Browsing by Author "Gibson, P."
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Item Characterization and Evaluation of Potato Genotypes (Solanum tuberosum L) for Tolerance to Drought in Uganda(American Journal of Potato Research, 2016) Kesiime, V. E.; Tusiime, G.; Kashaija, I. N.; Edema, R.; Gibson, P.; Namugga, P.; Kakuhenzire, R.Potato production in Uganda is being affected by rainfall fluctuations in both timing and amount, resulting into inadequate soil moisture availability and low productivity. Also, potato production is expanding into locations at lower altitudes, where drought is more common. Therefore, drought stress mitigation measures and coping mechanisms need to be devised to face future challenges of climate change, particularly in developing countries to ensure steady supply of adequate quantities of quality food. This study thus, aimed at characterizing new potato clones from CIP (International Potato Center) for tolerance to drought under Ugandan conditions. Consequently a screen house experiment was conducted twice at Kachwekano Zonal Agricultural Research and Development Institute (KAZARDI) from October 2011 to February 2012 and April to July 2012 to evaluate and characterize eight potato genotypes; five of which were obtained from CIP’s breeding collection for drought tolerance and low altitude areas, and three locally released varieties from Uganda. These clones were tested for drought tolerance at three levels of simulated moisture deficit; 25 % field capacity, 50 % and 100 % field capacity (FC). Data were collected on leaf chlorophyll content, relative leaf water content, number of days to 50 % flowering, percent ground cover, leaf area, plant height, number of stems per plant, stem diameter, stress score, increment in plant height after imposing stress, tuber dry matter content and yield components. Of all the traits evaluated, yield and number of days to 50 % flowering contributed most to drought tolerance among the potato genotypes evaluated. There were significant (P ≤ 0.05) differences among genotypes for all evaluated traits. Results from both growth, physiological and yield parameters revealed that the new potato clones were less affected by drought stress compared to adapted varieties. Total tuber yield was 23 tons per hectare, 11.4 and 8.1 in plots at full field capacity, 50 % and 25 % moisture stressed plots respectively in the first experiment. A similar trend was obtained in the second experiment with 19 tons per hectare, 13.7 and 11.3 respectively. The new clones at highest moisture stress had significantly (P ≤ 0.05) higher yields than adapted varieties providing a promise for possible new varieties and breeding stock in extreme conditions of moisture deficit.Item Evaluation of Genomic Prediction Algorithms for Reducing Selection and Breeding Cycles in Shea Tree (Vitellaria Paradoxa)(Uganda Journal of Agricultural Sciences, 2021) Odoi, J. B.; Prasad, H.; Arfang, B.; Kitiyo, R.; Ozimati, A.; Gibson, P.; Edema, R.; Gwali, S.; Odong, T. L.The focus of this study was to determine the genomic prediction (GP) algorithms with the highest prediction accuracies for reducing the breeding and selection cycles in Vitellaria paradoxa. The efficiency of the GP algorithms were compared to evaluate five Shea tree growth traits in 708 genotypes with 30734 Single Nucleotide Polymorphic (SNPs) markers, which were reduced to 27063 after removing duplicates. Five hundred forty-nine (77.54%) Shea tree training population and 159 (22.46%) training population were genotyped for 30734 single nucleotide polymorphisms (SNPs) and phenotyped for five Shea tree growth traits. We built a model using phenotype and marker data from a training population by optimizing its genomic prediction accuracy for effectiveness of GS. The phenotype and marker data were used for cross validation of the prediction accuracies of the different models. Prediction accuracies varied among the genomic prediction algorithms based on the five phenotypic traits. We determined the best genomic algorithm that is more suitable for reduction of selection and breeding cycles in Vitellaria paradoxa. The GP algorithms were evaluated and we conclude that rrBLUP is the best for improving the prediction accuracy for reducing the breeding cycle in Shea tree.Item Farmers’ Perceptions On Maize Ear Rots And The Prospects For Breeding Farmer Preferred Varieties In Uganda(In Proceedings of The Second RUFORUM Biennial Meeting, 2010) Tembo, L.; Okori, P.; Asea, G.; Gibson, P.Maize ear rots are a major constraint to maize production globally, and yield loses of up to 70% have been reported in Uganda. Developing varieties resistant to ear rots is a practical strategy that provides better insurance for the small scale farmers. To enhance the adoption of varieties, farmers’ perceptions should be included early in the breeding programme. In this study a survey was done in four districts of Uganda to examine farmers’ perception on ear rots and their views on agronomic desirable traits. High yield and earliness were the most preferred traits by the farmers.Item Identification of Common Bean Genotypes with Dual Leaf And Pod Resistance to Common Bacterial Blight Disease in Uganda(Crop Science Journal, 2018) Alladassi, B.M.E.; Nkalubo, S.T.; Mukankusi, C.; Kayaga, H.N.; Gibson, P.; Edema, R.; Urrea, C.A.; Kelly, J.D.; Rubaihayo, P.R.Common Bacterial Blight (CBB), caused by Xanthomonas axonopodis pv. phaseoli (Xap) and Xanthomonas axonopodis pv. phaseoli var. fuscans (Xapf), is a serious disease that affects common bean production worldwide. In Uganda, it is the most severe and widely occurring bacterial disease, causing significant yield losses in common bean. Although various sources of resistance have been developed around the world, none of the varieties grown in Uganda is known to be resistant. The objective of this study was to identify lines with combined leaf and pod resistance for introgression into locally adapted but susceptible Ugandan genotypes. A total of 132 common bean accessions was evaluated in a screenhouse and under field conditions, in an 11x12 alpha lattice design. Genotypes were inoculated with a local isolate in a screenhouse; while the plants were left to undergo natural infestation in field. Results indicated significant differences (P<0.001) in genotypic reactions against the CBB disease, with a range of disease scores of 2.2 - 7.8 on leaves and 2.6 - 7.1 on pods (1-9 CIAT disease scale), suggesting high genetic variability among the tested germplasm. Relatively low correlation (r = 0.39) was observed between leaf and pod reactions, suggesting differential expression of CBB resistance in these two plant organs. Overall, four genotypes, NE2-14-8, NE17-14-29, NE14-09-78 and VAX3, consistently showed resistance in both screenhouse and field evaluations, leaf and pod inoculations and at all sampling stages. These genotypes were, therefore, identified for transferring CBB resistance into Ugandan susceptible market class bean varieties.Item Improvement of Resistance to Fusarium Root Rot through Gene Pyramiding in Common Bean(African Crop Science Journal, 2012) Obala, J.; Mukankusi, C.; Rubaihayo, P.R.; Gibson, P.; Edema, R.Fusarium root rot (FRR), caused by Fusarium solani f.sp. phaseoli, is one of the most serious root rot diseases of common bean (Phaseolus vulgaris L.) throughout the world. Yield losses of up to 84% have been attributed to the disease. Development and deployment of resistant materials is the most feasible approach to managing the disease. The objective of this study was to estimate the number of pyramided Fusarium root rot resistance genes among the four resistant lines and determine their effectiveness in improving levels of resistance to Fusarium root rot in the susceptible bean cultivars. Crosses among four Fusarium root rot (Fusarium solani f.sp. phaseoli) resistant common bean (Phaseolus vulgaris) were developed. They involved six inbred lines, MLB-48-89A (M48), MLB-49-89A (M49), G2333 (G2) and G685 (G6), and two susceptible cultivars, K20 and Kanyebwa, The resistant lines were used to develop a double cross (DC) population. The DC F1 and each resistant parent were crossed to each of the two susceptible cultivars to form five-parent and single crosses, respectively. Developed populations were subjected to Fusarium solani f. sp. phasoeli isolate-3 under screenhouse conditions. There were segregation ratios of 15:1 (χ2 = 1.89, P = 0.17), 61:3 (χ2 = 0.18, P = 0.67) and 249:7 (χ2 = 1.74, P = 0.19) indicating that two, three and four genes independently condition resistance to F. solani in lines G2 x G6, M49 x M48 and (M49 x M48) x (G2 x G6). A good fit of only four genes in the double cross compared to two in the G2 x G6 , and three genes in the M49 x M48 cross suggests that at least one parent in the G2 x G6 cross have the same or closely linked genes as a parent in the M49 x M48 cross. The F1 means of the five-parent cross (FPC) involving either susceptible parent had lower disease scores, though not significantly (P > 0.05), than the single-crosses from that parent. The F2 of both FPC showed less disease than the single-cross (SC) means (P < 0.05) compared to the single-cross (SC) while the F2 of both FPC had a significant negative deviation (P < 0.05). The F2 frequency distributions also showed that the FPC in both Kanyebwa and K20 populations had higher proportions of resistant plants than any of the single crosses in the respective populations. The superior performance of the FPC over the SC demonstrates that combining resistance genes form different FRR resistance sources can provide a stable source of resistance than using single sources of resistance.Item 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.Item Potential sources of high iron and zinc content in Ugandan bean germplasm(RUFORUM, 2012) Mukamuhirwa, F.; Tusiime, G.; Mukankusi, C.; Gibson, P.; Edema, R.The study was conducted at National Agricultural Research Laboratories (NARL) at Kawanda in order to identify potential sources of high iron and zinc content, Such varieties would contribute to improved health of bean (Phaseolus vulgaris) consumers, who, despite a high consumption of beans, suffer from anemia caused by micronutrient malnutrition (especially iron and zinc). One hundred and eighty seven genotypes from Uganda were screened for iron (Fe) and zinc (Zn) content. The mineral analysis revealed that there was significant (P=0.001) diversity in Fe and Zn content among the Ugandan genotypes with the range of 45 to 87mg/kg of iron and 22 to 40 mg/kg of zinc. Ten Ugandan bean varieties were identified as potential sources of both high iron and zinc content.Item 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.