National Agricultural Research Organisation Institutional Respoitory (NAROIR)

NAROIR preserves research output from the National Agricultural Research Organisation (NARO)

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Recent Submissions

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    Effects of acute and chronic gamma irradiations on regeneration of tissue types from selected Ugandan cassava genotypes
    (Frontiers in Plant Science, 2026-02-26) Hellen B. Apio; Emmanuel Ogwok; Norazlina Noordin; Peter Wasswa; Isaac Kofi Bimpong; Titus Alicai; Settumba B. Mukasa; John Odipio
    Acute and chronic gamma irradiations (ACGIs) has facilitated generation of new varieties that can withstand abiotic and biotic stresses. This study examined the impact of ACGI doses on the regenerative ability of in vitro embryogenic tissues into complete plants. Tissues from nine genotypes (Alado, NASE 13, NASE 19, NAROCASS 1, CV_193, CV_98/0505, CV_60444, BAO, and reference Ubi Putih) were subjected to acute gamma irradiation (AGI) across six dose levels (0, 5, 10, 15, 20, 25, 35 Gy). Five genotypes (Ubi Putih, CV_60444, Alado, NASE 13, NAROCASS 1) were exposed to chronic gamma irradiation (CGI) for one to four weeks. Ten explants per genotype per dose were evaluated. Mean shoot length was used to calculate the growth reduction dose (GR50), and cell structure changes were analyzed using hematoxylin and eosin staining. Exposure of tissues to AGI and CGI enhanced shoots, roots, leaf regeneration as well as shoot length at dose rates of 5-20 Gy (AGI) and 46 Gy (CGI) at two weeks. The calculated GR50 varied across genotypes and irradiation types. Histological analysis confirmed that distinct structural changes in cell and tissue morphology were linked to irradiation exposure. These results demonstrate that ACGIs can induce accelerated regeneration and structural variation in embryogenic cassava tissues, revealing the potential to develop novel varieties with improved stress resilience. The study underscores ACGIs as a viable biotechnological tool in mutation breeding and genetic improvement of root crops.
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    Virus-Specific Defense Responses in Sweetpotato: Transcriptomic Insights into Resistance and Susceptibility to SPFMV, SPCSV, and SPVD
    (Biology, 2025-11-03) Joanne Adero; Reuben Ssali; Fuentes Segundo; David Maria; Mercy Kitavi; Benard Yada; Denis Karuhize Byarugaba; Faruk Dube; Peace Proscovia Aber; Stephen Obol Opiyo; Zhangjun Fei; Jan Frederik Kreuze
    Sweetpotato (Ipomoea batatas L. Lam) production is threatened by complex viral diseases, notably sweet potato virus disease (SPVD) worldwide, which results from co-infection by sweet potato feathery mottle virus (SPFMV) and sweet potato chlorotic stunt virus (SPCSV). This study provides virus-specific transcriptomic insights into the immune responses of three sweetpotato cultivars, ‘Beauregard’, ‘Tanzania’, and ‘New Kawogo’, to SPFMV, SPCSV, and SPVD. Using RNA-seq profiling across three timepoints post-infection at 3, 6, and 12 weeks, we identified distinct virus- and genotype-specific gene expression responses. ‘New Kawogo’ activated early and sustained immune pathways involving redox regulation, transcriptional control, and hormonal signaling in response to both SPCSV and SPFMV, while showing minimal transcriptional disruption under SPVD, reflecting robust tolerance. ‘Beauregard’ exhibited early suppression of immune and metabolic genes, with delayed and disorganized recovery efforts, particularly under SPVD. Defense-related pathways including NBS-LRR signaling, RNA silencing, and hormonal regulation were consistently upregulated in ‘New Kawogo’ and to a lesser extent in ‘Tanzania’, but remained inactive in ‘Beauregard’. This study highlights candidate resistance and susceptibility genes for each virus, providing a molecular basis for developing virus-resilient sweetpotato cultivars through functional genomics and marker-assisted breeding. These findings elucidate the molecular basis of virus resistance in sweetpotato and identify candidate genes for marker-assisted breeding, despite limitations arising from the use of a diploid reference genome and discrete sampling intervals.
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    Genetic Characterization and Variability of Cassava (Manihot esculenta) Accessions Cultivated in Southwest and North Central Nigeria Using Agromorphological Markers
    (International Journal of Plant Biology, 2025-11-20) Isaac O. Abegunde; Oghenevwairhe P. Efekemo; Olabode Onile-Ere; Folashade Otitolaye; Olusegun A. Oduwaye; Thomas O. Fabunmi; Emmanuel O. Idehen; Justin S. Pita; Fidèle Tiendrébéogo; Titus Alicai; Angela O. Eni
    Understanding the genetic variability among Nigerian cassava accessions is a crucial pre- requisite for its improvement. The objective of this study was to estimate the genetic variability among 477 cassava accessions and to classify them based on their genetic similarities for effective utilization in breeding programs. The accessions were evaluated at the Federal University of Agriculture, Abeokuta experimental site from 2023–2024, using an augmented randomized complete block design with two checks (TME 419 and NR 87184). Agromorphological descriptors were collected at 3-month intervals for 12 months. Broad sense heritability and genetic advance as percent of mean (GAM) were high, indicating that the overall phenotypic expressions observed were largely influenced by genetic factors. Multiple correspondence analysis (MCA) showed that petiole color, number of leaf lobes, color of leaf veins, and parenchyma contributed the most to the overall variability observed in the study population. Principal component analysis (PCA) identified petiole length, length of leaf lobe, width of leaf lobe, and plant height as primary contributors to the overall phenotypic variations observed in the population. Hierarchical clustering of accessions using Euclidean distance revealed two and three clusters based on qualitative and quantitative traits respectively. This study has shown the existence of wide genetic variations in several cassava traits, providing a valuable resource for breeding programs.
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    Yield and climatic parameters in a common bean (Phaseolus vulgaris L.) regional trial
    (Crop Science, 2025-04-08) Winnyfred Amongi; Kijana Ruhebuza; David Karanja; Stanley Nkalubo; Teshale Mamo; Johan Aparicio; Eric Nduwarugira; Blaise Ndabashinze; Rueben Otsyula; Shamir Misango; Eliezah Kamau; Wincaster Mutuli Makoani; Annuarite Uwera; Shida Nestory; Eunice Kesiime; Abel Moges; Kidane Tumsa; Steve Beebe; Clare Mukankusi
    Understanding patterns of crop response to environmental factors is critical to simulating target environments in selection environments. In early stages of varietal development, breeding lines are usually developed in centralized facilities. Subsequently, testing continues on a broader array of research stations before dissemination to farmers, fields. Such a system is practiced in common bean (Phaseolus vulgaris L.) breeding in East Africa. A regional yield trial called the East Central Africa bean yield trial was distributed in three separate groups that aligned with three breeding pipelines: Andean bush beans (Group 1 or G1), Mesoamerican bush beans (G2), and climbing beans (G3). Forty-three trials met minimal standards of data quality. Trial environments composed of a site, planting date, and its climatic parameters were clustered based on 13 variables of temperature, rainfall, relative humidity, vapor pressure deficit, and altitude. Climatic data were derived from the NASA Prediction of Worldwide Energy Resources (POWER) database, which estimates day-by-day weather for each site. Four climate clusters emerged from this analysis. Climbing bean yield corresponded to climate clusters and heavily responded to high altitude and temperature. Most Andean bush bean environments occupied a centric cluster with few extreme variables. No patterns were observed in the Mesoamerican bush beans. This method should be extended to a larger set of trials and should be used to compare research station environments with farmer production environments.
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    Farmers’ Perceptions, Preferences and Choices of Commercial Tea Clones in Uganda: From the Smallholder Out-Growers’ Perspective
    (Horticulturae, 2025-11-20) Kenneth Akankwasa; Tadeo Kaweesi; Venansio Tumwine; Peter B. Ssenyonga; Boaz B. Mwesigwa; Vereriano Turyahebwa; Gerald Agaba; Ronald Kawooya; Robooni Tumuhimbise; Ji Lingfei; Yang Yiyang; Stanley T. Nkalubo
    Tea (Camellia sinensis (L). Kuntze) cultivation by smallholder out-growers has grown significantly. Recent government initiatives have expanded production from traditional tea growing regions. This study investigated how smallholder farmers perceive and prefer different commercial tea clones. It also looked at the factors that influence their choices across major tea-growing regions of Uganda. A structured questionnaire was administered to 324 randomly selected tea out-growers from Central, Western, Kigezi, and West Nile regions. Data was analyzed using descriptive statistics, a Tea Preference Index (rating clone attributes on a 1–5 scale), and a multivariate Probit (MVP) model to evaluate farmers’ choices and preferences. Clone 303/577 is the most cultivated, accounting for 59%. Adoption rates were high in West Nile (98%), Kigezi (77%), and Central (67%) regions. Clone 6/8 ranked second at 47%, while clone 100/5 had the lowest cultivation rate at 10%. The ranking of clones by preference was 303/577, 6/8, 108/82, 31/8, and 100/5. Key attributes influencing preferences included, yield potential, canopy width, post-plucking/pruning recovery rate, shoot tenderness and cup quality. Results showed that a farmers’ choice of clone 303/577 was significantly influenced by shoot density, gender and tea farming experience. For clone 108/82, the most important factors were quick recovery after pluck- ing/pruning, education level and household size. This information is vital for agricultural policy, extension services, tea breeding and genetic improvement programs in the tea sector.