Browsing by Author "Tumwegamire, Silver"

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    Evaluation of the American Yam Bean (Pachyrhizus spp.) for Storage Root Yield Across Varying Eco-geographic Conditions in Uganda
    (Journal of Agricultural Science, 2019) Andiku, Charles; Tukamuhabwa, Phinehas; Mukasa Ssebuliba, James; Talwana, Hebert; Tumwegamire, Silver; Grüneberg, Wolfgang J.
    The American yam bean (Pachyrhizus spp.) is a legume crop that is exclusively used for its storage roots. The seeds are inedible due to presence of toxic rotenone. It produces high storage root yields comparable of major root crops like cassava or sweetpotato. And flower pruning more than doubles its root yield performance. Using twenty five yam bean accessions, the current study aimed to determine root yield stability and adaptability, and presence of yam bean production mega environments in Uganda. Trials were planted at three stations, Namulonge, Serere, and Kachwekano during two consecutive seasons of 2011. Fresh storage root yields were significantly different (p < 0.05) across locations with the ideal location being Namulonge (fresh storage root yield of 10.1 t ha-1), followed by Serere (8.0 t ha-1), and Kachwekano (3.1 t ha-1). Results of AMMI analysis indicated the presence of genotype-by-environment interaction for fresh storage root yield. Through AMMI estimates and GGE visual assessment, genotype 209017 was the highest yielding with mean yield of 20.7 t ha-1. Genotype 209018 with mean yield of 15.5 t ha-1 was the most stable and adapted accession in the entire discriminating environment in Uganda. From the environmental focusing plot, the six environments were grouped into two putative mega environments for yam bean production.
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    Exchanging and managing in-vitro elite germplasm to combat Cassava Brown Streak Disease (CBSD) and Cassava Mosaic Disease (CMD) in Eastern and Southern Africa
    (Food Security, 2018) Tumwegamire, Silver; Kanju, Edward; Legg, James; Shirima, Rudolph; Kombo, Salehe; Mkamilo, Geoffrey; Mtunda, Kiddo; Sichalwe, Karoline; Kulembeka, Heneriko; Ndyetabura, Innocent; Saleh, Haji; Kawuki, Robert; Alicai, Titus; Adiga, Gerald; Benesi, Ibrahim; Mhone, Albert; Zacarias, Anabela; Fenias Matsimbe, Sofrimento; Munga, Theresia; Ateka, Elijah; Navangi, Lynet; Narasegowda Maruthi, Midatharahally; Mwatuni, Francis; Ngundo, George; Mwangangi, Maureen; Mbugua, Edward; Ndunguru, Joseph; Rajabu, Cyprian; Mark, Deogratius
    Cassava varieties resistant to cassava mosaic disease (CMD) and cassava brown streak disease (CBSD) are needed for the food and income security of the rural poor in eastern and southern Africa (ESA). The International Institute of Tropical Agriculture led five national cassava breeding programs (Malawi, Mozambique, Kenya, Tanzania and Uganda) in virus-cleaning and exchanging elite cassava germplasm resistant to both diseases. This paper documents the experiences and lessons learned from the process. Thirty-one clones (25 elite, two standard and four national) were submitted by the five breeding programs to the Natural Resources Institute and Kenya Plant Health Inspectorate Services for virus cleaning and indexing. Subsequently, ca 75 invitro virus-indexed plantlets per clone were sent to Genetic Technologies International Limited (GTIL), a private tissue culture (TC) lab in Kenya, and micro-propagated to produce ≥1500 plantlets. After fulfilling all the formal procedures of germplasm exchange between countries ≥300 plantlets per clone were sent to each partner country. National check clones susceptible to CMD/CBSD were sent only to their countries of origin. In each country, the in-vitro plantlets were acclimatized under screen house conditions and transferred to clean isolated sites for field multiplication. All the clones were cleaned of the viruses, except Tomo. The cleaning process was slow for F19-NL, NASE1, and Kibandameno and TC micro-propagation at GTIL was less efficient for Pwani, Tajirika, NASE1, and Okhumelela than for the other clones. Difficulties in cleaning recalcitrant clones affected the timeline for establishing the multi-site evaluation trials in target countries. The initiative is the one of the kind to successfully clean and exchange elite germplasm as a joint action to combat CBSD in ESA. Adequate preparation in terms of infrastructure and personnel are critical to successfully receiving and adapting the indexed in-vitro plants as new germplasm.
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    Physicochemical Characteristics of Yam Bean (Pachyrhizus erosus) Seed Proteins
    (Journal of Food Research, 2014) Kisambira, Abbas; Muyonga, John H.; Byaruhanga, Yusuf B.; Tukamuhabwa, Phinehas; Tumwegamire, Silver; Gruenberg, Wolfgang
    This study sought to determine the physicochemical and functional properties of yam bean (Pachyrhizus erosus) seed proteins. Pachyrhizus erosus seeds from two accessions (UYB 06 and UYB 07) were milled into flours and then defatted. A portion of the defatted flour was used for production of protein isolates and protein fractions. The physicochemical and functional properties, in vitro digestibility and electrophoretic pattern of the flour and protein isolate were determined. The results showed that albumins (53.3%) were the dominant protein fraction followed by globulins (18.7%), glutelins (8.8%) and prolamins (2.7%). Regarding functional properties, the Pachyrhizus erosus seed protein isolates exhibited 8% of least gelation concentration, water absorption capacity of 3.0 g g-1, oil absorption capacity of 0.8 g g-1, protein solubility of 81.0%, foaming capacity of 37.1%, foam stability of 73.8%, emulsion activity of 13.8% and emulsion stability of 9.2%. In vitro protein digestibility of the raw and cooked beans was 87.6% and 84.3%, respectively. The electrophoretic pattern of Pachyrhizus erosus protein showed major bands corresponding to molecular weight 13.3, 15, 29.8, 54.4 and above 84.7 kDa. The results, suggest that Pachyrhizus erosus seed protein has potential for use in both food and non-food applications such as films and coating.