Browsing by Author "Namugga, Prossy"
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Item Combining ability analysis of dry matter content, reducing sugars and yield of potato (Solanum tuberosum L.) genotypes in Uganda(Journal of Scientific Agriculture, 2020) Muhumuza, Edgar; Edema, Richard; Namugga, Prossy; Barekye, AlexPotato (Solanum tuberosum L.) in Uganda is a major food and cash crop mainly grown in the highland regions by small-scale farmers. The increasing importance of potato as a processed product requires new varieties possessing quality processing attributes with acceptable yield. The objectives of this study were to estimate the combining ability effects for dry matter content, reducing sugars, and yield related traits in potato. Nineteen F1 families generated from eight parents using a half diallel mating design were evaluated for dry matter content, reducing sugars, average weight per tuber and total tuber yield at Kachwekano research station. Additive genetic effects were predominant for dry matter content while non-additive effects for the other traits. The GCA/SCA ratios were 0.58, 0.28, 0.17 and 0.44 for dry matter content, reducing sugars, average weight per tuber and total tuber yield respectively. Broad sense heritability estimates were 50.6% for dry matter content, 77.8% for reducing sugars, 90.3% for average weight per tuber and 29.5% for total tuber yield. Parents NAROPOT 3 and 395096.2 had desirable GCA effects for both dry matter content and reducing sugars. Families of nkrk19.17 x Rutuku had desirable SCA effects for dry matter content while Rutuku x 393077.54 and nkrk19.17 x 392657.8 had desirable SCA effects for reducing sugars. Additive genetic effects for dry matter content imply that, genetic gains can be achieved through different selection methods and trait transferred to the respective progenies. The selected parents and families will be subjected to further clonal evaluation and selection.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 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 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 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.