NRU :: Browsing by Author "Tugume, Arthur K."

Browsing by Author "Tugume, Arthur K."

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Antibiotic‑resistance in medically important bacteria isolated from commercial herbal medicines in Africa from 2000 to 2021: a systematic review and meta‑analysis
(Antimicrobial Resistance & Infection Control, 2022) Walusansa, Abdul; Asiimwe, Savina; Nakavuma, Jesca. L.; Ssenku, Jamilu. E.; Katuura, Esther; Kafeero, Hussein. M.; Aruhomukama, Dickson; Nabatanzi, Alice; Anywar, Godwin; Tugume, Arthur K.; Kakudidi, Esezah K.
Antimicrobial resistance is swiftly increasing all over the world. In Africa, it manifests more in pathogenic bacteria in form of antibiotic resistance (ABR). On this continent, bacterial contamination of commonly used herbal medicine (HM) is on the increase, but information about antimicrobial resistance in these contaminants is limited due to fragmented studies. Here, we analyzed research that characterized ABR in pathogenic bacteria isolated from HM in Africa since 2000; to generate a comprehensive understanding of the drug-resistant bacterial contamination burden in this region. Methods: The study was conducted according to standards of the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA). We searched for articles from 12 databases. These were: PubMed, Science Direct, Scifinder scholar, Google scholar, HerbMed, Medline, EMBASE, Cochrane Library, International Pharmaceutical Abstracts, Commonwealth Agricultural Bureau Abstracts, African Journal Online, and Biological Abstracts. Prevalence and ABR traits of bacterial isolates, Cochran’s Q test, and the I2 statistic for heterogeneity were evaluated using MedCalcs software. A random-effects model was used to determine the pooled prevalence of ABR traits. The potential sources of heterogeneity were examined through sensitivity analysis, subgroup analysis, and meta-regression at a 95% level of significance. Findings: Eighteen studies met our inclusion criteria. The pooled prevalence of bacterial resistance to at least one conventional drug was 86.51% (95% CI = 61.247–99.357%). The studies were highly heterogeneous (I2 = 99.17%; p < 0.0001), with no evidence of publication bias. The most prevalent multidrug-resistant species was Escherichia coli (24.0%). The most highly resisted drug was Ceftazidime with a pooled prevalence of 95.10% (95% CI = 78.51–99.87%), while the drug-class was 3rd generation cephalosporins; 91.64% (95% CI = 78.64–96.73%). None of the eligible studies tested isolates for Carbapenem resistance. Extended Spectrum β-lactamase genes were detected in 89 (37.2%) isolates, mostly Salmonella spp., Proteus vulgaris, and K. pneumonia. Resistance plasmids were found in 6 (5.8%) isolates; the heaviest plasmid weighed 23,130 Kilobases, and Proteus vulgaris harbored the majority (n = 5; 83.3%). Conclusions: Herbal medicines in Africa harbor bacterial contaminants which are highly resistant to conventional medicines. This points to a potential treatment failure when these contaminants are involved in diseases causation. More research on this subject is recommended, to fill the evidence gaps and support the formation of collaborative quality control mechanisms for the herbal medicine industry in Africa.
Application of Pollen Germination Media on Stigmas during Pollination Increases Seed Set in East African Highland Cooking Bananas (Musa spp.)
(Agronomy, 2021) Waniale, Allan; Swennen, Rony; Settumba, B. Mukasa; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Amah, Delphine; Tumuhimbise, Robooni
Seed set in East African Highland Cooking bananas (EAHBs) is extremely low and therefore hampers breeding. Pollen–pistil interaction is a key contributing factor. We assessed the effect of pollen germination media (PGM) on seed set in EAHBs. Five EAHB cultivars were pollinated with pollen from the wild banana ‘Calcutta 4’. Glucose-based PGM sprayed on freshly emerged stigmas significantly increased seed set per 100 fruits per bunch. Increases were 73.5% in ‘Enzirabahima’, 39.9% in ‘Mshale’, and 302.4% in ‘Nshonowa’. However, PGM did not increase seed set in the female sterile ‘Mlelembo’ and ‘Nakitembe’. As larger bunches were more fertile, good field management practices are also recommended to get more seed to improve breeding efficiency.
Early Withering of Enlarged Ovules in Pollinated Fruits of Bananas (Musa spp.) Suggest Abortion after Fertilization
(Horticulturae, 2022) Waniale, Allan; Mukasa, Settumba B.; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Tumuhimbise, Robooni
Sterility in edible bananas is as a result of a long history of anthropogenic-driven selection for sterile genotypes, since seed is not desirable in fruit pulp for human consumption. However, this poses a challenge to conventional genetic improvement by slowing breeding pipelines. In this study, we investigated whether pollen tubes reach all parts of the ovary, the position of fertilized ovule development in fruits, and potential seed set in selected banana genotypes. We selected four cultivars of East African Highland Cooking bananas (EAHBs), a Matooke hybrid ‘222K-1’, improved diploid ‘2905’, and wild bananas ‘Zebrina (G.F.)’ and ‘Calcutta 4’. There was evidence of pollen tubes in the distal, mid and proximal sections of the fruit, irrespective of hand position and genotype. Fertilization, as indicated by an increase in ovule size, happened along the entire length of the fruit but complete development was biased at the distal end in some genotypes. There were some differences in ovule fertilization rates between hands, with distal hands having more ovules and higher ovule fertilization rates. Ovule fertilization happens in bananas but the vast majority aborts, especially at the proximal end of the ovary. Ovule fertilization rates are generally much lower than available ovules.
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.
In vitro embryo rescue and plant regeneration following self-pollination with irradiated pollen in cassava (Manihot esculenta Crantz)
(African Journal of Biotechnology, 2015) Buttibwa, Mary; Kawuki, Robert S.; Tugume, Arthur K.; Akol, Jacinta; Magambo, Stephen; Apio, Hellen; Heberle-Bors, Erwin; Wedzony, Maria; Ceballos, Hernán; Hershey, Clair; Baguma, Yona
Cassava is a highly heterozygous species; hence, current methods used in classical cassava breeding cannot match the urgent need to high yielding varieties. Recently, progress was made through androgenesis and gynogenesis as pathways for raising doubled cassava haploid lines to overcome problems associated with cassava’s inherent reproductive biology, but these efforts were limited (no candidate cassava plantlets were regenerated). For the first time, this study shows that pollen irradiation coupled with self-pollination and embryo rescue regenerated 62 candidate cassava plantlets. Plants of an elite cassava variety, Nase14, served as a mother plant and as the pollen donor for the irradiation. Irradiation dosages of 50 to 250 Gray studied across five pollination events and 300 or 500 Gray in one pollination event caused a reduction in pollen germination up to 67.0%. By 15 days after pollination (DAP) with irradiated pollen, up to 89.7% of the pollinated flowers had aborted. By embryo rescue time (42 DAP), significant differences were observed in number of fruits, seeds and embryos generated, with the non-irradiated pollen treatments having significantly higher numbers. Sixteen (16) heterozygous SSR markers in the parent and ploidy analysis showed that none of the regenerated plants was haploid or homozygous. However, the plantlets resulting from pollination with non-irradiated pollen had 56.2% homozygous loci, while progeny derived from irradiated treatments had frequencies of homozygous loci between 28.1 and 55.0%. This is the first time to use irradiated pollen in cassava as a pathway to generate candidate plantlets as an initial step in double haploid production.
Incidence of viruses and virus-like diseases of watermelons and pumpkins in Uganda, a hitherto none investigated pathosystem
(African Journal of Agricultural Research, 2017) Masika, Fred B.; Kisekka, Ronald; Alicai, Titus; Tugume, Arthur K.
Common impromptu observations between 2010 and 2012 of apparent virus-like disease symptoms in watermelons and pumpkins in Uganda prompted this study. However, there was no recorded evidence of virus infection in these crops anywhere in Uganda or eastern Africa as a region. Thus, 374 and 522 watermelon and pumpkin plants, respectively, growing in 13 fields were surveyed to record virus-like disease symptoms in Uganda’s four districts of Mbale and Kamuli (eastern region), Mpigi and Masaka (central region) during August to November 2013, and January to March 2014. Leaf samples were also collected and tested for four viruses known to commonly infect watermelons and pumpkins worldwide. Symptom severity was assessed using a scale of 0 to 5, while virus incidence was determined by serological methods. The four viruses tested were Cucumber mosaic virus (CMV), Watermelon mosaic virus (WMV), Zucchini yellow mosaic virus (ZYMV) and Cucurbit aphid borne-yellows virus (CABYV). In both crops, there was a higher incidence of virus-like diseases in central than in eastern region (P = 0.000). All the four viruses were detected with CMV as the most common, followed by WMV, ZYMV, and CABYV. Differences in virus incidences between the districts were not always significant. Single CMV, dual CMV+WMV and triple CMV+WMV+ZYMV were the most common single, and multiple infections in both crops. Watermelons contained more single virus infections than mixed infections (P < 0.001), but this difference was not significant in pumpkins (P = 0.468). In all, single virus infections were significantly higher in watermelons than pumpkins (P < 0.001). This is the first study to report incidence of viruses and virus-like diseases in watermelons and pumpkins in Uganda, and in eastern Africa as a region. The importance of these results with respect to crop production and next steps in virus disease management are discussed.
Medically important bacteria isolated from commercial herbal medicines in Kampala city indicate the need to enhance safety frameworks
(Scientific Reports, 2022) Walusansa, Abdul; Nakavuma, Jesca L.; Asiimwe, Savina; Ssenku, Jamilu E.; Aruhomukama, Dickson; Sekulima, Tahalu; Kafeero, Hussein M.; Anywar, Godwin; Katuura, Esther; Nabatanzi, Alice; Musisi, Nathan L.; Tugume, Arthur K.
The high global bacterial infection burden has created need to investigate the neglected potential drivers of pathogenic bacteria, to inform disease prevention. Kampala is facing a proliferation of herbalists, selling herbal medicine (HM), of largely unregulated microbiological quality. We evaluated the bacterial contamination burden in HM sold in Kampala, to support evidence-based redress. The total viable loads (TVL), total coliform counts (TCC), E. coli counts, and prevalence of selected bacterial strains in 140 HM were examined using conventional culture, following the guidelines of World Health Organization (WHO), and Uganda National Drug Authority (NDA). Data were analyzed using D’Agostino-Pearson test, frequencies, proportions, Chi-square, and Mann–Whitney U test with STATA version-15.0. Fifty (35.7%), fifty-nine (42.1%), and twelve (8.6%) HM were unsafe for human use because they exceeded WHO’s permissible limits for TVL, TCC, and E. coli counts respectively. Solids had significantly higher mean TVL than liquids. Violation of NDA’s guidelines was significantly associated with high TVL. Fifty-nine bacteria, viz., Klebsiella pneumoniae (n = 34; 57.6%), Escherichia. coli (12; 20.3%), Staphylococcus aureus (7; 11.9%), Klebsiella oxytoca (3; 5.1%), Bacillus cereus, Pseudomonas aeruginosa, and Enterobacter spp. (1; 1.7% each), were isolated from 45 (32.1%) samples. These bacteria can cause severe clinical diseases, and promote deterioration of HM potency.
Mixed Infections of Four Viruses, the Incidence and Phylogenetic Relationships of Sweet Potato Chlorotic Fleck Virus (Betaflexiviridae) Isolates in Wild Species and Sweetpotatoes in Uganda and Evidence of Distinct Isolates in East Africa
(PLoS ONE, 2016) Tugume, Arthur K.; Mukasa, Settumba B.; Valkonen, Jari P. T.
Viruses infecting wild flora may have a significant negative impact on nearby crops, and vice-versa. Only limited information is available on wild species able to host economically important viruses that infect sweetpotatoes (Ipomoea batatas). In this study, Sweet potato chlorotic fleck virus (SPCFV; Carlavirus, Betaflexiviridae) and Sweet potato chlorotic stunt virus (SPCSV; Crinivirus, Closteroviridae) were surveyed in wild plants of family Convolvulaceae (genera Astripomoea, Ipomoea, Hewittia and Lepistemon) in Uganda. Plants belonging to 26 wild species, including annuals, biannuals and perennials from four agroecological zones, were observed for virus-like symptoms in 2004 and 2007 and sampled for virus testing. SPCFV was detected in 84 (2.9%) of 2864 plants tested from 17 species. SPCSV was detected in 66 (5.4%) of the 1224 plants from 12 species sampled in 2007. Some SPCSV-infected plants were also infected with Sweet potato feathery mottle virus (SPFMV; Potyvirus, Potyviridae; 1.3%), Sweet potato mild mottle virus (SPMMV; Ipomovirus, Potyviridae; 0.5%) or both (0.4%), but none of these three viruses were detected in SPCFV-infected plants. Co-infection of SPFMV with SPMMV was detected in 1.2% of plants sampled. Virus-like symptoms were observed in 367 wild plants (12.8%), of which 42 plants (11.4%) were negative for the viruses tested. Almost all (92.4%) the 419 sweetpotato plants sampled from fields close to the tested wild plants displayed virus-like symptoms, and 87.1% were infected with one or more of the four viruses. Phylogenetic and evolutionary analyses of the 30-proximal genomic region of SPCFV, including the silencing suppressor (NaBP)- and coat protein (CP)-coding regions implicated strong purifying selection on the CP and NaBP, and that the SPCFV strains from East Africa are distinguishable from those from other continents. However, the strains from wild species and sweetpotato were indistinguishable, suggesting reciprocal movement of SPCFV between wild and cultivated Convolvulaceae plants in the field.
Molecular genetic analysis of virus isolates from wild and cultivated plants demonstrates that East Africa is a hotspot for the evolution and diversification of Sweet potato feathery mottle virus
(Molecular ecology, 2010) Tugume, Arthur K.; Cue´ Llar, Wilmer J .; Mukasa, Settumba B.; Valkonen, Jari P. T.
Sweet potato feathery mottle virus (SPFMV, genus Potyvirus) is globally the most common pathogen of cultivated sweet potatoes (Ipomoea batatas; Convolvulaceae). Although more than 150 SPFMV isolates have been sequence-characterized from cultivated sweet potatos across the world, little is known about SPFMV isolates from wild hosts and the evolutionary forces shaping SPFMV population structures. In this study, 46 SPFMV isolates from 14 wild species of genera Ipomoea, Hewittia and Lepistemon (barcoded for the matK gene in this study) and 13 isolates from cultivated sweet potatoes were partially sequenced. Wild plants were infected with the EA, C or O strain, or co-infected with the EA and C strains of SPFMV. In East Africa, SPFMV populations in wild species and sweet potato were genetically undifferentiated, suggesting inter-host transmission of SPFMV. Globally, spatial diversification of the 178 isolates analysed was observed, strain EA being largely geographically restricted to East Africa. Recombination was frequently detected in the 6K2-VPg-NIaPro region of the EA strain, demonstrating a recombination ‘hotspot’. Recombination between strains EA and C was rare, despite their frequent co-infections in wild plants, suggesting purifying selection against strain EA⁄C recombinants. Positive selection was predicted on 17 amino acids distributed over the entire coat protein in the globally distributed strain C, as compared to only four amino acids in the coat protein N-terminus of the EA strain. This selection implies a more recent introduction of the C strain and a higher adaptation of the EA strain to the local ecosystem. Thus, East Africa appears as a hotspot for evolution and diversification of SPFMV.
Recombination and selection pressure in the ipomovirus sweet potato mild mottle virus (Potyviridae) in wild species and cultivated sweetpotato in the centre of evolution in East Africa
(Journal of general virology, 2010) Tugume, Arthur K.; Mukasa, Settumba B.; Kalkkinen, Nisse; Valkonen, Jari P. T.
Sweet potato mild mottle virus (SPMMV) is the type member of the genus Ipomovirus (family Potyviridae). SPMMV occurs in cultivated sweetpotatoes (Ipomoea batatas Lam.; Convolvulaceae) in East Africa, but its natural wild hosts are unknown. In this study, SPMMV was detected in 283 (9.8 %) of the 2864 wild plants (family Convolvulaceae) sampled from different agro-ecological zones of Uganda. The infected plants belonged to 21 species that were previously not known to be natural hosts of SPMMV. The size of the SPMMV coat protein (CP) was determined by Western blot analysis, N-terminal protein sequencing and peptide mass fingerprinting. Data implicated a proteolytic cleavage site, VYVEPH/A, at the NIb/CP junction, resulting in a CP of approximately 35 kDa. Nearly complete sequences of 13 SPMMV isolates were characterized. Phylogenetic analysis of non-recombinant CP-encoding sequences placed five isolates from wild species sampled in the central zone of Uganda into a separate cluster. Recombination events were detected in the 59- and 39-proximal parts of the genome, providing novel evidence of recombination in the genus Ipomovirus. Thirteen amino acids in the N terminus of the P1 protein were under positive selection, whereas purifying selection was implicated for the HC-Pro-, P3-, 6K1- and CP-encoding regions. These data, supported by previous studies on ipomoviruses, provide indications of an evolutionary process in which the P1 proteinase responds to the needs of adaptation.
Seed Set Patterns in East African Cooking Bananas (Musa spp.) are Dependent on Weather Before, During, and After Pollination
(Research Square, 2020) Waniale, Allan; Mukasa, Settumba B.; Tugume, Arthur K.; Tumuhimbise, Robooni; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Batte, Michael; Brown, Allan; Swennen, Rony
Seed set in banana (Musa spp.) is influenced by weather but the most critical weather attribute(s) and the critical period are unknown. Such information is of paramount importance to increase seed set for banana breeding programs. Three female fertile East African cooking bananas (EACBs), ‘Enzirabahima’ (AAA), ‘Mshale’ (AA), and ‘Nshonowa’ (AA) were pollinated with the highly male fertile wild banana ‘Calcutta 4’ (AA). At full maturity, bunches were harvested and ripened and seeds extracted from ripe fruit pulp. Seed set was then correlated with weather before, during, and after pollination. Results: Seed set was positively correlated with high temperatures (r=0.172 – 0.488), solar radiation (r=0.181 – 0.282) and negatively correlated with rainfall (r=-0.214 – -0.238) and relative humidity (RH) (r=-0.158 – -0.438) between 75 and 15 days before pollination (DBP). The pattern of weather association was cultivar-dependent with ‘Nshonowa’ having the strongest significant associations. At the time of pollination, high average temperatures were critical for seed set in ‘Enzirabahima’ (r=0.214, P<0.01) while high morning RH was critical for ‘Mshale’ (r=0.299, P<0.01). After pollination, high morning temperatures were associated with seed set (r=0.150 – 0.429) between 15 days to 90 days after pollination (DAP). High average temperatures were negatively correlated with seed set in ‘Mshale’ and ‘Nshonowa’ from 45 DAP to time of harvest (r=-0.208 – -0.344). Coefficients of correlation were generally highest 15 DBP especially for ‘Mshale’ and ‘Nshonowa.’ Principle component analysis showed that average and maximum temperature are the most important variables in the entire data set. Conclusion: Coefficients of correlation were generally less than 0.5 partly as a result of weather involvement in seed set at several floral development stages; before, during, and after pollination. The most critical developmental stage is 15 DBP especially for ‘Mshale’ and ‘Nshonowa’ as they had the high correlation coefficients. Average temperature should be the main focus for seed set increase in banana.
Seed Set Patterns in East African Cooking Bananas are Asymmetric in Bunches and Fruits
(Research Square, 2020) Waniale, Allan; Mukasa, Settumba B.; Tugume, Arthur K.; Tumuhimbise, Robooni; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Batte, Michael; Brown, Allan; Swennen, Rony
Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African cooking bananas EACBs to inform future decisions on a more targeted approach of increasing seed set and subsequently banana breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are genetically distinct but belong to the same genetic complex, they referred to as EACBs. Seed set patterns in ‘Enzirabahima’ (AAA), ‘Mshale’ (AA) and ‘Nshonowa’ (AA) all with residual fertility were examined after hand pollination with a highly male fertile wild banana ‘Calcutta 4’ (AA). Results: Seed set in ‘Enzirabahima’ is predominant in distal hands. Mchare cultivars have a slightly more even distribution of seeds in their hands compared to ‘Enzirabahima.’ There is a gradual increase in seed set from proximal to distal hands with a slight drop in the last hand. This pattern is more definite in ‘Enzirabahima’ and ‘Mshale’ while ‘Nshonowa’ has a somewhat inconsistent pattern. There is also a drop in seed set per 100 fruits per hand from small to larger bunches. However, larger bunches have a higher pollination success compared to smaller bunches. They therefor set more seed on 100 fruits per hand and per bunch basis if bunches without seed are accounted for. Pollination success rate increases from smaller to larger bunches of EACBs. Seed set is biased toward the distal third part of fruits of examined EACBs as well tetraploid Matooke hybrid ‘401K-1’ (AAAA) and improved diploid ‘Zebrina’ GF (AA) that were used for comparison. In comparison, in the highly female fertile ‘Calcutta 4,’ seed set is along the entire length of the fruit. Conclusion: Seed set bias in the distal hands and distal end of fruits suggests a systematic mechanism rather than a random occurrence. It is expected that this information will provide a foundation for increased crossbreeding efficiency in bananas.
Seed Set Patterns in East African Highland Cooking Bananas Are Dependent on Weather before, during and after Pollination
(Horticulturae, 2021) Waniale, Allan; Swennen, Rony; Mukasa, Settumba B.; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Batte, Michael; Brown, Allan; Tumuhimbise, Robooni
Seed set in banana is influenced by weather, yet the key weather attributes and the critical period of influence are unknown. We therefore investigated the influence of weather during floral development for a better perspective of seed set increase. Three East African highland cooking bananas (EAHBs) were pollinated with pollen fertile wild banana ‘Calcutta 40 . At full maturity, bunches were harvested, ripened, and seeds extracted from fruit pulp. Pearson’s correlation analysis was then conducted between seed set per 100 fruits per bunch and weather attributes at 15-day intervals from 105 days before pollination (DBP) to 120 days after pollination (DAP). Seed set was positively correlated with average temperature (P < 0.05–P < 0.001, r = 0.196–0.487) and negatively correlated with relative humidity (RH) (P < 0.05–P < 0.001, r = 􀀀0.158–􀀀0.438) between 75 DBP and the time of pollination. After pollination, average temperature was negatively correlated with seed set in ‘Mshale’ and ‘Nshonowa’ from 45 to 120 DAP (P < 0.05–P < 0.001, r = 􀀀0.213–􀀀0.340). Correlation coefficients were highest at 15 DBP for ‘Mshale’ and ‘Nshonowa’, whereas for ‘Enzirabahima’, the highest were at the time of pollination. Maximum temperature as revealed by principal component analysis at the time of pollination should be the main focus for seed set increase.
Seed Set Patterns in East African Highland Cooking Bananas Show Asymmetric Distribution in Bunches and Fruits
(Agronomy, 2021) Waniale, Allan; Swennen, Rony; Mukasa, Settumba B.; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Batte, Michael; Brown, Allan; Tumuhimbise, Robooni
Low female fertility in bananas is the biggest hurdle for banana breeding. The aim of this study was to determine seed set patterns in East African Highland Cooking bananas (EAHBs) to inform future decisions on a more targeted approach of increasing seed set and subsequently banana-breeding efficiency. Matooke (AAA) and Mchare (AA) bananas are genetically distinct but belong to the same genetic complex, referred to as EAHBs. Seed set patterns in “Enzirabahima” (AAA), “Mshale” (AA), and “Nshonowa” (AA), all with residual fertility, were examined after hand pollination with a highly male fertile wild banana “Calcutta 4” (AA). Seed set in “Enzirabahima” is predominant in distal hands. Mchare cultivars have a slightly more even distribution of seeds in their hands compared to “Enzirabahima”. There is a gradual increase in seed set from proximal to distal hands with a slight drop in the last hand. This pattern is more definite in “Enzirabahima” and “Mshale”, while “Nshonowa” has a somewhat inconsistent pattern. There is also a drop in seed set per 100 fruits per hand from small to larger bunches. However, larger bunches have a higher pollination success compared to smaller bunches. They therefore set more seed on 100 fruits per hand and per bunch basis, if bunches without seed are accounted for. Pollination success rate increases from smaller to larger bunches of EAHBs. Seed set is biased toward the distal third part of fruits of examined EAHBs, as well as tetraploid Matooke hybrid “401K-1” (AAAA), and improved diploid “Zebrina” GF (AA) that were used for comparison. In comparison, in the highly female fertile “Calcutta 4”, seed set is along the entire length of the fruit. Seed set bias in the distal hands and distal end of fruits suggests a systematic mechanism rather than a random occurrence. It is expected that this information will provide a foundation for increased crossbreeding efficiency in bananas.
Small-RNA Deep Sequencing Reveals Arctium tomentosum as a Natural Host of Alstroemeria virus X and a New Putative Emaravirus
(PLoS ONE, 2012) Bi, Yaqi; Tugume, Arthur K.; Valkonen, Jari P. T.
Arctium species (Asteraceae) are distributed worldwide and are used as food and rich sources of secondary metabolites for the pharmaceutical industry, e.g., against avian influenza virus. RNA silencing is an antiviral defense mechanism that detects and destroys virus-derived double-stranded RNA, resulting in accumulation of virus-derived small RNAs (21–24 nucleotides) that can be used for generic detection of viruses by small-RNA deep sequencing (SRDS). Methodology/Principal Findings: SRDS was used to detect viruses in the biennial wild plant species Arctium tomentosum (woolly burdock; family Asteraceae) displaying virus-like symptoms of vein yellowing and leaf mosaic in southern Finland. Assembly of the small-RNA reads resulted in contigs homologous to Alstroemeria virus X (AlsVX), a positive/single-stranded RNA virus of genus Potexvirus (family Alphaflexiviridae), or related to negative/single-stranded RNA viruses of the genus Emaravirus. The coat protein gene of AlsVX was 81% and 89% identical to the two AlsVX isolates from Japan and Norway, respectively. The deduced, partial nucleocapsid protein amino acid sequence of the emara-like virus was only 78% or less identical to reported emaraviruses and showed no variability among the virus isolates characterized. This virus—tentatively named as Woolly burdock yellow vein virus—was exclusively associated with yellow vein and leaf mosaic symptoms in woolly burdock, whereas AlsVX was detected in only one of the 52 plants tested. Conclusions/Significance: These results provide novel information about natural virus infections in Acrtium species and reveal woolly burdock as the first natural host of AlsVX besides Alstroemeria (family Alstroemeriaceae). Results also revealed a new virus related to the recently emerged Emaravirus genus and demonstrated applicability of SRDS to detect negativestrand RNA viruses. SRDS potentiates virus surveys of wild plants, a research area underrepresented in plant virology, and helps reveal natural reservoirs of viruses that cause yield losses in cultivated plants.
Use of timelapse photography to determine flower opening time and pattern in banana (Musa spp.) for efficient hand pollination
(Scientific Reports, 2021) Waniale, Allan; Swennen, Rony; Mukasa, Settumba B.; Tugume, Arthur K.; Kubiriba, Jerome; Tushemereirwe, Wilberforce K.; Uwimana, Brigitte; Gram, Gil; Amah, Delphine; Tumuhimbise, Robooni
Sterility and low seed set in bananas is the main challenge to their conventional genetic improvement. The first step to seed set in a banana breeding program depends on pollination at the right time to ensure effective fertilization. This study aimed at determining bract opening time (BOT) to enhance efficient pollination and seed set in bananas. A Nikon D810 digital camera was set-up to take pictures of growing banana inflorescences at five-minute intervals and time-lapse movies were developed at a speed of 30 frames per second to allow real-time monitoring of BOT. Genotypes studied included wild banana (1), Mchare (2), Matooke (4), Matooke hybrid (1), and plantain (1). Events of bract opening initiated by bract lift for female flowers (P < 0.01) started at 16:32 h and at 18:54 h for male flowers. Start of bract rolling was at 18:51 h among female flowers (P < 0.001) and 20:48 h for male flowers. Bracts ended rolling at 02:33 h and 01:16 h for female and flowers respectively (P < 0.05). Total time of bract opening (from lift to end of rolling) for female flowers was significantly longer than that of male flowers (P < 0.001). On average, the number of bracts subtending female flowers opening increased from one on the first day, to between one and four on the fourth day. The number regressed to one bract on day eight before start of opening of bracts subtending male flowers. There was a longer opening interval between bracts subtending female and male flowers constituting spatial and temporal separation. Bract rolling increased from partial to complete rolling from proximal to the distal end of the inflorescence among female flower. On the other hand, bracts subtending male flowers completely rolled. Differences in BOT of genotypes with the same reference time of assessment may be partly responsible for variable fertility. Hand pollination time between 07:00 and 10:00 h is slightly late thus an early feasible time should be tried.
Xanthomonas campestris pv. musacearum bacterial infection induces organ-specific callose and hydrogen peroxide production in banana
(PhytoFrontiers, 2021) Sadik Mustafa, Abubakar; Tugume, Benison; Ssenku, Jamilu E.; Ssemanda, Paul; Athman, Shahasi Y.; Oryem-Origa, Hannington; Kubiriba, Jerome; Dinesh-Kumar, Savithramma P.; Tugume, Arthur K.
Xanthomonas campestris pv. musacearum (Xcm) bacteria cause banana Xanthomonas wilt (BXW), the most destructive disease of bananas in East and Central Africa. During early stages of infection in susceptible banana cultivars, incomplete systemic movement of Xcm limits bacterial colonization in the upper organs. Mechanistic basis of this delayed movement is unknown. We hypothesized that Xcm infection triggers basal pattern triggered immune (PTI) responses whose spatial and temporal variability along banana’s anatomical structure accounts for initially limiting Xcm in upper organs. Hence, we examined PTI responses such as callose deposition and hydrogen peroxide (H2O2) production in different organs in response to Xcm infection in BXW susceptible Kayinja and Mbwazirume banana cultivars and wild resistant progenitor Musa balbisiana. Xcm-induced callose increased and peaked at 14 days post inoculation (dpi) and 28dpi as assessed by fluorescence microscopy and enzyme-linked immunosorbent assays, respectively. The levels of Xcm-induced H2O2 and callose were highest in the pseudostems and corms, respectively, and were independent of host susceptibility or resistance to BXW. H2O2 production showed a biphasic transient pattern with an initial increase at 1-hour post Xcm-inoculation (hpi), followed by a decline 3- 6hpi and then a second increase by 12hpi. Our findings point to organ-specific responses to Xcm infection in bananas. The corm which doubles as a subterranean parenating organ and interface between mother plants and lateral shoots, was the most responsive organ in callose production while the pseudostem was the most responsive organ in H2O2 production, suggesting the significance of these organs in banana response to BXW.

Browsing by Author "Tugume, Arthur K."

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