Browsing by Author "Kubiriba, Jerome"
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Item Agrobacterium tumefaciens-Mediated Transformation of Pseudocercospora fijiensis to Determine the Role of PfHog1 in Osmotic Stress Regulation and Virulence Modulation(Frontiers in Microbiology, 2017) Onyilo, Francis; Tusiime, Geoffrey; Chen, Li-Hung; Falk, Bryce; Stergiopoulos, Ioannis; Tripathi, Jaindra N.; Tushemereirwe, Wilberforce; Kubiriba, Jerome; Changa, Charles; Tripathi, LeenaBlack Sigatoka disease, caused by Pseudocercospora fijiensis is a serious constraint to banana production worldwide. The disease continues to spread in new ecological niches and there is an urgent need to develop strategies for its control. The high osmolarity glycerol (HOG) pathway in Saccharomyces cerevisiae is well known to respond to changes in external osmolarity. HOG pathway activation leads to phosphorylation, activation and nuclear transduction of the HOG1 mitogen-activated protein kinases (MAPKs). The activated HOG1 triggers several responses to osmotic stress, including up or down regulation of different genes, regulation of protein translation, adjustments to cell cycle progression and synthesis of osmolyte glycerol. This study investigated the role of the MAPK-encoding PfHog1 gene on osmotic stress adaptation and virulence of P. fijiensis. RNA interference-mediated gene silencing of PfHog1 significantly suppressed growth of P. fijiensis on potato dextrose agar media supplemented with 1 M NaCl, indicating that PfHog1 regulates osmotic stress. In addition, virulence of the PfHog1-silenced mutants of P. fijiensis on banana was significantly reduced, as observed from the low rates of necrosis and disease development on the infected leaves. Staining with lacto phenol cotton blue further confirmed the impaired mycelial growth of the PfHog1 in the infected leaf tissues, which was further confirmed with quantification of the fungal biomass using absolutequantitative PCR. Collectively, these findings demonstrate that PfHog1 plays a critical role in osmotic stress regulation and virulence of P. fijiensis on its host banana. Thus, PfHog1 could be an interesting target for the control of black Sigatoka disease in banana.Item Allometric relationships and carbon content for biomass-carbon estimation of East African Highland Bananas (Musa spp. AAA-EAHB) cv. Kibuzi, Nakitembe, Enyeru and Nakinyika(African Journal of Agricultural Research, 2018) Kamusingize, Daphine; Mwanjalolo Majaliwa, Jackson; Komutunga, Everline; Tumwebaze, Susan; Nowakunda, Kephas; Namanya, Priver; Kubiriba, JeromeGlobally, interests to increase carbon stocks have gained momentum in both woody and non-woody ecosystems. Despite efforts made to generate appropriate methods to estimate these stocks, most equations developed do not cater for intraspecific variabilities across e.g. species, regions or growth stages; especially in the case of bananas. Therefore, there is need to develop more robust equations to improve on the precision of biomass-carbon prediction especially at local scales to facilitate estimation of specific carbon stocks often lost in global assessments. This study aimed at developing cultivarspecific biomass estimation relationships and determining carbon content of EAHB cultivars at two growth stages. Plant data were collected purposively using destructive sampling techniques on farmers’ plots for 4 cultivars (Kibuzi, Nakitembe, Enyeru and Nakinyika) in two agro-ecological zones: the L. Victoria crescent and the South-western farmlands in the districts of Lwengo and Mbarara respectively. Results show that biomass differed across cultivars (P<0.001); hence four equations (Enyeru, Nakinyika, Kibuzi_Nakitembe and Generic) were developed following an exponential function, y=Aexp(ax), using diameter at breast height (DBH) as the predictor variable with an R2 range of 82-94%. EAHB mean carbon content varied significantly with growth stage (P<0.05) (47.6% for maiden plants before flowering and 48.8% for mature plants with a developed bunch). This study concludes that it is important to develop cultivar-specific equations for biomass-carbon estimation of EAHB cultivars to help assess their contribution to the carbon cycle especially in future studies.Item Analysis of Genetic Diversity of Banana Weevils (Cosmopolites sordidus) (Coleoptera: Curculionidae) Using Transcriptome-Derived Simple Sequence Repeat Markers(Journal of Economic Entomology, 2022) Milton, Ali; Muhanguzi, Dennis; Male, Allan; Kajubi, Ali; Buah, Stephen; Kubiriba, Jerome; Tumuhimbise, RobooniThe banana weevil, Cosmopolites sordidus (Germar) (Coleoptera: Curculionidae) is an economically important insect pest of bananas. It causes up to 100% yield losses and substantial lifespan reduction in bananas. Advances in genomics, proteomics, and sequencing technologies have provided powerful pathways to genotyping disastrous pests such as C. sordidus. However, such technologies are often not available to the majority of rural subtropical African banana growers and pest control managers. This study was therefore motivated by the need to create cheap and easily accessible C. sordidus genotyping methods that could be deployed by banana pest control managers to the benefit of C. sordidus control programs in the tropics where such advanced technologies are not readily accessible. We used an in-house C. sordidus transcriptome from the an-ongoing study from which we mined an array of simple sequence repeat (SSR) markers. Of these, six highly polymorphic transcriptome-derived SSR markers were used to successfully genotype within and among banana weevil population genetic diversity of 12 C. sordidus populations collected from four bananagrowing agro-ecological zones (AEZs) in Uganda. The developed transcriptome-derived SSR markers can be used by researchers in population genetics for characterization of the C. sordidus and identification of new genes that are linked to traits of particular interest. The significant genetic diversity revealed in C. sordidus provides pertinent information for integrated pest management strategies.Item Application of Pollen Germination Media on Stigmas during Pollination Increases Seed Set in East African Highland Cooking Bananas (Musa spp.)(Agronomy, 2021) Waniale, Allan; Swennen, Rony; Settumba, B. Mukasa; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Amah, Delphine; Tumuhimbise, RobooniSeed set in East African Highland Cooking bananas (EAHBs) is extremely low and therefore hampers breeding. Pollen–pistil interaction is a key contributing factor. We assessed the effect of pollen germination media (PGM) on seed set in EAHBs. Five EAHB cultivars were pollinated with pollen from the wild banana ‘Calcutta 4’. Glucose-based PGM sprayed on freshly emerged stigmas significantly increased seed set per 100 fruits per bunch. Increases were 73.5% in ‘Enzirabahima’, 39.9% in ‘Mshale’, and 302.4% in ‘Nshonowa’. However, PGM did not increase seed set in the female sterile ‘Mlelembo’ and ‘Nakitembe’. As larger bunches were more fertile, good field management practices are also recommended to get more seed to improve breeding efficiency.Item Biofortified East African Highland Bananas to Alleviate Vitamin A Deficiency in Uganda(Gates Open Res, 2019) Buah, Stephen; Tindamanyire, Jimmy M.; Namanya, Priver; Kubiriba, Jerome; Paul, Jean-Yves; Dale, James L.; Tushemereirwe, WilberforceMicronutrient deficiency, also referred to as hidden hunger, is a global public health problem that affects over two billion people (Tulchinsky, 2010). In Uganda, micronutrient deficiency is the third most important public health problem after HIV/AIDS and malaria. Vitamin A deficiency (VAD) and Iron Deficiency Anaemia (IDA) are the major causes of anaemia in Uganda. VAD affects 20-35% of children below five years of age and the same proportion of women of child-bearing age. The aim of the Banana 21 project is to alleviate vitamin A deficiency through biofortification of Uganda’s major staple food, banana.Item Breeding banana (Musa spp.) for drought tolerance: A review(Plant Breeding, 2020) Nansamba, Moureen; Sibiya, Julia; Tumuhimbise, Robooni; Karamura, Deborah; Kubiriba, Jerome; Karamura, EldadDrought is a major abiotic stress affecting banana production worldwide, leading to yield losses of up to 65%. Consequently, numerous efforts to understand and mitigate drought effects that include developing tolerant crop varieties are ongoing in several banana breeding programmes. The breeding efforts, however, have been greatly slowed down by inherent banana problems (polyploidy and male or female sterility) and complexity of drought tolerance (reportedly controlled by several genes). This review summarizes the pertinent research findings on water requirements of banana for its proper growth and productivity, symptoms of drought-sensitive varieties and field management strategies to cope with drought stress. The coping strategies deployed by resistant cultivars include high assimilation rates and water retention capacity as well as minor losses in leaf area and gaseous exchange. Reduced bunch weight, leaf chlorosis, wilting and strangled birth are underlined to be directly associated with drought susceptibility. Integration of conventional, molecular breeding and biotechnological tools as well as exploitation of the existing banana genetic diversity presents a huge opportunity for successful banana improvement.Item Building agricultural networks of farmers and scientists via mobile phones: case study of banana disease surveillance in Uganda(Canadian Journal of Plant Pathology, 2016) Nakato, Gloria Valentine; Beed, Fenton; Bouwmeester, Hein; Ramathani, Idd; Mpiira, Samuel; Kubiriba, Jerome; Nanavati, SaurinAn important challenge threatening agriculture in Africa is the difficulty to collect timely data on disease spread and effectiveness of on-farm control methods. This study served as a case study for assessing the viability of a participatory GIS (Geographic Information System) to enable plant diagnostics network with field workers. The use of mobile phone applications and a centralized database were integrated to provide a blueprint for how a range of agriculture-focused field organizations can collect data, explain events, predict outcomes, and adapt and refine strategies with more accurate, cost-efficient, and timely information. Over the course of two months, 38 Community Knowledge Workers (CKWs) using mobile phones, MTN Mobile Internet, and GPS devices collected 3,018 surveys documenting the presence/absence of three banana diseases: Banana Xanthomonas Wilt (BXW), Fusarium Wilt (FW) and Banana Bunchy Top disease (BBTD) in Bushenyi and Mbale districts in Uganda. Costs were saved by only mobilizing CKWs who then trained the communities on methods of banana disease detection, preventative measures, and disease control procedures; only when doubts over identification or control occurred did the IITA and NARO technical team then prioritize visits. Although the CKWs provided an efficient and cost effective information channel that can be leveraged to integrate the efforts of scientists with the needs of rural communities, there were significant gaps in prior farmer knowledge on the three targeted diseases, including how to identify or control them, despite extensive awareness campaigns preceding this initiative. Factsheets used for reference following training greatly improved CKW prior knowledge of disease recognition and control methods; hence, 90% of the surveys conducted during the second month met the data quality standards based on survey completeness, GPS accuracy, and quality of symptomatic plant photos. There was significant and consistent demand by farmers for CKW services throughout the pilot period. In-depth training and continuous support of CKWs is thus essential. The technology infrastructure is scalable, and further integration of technology components G.V. Nakato et al. Building agricultural networks via mobile phones promises a customizable web-based tool for data collection, GIS analysis, information dissemination and management of agriculture extension operations.Item Carbon sequestration potential of East African Highland Banana cultivars (Musa spp. AAA-EAHB) cv. Kibuzi, Nakitembe, Enyeru and Nakinyika in Uganda(Journal of Soil Science and Environmental Management, 2017) Kamusingize, Daphine; Mwanjalolo Majaliwa, Jackson; Komutunga, Everline; Tumwebaze, Susan; Nowakunda, Kephas; Namanya, Priver; Kubiriba, JeromeDespite the global interest to increase the world's carbon stocks, most carbon sequestration strategies have largely depended on woody ecosystems whose production is threatened by the continuous shortage of land, hence the need to explore viable alternatives. The potential of bananas to sequester carbon has been reported but there is limited knowledge on the performance of various cultivars as specific carbon stocks are often lost in global assessments. Therefore, this study aimed at exploring the potential of and variability in carbon stocks of selected East African Highland Banana (EAHB) cultivars. Plant and soil data were collected using destructive and non-destructive techniques in 30×30m2 sampling plots for 4 cultivars Kibuzi, Nakitembe, Enyeru and Nakinyika growing in two agroecological zones of Uganda being the L.Victoria Crescent and the South-western region. Total carbon and Soil Organic Carbon (SOC) stocks did not differ considerably across cultivars (P>0.05). However, there was significant variation (P<0.05) in plant carbon stock being lowest in two cultivars: Nakinyika at 0.37±0.19 Mgha-1 and Nakitembe at 0.40±0.19Mgha-1; and highest in Enyeru at 1.64±0.18 Mgha-1. The SOC stock variation difference across depth was 2.9-8.5 Mgha-1 being higher in top soil than sub-soil. Despite the small plant carbon stock amounts, the system enables much more carbon to be stored in the soil considering the proportion of what is contained in the plant to that in the soil across all cultivars (0.4-2%). The study therefore recommends revision of existing carbon frameworks to incorporate the contribution of non-woody perennials like bananas in the carbon cycle so that the poor small scale farmers who cannot afford large acreages to establish tree plantations can also benefit from such initiatives.Item Comparative pathogenicity studies of the Xanthomonas vasicola species on maize, sugarcane and banana(African Journal of Plant Science, 2015) Karamura, G.; Smith, Julian; Studholme, David; Kubiriba, Jerome; Karamura, E.Previous biochemical and molecular sequence analyses of Xanthomonas campestris pathovar musacearum, the etiological agent of banana Xanthomonas wilt, suggest that it belongs within the species Xanthomonas vasicola (X. vasicola pv. vasculorum and X. vasicola pathovar holcicola. However, the X. vasicola pathovar names were considered invalid according to pathovar naming standards and placed as one X. vasicola species; this was also not helped by the lack of sufficient comparative pathogenicity studies. Hence the proposal to rename X. campestris pathovar musacearum was no longer further supported. This study therefore carried out large scale comparative pathogenicity trial studies on the X. vasicola strains and X. campestris pathovar musacearum on 112 plants for banana and maize, and 84 plants for sugarcane, to establish or support the proper X. vasicola pathovar designations. The study also included nine common plant pathogenic Xanthomonas pathovars and one non-Xanthomonas strain. The six strains of X. campestris pathovar musacearum used in the study caused disease in sugarcane and banana but not on maize. 2 and 4 strains of X. vasicola pathovar vasculorum and X. vasicola pathovar holcicola, respectively were not only pathogenic on maize and sugarcane but each also caused distinct symptoms on maize. X. vasicola pathovar vasculorum caused deformation of the plant while X. vasicola pathovar holcicola caused stunted growth.Item Determinants of Farm-Level Adoption of Cultural Practices for Banana Xanthomonas Wilt Control in Uganda(Journal of Agricultural Science, 2013) Jogo, Wellington; Karamura, Eldad; Tinzaara, William; Kubiriba, Jerome; Rietveld, AnneUnderstanding the factors influencing farmers’ adoption decisions of the disseminated Banana Xanthomonas wilt (BXW) control package is critical for successful management of the disease. This paper analysed the determinants of farmers’ decisions to adopt the control package by smallholder banana farmers in Uganda. A binomial Logit model is applied to household survey data collected from 350 households. Results from the study show that household labour availability, technology package attributes such as labour demand and perceived effectiveness of the practices in managing the disease; and agro-ecological location and banana production system significantly influence adoption decisions. These results suggest the need for adaptation of the technology package to better suit the needs and socio-economic conditions of smallholder farmers through a farmer participatory technology development approach that takes into account research findings, farmers’ indigenous knowledge and resource constraints to enhance adoption.Item Development of two high-yielding, consumeracceptable apple banana hybrids (Musa species, AAB genome group) with resistance to Fusarium oxysporum f. sp. cubense race 1(Journal of Plant Breeding and Crop Science, 2018) Buregyeya, Henry; Tumuhimbise, Robooni; Kubiriba, Jerome; Talengera, David; Nowankunda, Kephas; Arinaitwe, Geofrey; Tushemereirwe, Wilberforce K.; Karamura, Deborah; Karamura, Eldad; Rubaihayo, PatrickFusarium wilt of bananas (Musa species) is caused by Fusarium oxysporum f. sp. cubense (Foc). Foc race 1 in particular affects dessert bananas in Uganda, causing >60% yield loss. This study was conducted to assess the performance of two new apple banana genotypes for bunch yield, resistance to Foc race 1 and consumer acceptability. The new apple banana genotypes (NAMU1 and NAMU2), along with two check cultivars, one susceptible but preferred by consumers (Sukali ndiizi) and the other resistant (Yangambi-KM5), were evaluated at the National Agricultural Research Laboratories in Uganda. Bunch yields of the two new apple bananas were higher than those of check cultivars by >50%. NAMU1 and Yangambi-KM5 showed no symptoms of Foc race 1, whereas NAMU2 showed mild symptoms on its corms. Sukali ndiizi showed severe pseudostem splitting and corm discoloration as the key symptoms of Foc race 1. The consumer acceptability of NAMU1 and NAMU2 was as high as that of Sukali ndiizi, implying that they can be perfect substitutes for the Foc race 1 susceptible Sukali ndiizi.Item Does gender matter in effective management of plant disease epidemics? Insights from a survey among rural banana farming households in Uganda(Journal of Development and Agricultural Economics, 2018) Mutebi Kikulwe, Enoch; Okurut, Stanslus; Ajambo, Susan; Gotor, Eisabetta; Tendo Ssali, Reuben; Kubiriba, Jerome; Karamura, EldadCrop diseases significantly suppress plant yields and in extreme cases wipe out entire crop species threatening food security and eroding rural livelihoods. It is therefore critical to estimate the extent to which shocks like disease epidemics can affect food availability and the capacity of smallholder farmers to mitigate and reverse the effects of such shocks. This study utilizes sex-disaggregated data from 341 households in Uganda to analyze: first, gender and access to agricultural resources and their control; second, whether men and women in the targeted banana-farming communities share similar perceptions toward the effectiveness of the banana Xanthomonas wilt (BXW) control technologies and their respective information dissemination pathways; third, whether gender and farmer perceptions influence on farm adoption of BXW management practices. Lastly, it determines the impact of adoption of BXW control practices on food security. Results show that whereas most household assets are jointly owned, men have more individual ownership, control, and decision-making on income from household assets than women. Perceptions on effectiveness of BXW control practices and communication channels also differed between men and women. Men rated cutting down of infected plants to be more effective than women, but tissue culture, removal of male buds and disinfecting of farm tools were perceived to be equally effective by both men and women. In addition, apart from newspapers which were more effective in delivering BXW information to men, we found no differences in the effectiveness of other BXW information sources. More importantly, the study finds both gender and farmer perceptions on BXW control to significantly affect adoption of BXW control practices and household food security. For better and sustainable management of plant epidemics in Uganda, it is therefore critical that existing gender-based and underlying perception constraints are addressed.Item Early Withering of Enlarged Ovules in Pollinated Fruits of Bananas (Musa spp.) Suggest Abortion after Fertilization(Horticulturae, 2022) Waniale, Allan; Mukasa, Settumba B.; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Tumuhimbise, RobooniSterility in edible bananas is as a result of a long history of anthropogenic-driven selection for sterile genotypes, since seed is not desirable in fruit pulp for human consumption. However, this poses a challenge to conventional genetic improvement by slowing breeding pipelines. In this study, we investigated whether pollen tubes reach all parts of the ovary, the position of fertilized ovule development in fruits, and potential seed set in selected banana genotypes. We selected four cultivars of East African Highland Cooking bananas (EAHBs), a Matooke hybrid ‘222K-1’, improved diploid ‘2905’, and wild bananas ‘Zebrina (G.F.)’ and ‘Calcutta 4’. There was evidence of pollen tubes in the distal, mid and proximal sections of the fruit, irrespective of hand position and genotype. Fertilization, as indicated by an increase in ovule size, happened along the entire length of the fruit but complete development was biased at the distal end in some genotypes. There were some differences in ovule fertilization rates between hands, with distal hands having more ovules and higher ovule fertilization rates. Ovule fertilization happens in bananas but the vast majority aborts, especially at the proximal end of the ovary. Ovule fertilization rates are generally much lower than available ovules.Item Evaluation of a lateral flow device for in-field detection of Banana Xanthomonas Wilt and its application in tracking the systemicity of Xanthomonas campestris pv. musacearum(African Journal of Agricultural Research, 2016) Karamura, Georgina; Ochola, Dennis; Smith, Julian; Kubiriba, Jerome; Karamura, EldadEarly detection of Banana Xanthomonas Wilt (BXW) in the field and immediate destruction of infected plants or plant tissue are key control methods to prevent the introduction and spread of BXW. This requires rapid, cost-effective and an on- site diagnostic tool to detect the bacterium, Xanthomonas campestris pv musacearum (Xcm). Polymerase chain reaction (PCR) detection technique for BXW is efficient but requires expensive equipment and knowledgeable expertise; this limits PCR application to the laboratory. This study therefore was carried out to evaluate the enzyme-linked immunosorbent assay (ELISA) tool configured as a lateral flow device (LFD) for detection of Xcm. Studies on the systemicity of Xcm in banana were carried out using the BXW-LFD in a field trial of 300 banana plants of Pisang Awak inoculated with the Xcm at Kiifu Forest, Mukono District, Uganda. Pseudo-stem samples from symptomatic and asymptomatic suckers were collected and tested with the LFD and the results compared with conventional PCR using the GspDm BXW primers. The LFD was able to detect Xcm 3 days post inoculation (dpi), 2 cm above and below inoculation site, 15 to 35 days in the pseudo-stem, 35 to 42 days to reach the corm and 81 days in the lateral roots. The rate of Xcm movement in banana was found to be sigmoid in nature, leveling off as the bacteria moved down the pseudo-stem towards the corm. Conventional PCR was only 24% more sensitive than the LFD. The use of the BXW LFD can therefore boost BXW control measures through improved surveillance and quarantine services to arrest the introduction and spread of the disease within and between national borders.Item Evaluation of banana germplasm and genetic analysis of an F1 population for resistance to Fusarium oxysporum f. sp. cubense race 1(Euphytica, 2019) Kabiita Arinaitwe, Ivan; Teo, Chee How; Kayat, Fatimah; Tumuhimbise, Robooni; Uwimana, Brigitte; Kubiriba, Jerome; Swennen, Rony; Ann, Jennifer; Rofina Yasmin Othman, HarikrishnaFusarium wilt of bananas (Musa spp.), caused by Fusarium oxysporum f. sp. cubense (Foc) causes up to 100% yield loss in bananas. Foc race 1 in particular is very devastating to dessert bananas in Uganda. One of the effective control strategies for the disease is the development of resistant cultivars through breeding. The objectives of this study were to identify suitable banana germplasm for generating a segregating population for resistance to Foc race 1 and understand the mode of inheritance of resistance to Foc race 1. Twenty-two banana accessions sourced from the National Agricultural Research Organisation in Uganda were challenged with Foc race 1 in a screen house experiment. Monyet, resistant to Foc race 1 and Kokopo, susceptible, were selected and crossed to generate 142 F1 genotypes. These F1 genotypes were also challenged with Foc race 1 in a screen house experiment. Data were collected on rhizome discoloration index (RDI), leaf symptom index (LSI) and pseudo-stem splitting (PSS), and analysed for variability. The banana accessions evaluated showed varying degrees of resistance to Foc race 1. Segregation ratios for resistant versus susceptible progenies fitted 13:3 (v2 = 0.12, P = 0.73) for RDI and 11:5 (v2 = 3.04, P = 0.08) for PSS. Estimated broad sense heritability was 27.8% for RDI, 13.9% for LSI and 14.7% for PSS. The results suggest that resistance to Foc race 1 in banana is controlled by at least two dominant genes with epistatic interaction and thatItem Farmers’ awareness and application of banana Xanthomonas wilt control options: The case of Uganda and Kenya(Journal of Development and Agricultural Economics, 2011) Jogo, Wellington; Karamura, Eldad; Kubiriba, Jerome; Tinzaara, William; Rietveld, Anne; Onyango, Margaret; Odongo, MichaelBanana is a key staple and cash crop in east and central Africa. However, the recent outbreak of Banana Xanthomonas wilt (BXW) has threatened farmers whose livelihoods depend on the crop. Since 2002, stakeholders embarked on campaigns to sensitize farmers on the disease and its management. This study evaluated the effectiveness of these efforts by examining farmers’ awareness of the disease, control options and their application in Uganda and Kenya. Data on BXW distribution and incidence, farmers’ awareness of symptoms, mechanisms of spread and control options of the disease and banana production were collected through household surveys conducted in 2010. The results indicated that most farmers (> 90%) were aware of the disease and its symptoms and more than 50% were aware of the recommended control measures. Farmers obtained information on the disease from multiple sources but farmer-to-farmer interaction was the main source suggesting the key role rural social networks play in managing the disease. Not all affected farmers were able to apply control measures due to cost of intervention, lack of labour and inputs. The study recommends strengthening of linkages among stakeholders for better coordination of efforts and participatory development and promotion of farmer-oriented interventions that address farmer constraints.Item Fine-tuning banana Xanthomonas wilt control options over the past decade in East and Central Africa(European journal of plant pathology, 2014) Blomme, Guy; Jacobsen, Kim; Ocimati, Walter; Beed, Fen; Ntamwira, Jules; Sivirihauma, Charles; Ssekiwoko, Fred; Nakato, Valentine; Kubiriba, Jerome; Tripathi, Leena; Tinzaara, William; Mbolela, Flory; Lutete, Lambert; Karamura, EldadXanthomonas wilt, caused by Xanthomonas campestris pv. musacearum has, since 2001, become the most important and widespread disease of Musa in East and Central Africa. Over the past decade, new research findings and especially feedback from smallscale farmers have helped in fine-tuning Xanthomonas wilt control options. During the initial years of the Xanthomonas wilt epidemic in East Africa, the complete uprooting of diseased mats and the burning or burying of plant debris was advocated as part of a control package which included the use of clean garden tools and early removal of male buds to prevent insect vector transmission. Uprooting a complete mat (i.e. the mother plant and a varying number of lateral shoots) is understandably time-consuming and labour intensive and becomes very cumbersome when a large number of diseased mats have to be removed. Recent research findings suggest that Xcm bacteria do not colonize all lateral shoots (i.e. incomplete systemicity occurs) and even when present that this does not necessarily lead to symptom expression and disease.Item First Evidence of Feeding-Induced RNAi in Banana Weevil via Exogenous Application of dsRNA(Insects, 2022) Shaykins Mwaka, Henry; Christiaens, Olivier; Namanya Bwesigye, Priver; Kubiriba, Jerome; Kateera Tushemereirwe, Wilberforce; Gheysen, Godelieve; Smagghe, GuyBanana weevil (Cosmopolites sordidus) is the most devastating pest of banana and plantain worldwide, yet current control measures are neither effective, sustainable, nor environmentally sound, and no resistant farmer-preferred cultivars are known to date. In this paper, we examined the ability to induce RNA interference (RNAi) in the banana weevil via feeding. We first developed an agar- and banana corm (rhizome) flour-based artificial diet in a multi-well plate setup that allowed the banana weevils to complete their life cycle from egg through the larval instars to the pupal stage in an average period of 53 days. Adults emerged about 20 days later. The artificial diet allowed the tunneling and burrowing habits of the larvae and successful metamorphosis up to adult eclosion. Adding dsRNA for laccase2 to the artificial diet resulted in albino phenotypes, confirming gene-silencing. Finally, C. sordidus was fed with dsRNA against a selection of essential target genes: snf7, rps13, mad1, vha-a, vha-d, and lgl for a period of 45 days. 100% mortality within 9–16 days was realized with dssnf7, dsrps13, and dsmad1 at 200 ng/mL artificial diet, and this corresponded to a strong reduction in gene expression. Feeding the dsRNA targeting the two vha genes resulted in 100% mortality after about 3–4 weeks, while treatment with dslgl resulted in no mortality above the dsgfp-control and the water-control. Our results have implications for the development of RNAi approaches for managing important crop pests, in that banana weevils can be controlled based on the silencing of essential target genes as snf7, rps13, and mad1. They also highlight the need for research into the development of RNAi for banana protection, eventually the engineering of host-induced gene-silencing (HIGS) cultivars, given the high RNAi efficacy and its species-specific mode of action, adding the RNAi approach to the armory of integrated pest management (IPM).Item Fusarium oxysporum Race 1 resistance and quality traits variations in apple banana germplasm(Journal of Plant Breeding and Crop Science, 2020) Buregyeya, Henry; Tumuhimbise, Robooni; Matovu, Moses; Tumwesigye, Kashub S.; Kubiriba, Jerome; Nowankunda, Kephas; Tushemereirwe, Wilberforce K.; Karamura, Deborah; Karamura, Eldad; Kityo, Robert M.; Rubaihayo, PatrickMusa species, AAB genome group, commonly known as Sukali Ndizi (SND) in Uganda, has attained a substantial commercial value in the recent past owing to its superior fruit quality attributes and better prices. However, its sustainable production and productivity are highly threatened by Fusarium wilt. To facilitate large scale area expansion of this important dessert banana, the present study was carried out to identify the near-ideotypic lines of best quality fruit traits that are also resistant to Fusarium wilt. Nineteen SND ecotypes were subsequently collected from nine key SND growing districts of Uganda and evaluated in the field and laboratory for different fruit quality attributes and response to Fusarium wilt. Results showed a wide diversity among SND ecotypes for fruit-quality traits (fruit pulp texture, flavor and taste). The ecotypes were, however, not significantly different (p > 0.05) for susceptibility to FOC race 1. Cluster analysis based on organoleptic and physio-chemical properties grouped the 19 ecotypes into two major-clusters, each of which was also split into two sub-clusters. Individual subclusters summarize levels of similarity amongst the different ecotypes. The study confirmed the presence of diversity in SND germplasm that could be exploited for SND genetic improvement of the crop through hybridization and selection.Item Genetic Analysis of Weevil (Cosmopolites Sordidus) Resistance in an F2 Diploid Banana Population(Journal of Plant Breeding and Genetics, 2015) Arinaitwe, Ivan K.; Barekye, Alex; Kubiriba, Jerome; Sadik, Kassim; Karamura, Eldad; Edema, RichardThe East African highland bananas (Musa spp. AAA), an important staple food in Uganda, are highly susceptible to the banana weevil (Cosmopolites sordidus Germar). Sources of host plant resistance to the banana weevil exist in wild diploid bananas. The use of wild diploid bananas to improve East African highland bananas can be facilitated by studying genetics of host plant resistance of inter-diploid crosses. The objectives of this study were a) to identify segregating weevil resistance and agronomic traits in an F2 diploid population, and, b) to determine the inheritance of banana weevil resistance and agronomic traits based on an F2 banana diploid population. An F1 population developed from Musa acuminata subsp. banksii acc. Kasaska (ITC0591) and M. acuminata subsp. microcarpa acc. Borneo (ITC0253) was selfed to generate an F2 diploid population. The F2 population was screened against weevil resistance and agronomic traits in the laboratory, pot and field experiments. There were significant differences (P < 0.05) among the different genotypes for banana weevil resistance traits such as head capsule width, body length, body weight, larval mortality, total damage, peripheral damage, dead weevils and larvae retrieved. There were also significant differences (P < 0.05) for agronomic traits such as inner corm hardness and total corm hardness. The histograms for the banana weevil resistance traits such as head capsule width, body length, body weight and larval mortality, total damage, peripheral damage, cross sectional inner and outer damage, larvae retrieved and dead weevils showed continuous distribution. Similarly, histograms for agronomic parameters such as height of plant at flowering and girth at 1 meter at flowering showed continuous distribution. The Chi-square test of goodness of fit indicated that weevil growth and damage parameters had significant modifications of the expected 9:3:3:1 ratio for two independent loci, thus suggesting epistasis affects their inheritance.
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