Browsing by Author "Lamo, J."

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    Allelic Variations in Aroma Gene in Cultivated Rice Varieties
    (African Crop Science Journal, 2020) Akwero, A.; Ocan, D.; Akech, W.; Lamo, J.; Ochwo-Ssemakula, M.; Rubaihayo, P.
    Germplasm is a valuable source of genetic diversity that supports crop improvement efforts in any breeding programme but it must first be fully characterised for economically valuable traits before it can be effectively utilised. In rice (Oryza sativa), the development of new varieties with improved aroma requires correct phenotyping and prior knowledge of the available genes and alleles governing the aroma trait in the gene pool. Correct phenotyping and genotyping can be achieved using sensory methods and functional markers associated with polymorphisms that define the aroma genes. The objective of this study was to evaluate the aroma status of rice accessions and to assess for the various alleles of badh2 gene using functional markers. A total of 56 rice accessions were evaluated at National Crops Resources Research Institute (NaCRRI) in Uganda for their aroma using sensory methods and a molecular marker to differentiate between aromatic and non- aromatic accessions. The aromatic accessions were then evaluated for variations within the betaine aldehyde dehydrogenase2 (badh2) gene responsible for aroma in rice using functional markers. Sensory evaluation of aroma identified 23 accessions to be aromatic; while 33 were non-aromatic. Molecular results identified 20 accessions as aromatic; while 36 accessions were non-aromatic. Functional marker analysis indicated the presence of badh2-E7 allele in 20 aromatic accessions within this collection that could be employed in the breeding programme for the rice aromatic trait.
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    Does root cutting in seedlings before transplanting affect growth and yield of lowland rice (Oryza sativa L.)?
    (ScienceOpen Posters, 2019) Alibu, S.; Asea, G.; Lamo, J.; Otim, M.; Ekobu, M.; Onaga, G.; Adur, S.; Tsuboi, T.
    Lowland rice cultivation is just beginning to take root in much of Sub-Sahara Africa, but transplanting is unpopular as it is labor-intensive and labor is becoming scarce and expensive. A substantial share of labor and time goes into preparing rice seedlings before transplanting, including carefully uprooting and washing the seedlings to minimize root injury. This study examined whether cutting the roots of rice seedlings before transplanting affects growth and yield of lowland rice.
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    Inheritance of resistance to bacterial blight and implication for rice improvement in Uganda
    (RUFORUM, 2010) Habarurema, I.; Asea, G.; Lamo, J.; Gibson, P.; Edema, R.
    Bacterial blight caused by Xanthomonas oryzae pv.oryzae, is a destructive disease of rice worldwide. Resistant varieties are the best option to avert the disease. Thirty resistance genes identified face a wide genetic diversity exhibited by the pathogen. Information on local isolates is not available and genetic mechanism for resistance harbored in Ugandan germplasm is unknown. Experimental sites were Makerere University and NaCRRI. Differential cultivars from Africa Rice were used to group Ugandan isolates. Seven parents were crossed into a half diallel to produce F1 and F2 progenies for determining the inheritance of resistance through inoculation. Preliminary results are reported.
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    Occurrence of Rice Yellow Mottle Virus resistance breaking isolates in Lowland Catchment Zones of Uganda
    (African Crop Science Journal, 2021) Ramathani, I.; Mukasa, S. B.; Alicai, T.; Nanyiti, S.; Lamo, J.
    Rice (Oryza spp; 2n=24.) production in Uganda and Africa in general, is seriously threatened by the Rice yellow mottle virus disease (RYMVD), a disease caused by Rice yellow mottle virus (RYMV) within the genus Sobemovirus; family Sobemoviridae. This study investigated the existence and distribution of resistance-breaking RYMV pathotype in the three major lowland rice catchment areas in Uganda. Four known rice accessions resistant to Rice yellow mottle virus (RYMV) namely; Gigante, Tog5672, Tog5674 and Tog5681, carrying resistant allele’s rymv1-2, rymv1-4 & RYMV3, rymv1-5 and rymv1-3, respectively, were tested for their response to different RYMV isolates. The isolates were collected from three major lowland rice catchment areas of Doho, Kibimba, and Olweny in Uganda. Out of 100 leaf samples collected from the field and assayed for RYMV and confirmed to be positive using RT-PCR, 83 isolates induced symptoms on IR64- the RYMV susceptible line. Seventyseven (92.8%) isolates were able to overcome resistance in at least one of the four differential rice accessions, as confirmed by the presence of RYMV symptoms; while 6 (7.2%) isolates were asymptomatic. Variation in time (days) for symptom development post-inoculation (dpi) and AUDPC were observed. Symptoms appeared within 5-7 days on IR64; while it took on average 11, 18, 36, and 18 days to appear on Gigante, Tog5672, Tog5674 and Tog5681, respectively. The highest AUDPC was observed on IR64 (254.7); while the lowest was observed on Tog5681 (74.1). Two major patho-groups were observed; those that broke down resistance in Gigante only (25.3%) and Gigante & Tog5672 (33.7%). Five isolates from Doho (Budaka & Bugiri districts) and Kibimba (Butaleja district) catchment areas broke down RYMV resistance in three accessions i.e. (Tog5681, Gigante & Tog5672) and (Tog5674, Gigante & Tog5672), respectively. Resistance breaking isolates were confirmed in all the three sampled catchment zones, however, Doho and Kibimba had some unique isolates that broke down resistance in accessions carrying resistance allele rymv 1-3 and rymv1-5 in addition to rymv1-2. Results from this study showed that RYMV isolates in Uganda can break down resistance conferred by the rymv1-2 resistance gene allele. However, accessions Tog5681 and Tog5674 seem to hold stable RYMV resistance and, thus are recommended for RYMV breeding.
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    Reaction of upland rice genotypes to the brown spot disease pathogen Bipolaris oryzae
    (African Journal of Rural Development (AFJRD), 2017) Mwendo, M. M.; Ochwo-Ssemakula, M.; Lamo, J.; Gibson, P.; Edema, R.
    Low yields in rice (Oryza sativa L.) are attributed to several factors but diseases represent one of the main constraints. The Brown spot disease (caused by Bipolaris oryzae (Breda de Haan) Shoem) in most cases causes considerable losses in rice growing areas. These yield loses could be averted through development and deployment of resistant varieties. In this study, a field experiment was conducted at the National Crops Resources Research Institute (NaCRRI) – Namulonge, Uganda during 2013 with the objective of identifying new sources of resistance to brown spot disease. Among the 100 tested rice lines, 18 lines were rated as highly resistant, 52 resistant, 27 moderately resistant and three lines including the checks were susceptible. The results revealed that there was significant variation in brown spot resistance among the genotypes tested. The identified resistant lines will be utilized in rice breeding program in Uganda for development of brown spot resistant genotypes.