NRU :: Browsing by Author "Ochwo-Ssemakula, M."

Browsing by Author "Ochwo-Ssemakula, M."

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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.
Characterization and Distribution of a Potyvirus Associated with Passion Fruit Woodiness Disease in Uganda
(Plant Disease, 2012) Ochwo-Ssemakula, M.; Sengooba, T.; Hakiza, J. J.; Adipala, E.; Edema, R.; Redinbaugh, M. G.; Aritua, V.; Winter, S.
This article describes the incidence and etiology of a viral disease of passion fruit in Uganda. Symptoms, including those characteristic of passion fruit woodiness disease (PWD), were observed on 32% of plants in producing areas. Electron microscopic observations of infected tissues revealed flexuous filaments of ca. 780 nm. Enzymelinked immunosorbent assays indicated a serological relationship with Cowpea aphid-borne mosaic virus (CABMV) and Passion fruit ringspot virus (PFRSV). In host range studies, only species in the families Solanaceae and Chenopodiaceae were susceptible, and neither Vigna unguiculata nor Phaseolus vulgaris became infected. Coat protein (CP) gene sequences of eight isolates exhibited features typical of potyviruses and were highly similar (88 to 100% identity). However, the sequences had limited sequence identity with CP genes of two of the three potyviruses reported to cause PWD: East Asian Passiflora virus and Passion fruit woodiness virus (PWV). Deduced amino acid sequences for the CP of isolates from Uganda had highest identity with Bean common mosaic necrosis virus (BCMNV) (72 to 79%, with evolutionary divergence values between 0.17 and 0.19) and CABMV (73 to 76%, with divergence values between 0.21 and 0.25). Based on these results and in accordance with International Committee for Taxonomy of Viruses criteria for species demarcation in the family Potyviridae, we conclude that a previously unreported virus causes viral diseases on passion fruit in Uganda. The name “Ugandan Passiflora virus” is proposed for this virus.
Distribution and Variability of Pseudocercospora griseola in Uganda
(Journal of Agricultural Science, 2012) Ddamulira, G.; Mukankusi, C.; Ochwo-Ssemakula, M.; Edema, R.; Sseruwagi, P.; Gepts, P.
is highly variable with many different races occurring in different agro-ecological zones. Therefore, for an effective breeding program, there is a need to continuously monitor the distribution and variability of the pathogen as a means of guiding breeders on which races to target. A study was conducted to assess the incidence, severity and variability of P. griseola in bean growing districts of Dokolo, Lira, Apac, Sironko, Mbale, Rakai, Lwengo, Bukomansibi, Kabale and Kisoro in Uganda. Forty five out of 80 isolates collected were tested on a set of 12 international bean differentials cultivars for ALS. Molecular markers were also used to elucidate the variability among isolates. In all districts, ALS was found wide spread with a mean incidence of 49.9%. Dokolo district had the highest disease incidence and severity, while Kisoro registered the lowest values respectively. In terms of altitude, incidence (60%) and severity (45%) were high for bean fields located between 1000-1200 m and low disease incidence (33.6%) and severity (20.7%) for fields lying above 1500 m. The standard differential cultivars and molecular markers defined 12 pathotypes and 30 haplotypes respectively. These belonged to Middle America and Andean group with considerably high level of diversity. Our findings indicated the presence of ALS in Uganda with high incidence, severity and variability across districts and altitudes. Hence strategic interventions involving integrated disease management and breeding for durable resistance are required to manage the disease.
Genetic Basis of Maize Resistance to Multiple Insect Pests: Integrated Genome-Wide Comparative Mapping and Candidate Gene Prioritization
(Genes, 2020) Badji, A.; Kwemoi, D. B.; Machida, L.; Okii, D.; Mwila, N.; Agbahoungba, S.; Kumi, F.; Ibanda, A.; Bararyenya, A.; Solemanegy, M.; Odong, T.; Wasswa, P.; Otim, M.; Asea, G.; Ochwo-Ssemakula, M.; Talwana, H.; Kyamanywa, S.; Rubaihayo, P.
Several species of herbivores feed on maize in field and storage setups, making the development of multiple insect resistance a critical breeding target. In this study, an association mapping panel of 341 tropical maize lines was evaluated in three field environments for resistance to fall armyworm (FAW), whilst bulked grains were subjected to a maize weevil (MW) bioassay and genotyped with Diversity Array Technology’s single nucleotide polymorphisms (SNPs) markers. A multi-locus genome-wide association study (GWAS) revealed 62 quantitative trait nucleotides (QTNs) associated with FAW and MW resistance traits on all 10 maize chromosomes, of which, 47 and 31 were discovered at stringent Bonferroni genome-wide significance levels of 0.05 and 0.01, respectively, and located within or close to multiple insect resistance genomic regions (MIRGRs) concerning FAW, SB, and MW. Sixteen QTNs influenced multiple traits, of which, six were associated with resistance to both FAWandMW, suggesting a pleiotropic genetic control. Functional prioritization of candidate genes (CGs) located within 10–30 kb of the QTNs revealed 64 putative GWAS-based CGs (GbCGs) showing evidence of involvement in plant defense mechanisms. Only one GbCG was associated with each of the five of the six combined resistance QTNs, thus reinforcing the pleiotropy hypothesis. In addition, through in silico co-functional network inferences, an additional 107 network-based CGs (NbCGs), biologically connected to the 64 GbCGs, and di erentially expressed under biotic or abiotic stress, were revealed within MIRGRs. The provided multiple insect resistance physical map should contribute to the development of combined insect resistance in maize.
Genomic Prediction of Tropical Maize Resistance to Fall Armyworm and Weevils: Genomic Selection Should Focus on Effective Training Set Determination
(ResearchGate, 2020) Badji, A.; Machida, L.; Kwemoi, D. B.; Kumi, F.; Okii, D.; Mwila, N.; Agbahoungba, S.; Ibanda, A.; Bararyenya, A.; Nghituwamhata, S. N.; Odong, T.; Wasswa, P.; Otim, M.; Ochwo-Ssemakula, M.; Talwana, H.; Asea, G.; Kyamanywa, S.; Rubaihayo, P.
Genomic selection (GS) can accelerate variety release by shortening variety development phase when factors that influence prediction accuracies (PA) of genomic prediction (GP) models such as training set (TS) size and relationship with the breeding set (BS) are optimized beforehand. In this study, PAs for the resistance to fall armyworm (FAW) and maize weevil (MW) in a diverse tropical maize panel composed of 341 double haploid and inbred lines were estimated. Both phenotypic best linear unbiased predictors (BLUPs) and estimators (BLUEs) were predicted using 17 parametric, semi-parametric, and nonparametric algorithms with a 10-fold and 5 repetitions cross-validation strategy. n. For both MW and FAW resistance datasets with an RBTS of 37%, PAs achieved with BLUPs were at least as twice as higher than those realized with BLUEs. The PAs achieved with BLUPs for MW resistance traits: grain weight loss (GWL), adult progeny emergence (AP), and number of affected kernels (AK) varied from 0.66 to 0.82. The PAs were also high for FAW resistance RBTS datasets, varying from 0.694 to 0.714 (for RBTS of 37%) to 0.843 to 0.844 (for RBTS of 85%). The PAs for FAW resistance with PBTS were generally high varying from 0.83 to 0.86, except for one dataset that had PAs ranging from 0.11 to 0.75. GP models showed generally similar predictive abilities for each trait while the TS designation was determinant. There was a highly positive correlation (R=0.92***) between TS size and PAs for the RBTS approach while, for the PBTS, these parameters were highly negatively correlated (R=-0.44***), indicating the importance of the degree of kinship between the TS and the BS with the smallest TS (31%) achieving the highest PAs (0.86). This study paves the way towards the use of GS for maize resistance to insect pests in sub-Saharan Africa.
Identification of new sources of resistance to angular leaf spot among Uganda common bean landraces
(Canadian Journal of Plant Breeding, 2014) Ddamulira, G.; Mukankusi, C.; Ochwo-Ssemakula, M.; Edema, R.; Sseruwagi, P.; Gepts, P.
Breeding for resistance to Angular Leaf spot (ALS), a fungal disease caused by Pseudocercospora griseola (Sacc), is faced with a challenge of the existence of a few resistance sources that are exotic and not well adapted to environmental conditions in Uganda. In addition, P. griseola is a highly variable pathogen that co-evolves with its host, therefore necessitating the continuous identification of new and stronger sources of resistance. Identification of local bean landraces/adapted bean varieties with resistance to ALS would probably quicken the progress of development of resistant cultivars, and reduce yield losses. Seventy four landraces, four commercial varieties, and two controls were screened with four P. griseola pathotypes 1:6, 17:39, 21:39, and 61:63 to determine their ALS resistance levels. One landrace, U00297, showed consistent and strong resistance to the four pathotypes. The inheritance of resistance in U00297 was established from three individual populations derived from crosses with three susceptible cultivars, K132, K131, and Kanyebwa, commercially grown in Uganda. The allelic relationships between U00297 and two existing ALS resistance sources, AND277 and G5686 were tested. Segregation ratios of F2 populations revealed that U00297 resistance to pathotype 17:39 is conferred by a single dominant gene, while digenic epistatic gene interactions were suggested for resistance to other pathotypes. The general and specific combining abilities were significant for resistance revealing the importance of additive and dominant components in the inheritance of ALS resistance. As a resistant parent, U00297 was a good combiner for resistance to pathotype 17:39, and effective resistance source to pathotypes 17:39 and 61:63. The allelic test indicated that the dominant gene in U00297 is independent of resistance genes harboured by resistance sources AND277 and G5686. The information generated is useful to breeding programs targeting developing bean cultivars carrying novel ALS resistance based on genes derived from U00297.
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.

Browsing by Author "Ochwo-Ssemakula, M."

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