Browsing by Author "Sibiya, Julia"
Now showing 1 - 9 of 9
Results Per Page
Sort Options
Item Breeding banana (Musa spp.) for drought tolerance: A review(Plant Breeding, 2020) Nansamba, Moureen; Sibiya, Julia; Tumuhimbise, Robooni; Karamura, Deborah; Kubiriba, Jerome; Karamura, EldadDrought is a major abiotic stress affecting banana production worldwide, leading to yield losses of up to 65%. Consequently, numerous efforts to understand and mitigate drought effects that include developing tolerant crop varieties are ongoing in several banana breeding programmes. The breeding efforts, however, have been greatly slowed down by inherent banana problems (polyploidy and male or female sterility) and complexity of drought tolerance (reportedly controlled by several genes). This review summarizes the pertinent research findings on water requirements of banana for its proper growth and productivity, symptoms of drought-sensitive varieties and field management strategies to cope with drought stress. The coping strategies deployed by resistant cultivars include high assimilation rates and water retention capacity as well as minor losses in leaf area and gaseous exchange. Reduced bunch weight, leaf chlorosis, wilting and strangled birth are underlined to be directly associated with drought susceptibility. Integration of conventional, molecular breeding and biotechnological tools as well as exploitation of the existing banana genetic diversity presents a huge opportunity for successful banana improvement.Item Combining ability analysis of earliness and yield of potato (Solanum tuberosum L.) genotype in Uganda(Euphytica, 2018) Namugga, Prossy; Sibiya, Julia; Melis, Rob; Barekye, AlexPotato (Solanum tuberosum L.) is a major food and cash crop mainly grown by small-scale farmers in the highland regions of Uganda. Changing global weather patterns require varieties that are able to grow within the short rainfall cycles and yield optimally under the prevailing conditions. The objectives of this study were to estimate the combining ability effects for early maturity, yield and yield related traits in potato. Eighteen F1 families generated from two sets of 12 parents using a North Carolina Design II were evaluated for days to 50% flowering, leaf senescence, yield and yield related traits in two different locations. Both additive and non-additive genetic effects influenced the expression of traits. However, additive genetic effects were predominant over the non-additive for most of the traits. The GCA/SCA ratios were 0.68 and 0.78 for days to 50% flowering and average tuber weight. Broad sense heritability estimates were 0.70 for total tuber weight and 0.78 for days to 50% flowering. The predominance of additive genetic effects implies that, genetic gains can be achieved through different selection methods and traits transferred to the respective progenies. Parents Rwangume, 396,038.107, 395,011.2, NKRK19.17, 393,077.54, Kimuri, and 392,657.8 had desirable GCA effects for the number of days to flowering and yield-related traits. Families of Rwangume × NKRK19.17, 393,077.54 × 395,011.2, 396,038.107 × Rwangume, and 396,038.107 × 395,011.2 had desirable SCA effects for yield and number of days to 50% flowering. The selected parents and families will be subjected to further clonal evaluation and selection.Item Development of sequence-based markers for seed protein content in pigeonpea(Molecular Genetics and Genomics, 2019) Obala, Jimmy; Saxena, Rachit K.; Singh, Vikas K.; Sameer Kumar, C. V.; Saxena, K. B.; Tongoona, Pangirayi; Sibiya, Julia; Varshney, Rajeev K.Pigeonpea is an important source of dietary protein to over a billion people globally, but genetic enhancement of seed protein content (SPC) in the crop has received limited attention for a long time. Use of genomics-assisted breeding would facilitate accelerating genetic gain for SPC. However, neither genetic markers nor genes associated with this important trait have been identified in this crop. Therefore, the present study exploited whole genome re-sequencing (WGRS) data of four pigeonpea genotypes (~ 12X coverage) to identify sequence-based markers and associated candidate genes for SPC. By combining a common variant filtering strategy on available WGRS data with knowledge of gene functions in relation to SPC, 108 sequence variants from 57 genes were identified. These genes were assigned to 19 GO molecular function categories with 56% belonging to only two categories. Furthermore, Sanger sequencing confirmed presence of 75.4% of the variants in 37 genes. Out of 30 sequence variants converted into CAPS/dCAPS markers, 17 showed high level of polymorphism between low and high SPC genotypes. Assay of 16 of the polymorphic CAPS/dCAPS markers on an F2 population of the cross ICP 5529 (high SPC) × ICP 11605 (low SPC), resulted in four of the CAPS/dCAPS markers significantly (P < 0.05) co-segregated with SPC. In summary, four markers derived from mutations in four genes will be useful for enhancing/regulating SPC in pigeonpea crop improvement programs.Item Diversity analysis and genomewide association studies of grain shape and eating quality traits in rice (Oryza sativa L.) using DArT markers(PLoS ONE, 2019) Mogga, Maurice; Sibiya, Julia; Shimelis, Hussein; Mbogo, Daniel; Muzhingi, Tawanda; Lamo, Jimmy; Yao, NasserMicroarray-based markers such as Diversity Arrays Technology (DArT) have become the genetic markers of choice for construction of high-density maps, quantitative trait loci (QTL) mapping and genetic diversity analysis based on their efficiency and low cost. More recently, the DArT technology was further developed in combination with high-throughput next-generation sequencing (NGS) technologies to generate the DArTseq platform representing a new sequencing tool of complexity-reduced representations. In this study, we used DArTseq markers to investigate genetic diversity and genome-wide association studies (GWAS) of grain quality traits in rice (Oryza sativa L.). The study was performed using 59 rice genotypes with 525 SNPs derived from DArTseq platform. Population structure analysis revealed only two distinct genetic clusters where genotypes were grouped based on environmental adaptation and pedigree information. Analysis of molecular variance indicated a low degree of differentiation among populations suggesting the need for broadening the genetic base of the current germplasm collection. GWAS revealed 22 significant associations between DArTseq-derived SNP markers and rice grain quality traits in the test genotypes. In general, 2 of the 22 significant associations were in chromosomal regions where the QTLs associated with the given traits had previously been reported, the other 20 significant SNP marker loci were indicative of the likelihood discovery of novel alleles associated with rice grain quality traits. DArTseq-derived SNP markers that include SNP12_100006178, SNP13_3052560 and SNP14_3057360 individually co-localised with two functional gene groups that were associated with QTLs for grain width and grain length to width ratio on chromosome 3, indicating trait dependency or pleiotropic-effect loci. This study demonstrated that DArTseq markers were useful genomic resources for genome-wide association studies of rice grain quality traits to accelerate varietal development and release.Item Genetic Characterisation and Diversity Assessment of Potato Genotypes Using SSR Markers(Journal of Agricultural Science, 2017) Namugga, Prossy; Sibiya, Julia; Melis, Rob; Barekye, AlexInformation on diversity of genetic materials is vital for choosing parents in a breeding program. The objective of the study was to determine the pattern and level of genetic diversity among the selected 20 tetraploid potato genotypes using 16 SSR markers to identify suitable parents for breeding purposes. The microsatellites showed considerable variation among genotypes and sixty four alleles were amplified by the 16 primer pairs. The number of polymorphic alleles per locus ranged from 2 to 8 with an average of 3.9. The highest number of null alleles was observed was six for genotype Nakpot1. The overall size of the amplified product varied from 48 bp (marker STI0023) to 309 bp (marker STM5121). PIC values ranged from 0.0948 to 0.7832, with an average of 0.4307 per locus. Heterozygosity values ranged from 0.0997 to 0.805 with an average of 0.466919. Significant positive linear correlations were observed between PIC values and number of alleles (r = 0.905); and heterozygosity and number of alleles (r = 0.8659) at p < 0.001. Cluster analysis separated the genotypes into three different groups. The genetic distance between clones ranged from 1 to 5.7. Cruza had the highest genetic distance while the shortest genetic distance was observed between 396026.103 and 396034.104. The microsatellites used in this study provided useful information regarding the variability of the tested genotypes and their selection for breeding purposes.Item Pearl Millet Socioeconomic and Production Characteristics in Uganda(National Semi Arid Resources Research Institute, 2015) Lubadde, Geofrey; Tongoona, Pangirai; Derera, John; Sibiya, JuliaPearl millet is an important cereal grown by farmers in environmentally marginalised areas. In Uganda it is mainly grown in northern (Acholi), northeastern (Karamoja) and eastern (Teso) regions. The regions are characterised by semi-arid conditions with high temperatures, low mean annual rainfall and widespread chronic food insecurity. Technologies that increase pearl millet productivity under such conditions have been developed in international research institutes to highlight the importance of pearl millet as a resilient crop suitable for drought conditions. However, not much is known about the importance of the crop in Uganda. A baseline survey was thus conducted to document pearl millet farmers’ socioeconomic and production characteristics in the country. Information was collected about demography and food security situation, livelihood, social capital and trainings, importance and utilisation of pearl millet, agronomic characteristics, desirable and undesirable traits, factors of crop and animal production, post-harvest handling, production and marketing constraints and coping strategies. Results indicated that the average age of heads of households (mainly males) was 45.78 years while that of their spouses was 37.22 years; with a pearl millet growing experience of over six years. In addition, majority of the households had 6-10 members many of whom were below 15 years. The heads of households were married with education experience of more than five years while their spouses were generally illiterate. The household heads and their spouses farmed the land as their main economic activity. Furthermore, majority of the households lived under poor conditions where the main house had a single room built of mud and wattle with grass as the main roofing material and earth floor. The poor living standards were worsened by majority of the households facing perpetual food insecurity mainly due to drought, insect pests, plant diseases and lack of improved planting materials.Item Phenotypic characterisation of potato (Solanum tuberosum) genotypes in Uganda(South African Journal of Plant and Soil, 2017) Namugga, Prossy; Sibiya, Julia; Melis, Rob; Barekye, AlexIdentification of genetic variation and interrelationships among germplasm collections is essential for parental selection and trait identification among parents for use in breeding programmes. The aim of this study was to characterise 48 potato genotypes to identify suitable parents for crop improvement purposes. Genotypes were evaluated in the field using an alpha lattice design with three replications at the Kachwekano and Karengyere research stations in Uganda. Site had significant effects on genotype performance for all measured parameters. Genotypic effects were significant (p < 0.01) for total tuber yield, main stem number and plant height. The mean tuber yield for the two sites was 29.8 t ha−1 and tuber yield was higher in Kachwekano than Karengyere. The highestyielding genotype in Kachwekano was 396038.105 (54.5 t ha−1) and in Karengyere was NAKPOT5 (50.9 t ha−1). Significant positive correlations (p ≤ 0.001) were observed between tuber yield and plant height; duration of flowering, and days to flowering and plant height. The most stable genotypes with regard to tuber yield were Rutuku, 395112.32, 395017.14 and 393220.54. Cluster analysis revealed three principal clusters with nine subclusters. Variation for the different traits exhibited by genotypes in this study should be exploited in crop improvement programmes.Item Seed protein content and its relationships with agronomic traits in pigeonpea is controlled by both main and epistatic effects QTLs(Scientific reports, 2020) Obala, Jimmy; Saxena, Rachit K.; Singh, Vikas K.; Kale, Sandip M.; Garg, Vanika; Sameer Kumar, C. V.; Saxena, K. B.; Tongoona, Pangirayi; Sibiya, Julia; Varshney, Rajeev K.The genetic architecture of seed protein content (SPC) and its relationships to agronomic traits in pigeonpea is poorly understood. Accordingly, five F2 populations segregating for SPC and four agronomic traits (seed weight (SW), seed yield (SY), growth habit (GH) and days to first flowering (DFF)) were phenotyped and genotyped using genotyping-by-sequencing approach. Five high-density population-specific genetic maps were constructed with an average inter-marker distance of 1.6 to 3.5 cM, and subsequently, integrated into a consensus map with average marker spacing of 1.6 cM. Based on analysis of phenotyping data and genotyping data, 192 main effect QTLs (M-QTLs) with phenotypic variation explained (PVE) of 0.7 to 91.3% were detected for the five traits across the five populations. Major effect (PVE ≥ 10%) M-QTLs included 14 M-QTLs for SPC, 16 M-QTLs for SW, 17 M-QTLs for SY, 19 M-QTLs for GH and 24 M-QTLs for DFF. Also, 573 epistatic QTLs (E-QTLs) were detected with PVE ranging from 6.3 to 99.4% across traits and populations. Colocalization of M-QTLs and E-QTLs explained the genetic basis of the significant (P < 0.05) correlations of SPC with SW, SY, DFF and GH. The nature of genetic architecture of SPC and its relationship with agronomic traits suggest that genomics-assisted breeding targeting genome-wide variations would be effective for the simultaneous improvement of SPC and other important traits.Item Yield Response of Potato (Solanum tuberosum L.) Genotypes to Late Blight Caused by Phytophthora infestans in Uganda(American Journal of Potato Research, 2018) Namugga, Prossy; Sibiya, Julia; Melis, Rob; Barekye, AlexPotato (Solanum tuberosum L.) is a major food and cash crop, mainly grown by small-scale farmers in the highland regions of Uganda. Potato late blight is one of the major diseases limiting production with potential yield losses over 70%, making host resistance a strong element in integrated disease management. This study was carried out to screen and select high yielding potato genotypes with resistance to late blight in Uganda. Forty-eight genotypes, including advanced clones from the population B3C2 of the International Potato Centre, commercial and farmers’ varieties, were evaluated under two environments for two seasons. Trials were laid out in an 8 × 6 alpha lattice design with three replications. Genotypes showed significant differences in yield and resistance to blight. A higher disease severity was observed in Karengyere (56%). The average RAUDPC (= 100 max) across locations indicated that genotypes 395,077.12 and 392,657.8, with disease severity of 12% and 14%, respectively, were the most resistant. Genotypes Victoria (53%) and NKRN59.124 (48%) were the most susceptible. Mean tuber yield under late blight infection was19.8 t ha−1. The best yielding genotype across sites was 395,112.32 (35.6 t ha−1) while 394,905.8 (10.3 t ha−1), yielded the lowest. The mean marketable tuber weight was 8.9 kg with genotypes 395,112.32 and 395,109.34 having the highest marketable weight of 16.5 kg and 15.6 kg respectively. Correlations between yield and yield related parameters were positive (p ≤ 0.001), while those between RAUDPC were negative. The following genotypes, 395,112.32, 391,919.3, 393,220.54. 393,077.54, 396,038.107. 392,657.8, Kinigi, 395,014.17, NKRN59.58, NKRK19.17 and 395,011.2, were identified as promising parents for a late blight resistance breeding program. These exhibited high to medium resistance to late blight disease and high yields.