Browsing by Author "Byarugaba, Arinaitwe Abel"
Now showing 1 - 8 of 8
Results Per Page
Sort Options
Item Bridging the gap in quality and quantity of seed potatoes through farmer managed screen houses in Uganda(African Journal of Plant Science, 2017) Byarugaba, Arinaitwe Abel; Kyooma, John; Aheisibwe, Rwaheru Ambrose; Tibanyedera, Deo; Barekye, AlexQuality seed potato is a key factor in enhancing potato yields in Uganda. Available disease-free seed potato accounts for less than 5% of the whole potato seed market demand in Uganda leaving 95% as seed availability gap. This study was conducted to explore the potential of using farmer managed screen houses to alleviate the seed potato availability gap that exists in Uganda. Six screen houses of 7 m × 14 m each with capacity of 1620 plants were set up, three (3) screen houses in Bukimbiri, one (1) in Kisoro, one (1) in Hamurwa and one (1) in Maziba sites. All the sites were managed by trained six famers. Sterilized soil was used to reduce the incidence of pathogens and to ensure that clean minitubers were produced. Seed production was done in 2015 for two consecutive seasons (A and B). From the 6 screen houses, a total of 107,638 clean mini-tubers were generated across the sites for both seasons. At multiplication ratio of 1: 9 the generated mini-tubers have the potential of generating 968,742 tubers. This would reduce on existing seed gap for the next season. It was noted during the study that mini-tuber production, vigour and rate of growth varied significantly (P<0.001) across the varieties with ‘Rwangume’ achieving the highest yield in terms of tuber number per plant and height, compared to other 4 varieties (Kiningi, Rwashaki, Kachpot 1 and Victoria). This study showed that production of disease free mini-tuber at farmer level is possible using screen house technology and has a potential of reducing the seed availability gap through production of quality seed that can be accessed by other farmersItem Comparative Phenotypic and Agronomic Assessment of Transgenic Potato with 3R-Gene Stack with Complete Resistance to Late Blight Disease(Biology, 2021) Byarugaba, Arinaitwe Abel; Baguma, Gerald; Mutebi Jjemba, Douglas; Aharinta, Kenneth Faith; Wasukira, Arthur; Magembe, Eric; Njoroge, Anne; Barekye, Alex; Ghislain, MarcTransgenic potato event Vic.172, expressing three naturally occurring resistance genes (R genes) conferring complete protection against late blight disease, was evaluated for resistance to late blight, phenotypic characterization, and agronomic performance in field conditions at three locations during three seasons in Uganda. These trials were conducted by comparison to the variety Victoria from which Vic.172 derives, using identical fungicide treatment, except when evaluating disease resistance. During all seasons, the transgenic event Vic.172 was confirmed to have complete resistance to late blight disease, whereas Victoria plants were completely dead by 60–80 days after planting. Tubers from Vic.172 were completely resistant to LB after artificial inoculation. The phenotypic characterization included observations of the characteristics and development of the stems, leaves, flowers, and tubers. Differences in phenotypic parameters between Vic.172 and Victoria were not statistically significant across locations and seasons. The agronomic performance observations covered sprouting, emergence, vigor, foliage growth, and yield. Differences in agronomic performance were not statistically significant except for marketable yield in one location under high productivity conditions. However, yield variation across locations and seasons was not statistically significant, but was influenced by the environment. Hence, the results of the comparative assessment of the phenotype and agronomic performance revealed that transgenic event Vic.172 did not present biologically significant differences in comparison to the variety Victoria it derives from.Item Genotype by environment interaction (GxE) as a measure of yield stability of Dutch potato varieties in Uganda(African Journal of Agricultural Research, 2018) Byarugaba, Arinaitwe Abel; Benon, Mateeka; Tibanyedera, Deo; Barekye, AlexTwenty one (21) Dutch potato varieties were introduced in Uganda during 2015-2016 seasons for national yield performance and adaptability studies so that most stable varieties could be identified for production. The effect of genotype (G), environment (E) and their interaction (G x E) on tuber yield was assessed to establish variety adaptation in different agro ecologies. Five sites were used in the study that included; Kalegyere (2450 m/asl), Kachwekano (2225m/asl), Rwebitaba (1531m/asl), Buginyanya (1887m/asl) and Zeu-DFI (1642m/asl). The varieties that yielded highest were; El-mundo (22 t ha-1), Sarpomira (22 t ha-1), Connect (21.7T/ha), Rudolph (21.4t ha-1), Arizona (20.3 t ha-1), Voyager (20 t ha-1), Faluka (19.9 t ha-1) and Sagitta (19.9 t ha-1). GxE analysis was done using Additive main effects and multiplicative interaction (AMMI) and results showed that GxE interaction accounted for 12.6% of the total variation, while genotypes and environments accounted for 5.7% and 59.7% of the total variation respectively. The AMMI bi-plots identified varieties Caruso, Derby, Voyager, Royal, Navigator, Manitou, Destiny, Musica and Markies to have the lowest (0.00033-0.6609) IPCA 1 score hence were most adapted. Varieties Rwagume, Sarpo Mira, Connect and Kachpot 1 were more adapted at Kalegyere site (-3.601 IPCA1 score) while Sarpo Mira, Connect, El-Mundo and Rudolph were adapted at Kachwekano site (-0.562 IPCA1 score). Varieties Arizona, Faluka, Panamera and Connect were adapted at Zeu (0.125 IPCA1 score). Varieties El-Mundo, Arizona, Rudolph and Connect were more adapted at Buginyanya ZARDI (0.498 IPCA1 score) while El-Mundo, Rudolph, Sagitta and Royal most adapted at Rwebitaba ZARDI (3.54 IPCA1 score). The most interactive genotype was Rwagume with interaction score of - 2.30516 while the least interactive genotype were Caruso and Taurus with IPCA 1 score of 0.00033 and 0.01086 respectively.Item In vitro somatic embryogenesis and regeneration potential of two potato varieties in Uganda(African Journal of Biotechnology, 2018) Byarugaba, Arinaitwe Abel; Eric, Magembe; Alex, Barekye; Skilton, RobIn vitro somatic embryogenesis and regeneration are important techniques for crop improvement and mass propagation. This study was conducted to establish and optimize a regeneration system for agronomically important potato cultivars (‘Victoria’ and ‘Rutuku’) of Solanum tuberosum L. in Uganda. Completely randomized design experiments were set up at Bioscience East and Central Africa (BecA) Tissue Culture Laboratory for this purpose. Callus induction and plant regeneration were initiated on internodes and leaf segments of the two potato cultivars in vitro on Murashige and Skoog (MS) medium supplemented with different phytohormones that included auxins such as α naphthalene acetic acid (NAA), cytokinins like benzyl amino purine (BAP), gibberellic acid (GA3), 2,4-dichlorophenoxyacetic acid (2,4-D) and Zeatin at varying concentrations. Callus response depended on the genotype, the concentrations and composition of growth substances. Hormone combination MS + Sucrose 30% + NAA (2 mg/l) + 2,4-D (2 mg/l) + KN (2 mg/l) was found to have the highest callusing rate, that is, 95 and 53%, respectively for internodes and leaf explants. The calli formed from internodes and leaves were friable and soft. The callus colour in all cases ranged from light brown to light cream and in some cases to light green. Shoot bud initiation was observed in all regeneration culture media, with media combination MS + KN (2 mg/l) + Zeatin (2 mg/l) giving the highest shooting rate. The intervening callus phase led to less number of shoot buds for each callus leading to long incubation period. The study showed that it is possible to regenerate potato cultivars (‘Victoria’ and ‘Rutuku’) from cell suspension culture using Murashige and Skoog (MS) medium supplemented with different phytohormones. Combination of MS with NAA + 2,4-D + Kinetin is suitable for callus induction while MS + kinetin and zeatin was better for shoot induction on calli of potato cultivars ‘Victoria’ and ‘Rutuku’.Item Interactive effects of Potato virus Y and Potato leafroll virus infection on potato yields in Uganda(Open Agriculture, 2020) Byarugaba, Arinaitwe Abel; Mukasa, Settumba B.; Barekye, Alex; Rubaihayo, Patrick R.Potatoes are prone to attack by multiple viruses, which contribute greatly to yield and quality decline depending on the cultivar and the virus involved. This study investigated the effect of co-infection involving Potato virus Y (potyvirus) and Potato leafroll Virus (pelero virus) on productivity of five potato cultivars in Uganda and the nature of virus interaction during co-infection process. Variety response to virus infection by PVY, PLRV and co-infection (PVY + PLRV) varied across different varieties. The plants that were infected with PLRV had leaf rolling, stuntedness, leaf distortion, reduction in leaf size and mottling and light yellow mosaics, and in some cases, purple or red margins were observed, while single infection of PVY induced necrosis, leaf rugosity, crinkling, stunting, interveinal necrosis, blotching of the margins, leaf distortion andmottling. When the two viruses were combined during co-infection with PVY + PLRV, the symptoms were characterized by bright blotching and necrotic leaf margins with purpling of the leaf tips and leaf margins, stuntedness and leaf distortions. The virus disease severity was higher under mixed infected plants than single infected plants. The high disease severity culminated in a significant effect on yield, marketable tuber number per plant, plant growth height and plant vigor, which were different across the varieties. Co-infection involving PVY and PLRV caused a reduction in the marketable yield of 95.2% (Kinigi), 94% (Victoria), 89.5 (Rwagume), 45.3% (Royal) and 23.7% (Sifra). Single infection by PLRV caused a reduction in amarketable yield in Victoria (91.8%), Kinigi (84.8%), Rwagume (73.3%), Royal (47.2%) and Sifra 22.1%, while PVY caused a marketable yield reduction in Victoria (87.2%), Rwagume (85.9.7%), Kinigi (85.1%), Royal (37.4%) and Sifra (14.1%). The effects associated with the coinfection of PVY and PLRV were lower than the combined value of the single infections, suggesting that the two viruses were interacting to affect the potato productivity. The high yield loss suggested that effective resistance strategy targeting PVY, PLRV and their combination was required to save the potato industry in Uganda.Item Interactive effects of Potato virus Y and Potato leafroll virus infection on potato yields in Uganda(Open Agriculture, 2020-11-05) Byarugaba, Arinaitwe Abel; Mukasa, Settumba B.; Barekye, Alex; Rubaihayo, Patrick R.Potatoes are prone to attack by multiple viruses, which contribute greatly to yield and quality decline depending on the cultivar and the virus involved. This study investigated the effect of co-infection involving Potato virus Y (potyvirus) and Potato leafroll Virus (pelero virus) on productivity of five potato cultivars in Uganda and the nature of virus interaction during co-infection process. Variety response to virus infection by PVY, PLRV and co-infection (PVY + PLRV) varied across different varieties. The plants that were infected with PLRV had leaf rolling, stuntedness, leaf distortion, reduction in leaf size and mottling and light yellow mosaics, and in some cases, purple or red margins were observed, while single infection of PVY induced necrosis, leaf rugosity, crinkling, stunting, interveinal necrosis, blotching of the margins, leaf distortion and mottling. When the two viruses were combined during co-infection with PVY + PLRV, the symptoms were characterized by bright blotching and necrotic leaf margins with purpling of the leaf tips and leaf margins, stuntedness and leaf distortions. The virus disease severity was higher under mixed infected plants than single infected plants. The high disease severity culminated in a significant effect on yield, marketable tuber number per plant, plant growth height and plant vigor, which were different across the varieties. Co-infection involving PVY and PLRV caused a reduction in the marketable yield of 95.2% (Kinigi), 94% (Victoria), 89.5 (Rwagume), 45.3% (Royal) and 23.7% (Sifra). Single infection by PLRV caused a reduction in a marketable yield in Victoria (91.8%), Kinigi (84.8%), Rwagume (73.3%), Royal (47.2%) and Sifra 22.1%, while PVY caused a marketable yield reduction in Victoria (87.2%), Rwagume (85.9.7%), Kinigi (85.1%), Royal (37.4%) and Sifra (14.1%). The effects associated with the co-infection of PVY and PLRV were lower than the combined value of the single infections, suggesting that the two viruses were interacting to affect the potato productivity. The high yield loss suggested that effective resistance strategy targeting PVY, PLRV and their combination was required to save the potato industry in Uganda.Item Prevalence of R Genes for Resistance to Potato Viruses in Uganda Germplasm(Potato Research, 2021) Byarugaba, Arinaitwe Abel; Mukasa, Settumba B.; Barekye, Alex; Rubaihayo, Patrick R.The most important potato viruses in Uganda are Potato virus Y (PVY), Potato leaf roll virus (PLRV), Potato virus X (PVX), Potato virus S (PVS), Potato virus A (PVA) and Potato virus M (PVM). Utilization of R genes in breeding for resistance to viruses has not been explored in Uganda due to limited information on the prevalence of R genes in the available genotypes. This study aimed at identifying potato genotypes with R genes for resistance to potato viruses important in Uganda. The study screened 71 potato accessions from the National Potato Breeding Programme at Kachwekano Zonal Agricultural Research and Development Institute for the presence of resistance genes to viruses using diagnostic molecular markers. The results indicated that 21 out of 71 genotypes had resistance markers, of which nine genotypes, NKRN59.58, Derby, Markies, Sifra, 395017.229, Nakpot 5, 20108.5, Royal and 393220.54, had Ryadg gene for PVY resistance and two genotypes, Kimuri and 319919.3, had Rysto gene for resistance to PVY and PVA. Nine genotypes, 395011.2, Markies, Nakpot 5, 20108.5, Sifra, 20157.6, Royal, 2015.8 and Ambition, had the Nbtbr gene for resistance to PVX. In addition, 14 genotypes, 395011.2, Markies, Nakpot 5, Sarpouna, 393220.54, 391046.14, Sarpomira, 395077.12, Sifra, 20157.6, Royal, Ambition, Kimuri and Caruso, had the Nsadg gene conferring resistance to PVS. Four genotypes, Markies, Sifra, Nakpot 5 and Royal, had the Ryadg, Nbtbr and Nsadg genes for combined resistance to PVY, PVX and PVS. The resistant genotypes could be used as parents to introgress resistance genes into susceptible cultivars.Item Stacking three late blight resistance genes from wild species directly into African highland potato varieties confers complete field resistance to local blight races(Plant Biotechnology Journal, 2019) Ghislain, Marc; Byarugaba, Arinaitwe Abel; Magembe, Eric; Njoroge, Anne; Rivera, Cristina; Lupe Roman, Marıa; Carlos Tovar, Jose; Gamboa, Soledad; Forbes, Gregory A.; Kreuze, Jan F.; Barekye, Alex; Kiggundu, AndrewConsidered responsible for one million deaths in Ireland and widespread famine in the European continent during the 1840s, late blight, caused by Phytophthora infestans, remains the most devastating disease of potato (Solanum tuberosum L.) with about 15%–30% annual yield loss in sub-Saharan Africa, affecting mainly smallholder farmers. We show here that the transfer of three resistance (R) genes from wild relatives [RB, Rpi-blb2 from Solanum bulbocastanum and Rpi-vnt1.1 from S. venturii] into potato provided complete resistance in the field over several seasons. We observed that the stacking of the three R genes produced a high frequency of transgenic events with resistance to late blight. In the field, 13 resistant transgenic events with the 3R-gene stack from the potato varieties ‘Desiree’ and ‘Victoria’ grew normally without showing pathogen damage and without any fungicide spray, whereas their non-transgenic equivalent varieties were rapidly killed. Characteristics of the local pathogen population suggest that the resistance to late blight may be long-lasting because it has low diversity, and essentially consists of the single lineage, 2_A1, which expresses the cognate avirulence effector genes. Yields of two transgenic events from ‘Desiree’ and ‘Victoria’ grown without fungicide to reflect small-scale farm holders were estimated to be 29 and 45 t/ha respectively. This represents a three to four-fold increase over the national average. Thus, these late blight resistant potato varieties, which are the farmers’ preferred varieties, could be rapidly adopted and bring significant income to smallholder farmers in sub-Saharan Africa.