Browsing by Author "Rubaihayo, Patrick R."
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Item Assessment of Groundnut (Arachis hypogaea L.) Genotypes for Yield and Resistance to Late Leaf Spot and Rosette Diseases(Journal of Experimental Agriculture International, 2018) Elsiddig Mohammed, Khalid; Afutu, Emmanuel; Odong, Thomas L.; Okello, David K.; Nuwamanya, Ephraim; Grigon, Olupot; Rubaihayo, Patrick R.; Okori, PatrickGroundnut which is a major staple food crop in Uganda is constrained by late leaf spot (LLS) and groundnut rosette disease (GRD), accounting for major economic yield loss. This study was conducted to identify sources of resistance to LLS and GRD and yield potential of selected groundnut genotypes that could be used in breeding programs. Thirty-eight groundnut genotypes were evaluated at the National Semi Arid Resources Research Institute (NaSARRI)-Serere, Eastern Uganda during the first and second seasons of 2015. The experiment was arranged in randomized complete block design with four replications. The results showed highly significant (P < 0.01) genotype-by-season interaction for most of the traits studied. There were significant differences among the genotypes for 100 seed weight (P < 0.01), and dry pod yield and unshelled sample of 100 pods at P < 0.05. Late leaf spot severity (at harvest), GRD incidence (at 12 weeks) and severity (at harvest) were significantly (P < .01) different and positively correlated with Area Under Disease Progress Curve (AUDPC). GRD severity at harvest showed highly significant (P < 0.001) negative correlation with shelling percentage. Both 100 seed weight and unshelled sample of 100 pod showed highly significant (P < 0.01) negative correlations with LLS at harvest, LLS AUDPC, GRD at 12 weeks, GRD AUDPC, and GRD severity. Genotypes susceptible to both LLS and GRD recorded the lowest 100 seed weight. Nine genotypes (Serenut.2, SGV 0001, SGV 0005, SGV 0006, SGV 0019, SGV 0071, SGV 0082, SGV 0083, and SGV 89751T) showed resistance to both diseases with high yield potential. These genotypes could be used to introgress resistance to both diseases in acceptable cultivars which are susceptible.Item Cowpea Scab Disease (Sphaceloma sp.) in Uganda(Crop Protection, 2017-02-27) Afutu, Emmanuel; Agoyi, Eric E.; Amayo, Robert; Biruma, Moses; Rubaihayo, Patrick R.Cowpea (Vigna unguiculata L. Walp) is the third most important legume food crop in Uganda. It is the main legume food crop in the Eastern and Northern regions of the country, however, its mean yield is less than 400 kg ha−1. Scab (Sphaceloma sp.) which is a seed-borne disease is one of the major constraints of cowpea production in the country, capable of causing yield losses of up to 100%. Cowpea scab is the anamorph of Elsinoe phaseoli in common bean (bean scab). The disease affects all the above ground parts of the cowpea plant. A study was conducted in the country to determine the incidence, severity and distribution of scab disease in 17 cowpea growing districts across three agro-ecological zones over a two year period. The results indicated that scab disease was widespread in all the districts with mean incidence ranging between 35 and 70% and mean severity 2–4. Tororo and Amuria districts had the highest incidence and severity, while Bukedea and Arua districts recorded the least disease incidence and severity. Cowpea fields located at altitudes above 1200 m.a.s.l had the highest mean disease incidence (82%) and severity (score = 3.4), while fields located on altitudes lying between 771 and 990 m.a.s.l registered the least disease incidence (64.7%) and severity (score = 2.7). The type of cultivar grown and cropping system practiced influenced the incidence and severity of the scab disease. The results of this study also showed that scab had high incidence and severity across districts and altitudes in Uganda suggesting the need to develop resistant cultivars. This indicates the need to establish the variability of the pathogen to inform the breeding programme for development of resistant varieties.Item Genetic Variability and Evolutionary Implications of RNA Silencing Suppressor Genes in RNA1 of Sweet Potato Chlorotic Stunt Virus Isolates Infecting Sweetpotato and Related Wild Species(PLoS ONE, 2013) Tugume, Arthur K.; Amayo, Robert; Weinheimer, Isabel; Mukasa, Settumba B.; Rubaihayo, Patrick R.; Valkonen, Jari P. T.The bipartite single-stranded RNA genome of Sweet potato chlorotic stunt virus (SPCSV, genus Crinivirus; Closteroviridae) encodes a Class 1 RNase III (RNase3), a putative hydrophobic protein (p7) and a 22-kDa protein (p22) from genes located in RNA1. RNase3 and p22 suppress RNA silencing, the basal antiviral defence mechanism in plants. RNase3 is sufficient to render sweetpotato (Ipomoea batatas) virus-susceptible and predisposes it to development of severe diseases following infection with unrelated virus. The incidence, strains and gene content of SPCSV infecting wild plant species have not been studied. Methodology/Principal Findings: Thirty SPCSV isolates were characterized from 10 wild Ipomoea species, Hewittia sublobata or Lepistemon owariensis (family Convolvulaceae) in Uganda and compared with 34 local SPCSV isolates infecting sweetpotatoes. All isolates belonged to the East African (EA) strain of SPCSV and contained RNase3 and p7, but p22 was not detected in six isolates. The three genes showed only limited genetic variability and the proteins were under purifying selection. SPCSV isolates lacking p22 synergized with Sweet potato feathery mottle virus (SPFMV, genus potyvirus; Potyviridae) and caused severe symptoms in co-infected sweetpotato plants. One SPCSV isolate enhanced accumulation of SPFMV, but no severe symptoms developed. A new whiteflytransmitted virus (KML33b) encoding an RNase3 homolog (<56% identity to SPCSV RNase3) able to suppresses sense-mediated RNA silencing was detected in I. sinensis. Conclusions/Significance: SPCSV isolates infecting wild species and sweetpotato in Uganda were genetically undifferentiated, suggesting inter-species transmission of SPCSV. Most isolates in Uganda contained p22, unlike SPCSV isolates characterized from other countries and continents. Enhanced accumulation of SPFMV and increased disease severity were found to be uncoupled phenotypic outcomes of RNase3-mediated viral synergism in sweetpotato. A second virus encoding an RNase3-like RNA silencing suppressor was detected. Overall, results provided many novel and important insights into evolutionary biology of SPCSV.Item Genotype × Environment Interactions for East African Orange-Fleshed Sweetpotato Clones Evaluated across Varying Ecogeographic Conditions in Uganda(Crop Science, 2016-05-27) Tumwegamire, Silver; Rubaihayo, Patrick R.; Mwanga, Robert O. M.; Kapinga, ReginaAfrican dry and starchy (DS) orange-fleshed sweetpotato [Ipomoea batatas (L.) Lam] (OFSP) cultivars, distinct from American moist or medium dry and sweet OFSP, have potential to fight vitamin A deficiency (VAD) in the world. This study assessed the genotype × environment (G × E) interactions in multienvironment trials (METs), the genetic correlations for total root yield (TYLD), biomass (BIOM), harvest index (HI), root dry matter (RDM), root starch (RST), root sucrose (RSU), root β-carotene, (RBC), root Fe (RFE), root Zn (RZN), root Ca (RCA), and root Mg (RMG) and the potential contributions of the cultivars to fight VAD and mineral deficiencies. Nine DS OFSP cultivars, (Ejumula, Zambezi, Carrot_C, Kakamega, KMI61, Abuket_1, SPK004/6/6, SPK004/6 and Naspot_5/50) and a medium dry and sweet OFSP cultivar (Resisto) were tested in METs in Uganda. The urn:x-wiley:0011183X:media:csc2cropsci2015100612:csc2cropsci2015100612-math-0064 components were smaller than urn:x-wiley:0011183X:media:csc2cropsci2015100612:csc2cropsci2015100612-math-0065 components for HI, RDM, RST, RSU, and RBC, making it possible to ably select for the traits in the early stages. The urn:x-wiley:0011183X:media:csc2cropsci2015100612:csc2cropsci2015100612-math-0066 components were larger than urn:x-wiley:0011183X:media:csc2cropsci2015100612:csc2cropsci2015100612-math-0067 components for TYLD and mineral traits. Thus, like yield, breeding for mineral traits in sweetpotato is complex, requiring prior data on the causes of the G × E interactions. Medium to high positive correlations among mineral traits favor parallel selection, and it merits further study to efficiently improve the mineral trait complex by an index. Clearly, a 50- to 100-g ration of all the cultivars, except Naspot_5/50, can provide 100% recommended dietary allowance of vitamin A for a 5- to 8-yr-old child.Item Harnessing genotype-by-environment interaction to determine adaptability of advanced cowpea lines to multiple environments in Uganda(Journal of Plant Breeding and Crop Science, 2020) Abiriga, Francis; Ongom, Patrick O.; Rubaihayo, Patrick R.; Edema, Richard; Gibson, Paul T.; Dramadri, Isaac; Orawu, MartinThis study was conducted to determine the yield stability of advanced cowpea lines in diverse agroecological zones of Uganda in order to facilitate documentation requirements for national performance trials (NPT). Thirty cowpea genotypes were evaluated against six checks in three localities, over three growing seasons, making a total of 9 unique environments. The trials were laid in a 6x6 alpha lattice design with three replications and grain yield was the principal trait measured. Single-site and multilocation data were summarized using analysis of variance. Further analysis of stability was visualized using the genotype and genotype by environment interaction (GGE) biplot and the additive main effect and multiplicative interaction (AMMI) models. ANOVA depicted highly significant differences among the genotypes, locations, seasons and GEI for grain yield. Based on AMMI analysis, environmental effect accounted for the most variation (84.7%) in the phenotype followed by GE (9.45%) and genotypes (4.45%), alluding to the complex inheritance of grain yield in cowpea. The polygon view and the average environment coordination view of the GGE biplot revealed Ayiyi as the wining genotype in the major mega environment and the most stable and high yielding across environments respectively. The genotypes Ayiyi, WC64 and ALEGIxACC2 yielded higher than the checks and were very stable. The other genotypes G36 (WC 36), G3 (ACC12xSECOW3B), G32 (WC16), and G14 (MU9) did not outperform the checks but displayed high yield stability and the mean yields were above the overall average. These genotypes were considered desirable for advancement to National Performance Trial for potential release as new improved cowpea cultivars.Item Inheritance of cowpea resistance to flower thrips in Uganda germplasm(Journal of Plant Breeding and Crop Science, 2018) Agbahoungba, Symphorien; Karungi, Jeninah; Badji, Arfang; Sadik, Kassim; Gibson, Paul; Edema, Richard; Assogbadjo, Achille E.; Rubaihayo, Patrick R.Flower thrips [Megalurothrips sjostedti (Trybom)] is the most damaging insect pest on cowpea. However, information regarding the nature of gene action governing the inheritance of resistance to thrips is not available for cowpea genotypes in Uganda. This study was carried out to determine the inheritance pattern of cowpea resistance to flower thrips. Five resistant cowpea genotypes and three susceptible genotypes were crossed in full diallel mating design. F2 progenies were evaluated along with the parents in alpha lattice design with two replications under natural thrips infestation at Kabanyolo, Arua and Serere in Uganda. Combining ability analysis was performed using method one and model one of diallel analysis. The results showed that the environmental effects were highly significant (P<0.001). Additive, dominance and epistasis effects had major contributions. The broad sense heritability varied from 18 to 42% for thrips damage scores and from 0 to 6% for thrips counts. The estimates of narrow sense heritability were low for thrips damage score (2 to 18%) and thrips counts (0 to 9%). Genotypes TVU-1471 and TVU-1509 were identified as good transmitters of resistance to flower thrips. Crosses TVU-1509 x NE5, TVU-473 x Sanzi, TVU-123 x Sanzi, TVU-123 x TVU-473, and TVU-473 x TVU-1509 presented significant (P<0.05) and negative SCA effects for thrips damage scores and thrips counts and would be the most useful in breeding as some of their progenies would have high resistance to flower thrips. This study provides the basis of an efficient breeding program of cowpea for flower thrips resistance.Item Inheritance of Cowpea Resistance to Flower Thrips in Uganda Germplasm(Journal of Plant Breeding and Crop Science, 2018-01-31) Agbahoungba, Symphorien; Karungi, Jeninah; Edema, Richard; Assogbadjo, Achille E.; Rubaihayo, Patrick R.Flower thrips [Megalurothrips sjostedti (Trybom)] is the most damaging insect pest on cowpea. However, information regarding the nature of gene action governing the inheritance of resistance to thrips is not available for cowpea genotypes in Uganda. This study was carried out to determine the inheritance pattern of cowpea resistance to flower thrips. Five resistant cowpea genotypes and three susceptible genotypes were crossed in full diallel mating design. F2 progenies were evaluated along with the parents in alpha lattice design with two replications under natural thrips infestation at Kabanyolo, Arua and Serere in Uganda. Combining ability analysis was performed using method one and model one of diallel analysis. The results showed that the environmental effects were highly significant (P<0.001). Additive, dominance and epistasis effects had major contributions. The broad sense heritability varied from 18 to 42% for thrips damage scores and from 0 to 6% for thrips counts. The estimates of narrow sense heritability were low for thrips damage score (2 to 18%) and thrips counts (0 to 9%). Genotypes TVU-1471 and TVU-1509 were identified as good transmitters of resistance to flower thrips. Crosses TVU-1509 x NE5, TVU-473 x Sanzi, TVU-123 x Sanzi, TVU-123 x TVU-473, and TVU-473 x TVU-1509 presented significant (P<0.05) and negative SCA effects for thrips damage scores and thrips counts and would be the most useful in breeding as some of their progenies would have high resistance to flower thrips. This study provides the basis of an efficient breeding program of cowpea for flower thrips resistance.Item Interactive effects of host, pathogen and mineral nutrition on grey leaf spot epidemics in Uganda(European Journal of Plant Pathology, 2004-02-08) Okori, Patrick; Rubaihayo, Patrick R.; Ekwamu, Adipala; Christina, DixeliusGrey leaf spot incited by Cercospora zeae-maydis is a new devastating foliar disease of maize in East Africa. For effective control, elucidation of the most critical elements of the grey leaf spot disease pyramid is important. This study investigated the role of mineral nutrition, pathogen variability and host resistance in the epidemic. Trials were conducted under field and controlled environments. The 28 isolates used in the controlled environment varied significantly (P ≤ 0.05) in parasitic fitness measured indirectly as disease efficiency, but no infection pattern could be attributed to known C. zeae-maydis pathotypes. Data from field trials showed that host resistance and mineral nutrition significantly (P ≤ 0.05) affected disease efficiency, with highest disease development occurring in nitrogen-augmented plots. Exclusive phosphorus application had no clear effect on grey leaf spot epidemics but combined application with nitrogen significantly (P ≤ 0.05) reduced the predisposition effects of nitrogen to the disease. Overall, treated plots had less disease than unfertilised plots. Fertiliser application had no effect on sporulation capacity, while cultivars significantly affected it. Geographic differences in amount of disease were observed, suggesting environment influences on grey leaf spot incidence. The results suggest that the current grey leaf spot epidemics in East Africa are due to favourable cultivars, poor mineral nutrition and environmental interactions.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 Microsatellites markers associated with resistance to flower bud thrips in a cowpea F2 population derived from genotypes TVU-123 and WC36(African Journal of Biotechnology, 2018) Agbahoungba, Symphorien; Karungi, Jeninah; Sadik, Kassim; Gibson, Paul; Edema, Richard; Assogbadjo, Achille E.; Rubaihayo, Patrick R.Breeding for resistance to flower bud thrips (Megalurothrips sjostedti) in cowpea has been hindered by the quantitative nature of resistance. To identify simple sequence repeat (SSR) markers associated with resistance to flower bud thrips that could be used for marker-assisted breeding, a F2 population was generated from a cross between genotypes TVU-123 (resistant) and WC36 (susceptible). The population was evaluated for thrips damage scores, thrips counts, and pods number per plant under artificial infestation. Sixty-six microsatellites markers were screened between the two parental lines and seven polymorphic markers were used for genotype 100 F2 plants. Single marker analysis was used to evaluate an association between the markers and traits. Transgressive segregation among the F2 plants for resistance to flower thrips was observed. A significant negative relationship was observed between thrips damage scores and pods number per plant. Markers CP37/38 and CP215/216 were significantly associated with thrips damage scores and thrips counts, respectively. The two markers explained 7 and 11.2% of the total variation in thrips damage scores and thrips counts with positive and negative effects, respectively. Mainly additive gene effects were observed. A more detailed study using more markers on these loci should provide better understanding of this complex trait.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 Volatile Organic Compound Based Markers for the Aroma Trait of Rice Grain(Journal of Agricultural Science, 2020) Ocan, David; Rongrong, Zhang; Odoch, Martin; Nuwamanya, Ephraim; Ibanda, Angele P.; Odong, Thomas L.; Lamo, Jimmy; Fitzgerald, Anne M.; Daygon, Venea D.; Rubaihayo, Patrick R.A study was conducted to determine the volatile organic compounds (VOCs) associated with rice grain aroma in 37 commonly grown lines within Uganda, as well as elites. The aim of the study was to identify potential volatile biochemical markers, if any, for the rice grain aroma trait. Certified rice seeds were obtained from the Uganda National Crops Resources Research Institute germplasm collection. The seeds were sown into experimental plots, under field conditions and the mature paddy harvested. Polished rice grains were heated to 80 oC and the liberated VOCs subjected to untargeted metabolite analysis using gas chromatography-time-of-flight mass spectrometry. In total, nine functional groups were present; hydrocarbons, alcohols, ketones, aldehydes, N-containing compounds, S-containing compounds, esters, oxygen heterocycles and carboxylic acids. More specifically, 148 VOCs were identified across the 37 rice lines, of which 48 (32.4%) including 2-acetyl-1-pyrroline (2-AP) appeared to elucidate the difference between non-aromatic and aromatic rice. Furthermore, 41 (27.7%) VOCs were found to be significantly correlated with 2-AP abundance, the principle rice aroma compound. Amongst the 41 VOCs, only ten compounds were found to contribute highly towards variation in 2-AP abundance, indicative of their possible modulation roles in regard to rice aroma. Within the ten influential volatiles, three aroma active compounds; toluene, 1-hexanol, 2-ethyl and heptane, 2,2,4,6,6-pentamethyl- were established as the most reliable biochemical surrogates to the rice aroma trait. Thus, the aforementioned compounds may be used in rice breeding programme for enhancing development of the grain aroma trait.