Githiri, MwangiMaize (Zea mays L.) is third most consumed crop worldwide after rice and wheat. Maize is the main staple food in sub-Saharan Africa and Kenya, however, production has continuously been low over the past years. A line by tester analysis was carried out for 30 inbred lines and two testers to evaluate the GCA and SCA effects for yield and associated traits at three locations in Kenya during the 2016/2017 growing season. There were significant GCA and SCA mean squares indicating that both additive and non-additive gene effects contributed to the inheritance of the traits studied. Sum of squares of GCA was more than of SCA hence additive main effects contributed more to the inheritance of the traits than non-additive gene effects. Lines 1, 17, 6, 29 and 30 were good general combiners for grain yield. Testcrosses L30×T2 (4.40 t ha-1), L13×T1 (3.85 t ha-1), L20×T1 (3.59 t ha-1) and L9×T1 (3.52 t ha-1) yielded higher than best check mean and had good specific combining ability for grain yield and earliness in anthesis and silking dates. These genotypes can be evaluated further for grain yield and earliness and commercially released for use in areas with short rains.Publication Advancement and practical applications of rhizobacterial biofertilizers for sustainable crop production in sub-Saharan Africa(BioMed Central (BMC), 2021-12-13) Aloo, B. N.; Mbega, E. R.; Tumuhairwe, J. B.; Makumba, B. A.Agricultural intensification continues in Africa in attempts to meet the rising food demands of the equally rising population. However, most arable lands in the region are characterized by nutrient deficiency and over-reliance on synthetic fertilizers which consequently contributes to increased production costs, environmental pollution, and global warming. Decades of research on plant–rhizobacterial interactions have led to the formulation and commercialization of rhizobacterial biofertilizers globally for sustainable soil and crop health. Nevertheless, this promising technology has not received much attention in Africa and remains largely unexplored due to several constraints. This article discusses the practical applications of rhizobacterial biofertilizers for sustainable crop production in sub-Saharan Africa. The challenges of soil infertility and the use of conventional synthetic fertilizers in crop production in Africa are critically evaluated. An overview of the potential of rhizobacteria as biofertilizers and alternatives to synthetic fertilizers for soil fertility and crop productivity in the continent is also provided. The advantages that these biofertilizers present over their synthetic counterparts and the status of their commercialization in the African region are also assessed. Finally, the constraints facing their formulation, commercialization, and utilization and the prospects of this promising technology in the region are deliberated upon. Such knowledge is valuable towards the full exploitation and adoption of this technology for sustainable agriculture for Africa’s food security.Publication Genetic diversity and population structure of Plasmodium falciparum in Kenyan–Ugandan border areas(wiley publishers, 2019) Nderu, David; Kimani, Francis; Karanja, Evaline; Thiong'o, Kelvin; Akinyi, Maureen; Too, Edwin; Chege, William; Nambati, Eva; Wangai, Laura N.; Meyer, Christian G.; Velavan, Thirumalaisamy P.Kenya has, in the last decade, made tremendous progress in the fight against malaria. Nevertheless, continued surveillance of the genetic diversity and population structure of Plasmodium falciparum is required to refine malaria control and to adapt and improve elimination strategies. Twelve neutral microsatellite loci were genotyped in 201 P. falciparum isolates obtained from the Kenyan–Ugandan border (Busia) and from two inland malaria-endemic sites situated in western (Nyando) and coastal (Msambweni) Kenya. Analyses were done to assess the genetic diversity (allelic richness and expected heterozygosity, [He]), multilocus linkage disequilibrium () and population structure. A similarly high degree of genetic diversity was observed among the three parasite populations surveyed (mean He = 0.76; P > 0.05). Except in Msambweni, random association of microsatellite loci was observed, indicating high parasite out-breeding. Low to moderate genetic structure (FST = 0.022–0.076; P < 0.0001) was observed with only 5% variance in allele frequencies observed among the populations. This study shows that the genetic diversity of P. falciparum populations at the Kenyan–Ugandan border is comparable to the parasite populations from inland Kenya. In addition, high genetic diversity, panmixia and weak population structure in this study highlight the fitness of Kenyan P. falciparum populations to successfully withstand malaria control interventions.Publication Genetic Transformation of Sweet Potato for Improved Tolerance to Stress: A Review(IISTE, 2016-10) Imbo, Mary C.; Budambula, Nancy; Mweu, Cecilia M.; Muli, Joshua K.; Anami, Sylvester E.The sweet potato (Ipomoea batatas Lam) is a major staple food in many parts of the world. Sweet potato leavesand tubers are consumed as food and livestock feed. Biotic and abiotic stresses affect yield leading to a reductionin production. This review analyzes factors limiting sweet potato production and the progress made towardsstress tolerance using genetic transformation. Genetic transformation could enhance yield, nutritional value andtolerance to stress. Transgenic sweet potatoes tolerant to biotic and abiotic stress, improved nutritional value andhigher yields have been developed. Sweet potato expressing the endotoxin cry8Db, cry7A1 and cry3Ca genesshowed lower sweet potato weevil infestation than non-transformed lines. Transgenic cultivar ‘Xushu18’expressing the oryzacystatin-1 (OC1) gene showed enhanced resistance to sweet potato stem nematodes. Sweetpotato line ‘Chikei 682-11’ expressing the coat protein (CP) exhibited resistance to the sweet potato featherymottle virus (SPFMV). Transgenics expressing the rice cysteine inhibitor gene oryzacystatin-1 (OC1) alsoexhibited resistance to the SPFMV. Transgenic cultivar ‘Kokei’ expressing the spermidine synthetase geneFSPD1 had higher levels of spermine in the leaves and roots, and displayed enhanced tolerance to drought andsalt stress. ‘Shangshu’ variety expressing the IbMas has shown enhanced tolerance to salt stress. Transgenic‘Lixixiang’ expressing IbMIPSI showed an up-regulation of metabolites involved in stress response to drought,salinity and nematode infestation. Transgenic ‘Yulmi’ sweet potato transformed with copper/zinc superoxidedismutase (CuZnSOD) gene showed an enhanced tolerance to methyl viologen induced oxidative and chillingstress. Similarly, transformation of cultivar ‘Sushu-2’ with betaine aldehyde dehydrogenase (BADH) generesulted in transgenics tolerant to salt, chilling and oxidative stress. Sweet potato varieties ‘Kokei14’ and ‘Yulmi’transformed with the bar gene were shown to be tolerant to application of the herbicide Basta. The developmentof stress tolerant varieties will immensely increase the area under sweet potato production and eventuallypromote the adoption of sweet potato as a commercial crop. Sweet potato research and breeding for stresstolerance still faces technical and socio-political hurdles. Despite these challenges, genetic transformationremains a viable method with immense potential for the improvement of sweet potato.Publication Identification of drought tolerant Kenyan brachiaria ecotypes using drought tolerance indices(Taylor & Francis., 2023-06) Awalla, B. J.; Were, B. A.; Binnot, J.Drought is one of the major abiotic stress factors limiting agricultural productivity globally. Brachiaria also known as signal grass is a native of sub-tropical and tropical Africa and important in livestock production. The grass has many advantages including; high biomass, high nutritional value, adaptation to drought and low fertility soils, sequestration of carbon, enhanced nitrogen uses efficiency and low greenhouse gas emissions. Emergence of climate change with increased global temperatures has led to prolonged drought which has adversely affected the improved Brachiaria hybrids. Locally available ecotypes are a rich source of unique genes and characteristics that could be key in developing drought resilient hybrids. The objectives of this study were to i) assess the effectiveness of various indices in selection of drought tolerant Kenyan Brachiaria ecotypes, ii) evaluate the relationship between the indices and iii) to identify high yielding and stable ecotypes under stressed condition. The design of the experiment was completely randomized design (CRD) with three replications in a factorial arrangement (3 x 25). A total of 11drought tolerance indices; tolerance (TOL), stress Tolerance Index (STI), mean productivity (MP), yield stability index (YSI), Geometric Mean Productivity (GMP), stress susceptibility index (SSI), Yield Index (YI), harmonic Mean (HM), drought intensity index (DII), modified stress tolerance k1 and modified stress tolerance k2 were calculated based on shoot biomass production under non-stressed (YP) and stressed (YS) conditions. Rank means, rank sum and standard deviation were also used to identify the tolerant materials. In the previous experiment, various physiological parameters were scored which included; leaf relative water content, relative chlorophyll content using SPAD -502 Chlorophyll meter (Minota Co), leaf fresh weight, leaf dry weight and leaf relative water content. Relative water content was also estimated and comparative scores were done between control, medium and extreme or water deficit experiments. Based on all the indices and ranking, BrK 1, BrK 6, BrK 7, BrK13 and BrK 18 were the most tolerant in stressed condition. These ecotypes can be recommended for planting in areas prone to drought. More studies on the identified tolerant ecotypes are essential to ascertain whether the materials hold unique genes that could later be introgressed into various breeding schemes to confer tolerance.Publication Determination of the Effect of the System of Rice Intensification (SRI) on Rice Yields and Water Saving in Mwea Irrigation Scheme, Kenya(Multidisciplinary Digital Publishing Institute, 2014-07-28) Omwenga, Kepha G.; Mati, Bancy M.; Home, Patrick G.Irrigated rice cultivation has long been associated with large amounts of water. Currently convectional rice production is faced with major challenges of water shortage as a result of increasing population sharing the same water resources, as well as global environmental changes. The System of Rice Intensification (SRI), as opposed to conventional rice production, involves alternate wetting and drying (AWD) of rice fields. The objective of this study was to determine the optimum drying days period of paddy fields that has a positive effect on rice yields and the corresponding water saving. The experimental design used was randomized complete block design (RCBD). Four treatments and the conventional rice irrigation method were used. The treatments were the dry days allowed after draining the paddy under SRI before flooding again. These were set as 0, 4, 8, 12 and 16 day-intervals. Yield parameters were monitored during the growth period of the crop where a number of tillers, panicles, panicle length and panicle filling were monitored. Amount of water utilized for crop growth for each treatment was measured. Average yield and corresponding water saving were determined for each treatment. The results obtained show that the 8 days drying period gave the highest yield of 7.13 tons/ha compared with the conventional method of growing rice which gave a yield of 4.87 tons/ha. This was an increase of 46.4% above the conventional method of growing rice. Water saving associated with this drying regime was 32.4%. This was taken as evidence that SRI improved yields with reduction in water use.
Publication A virus-induced gene silencing (VIGS) system for functional genomics in the parasitic plant Striga hermonthica(springer, 2014-06-03) Kirigia, Dinah; Runo, Steven; Alakonya, AmosStriga hermonthica is a hemiparasitic weed that infects cereals in Sub Sahara Africa (SSA) resulting in up to 100% grain yield loss. This significant loss in grain yields is a major contributor to food insecurity and poverty in the region. Current strategies to control the parasite are costly, unavailable and remain unpracticed by small-scale farmers, underscoring the need for more economical and sustainable control strategies. Development of resistant germplasm is the most sustainable strategy in the control of S. hermonthica, but is constrained by paucity of resistance genes for introduction into crop germplasm. RNA interference (RNAi) has potential for developing host-derived resistance against S. hermonthica by transformation of host crops with RNAi sequences targeted at critical Striga genes. The application of RNAi in management of S. hermonthica is however constrained by lack of efficient high throughput screening protocols for the candidate genes for silencing, as well as sub optimal delivery of siRNAs into the parasite. In comparison to stable transformation, viral induced gene silencing (VIGS) is a rapid and powerful tool for plant functional genomics and provides an easy and effective strategy in screening for putative candidate genes to target through RNAi. In addition, VIGS allows for a secondary amplification of the RNAi signal increasing the siRNA threshold and facilitates siRNA transport through viral movement proteins. We tested the efficiency of the Tobacco rattle virus (TRV1 and TRV2) VIGS vectors in silencing S. hermonthica phytoene desaturase (PDS) gene through agrodrench and agro-infiltration.Publication Seed Quality and Variety Preferences Amongst Potato Farmers in North-Western Kenya: Lessons for the Adoption of New Varieties(Springer, 2023-04-16) Kwambai, Thomas K.; Griffin, Denis; Struik, Paul C.; Stack, Laura; Rono, Selly; Brophy, Caroline; Nyongesa, Moses; Gorman, MonicaPotato (Solanum tuberosum L.) is an important commercialised food crop in Kenya. Recently, Kenya has realised a huge increase in the number of formally released potato varieties. The performance of these varieties is not clear and their adoption across various growing environments is low. This study explored how availability, access, quality and systems of seed and storability and market demand of potatoes infuence farmers’ decisions on choice of varieties they grow and how they select seed for planting in the diferent seasons. Focus group discussions (83 farmers) and a household survey (225 farmers) were conducted in three major potato growing areas (Lelan, Saboti and Kaptama) in north-western Kenya. Results showed that farmers mainly used farm-saved seed and only 4.9% had used certifed seed, while 71% indicated that certifed seed was not available locally. Almost all farmers ensured they used healthy seed by visually examining the seed tubers while most farmers also examined the health of the crop in the feld before harvest. Farmers renewed their seed depending on the number of cycles used, infection, decline in yield and availability of clean seed. Seed was usually renewed for up to after 5 years of recycling, and generally involved the varieties Shangi, Kabale and Arka. Farmers ranked fve variety traits: tuber yield, disease resistance, market demand, early maturity and storability as most important in the choice of a variety. Farmers understood the importance of dormancy and had methods for managing dormancy, but their knowledge was biased to the few varieties they had, particularly Shangi, the predominant variety in the market. Despite agronomic attributes, market demand featured as a primary determinant of variety choice amongst farmers. The fndings from this paper can guide use of seed, adoption of new varieties and future breeding of potato varieties for Kenya.