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Search Results: 1 - 10 of 386 matches for " SB Mukasa "
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Prevalence and implications of sweetpotato recovery from sweet potato virus disease in Uganda
E Gasura, SB Mukasa
African Crop Science Journal , 2010,
Abstract: Sweet potato virus disease (SPVD) is the most important disease of sweetpotato in the tropics. It causes yield losses of up to 98% and extinction of elite cultivars. Although there are no reports of immune cultivars, disease recovery phenomenon (a manifestation of some form of resistance) was reported in many vegetatively propagated crops including sweetpotato. A total of 1320 sweetpotato cultivars from 3 major sweetpotato growing regions in Uganda were field evaluated for SPVD severity, of which 24% showed recovery from SPVD. The nature of SPVD recovery was assessed in the screenhouse using 20 distinct cultivars after graft inoculation with SPCSV and SPFMV, the SPVD causing viruses. SPVD progress in 20 graft inoculated cultivars was significantly (P<0.05) different; Munyeera was the most resistant cultivar followed by New Kawogo and Polyster. The 3 resistant cultivars (disease score 1-2) displayed recovery from SPVD which was correlated with a reduction in SPFMV titers as observed from quantitative ELISA. Reversion was not evident since all cuttings taken from recovered vine tips later tested positive for both viruses. Cultivars with the ability to recover were common in farmers’ fields in central (36.4%) and western (33.3%) regions of Uganda, which are high SPVD pressure zones. Conversely, fewer cultivars (5.6%) from the low disease pressure eastern region displayed recovery. The very susceptible cultivars (disease score of 4-5) were not prevalent in central and western regions. These observations suggest that SPVD recovery has an influence on the cultivars grown in different SPVD pressure zones, where more susceptible cultivars are preferred in areas of low disease pressure.
Male Fertility in Uganda Banana Germplasm
SB Mukasa, PR Rubaihayo
African Crop Science Journal , 1993,
Abstract: Identification of fertility levels in banana germplasm collection at Kabanyolo, Uganda, was conducted by dehiscing the anthers using a glass rod. The study involved 151 accessions. The quantity of pollen grains per anther was ranked 0-5; where 0 had no grains and 5 had abundant pollen grains. A correlation between pollen output and inflorescence characters revealed a positive relationship (r = 0.69, P ≤ 0.01) to inflorescence diagnostic characters. A quantitative determination of pollen output per anther and percentage pollen viability based on starch test using the Heamocytometer method revealed that the amount of starch filled grains did not proportionally vary with the total pollen output. Pollen output varied from cultivar to cultivar. Most East African highland banana cultivars were found to have more pollen than the recently introduced banana cultivars. A few highland banana cultivars were non-polleniferous. The results indicate the relative potential of using various cultivars in hybridization and, anther and pollen culture programmes.
Optimisation of in vitro techniques for cassava brown streak virus elimination from infected cassava clones
P Wasswa, AB Alicai, SB Mukasa
African Crop Science Journal , 2010,
Abstract: Cassava brown streak disease (CBSD), caused by Cassava brown streak virus (CBSV), is an economically important disease of cassava (Manihot esculenta Crantz) in East Africa. The objective of this study was to optimise in vitro techniques for CBSV elimination from infected Ugandan cassava cultivars. Using semi-solid halfstrength Murashige and Skoog (MS) basal medium, hormone concentration and heat treatment regimes were optimised for micropropagation of farmer’s preferred cassava cultivars and CBSV elimination. Single nodes from young cassava stems were cultured for four weeks on MS medium supplemented with 6-benzyl amino purine (BAP) and 2,4-dichlorophenoxy acetic acid (2,4-D). The BAP and 2,4-D concentration (mg l-1) combinations used were 0.0 and 0.0, 0.5 and 0.1, 1.0 and 0.2, 1.5 and 0.3, and 2.0 and 0.4, respectively. The optimum medium was used for in vitro thermotherapy using four temperature regimes, namely 30-34, 34-38, 36-40 and 38-42 oC for 8 hours darkness and 16 hours light, respectively, for four weeks. The best plantlet growth in terms of height was observed on MS medium supplemented with 0.5 mg l-1 BAP and 0.1 mg l-1 2,4-D. Highest CBSV elimination efficiency of 40%, with 49% plantlet survival was observed at 36 oC for 8 hours darkness and 40 oC for 16 hours light. These results indicate that in vitro techniques can greatly enhance CBSV elimination and, thus, provide a means of CBSD management through dissemination and conservation of popular but CBSD susceptible cultivars.
Genetic variability for tuber yield, quality, and virus disease complex traits in Uganda sweetpotato germplasm
E Gasura, AB Mashingaidze, SB Mukasa
African Crop Science Journal , 2008,
Abstract: Sweetpotato (Ipomoea batatas) is an important root crop in Uganda, where yield potential and quality attributes have not been fully exploited due to limited breeding efforts and poor knowledge on the inheritance of some of its agronomic traits. A study was carried out at Makerere University to phenotypically characterise selected sweetpotato cultivars with special reference to sweet potato virus disease (SPVD) resistance, growth habit, flowering and seed set ability, tuber yield and shape, tuber skin and flesh colour, dry matter, starch, sugar and a- carotene content. Twenty cultivars were selected for use in the assessment of their breeding potential and for improvement of yield and quality attributes. Cultivar Munyeera displayed the highest level of SPVD resistance followed by New Kawogo and Polyster as exhibited by relative area under disease progress curves following natural field infection and graft inoculation with SPVD causing viruses, Sweet potato chlorotic stunt virus and Sweet potato feathery mottle virus. Flowering ability was low in some cultivars and a few did not flower at all. Some cultivars e.g. Munyeera, New Kawogo, Silk and Sowola which showed high flowering ability failed to fertilise and set seed when crossed to specific cultivars. Preliminary genetic analysis for yield and quality following crossing elite 7 female and 6 male cultivars in a North Carolina 2 mating design showed wide genetic variability in the F1s for the important traits, and heterosis was observed for some traits such as tuber size and number of tubers per plant. Up to five genes may be involved in a-carotene synthesis and probably in combination with other genes in different genetic backgrounds that can modify flesh colour from white to purple. The results demonstrate the possibility to improve sweetpotato for yield and quality using the available germplasm.
Detection and elimination of sweetpotato viruses
RJ Rukarwa, AB Mashingaidze, S Kyamanywa, SB Mukasa
African Crop Science Journal , 2010,
Abstract: In sub-Saharan Africa, sweetpotato (Impomoea batatas L.) production is greatly constrained by sweetpotato virus disease (SPVD) complex. This study was conducted to assess the incidence of viruses in healthy-looking sweetpotato in Uganda and to optimise modern technologies for virus diagnosis. A collection of healthy-looking sweetpotato vines from central Uganda were serologically assayed for sweetpotato viruses and the positive samples were confirmed by RT-PCR. A multiplex RT-PCR assay was optimised for simultaneous detection of Sweet potato chlorotic stunt virus (SPCSV), Sweet potato feathery mottle virus (SPFMV) and Sweet potato mild mottle virus (SPMMV). The use of in vitro thermotherapy was also investigated as a means of eliminating sweetpotato viruses. Four viruses namely SPCSV, SPFMV, SPMMV and SPCFV were detected mostly as single infections in the healthy looking plants. SPCSV (70. 6%) recorded highest incidence followed by co-infection of SPFMV and SPCSV (8.3%). Based on shoot survival and effectiveness of virus elimination, the best results were obtained by exposing plantlets to daily temperature regime of 32 oC for 8 hr of darkness and 36 oC for 16 hr of light for four weeks. Meristem-tip culture combined with thermotherapy allowed elimination of SPFMV and SPMMV in 77% of plants that were previously infected with the respective viruses. However, elimination of SPCSV was unsuccessful.
Characterisation and role of Isoamylase1 (Meisa1) gene in cassava
D Beyene, Y Baguma, SB Mukasa, C Sun, C Jansson
African Crop Science Journal , 2010,
Abstract: The current concept for starch biosynthesis in plants is that amylopectin, the major fraction of starch, is synthesised by the concerted actions of ADP-Glc pyrophosphorylase (AGPase), soluble starch synthase (SS), starch-branching enzyme (BE), and starch-debranching enzyme (DBE). We have isolated a cDNA clone of Isoamylase1 gene, a member of DBE family from cassava (Manihot esculenta Crantz) storage root. The cloned cDNA fragment sequence (764 bp) showed high identity of 90% to Rcisa1, and 81% identity to Psisa1, Stisa1 and Atisa1. The deduced protein sequence showed highest (92%) identity with RCISA1. The comparative sequence analysis confirmed the cloned fragment to be M. esculenta isoamylase1 gene (Meisa1; accession number GU229751). Genomic analysis revealed occurrence of at least two copies of the Meisa1 gene. Highest Meisa1 transcript expression levels were detected in fibrous root followed by in the stem and least detected in the leaf and petiole. Analysis of the temporal expression pattern in the storage root showed initial and maximum expression at 90 days after planting (DAP), and declined thereafter to undetectable levels by 180 DAP. The results implicate a major role of Meisa1 in storage root differentiation and early starch granule initiation.
Proliferation and Shoot Recovery among the East African Highland Banana
K Sadik, G Arinaitwe, JM Ssebuliba, P Gibson, C Lugolobi, SB Mukasa
African Crop Science Journal , 2012,
Abstract: Production of East African highland banana (EA-AAA banana) (Musa spp.) is limited by scarcity of planting materials, attributable to their low natural proliferation ability. Under natural field conditions, the EA-AAA bananas greatly differ in suckering ability. In vitro micropropagation has been adopted as an alternative means for production of banana planting materials. In this study, the in vitro proliferation potential of seven EA-AAA banana cultivars, with different suckering ability was determined on Murashige and Skoog (MS) medium, to enhance development ofmicropropagation protocols for their multiplication. Commonly cultivated non EAAAA banana cultivars were used to compare proliferation of the seven EA-AAA cultivars. There was a wide variation in the number and morphology of shoots and buds produced by the different cultivars. The EA-AAA banana cultivars produced 3-4 new shoots in each subculture cycle, and 57-169 recoverable shoots from one starting shoot-tip explant in 18 weeks. Non-EA-AAA banana cultivars, namely Sukali Ndizi (AAB) and Yangambi Km5 (AAA), showed higher proliferation levels, 5 and 9 shoots, from each subculture cycle and 322 and 352 recoverable shoots, respectively. The EA-AAA banana cultivars showed higher efficiency to produce recoverable shoots from shoot buds (53 - 66% except for cv. Kabula at 36%) compared to Sukali Ndizi (52%) and Yangambi Km5 (32%). The study demonstrates the potential of in vitro approach for production of banana planting materials. In vitro proliferation ability and in particualr efficiency to produce recoverable shoots of the different EA-AAA banana cultivars could be improved by varying the culture conditions during the subsequent subculture cycles.
Thidiazuron improves adventitious bud and shoot regeneration in recalcitrant sweetpotato
A Sefasi, M Ghislain, A Kiggundu, G Ssemakula, R Rukarwa, SB Mukasa
African Crop Science Journal , 2013,
Abstract: Induction of adventitious buds and shoots from intact leaves and stem internode segments of two recalcitrant L.) cultivars was investigated in vitro on Murashige and Skoog (MS) medium, supplemented with 3 different levels (0.5, 2.0 and 4.0 ìM) of Thidiazuron (TDZ). Shoots were regenerated in all TDZ concentrations in cvs. Kyebandula and Bwanjule. The inclusion of 0.25 ìM á-Naphthalene acetic acid (NAA) in MS medium, containing TDZ (0.5 ìM), improved shoot regeneration frequency from 12.1 to 22.6% for cv. Kyebandula stems and from 21.61 to 42.9% for cv. Bwanjule stems. However, there was about 10% reduction in adventitious bud induction frequency for both cultivars, when NAA was included in the medium. The highest frequency (66.7%) of adventitious bud induction was achieved from stem explants of cv. Kyebandula. The conversion of adventitious buds into shoots was improved when TDZ was reduced or completely removed in subsequent stages of culture. The number of explants forming shoots was significantly (P<0.001) higher when stem explants were cultured for 7 days on TDZ-supplemented MS medium before transfer to TDZfree MS medium supplemented with NAA. Stem internode pieces from position 3 were the best (70.0%) in adventitious bud formation. However, most buds (76.2%) were not converted to shoots. The most important application of the de novo regeneration protocol developed in this study is in genetic transformation for improvement of sweetpotato productivity. Key Words: Bud induction, Ipomoea batatas, Naphthalene acetic acid
Good Governance, Efficiency and the Provision of Planned Land for Orderly Development in African Cities: The Case of the 20,000 Planned Land Plots Project in Dar es Salaam, Tanzania  [PDF]
Joseph Mukasa Lusugga Kironde
Current Urban Studies (CUS) , 2015, DOI: 10.4236/cus.2015.34028
Abstract: In many African cities, governments have been unable to provide sufficient appropriately located and priced planned and serviced urban land to meet demand. As a result, informal settlements are growing faster than the rest of the city. Efforts to deal with this situation are hampered by several factors including lack of resources to acquire and service land to forestall haphazard development. In 2003, the Ministry of Lands, using borrowed funds from the Treasury, undertook an ambitious land servicing project in Dar es Salaam. The aims were to: alleviate the shortage of surveyed and serviced urban plots; tackle the rapid increase of informal settlements; control land speculation; address corruption; complement the national drive to reduce poverty; develop satellite towns; and implement the ruling Party’s manifesto on liveable human settlements. This paper evaluates this undertaking from a good governance point of view. The Project was efficiently implemented. Over 40,000 plots were produced and sold; the invested billions of shillings were recouped several times over; and replication was enabled. However, it increased poverty among those whose land was acquired; and fuelled the growth of informal settlements. With less than 17% of the plots categorized as low cost, the Project was not pro-poor. Outcomes included the realization that land had value that could be unlocked with servicing. This has spawned several projects involving servicing land for sale, undertaken by other authorities and the private sector. This, however, is excluding low income households. The Project’s achievements were realized at the expense of good land governance exemplified by: lack of coordination among key players; shortfalls in transparency, public participation, institutional decentralisation and inclusiveness; and neglect of environmental fallouts. Low income households were in practice excluded from this and subsequent money-driven land delivery schemes, a trend that needs to be reversed to avoid social polarization.
A case for subduction involvement in the generation of high-MgO and high-SiO2 magmas in layered mafic intrusions
S. B. Mukasa
Chinese Science Bulletin , 1998, DOI: 10.1007/BF02891526
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