Browsing by Author "Oloka, Bonny"

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    Developing Lowland Rice Germplasm with Resistance to Multiple Biotic Stresses through Anther Culture in Uganda
    (The Korean Society of International Agriculture, 2015) Lamo, Jimmy; Gyoung-rae, Cho; Ininda, Jane; Kofi Ayirebi, Dartey Paul; Ekebu, James; Ekobu, Moses; Alibu, Simon; Okanya, Stephen; Oloka, Bonny; Otim, Michael; Asea, Godfrey; Kyung-Ho, Kang
    The lowland rice genotypes grown in Uganda were introduced in the 1970s. These genotypes (now landraces) are threatened by multiple biotic stresses namely; Rice Yellow Mottle Virus (RYMV) disease, Bacterial Leaf Streak(BLS). Bacterial Leaf Blight (BLB), and Rice Blast (BL). There are currently no rice lines with multiple resistance to these stresses although attempts have been made to develop them through hybridization involving cultivated, local and introduced lines and four varieties with tolerance to RYMV have been released. The use of potential resistance donor such as the traditional African cultivated rice, Oryza glaberrima, could be an alternative approach to furnish multiple resistance to the cultivated rice. The rice germplasm developed from a cross of an Oryza glaberrima from Niger Delta and Milyang23, a high-yielding Korean rice variety were evaluated for multiple resistance in Uganda as a Korea-Africa Food & Agriculture Cooperation Initiative (KAFACI)-Alliance for a Green Revolution in Africa (AGRA) joint cooperative project, “Enhancement of High Yielding Rice Germplasm in African Countries through Anther Culture Breeding”. Milyang23 was back crossed 4 times with Oryza. glaberrima and fixed through anther culture in Korea. An evaluation of 50 lines generated showed that up to 98%, 92%, 88% and 88% of the test plants showed resistance to the RYMV, BLS, BLB and BL diseases, respectively. There was no symptoms of the four diseases in 74% of the genotypes tested. The plants that showed symptoms of the three diseases had scores of not more than 3 on a 1 to 9 scale. This preliminary finding demonstrates that these generations of rice lines could help solving the current problem of susceptibility to multiple diseases.
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    Reaction of selected rice genotypes with monogenic resistance to the isolate of Magnaporthe Oryzae collected at Namulonge, Uganda
    (Journal of Plant Breeding and Crop Science, 2022) Nakiyaga, Solome; Chiteka, Zwenhamo Albert; Onaga, Geoffrey; Gibson, Paul; Oloka, Bonny; Badji, Arfang; Edema, Richard
    The fungus Magnaporthe oryzae causes rice blast disease leading to substantial yield losses. This study aims at understanding the effectiveness of R-genes to the isolate of M. oryzae from Namulonge in Central Uganda to decide the incorporation of their carrier lines in local gene pyramiding programs. Eighty-three genotypes (73 monogenic resistance lines and 10 local varieties) were evaluated in two different experiments along with two susceptible and one resistant check in the screen house in a 10 × 8 alpha lattice design with two replications, inoculated by spraying, phenotyped at 7, 14 and 21 days after inoculation (DAI), and data on for disease severity, severity percentage, disease incidence, and relative area under disease progression were analyzed using the restricted maximum likelihood (ReML) in Genstat. The tested genotypes were significantly (P<0.001) different for the first, second and across experiments at 7, 14 and 21 DAI for all the measured traits indicating genetic variability among the tested germplasm for rice resistance to blast disease caused by the Namulonge isolate of M. oryzae. Twenty-five out of eighty-three (22.9%) genotypes had consistently low disease severity scores during the two experiments with a range of 0-3. The R genes Pi3, Pi5 (t), Pi7 (t), Pi-b, Pik, Pi54, Pik-m, Pit, Pita, Pita-2, Piz, Piz-4, Piz-5 were considered effective to this particular isolate. The results of this study set the basis of a breeding program for rice resistance to blast disease caused by the Namulonge isolate of M. oryzae through gene pyramiding.