Browsing by Author "Deom, Carl Michael"

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    Genetic variability studies of Valencia groundnut varieties for late leaf spot (Phaeoisariopsis personata) resistance
    (African Journal of Plant Science, 2015-08-30) Wambi, Wilber; Tukamuhabwa, Pinehas; Okello, David Kalule; Deom, Carl Michael; Puppala, Naveen
    The study was initiated to determine the genetic variability of late leaf spot (LLS) resistance among segregating generations of Valencia groundnut varieties. Crosses were made between NuMex-M3 × ICGV-SM 02501, Valencia C × ICGV-SM 02501, Redbeauty × ICGV-SM 03590 and Valencia C × SGV-07009 parental lines and the resulting generations (F1, F2, BC1P1 and BC1P2,), along with parents for each cross, were evaluated for LLS resistance on a 1-9 scale under natural conditions in a randomized complete block design (RCBD) with three replications. Analysis of variance was performed for generations of each cross, coefficients of variation and heritability were estimated for all crosses except for the Valencia C × SGV-07009 cross. Three crosses showed highly significant differences among generations for LLS resistance (P≤ 0.05). The three crosses exhibited moderate to high levels of genotypic coefficient of variation (GCV) (15.43 to 23.13 %) and phenotypic coefficient of variation (PCV) (16.89 to 28.82%). The exception was the Redbeauty × ICGV-SM 03590 cross which showed low (9.50%) GCV. Broad-sense heritability (h2b) estimates for LLS disease scores were moderate to high (32 to 64%) for the three crosses. The results reveal substantial variation for LLS resistance in generations of these crosses indicating that the trait under study was heritable.
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    Molecular diagnostics of groundnut rosette disease agents in Uganda: Implications on epidemiology and management of groundnut rosette disease
    (Journal of plant breeding and crop science, 2017) Kalule Okello, David; Adrogu Ugen, Michael; Tukamuhabwa, Phinehas; Ochwo- Ssemakula, Mildred; Lapaka Odong, Thomas; Adriko, John; Kiconco, Faith; Male, Allan; Deom, Carl Michael
    The objective of this study was to use molecular diagnostic tools to detect the agents of groundnut rosette disease (GRD) to guide in varietal development and disease management. Samples were collected from both GRD infected and healthy plants and sites geo-referenced. RNA extraction, cDNA synthesis, polymerase chain reaction (PCR) amplification, electrophoresis, staining and visualization were performed according to standard procedures. Molecular diagnosis of the samples showed various combinations of the GRD agents, some in isolation and others a combination of two or three agents. This distribution is attributed to dependence on the aphid feeding behaviour and pathogenicity of GRD agents. Chlorotic and green rosette symptoms were observed throughout the sampling sites signifying the presence of satellite RNA (sat-RNA) variants. Some plants showing GRD symptoms tested negative for GRD, whereas some healthy-looking plants tested positive for the GRD complexes pointing to the ineffectiveness of phenotypic screening and the need for a molecular diagnostic tool that detects all three GRD agents both in absence or presence of disease symptoms. The absence of groundnut rosette assistor virus (GRAV) in some symptomatic samples signifies that they are epidemiologically dead end sources since GRV and sat-RNA must be packaged within the GRAV coat protein to be aphid transmissible. Oyado (Cassia obtusifolia) tested positive for all the GRD agents making it a potential alternative host. There is an urgent need for validation of the phenotypic screening with molecular tools in efficient diagnosis of the multi-pathogenic GRD in guiding both plant breeding and pathology work.