Browsing by Author "Baguma, Yona"
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Item African Cassava Whitefly, Bemisia tabaci, Resistance in African and South American Cassava Genotypes(Journal of integrative agriculture, 2012) Omongo, Christopher A.; Kawuki, Robert; Bellotti, Antony C.; Alicai, Titus; Baguma, Yona; Maruthi, M. N.; Bua, Anton; Colvin, JohnThe whitefly, Bemisia tabaci, is a major pest of cassava, particularly in Africa where it is responsible both for the transmission of plant viruses and, increasingly, for direct damage due to feeding by high populations. To date, there have been no practical solutions to combat this emerging problem, due to the inability of the subsistence farmers that grow cassava to afford expensive inputs such as insecticides. A programme of research was carried out linking institutes in Africa, the UK and South America, to identify possible resistance sources in cassava to the whitefly, Bemisia tabaci. The South American genotype MEcu 72 and several Ugandan cassava landraces including Ofumba Chai, Nabwire 1 and Mercury showed good levels of resistance to B. tabaci. Field and screen-house experiments showed that all of the improved, high-yielding cassava mosaic disease (CMD) resistant cassava genotypes assessed were highly susceptible to B. tabaci and supported high populations of all life stages. These data support the hypothesis that the continuing high populations of cassava B. tabaci in Uganda are due, in part, to the widespread adoption of CMD-resistant cassava varieties during the CMD pandemic. They also show that the whitefly, Aleurotrachelus socialis, resistance present in the South American cassava genotypes could have broader applicability in the Old World.Item Effect of drought early warning system on household food security in Karamoja subregion, Uganda(Agriculture & Food Security, 2017) Akwango, Damalie; Bonton Obaa, Bernard; Turyahabwe, Nelson; Baguma, Yona; Egeru, AnthonyDrought is regarded as a leading cause of food insecurity affecting about 220 million people in sub- Saharan Africa. Drought early warning systems (DEWSs) have the potential to strengthen capacity of communities in managing and reducing drought effects through building preparedness and providing coping strategies. The Karamoja subregion is the only region with a functional DEWS in Uganda. The subregion suffers from effects of recurrent episodes of drought with negative impacts on food security. Despite having DEWS in place, the subregion remains the most food insecure in the country. The extent to which DEWS has contributed to household food security in the subregion remains unclear. This study determined the effect of DEWS on agro-pastoral household food security in the subregion. The study was conducted in Nakapiripirit and Kotido districts of the Karamoja. A cross-sectional survey was conducted among 305 participating and non-participating households in DEWS. The effect of participating in DEWS on food security was analyzed using the generalized linear model. The level of food security and nutrition were measured using the household food insecurity access score and household dietary diversity score (HDDS), respectively. Results: Findings showed that all respondents had experienced food insecurity during the course of the year. Drought was indicated as the main cause of food insecurity in the households. Participation in DEWS significantly (p < 0.01) reduced the threat of food insecurity by 23.7% and increased the level of household nutrition by 30%. Better nutrition was realized in DEWS participating households (HDDS = 9.0) compared to non-participating households (HDDS = 6.6). Conclusion: Owing to intermittent drought events in the Karamoja subregion, DEWS contributes to household food security and nutrition by providing households with information on timely planting, crop diversification, farm equipment, drought management and drought-tolerant crop varieties. There is need for DEWS practitioners to focus on information dissemination, provision of drought-tolerant crops and provision of training opportunities to communities for increased production in semi-arid areas.Item Eleven years of breeding efforts to combat cassava brown streak disease(Breeding Science, 2016) Sezi Kawuki, Robert; Kaweesi, Tadeo; Esuma, Williams; Pariyo, Anthony; Kayondo, Ismail Siraj; Ozimati, Alfred; Kyaligonza, Vincent; Abaca, Alex; Orone, Joseph; Tumuhimbise, Robooni; Nuwamanya, Ephraim; Abidrabo, Philip; Amuge, Teddy; Ogwok, Emmanuel; Okao, Geoffrey; Wagaba, Henry; Adiga, Gerald; Alicai, Titus; Omongo, Christopher; Bua, Anton; Ferguson, Morag; Kanju, Edward; Baguma, YonaCassava (Manihot esculenta Crantz) production is currently under threat from cassava brown streak disease (CBSD), a disease that is among the seven most serious obstacles to world’s food security. Three issues are of significance for CBSD. Firstly, the virus associated with CBSD, has co-evolved with cassava outside its center of origin for at least 90 years. Secondly, that for the last 74 years, CBSD was only limited to the low lands. Thirdly, that most research has largely focused on CBSD epidemiology and virus diversity. Accordingly, this paper focuses on CBSD genetics and/or breeding and hence, presents empirical data generated in the past 11 years of cassava breeding in Uganda. Specifically, this paper provides: 1) empirical data on CBSD resistance screening efforts to identify sources of resistance and/or tolerance; 2) an update on CBSD resistance population development comprising of full-sibs, half-sibs and S1 families and their respective field performances; and 3) insights into chromosomal regions and genes involved in CBSD resistance based on genome wide association analysis. It is expected that this information will provide a foundation for harmonizing on-going CBSD breeding efforts and consequently, inform the future breeding interventions aimed at combating CBSD.Item Evaluation of Ugandan cassava germplasm for drought tolerance(2013) Turyagyenda, F. Laban; Kizito, Elizabeth B.; Baguma, Yona; Osiru, DavidIncreased pressure on prime arable land for agriculture to meet food demand for global population has resulted in shifting agriculture to marginal areas where drought is frequent. Focusing research towards development of drought tolerant varieties is thus necessary. Replicated field trials for farmer preferred cassava genotypes were established to evaluate their morphological and yield trait responses and adaptability to moisture stress. Results showed significant (P<0.05) differences among genotypes for all the parameters evaluated. Moisture stress resulted in a decline in Harvest Index by 22.34%, Fresh Root Yield by 37.04%, Number of Roots by 19.43%, Dry matter content by 16.58%, Root starch content of 20.81%, Leaf Retention by 25.72% and Plant height by 16.62%. Results therefore, evidently showed that water stress has significant devastating effects on vegetative and yield parameters of cassava. Breeding strategies to develop drought tolerant cassava varieties to cope up with increased water scarcity and semi-arid conditions are thus paramount. Varietal variability in response to water stress reported is a cornerstone in the breeding process. Besides genetic effects were dominant indicating breeding objectives would be easily achieved. Genotypes MH96/0686, Magana, Yellow, TME 204, Nyamutukura, MH97/2961, NASE 1, NASE 2 and NASE 12 were least affected by drought and may provide gene sources for cassava improvement. Genotype x Location was significant (P<0.05) suggesting that rational distribution of genotypes to agro-ecological zones with different levels of drought stress is possible. Some genotypes had stable yield and its components suggesting that cassava can easily adapt to dry environments.Item Expansion of the cassava brown streak pandemic in Uganda revealed by annual field survey data for 2004 to 2017(Scientific Data, 2019) Alicai, Titus; Szyniszewska, Anna M.; Omongo, Christopher A .; Abidrabo, Phillip; Okao-Okuja, Geoffrey; Baguma, Yona; Ogwok, Emmanuel; Kawuki, Robert; Esuma, Williams; Tairo, Fred; Bua, Anton; Legg, James P.; Stutt, Richard O. J. H.; Godding, David; Sseruwagi, Peter; Ndunguru, Joseph; Gilligan, Christopher A.Cassava brown streak disease (CBSD) is currently the most devastating cassava disease in eastern, central and southern Africa affecting a staple crop for over 700 million people on the continent. A major outbreak of CBSD in 2004 near Kampala rapidly spread across Uganda. In the following years, similar CBSD outbreaks were noted in countries across eastern and central Africa, and now the disease poses a threat to West Africa including Nigeria - the biggest cassava producer in the world. A comprehensive dataset with 7,627 locations, annually and consistently sampled between 2004 and 2017 was collated from historic paper and electronic records stored in Uganda. The survey comprises multiple variables including data for incidence and symptom severity of CBSD and abundance of the whitefly vector (Bemisia tabaci). This dataset provides a unique basis to characterize the epidemiology and dynamics of CBSD spread in order to inform disease surveillance and management. We also describe methods used to integrate and verify extensive field records for surveys typical of emerging epidemics in subsistence crops.Item Flowering problems and their possible solution in cassava breeding(Journal of Scientific Agriculture, 2020) Ibrahim, Yasmin; Baguma, Yona; Abincha, Wilfred; Gibson, Paul; Edema, Richard; Bisikwa, JenipherSix elite cassava clones were chosen from cassava breeding program at the National Crops Resource Research Institute (NaCRRI) based on their flowering characteristics and seed set. The clones were planted in randomized complete block experimental design with 3 replications. The floral biology of these cassava clones were studied, focusing on morphological traits and developmental timing. Since cassava develops branches in levels, data was sourced from the 1st level of branching through the 4th level of branching. The result indicated that days to branching generally varied among all the genotypes studied, indicating the need to use different planting dates for different genotypes to ensure synchronization of flowering. The time difference among genotypes from branching to visible inflorescence was not larger than one and a half days and this difference did not seem be a factor for synchronization. The general number of female flowers was low in all genotypes across branching levels. This suggests there is a need to apply techniques that could enhance flowering in cassava. Conversely, the number of male flowers outnumbered the female flowers, suggesting that male flower production may not be a limiting factor to hybrid seed production. Male flower opened 20 to 30 days later after the opening of the female flowers. This calls for delayed planting of the early flowering genotypes when used as female parent. It was recommended that in order to synchronize flowering, the late flowering genotypes have to be planted ahead of the early flowering genotypes. In addition, applying techniques such as growth regulators, red light and finding the most optimal locations for flowering is recommended for further study as a way of enhancing flowering among cassava genotypes.Item Genetic Relationships of Cassava Genotypes That are Susceptible or Tolerant to Cassava Brown Streak Disease in Uganda(Journal of Agricultural Science, 2013) Abaca, Alex; Kawuki, Robert; Tukamuhabwa, Phenihas; Baguma, Yona; Pariyo, Anthony; Alicai, Titus; Omongo, C. Christopher; Abidrabo, Phillips; Katono, Kasifa; Bua, AntonA total of 99 cassava genotypes whose field reaction to cassava brown streak disease (CBSD) was known, were assayed with 30 simple sequence repeat (SSR) markers to establish their genetic parallels. Two categories of CBSD reaction were considered: CBSD-susceptible genotypes (characterized by > 60% root and foliar CBSD incidence), and CBSD-tolerant genotypes (characterized by < 15% root and foliar CBSD incidence). DNA was extracted from leaf samples using the miniprep method and genotyped using ABI 3730 DNA sequencer. The test genotypes at 0.02 similarity coefficient, CBSD-tolerant and CBSD-susceptible genotypes clustered into 5 main sub-clusters. When data were subjected to principle component analysis (PCA) irrespective of the CBSD reaction grade, the first three principal components accounted for 68% of the total genetic variation. Despite having different number of individuals, the observed heterozygosity (Ho) for CBSD-susceptible (Ho = 0.58) and CBSD-tolerant (Ho = 0.66) were comparable and provide scope for long-term CBSD breeding and/or gene tapping.Item In vitro embryo rescue and plant regeneration following self-pollination with irradiated pollen in cassava (Manihot esculenta Crantz)(African Journal of Biotechnology, 2015) Buttibwa, Mary; Kawuki, Robert S.; Tugume, Arthur K.; Akol, Jacinta; Magambo, Stephen; Apio, Hellen; Heberle-Bors, Erwin; Wedzony, Maria; Ceballos, Hernán; Hershey, Clair; Baguma, YonaCassava is a highly heterozygous species; hence, current methods used in classical cassava breeding cannot match the urgent need to high yielding varieties. Recently, progress was made through androgenesis and gynogenesis as pathways for raising doubled cassava haploid lines to overcome problems associated with cassava’s inherent reproductive biology, but these efforts were limited (no candidate cassava plantlets were regenerated). For the first time, this study shows that pollen irradiation coupled with self-pollination and embryo rescue regenerated 62 candidate cassava plantlets. Plants of an elite cassava variety, Nase14, served as a mother plant and as the pollen donor for the irradiation. Irradiation dosages of 50 to 250 Gray studied across five pollination events and 300 or 500 Gray in one pollination event caused a reduction in pollen germination up to 67.0%. By 15 days after pollination (DAP) with irradiated pollen, up to 89.7% of the pollinated flowers had aborted. By embryo rescue time (42 DAP), significant differences were observed in number of fruits, seeds and embryos generated, with the non-irradiated pollen treatments having significantly higher numbers. Sixteen (16) heterozygous SSR markers in the parent and ploidy analysis showed that none of the regenerated plants was haploid or homozygous. However, the plantlets resulting from pollination with non-irradiated pollen had 56.2% homozygous loci, while progeny derived from irradiated treatments had frequencies of homozygous loci between 28.1 and 55.0%. This is the first time to use irradiated pollen in cassava as a pathway to generate candidate plantlets as an initial step in double haploid production.Item Performance of Bt maize event MON810 in controlling maize stem borers Chilo partellus and Busseola fusca in Uganda(Crop Protection, 2022) Otim, Michael H.; Alibu, Simon; Asea, Godfrey; Abalo, Grace; Sserumaga, Julius Pyton; Adumo, Stella; Alupo, Jane O. Oikeh; Ochen, Stephen; Tefera, Tadele; Bruce, Anani Y.; Beyene, Yoseph; Meisel, Barbara; Tende, Regina; Nang’ayo, Francis; Baguma, Yona; Mugo, Stephen; Oikeh, Sylvester O.Stem borers are major insect pests of maize in Uganda. A study was conducted in 2014–2016 to assess the performance of Bt hybrids expressing Cry1Ab (event MON810) against the two major stem borer species in Uganda – the African stem borer (Busseola fusca) and the spotted stem borer (Chilo partellus) – under artificial infestation. The study comprised 14 non-commercialized hybrids, including seven pairs of Bt and non-Bt hybrids (isolines), three non-Bt commercial hybrids and a conventional stem borer resistant check. All stem borer damage parameters (leaf damage, number of internodes tunneled and tunnel length) were generally significantly lower in Bt hybrids than in their isolines, the conventionally resistant hybrid, and local commercial hybrids. Mean yields were significantly higher by 29.4–80.5% in the Bt hybrids than in the other three categories of non-Bt hybrids. This study demonstrated that Bt maize expressing Cry1Ab protects against leaf damage and can limit entry of stem borers into the stems of maize plants, resulting in higher yield than in the non-transgenic hybrids. Thus, Bt maize has potential to contribute to the overall management package of stem borers in Uganda.Item Physiological and molecular characterization of drought responses and identification of candidate tolerance genes in cassava(AoB plants, 2013) Turyagyenda, Laban F.; Kizito, Elizabeth B.; Ferguson, Morag; Baguma, Yona; Agaba, Morris; Harvey, Jagger J. W.; Osiru, David S. O.Cassava is an important root crop to resource-poor farmers in marginal areas, where its production faces drought stress constraints. Given the difficulties associated with cassava breeding, a molecular understanding of drought tolerance in cassava will help in the identification of markers for use in marker-assisted selection and genes for transgenic improvement of drought tolerance. This study was carried out to identify candidate drought-tolerance genes and expression-based markers of drought stress in cassava. One drought-tolerant (improved variety) and one drought-susceptible (farmer-preferred) cassava landrace were grown in the glasshouse under well-watered and water-stressed conditions. Their morphological, physiological and molecular responses to drought were characterized. Morphological and physiological measurements indicate that the tolerance of the improved variety is based on drought avoidance, through reduction of water loss via partial stomatal closure. Ten genes that have previously been biologically validated as conferring or being associated with drought tolerance in other plant species were confirmed as being drought responsive in cassava. Four genes (MeALDH, MeZFP, MeMSD and MeRD28) were identified as candidate cassava drought-tolerance genes, as they were exclusively up-regulated in the drought-tolerant genotype to comparable levels known to confer drought tolerance in other species. Based on these genes, we hypothesize that the basis of the tolerance at the cellular level is probably through mitigation of the oxidative burst and osmotic adjustment. This study provides an initial characterization of the molecular response of cassava to drought stress resembling field conditions. The drought-responsive genes can now be used as expression-based markers of drought stress tolerance in cassava, and the candidate tolerance genes tested in the context of breeding (as possible quantitative trait loci) and engineering drought tolerance in transgenics.Item Production of friable embryogenic callus and regeneration of Ugandan farmer-preferred cassava genotypes(African Journal of Biotechnology, 2015) Apio, Hellen B.; Alicai, Titus; Baguma, Yona; Mukasa, Settumba B.; Bua, Anton; Taylor, NigelGeneration of embryogenic callus is a key step in genetic engineering of many crop species, including cassava. Protocols for generation of friable embryogenic callus (FEC) have been lacking for Ugandan cassava genotypes, thereby delaying their genetic engineering for agronomic and other desirable traits. The objective of this study was to determine conditions suitable for production and regeneration of FEC in the Ugandan cassava genotypes; Aladu, Bukalasa and Ebwanateraka, and control cultivar 60444. Immature leaf lobe explants were established on Murashige and Skoog (MS) based media for initiation of organized embryogenic callus (OES). To produce FEC, resulting OES were established on Gresshoff and Doy based callus induction media with varying levels of sucrose, maltose, tyrosine, tryptophan, naphthalene acetic acid (NAA) under light and dark conditions. Subsequently, FEC was subcultured to MS-based embryo maturation and embryo regeneration media. All genotypes produced OES. All genotypes produced FEC except Bukalasa. The amino acid tyrosine favoured production of FEC in Aladu and Ebwanatereka, but not in 60444, while 20 g/L of sucrose trigged production of FEC in Aladu and 60444, but 40 g/L of sucrose was superior for Ebwanatereka. Media supplemented with 1 ml/L naphthalene acetic acid NAA facilitated embryo regeneration in Ebwanatereka and 60444, while Aladu responded better to 5 ml/L NAA. Light, tyrosine and sucrose were essential for FEC production in Uganda cultivars while NAA was required for regeneration of somatic embryos. Ability to produce FEC in these genotypes lays a foundation for their improvement through genetic transformation for the desired and agronomic traits.Item Stability of Solanum aethiopicum Shum accessions under varied water deficit stress levels and identification of pertinent breeding traits for resistance to water shortage(Euphytica, 2018) Sseremba, Godfrey; Tongoona, Pangirayi; Yaw Eleblu, John Savior; Danquah, Eric Yirenkyi; Kaweesi, Tadeo; Baguma, Yona; Masanza, Michael; Balyejusa Kizito, ElizabethDrought is a major constraint to productivity of Solanum aethiopicum ‘Shum’ group due to loss in market and nutrient value of stressed plants. This study evaluated S. aethiopicum Shum group accessions to identify genotypes (G) that excel across moisture deficit stress levels (WLs). A split-plot arrangement composed of four WLs and twenty accessions of S. aethiopicum as main plot and subplot factors, respectively, was implemented in a screenhouse, and repeated for two experiments. In each experiment, there was a highly significant effect of at least two WLs on mean performance among at least two accessions for most of the traits at p\0.05. Further, very highly significant WL 9 G interactions were obtained for leaf relative water content (LRWC), leaves per plant (LPP) and plant height (PH), and nonsignificant for leaf blade length and leaf blade width. The order of priority as breeding traits for stability superiority across WLs was suggested as LRWC[PH[LPP. Consequently, based on LRWC, the most superiorly stable accessions were identified as accession 160 followed by accessions 145, 137, 108P and 184G while the least stable ones were identified as accessions 163G, 141, 163 and 108. The broad sense heritability (H2) for each of the three recommended traits for drought resistance breeding was above 0.9 thus supportive for a good response to selection. Drought stress negatively affected the performance of S. aethiopicum Shum group but the exhibited variation allowed for selection of superiorly stable genotypes.