NRU :: Browsing by Author "Edema, Richard"

Browsing by Author "Edema, Richard"

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Additive Main Effects and Multiplicative Interactions Analysis of Yield Performances in Cowpea Genotypes under Ugandan Environments
(International Journal of Advanced Research (IJAR), 2017) Agbahoungba, Symphorien; Karungi, Jeninah; Talwana, Herbert; Badji, Arfang; Kumi, Frank; Mwila, Natasha; Edema, Richard; Gibson, Paul; Rubaihayo, Patrick
Yield in legumes is the result of many plant processes, which are usually expressed in yield and have been shown to be affected by management, genotype and environment. The objectives of this study were to assess the extent of genotype x environment interaction and to select the stable cowpea genotypes in Ugandan environments over seasons. Seventy-two cowpea genotypes were evaluated for yield in three locations and two seasons in Uganda. The yield data were subjected to analysis of variance and additive main effects and multiplicative interactions (AMMI) analysis. The results showed a highly significant (P<0.001) genotype by location and by year (season) interaction effects for grain yield, with 69.16% of the total variation attributable to environmental effects, 5.36% to genotypic effects and 12.74% to G x E interactions effects. Genotype MU9 had the highest yield (854.68 kgha-1) but was only adapted to specific environments (Arua 2015B and 2016A). Hence, genotypes WC 30, NE 45, NE 31, NE 51 which were equally high yielding, stable and adapted to the tested environments, and should be recommended for genetic improvement of cowpea germplasm in Uganda.
Azadirachta indica reduces black sigatoka in east african highland banana by direct antimicrobial effects against Mycosphaerella fijiensis without inducing resistance
(Journal of Agricultural Science, 2017) Kumakech, Alfred; Jørgensen, Hans Jørgen Lyngs; Collinge, David B.; Edema, Richard; Okori, Patrick
Black Sigatoka is a major disease of East African highland cooking bananas in Uganda. Aqueous extracts of Azadirachta indica, Cinnamomum zeylanicum and Capsicum annuum have shown the potential to reduce Black Sigatoka in banana plantlets. The mechanisms by which plant extracts confer protection against plant pathogens has previously been reported to involve activation of defence and direct antimicrobial activity. In the current study, both antimicrobial activities of selected extracts were studied as well as expression of three defence-related genes using quantitative real-time PCR. Gene expression was compared in susceptible (cv. Musakala, genomic group AAA-EA) and resistant (cv. Kayinja, genomic group ABB) banana cultivars. Additionally, Musakala treated with A indica extract at 1 day before inoculation (DBI) was tested for induction of defence-related genes at 0, 10 and 20 days after inoculation (DAI). Pathogenesis-related genes (PR-1 and PR-3) and non-expressor of PR-genes (NPR1B) were up-regulated in the resistant cultivar. The genes analysed responded at late time points to M. fijiensis inoculation in both extract-treated and control plants in the susceptible cv. Musakala. On the other hand, A. indica and C. annuum completely inhibited mycelial growth of M. fijiensis at 30% (w/v). These findings suggest that the effect of plant extracts on Black Sigatoka is strongly associated with the direct antimicrobial effects.
Combining ability analysis of dry matter content, reducing sugars and yield of potato (Solanum tuberosum L.) genotypes in Uganda
(Journal of Scientific Agriculture, 2020) Muhumuza, Edgar; Edema, Richard; Namugga, Prossy; Barekye, Alex
Potato (Solanum tuberosum L.) in Uganda is a major food and cash crop mainly grown in the highland regions by small-scale farmers. The increasing importance of potato as a processed product requires new varieties possessing quality processing attributes with acceptable yield. The objectives of this study were to estimate the combining ability effects for dry matter content, reducing sugars, and yield related traits in potato. Nineteen F1 families generated from eight parents using a half diallel mating design were evaluated for dry matter content, reducing sugars, average weight per tuber and total tuber yield at Kachwekano research station. Additive genetic effects were predominant for dry matter content while non-additive effects for the other traits. The GCA/SCA ratios were 0.58, 0.28, 0.17 and 0.44 for dry matter content, reducing sugars, average weight per tuber and total tuber yield respectively. Broad sense heritability estimates were 50.6% for dry matter content, 77.8% for reducing sugars, 90.3% for average weight per tuber and 29.5% for total tuber yield. Parents NAROPOT 3 and 395096.2 had desirable GCA effects for both dry matter content and reducing sugars. Families of nkrk19.17 x Rutuku had desirable SCA effects for dry matter content while Rutuku x 393077.54 and nkrk19.17 x 392657.8 had desirable SCA effects for reducing sugars. Additive genetic effects for dry matter content imply that, genetic gains can be achieved through different selection methods and trait transferred to the respective progenies. The selected parents and families will be subjected to further clonal evaluation and selection.
Combining ability and heritability analysis of sweetpotato weevil resistance, root yield, and dry matter content in sweetpotato
(Frontiers Media S.A., 2022-09) Mugisa, Immaculate; Karungi, Jeninah; Musana, Paul; Odama, Roy; Alajo, Agnes; Chelangat, Doreen M; Anyanga, Milton O; Oloka, Bonny M.; Gonçalves dos Santos, Iara; Talwana, Herbert; Ochwo-Ssemakula, Mildred; Edema, Richard; Gibson, Paul; Ssali, Reuben; Campos, Hugo; Olukolu, Bode A; Guilherme; Yencho, Craig; Yada, Benard; da Silva Pereira, Guilherme; Yencho, Craig
Efficient breeding and selection of superior genotypes requires a comprehensive understanding of the genetics of traits. This study was aimed at establishing the general combining ability (GCA), specific combining ability (SCA), and heritability of sweetpotato weevil (Cylas spp.) resistance, storage root yield, and dry matter content in a sweetpotato multi-parental breeding population. A population of 1,896 F1 clones obtained from an 8 × 8 North Carolina II design cross was evaluated with its parents in the field at two sweetpotato weevil hotspots in Uganda, using an augmented row-column design. Clone roots were further evaluated in three rounds of a no-choice feeding laboratory bioassay. Significant GCA effects for parents and SCA effects for families were observed for most traits and all variance components were highly significant (p ≤ 0.001). Narrow-sense heritability estimates for weevil severity, storage root yield, and dry matter content were 0.35, 0.36, and 0.45, respectively. Parental genotypes with superior GCA for weevil resistance included “Mugande,” NASPOT 5, “Dimbuka-bukulula,” and “Wagabolige.” On the other hand, families that displayed the highest levels of resistance to weevils included “Wagabolige” × NASPOT 10 O, NASPOT 5 × “Dimbuka-bukulula,” “Mugande” × “Dimbuka-bukulula,” and NASPOT 11 × NASPOT 7. The moderate levels of narrow-sense heritability observed for the traits, coupled with the significant GCA and SCA effects, suggest that there is potential for their improvement through conventional breeding via hybridization and progeny selection and advancement. Although selection for weevil resistance may, to some extent, be challenging for breeders, efforts could be boosted through applying genomics-assisted breeding. Superior parents and families identified through this study could be deployed in further research involving the genetic improvement of these traits.
Combining ability for resistance to rice yellow mottle virus disease in interspecific and intraspecific rice Genotypes
(African Journal of Crop Science, 2015) Munganyinka, Esperance; Edema, Richard; Lamo, Jimmy; Gibson, Paul; Rukundo, Placide
Estimates of combining ability for resistance to rice yellow mottle virus disease (RYMV) were obtained in the green house of National Crops Resources Research Institute, Uganda. The study involved forty-one F2’s diallel crosses and their five intraspecific and four interspecific parental lines. Effects of both general combining ability (GCA) and specific combining ability (SCA) for RYMV reactions were significant, with a preponderance of GCA effects. Of parental lines used in this study, Naric 1, Nerica 6 and WAC 116 were good combiners for transferring resistance genes to their progenies. In this study, most genotypes with good resistance were good general combiners expect Gigante, that despite its good mean performance, combined badly for resistance to RYMV. The crosses with the best resistance were Naric 1x Gigante, Naric 1x Nerica 6, Nerica 6 x Nerica 4 and Nerica 1 x Nerica 6. From this study, we suggest that selection of parents as donors for resistance should consider both GCA and parental performance. On the basis of predominant additive genetic effects observed in the present study, we believe that combinations of interspecific parents may be used to produce rice varieties resistant to RYMV, and that selection in early selfing generations should be effective.
A Comparative Analysis of Conventional and Marker-Assisted Selection Methods in Breeding Maize Streak Virus Resistance in Maize
(Crop Science, 2009) Abalo, Grace; Tongoona, Pangirayi; Derera, John; Edema, Richard
Reliable information regarding comparative advantage of marker-assisted selection (MAS) over conventional selection (CS) in breeding for maize streak virus (MSV) resistance in maize (Zea mays L.) is scarcely available. A comparative study was, therefore, conducted to determine the effi ciency of both methods in breeding for MSV resistance in Uganda. Backcross and selfed-progenies were derived from inbred lines CML202 (resistant), CML321, and CML384 (susceptible) using MAS and CS. The experimental lines and their testcross progenies were evaluated for MSV resistance and yield across three locations. Although both breeding approaches were effective in generating MSV-resistant lines, disease incidence was higher in populations under CS (79%) than MAS (62%). A similar trend was observed for area under disease progress curve. However, an equal number of lines generated by MAS and CS displayed high yield potential and MVS resistance in testcrosses. Because all required DNA analysis was performed in an existing laboratory and on a well-characterized quantitative trait locus, costs of capital, equipment maintenance, and marker development were excluded in costing the MAS procedure. Considering total running costs, MAS was cheaper than CS by 26%, which was realized by using fewer plants. Therefore, when laboratory facilities are already established MAS would be recommended in breeding for MSV resistance.
Distribution and Biocontrol Potential of phlD+ Pseudomonads in Corn and Soybean Fields
(Biological Control, 2005) McSpadden Gardener, Brian B.; Gutierrez, Laura J.; Joshi, Raghavendra; Edema, Richard; Lutton, Elizabeth
The abundance and diversity of phlD+ Pseudomonas spp. colonizing the rhizospheres of young, field-grown corn and soybean plants were assayed over a 3-year period. Populations of these bacteria were detected on the large majority of plants sampled in the state of Ohio, but colonization was greater on corn. Although significant variation in the incidence of rhizosphere colonization was observed from site to site and year to year on both crops, the magnitude of the variation was greatest for soybean. The D genotype was detected on plants collected from all 15 counties examined, and it represented the most abundant subpopulation on both crops. Additionally, six other genotypes (A, C, F, I, R, and S) were found to predominate in the rhizosphere of some plants. The most frequently observed of these were the A genotype and a newly discovered S genotype, both of which were found on corn and soybean roots obtained from multiple locations. Multiple isolates of the most abundant genotypes were recovered and characterized. The S genotype was found to be phylogenetically and phenotypically similar to the D genotype. In addition, the novel R genotype was found to be most similar to the A genotype. All of the isolates displayed significant capacities to inhibit the growth of an oomycete pathogen in vitro, but such phenotypes were highly dependent on media used. When tested against multiple oomycete pathogens isolated from soybean, the A genotype was significantly more inhibitory than the D genotype when incubated on 1/10× tryptic soy agar and 1/5× corn meal agar. Seed inoculation with different isolates of the A, D, and S genotypes indicated that significant root colonization, generally in excess of log 5 cells per gram of root, could be attained on both crops. Field trials of the A genotype isolate Wayne1R indicated the capacity of inoculant populations to supplement the activities of native populations so as to increase soybean stands and yields. The relevance of these findings to natural and augmentative biocontrol of root pathogens by these bacteria is discussed.
Effect of low temperature stress on field performance of highland sorghum (Sorghum bicolor (L.) Moench) at flowering stages
(Journal of Plant Breeding and Crop Science, 2020) Rutayisire, Amandin; Mukayiranga, Alice; Habineza, Jean Claude; Avosa, Millicent; Edema, Richard; Lubadde, Geofrey
Sorghum is a C4 grass native in the semi-arid environments of the African sub-Saharan and consequently chilling stress can affect the performance of the crop, especially at the reproductive stages. Moreover, a significant delay of flowering and maturity was observed when sorghum grows under low temperatures regions, and consequently farmers in highland areas of Uganda face yield penalties. Forty genotypes were evaluated in 2017B and 2018A seasons under non-stress (Kabanyolo) and cold stress (Kachwekano and Zombo) field conditions. Data were recorded on: Days to 50% flowering, days to physiological maturity, culm height, panicle length, panicle weight, kernel weight per panicle, and thousand grain weight. Mean comparison of most agronomic traits recorded indicated high significant differences for season-by-genotype, location-by-genotypes, and the three-way interaction (GxLxS). This indicates that cold stress significantly affects yield components. Significant positive correlation was obtained between days to 50% flowering, days to maturity, and culm height, which suggested that simultaneous improvement of these traits is possible. Some genotypes (IESV 91003LT, IESV 91105LT and IS 29376) were best ranked in normal environment but poorly performed in cold environments, which indicates lack of adaptation in highland. BM6, Cytanobe, IESV 91018, IESV 91609, IS 25563 showed generally good performance and stability in all locations. Therefore, these genotypes can be used as parental lines for further breeding process.
Establishment of an early selection method (criteria) for breeding in cowpea (Vigna unguiculata)
(Journal of Plant Breeding and Crop Science, 2020) Oside Millicent, Avosa; Orawu, Martin; Ongom Obia, Patrick; Dramadri Onziga, Isaac; Rutayisire, Amandin; Osundwa, Cynthia; Paul, Gibson; Edema, Richard
Populations with high genetic variability are targeted by breeders as they create opportunity for selection and genetic improvement. To achieve this, multiple populations are created, but resources are often scarce. This calls for identification of populations with the desired traits at early generation. The study was carried out at MUARIK in seasons 2017A and 2017B on 135 F2 and 40 F3 cowpea populations respectively together with 25 parental lines aimed at: Determining best performing populations for yield, resistance to scab, virus and flower thrip based on usefulness criterion and selection index methods. Usefulness criterion computed for yield identified NE 36 x 2392 as the best population. Usefulness criterion computed for yield and its components identified NE 5 x Sanzi as the best population. WC 48A x 2392 was identified as the best population using selection index values that included resistance to virus, thrips, scab, yield and its component and when only yield and its components were fitted in the model. Variability and high yield performance was maintained in the forty best populations identified and therefore amendable for future improvement. No differences were shown among the methods used for selection hence can be adapted for breeding in cowpea.
Estimates of combining ability and heritability in cowpea genotypes under drought stress and nonstress conditions in Uganda
(Journal of Plant Breeding and Crop Science, 2017) Mwale, Saul Eric; Ochwo Ssemakula, Mildred; Sadik, Kassim; Alladassi, Boris; Rubaihayo, Patrick; Gibson, Paul; Singini, Wales; Edema, Richard
Cowpea is an important source of food and income for small scale farmers in Uganda. Production is, however, affected by both biotic and abiotic stresses. Drought stress has recently emerged as a serious concern due to the effects of climate change. This study was therefore undertaken to estimate the general and specific combining ability effects of parents and crosses as well as estimate the heritability of delayed leaf senescence, seed yield and its components under drought stress. Five drought tolerant genotypes were crossed with four drought sensitive genotypes in a North Carolina II mating design. The study revealed that drought tolerance is conditioned by both additive and non-additive genetic effects with the predominance of non-additive genetic effects for seed yield, 100 seed weight and number of pods per plant. Delayed leaf senescence was however, controlled by additive genetic effects, implying that progenies performance could be predicted from parents General Combining Ability (GCA) effects. The cultivars SECOW 5T, IT93K-452-1 and IT98K-205-8 were good combiners for drought tolerance. The F2 families: SECOW 3B x IT98K-205-8, SECOW 5T x IT98K-205-8, SECOW 4W x IT98K- 205-8 and SECOW 1T x IT98K-205-8 had positive Specific Combining Ability(SCA) effects in seed yield, number of pods per plant and 100 seed weight, implying that they performed better than what was predicted by their parents GCA effect. As such, they are promising cross combinations that can be advanced for later generation selection.
Evaluation of Cowpea Genotypes for Resistance to Fusarium redolens in Uganda
(American Journal of Plant Sciences, 2017) Wanjala Namasaka, Roy; Tusiime, Geoffrey; Orawu, Martin; Gibson, Paul; Nyiramugisha, Josiane; Edema, Richard
Fusarium redolens, a virulent fungus which causes damping off, leaf yellowing, wilting and root rots has recently been devastating cowpea fields in Uganda. This study aimed at identifying cowpea genotypes that are resistant to Fusarium redolens. Therefore, ninety cowpea genotypes were evaluated two times against a highly virulent Fusarium redolens (isolate from Zombo in Paidha district) in the screen house in 2016. Genotype effect was highly significant (P < 0.001) for root rot severity. Based on the Index of Susceptibility (IS), three genotypes (Asontem, Dan1 LA and IT89KD-88) remained resistant (IS < 3.5) over the two screening periods, 72 moderately resistant (3.5 ≤ IS < 6.5) and 11 susceptible (IS ≥ 6.5). Resistance was found to be enhanced by presence of lateral roots above or at the ground level. Further results suggested a difference in genetic control of resistance to root rots and seed rots caused by Fusarium redolens . All the released varieties tested (SECOW 1 T, SECOW 2 W, SECOW 3 B, SECOW 4 W and SECOW 5 T) had moderate resistance to Fusarium redolens . Correlation analysis revealed root rot severity was strongly correlated to disease incidence (+0.64, P < 0.001), to proportion of plants with lateral roots (−0.56, P < 0.001), to amount of leaf chlorophyll (−0.53, P < 0.001) and to proportion of plants that died prematurely due to Fusarium redolens infection (+0.45, P < 0.001). No significant correlation was detected between root rot severity and proportion of plants that germinated. The established resistance could be exploited for improvement of farmer preferred cowpea varieties towards Fusarium redolens resistance in Uganda.
Exploiting Grain-Filling Rate and Effective Grain-Filling Duration to Improve Grain Yield of Early-Maturing Maize
(Crop Science, 2013) Gasura, Edmore; Setimela, Peter; Edema, Richard; Gibson, Paul T.; Okori, Patrick; Tarekegne, Amsal
Early-maturing maize (Zea mays L.) genotypes yield 15 to 30% less than late-maturing genotypes. One strategy for improving grain yield in the early-maturing group involves assessment of grain-filling traits as secondary traits for selection for high grain yield. In this study, we investigated the possibility of using grainfilling rate and duration for improving grain yield in early-maturing tropical maize. Forty-four hybrids generated using North Carolina design II were evaluated at CIMMYT-Zimbabwe during the 2011/2012 season under irrigated and nonirrigated environments. Although grain-filling rate and effective grain-filling duration were negatively correlated, several hybrids were distinctly above the trend line. The earliest-maturing hybrid took 127 d to reach physiological maturity and produced grain yields comparable to those of the medium-maturing genotypes (7 t ha-1). It had a high grain-filling rate of 2.40 g per plant d-1 (18% higher than those of the lowyielding hybrids) and a relatively longer effective grain-filling duration. Grain-filling rate and effective grain-filling duration had high coefficients of genetic determination, positive correlations with grain yield, low error terms, and low genotype × environment interactions, making them appropriate selection traits for improved grain yield. The study shows that it is possible to develop high-yielding early- to medium-maturing maize hybrids based on favorable combining ability values for grain-filling rate and duration.
Flowering problems and their possible solution in cassava breeding
(Journal of Scientific Agriculture, 2020) Ibrahim, Yasmin; Baguma, Yona; Abincha, Wilfred; Gibson, Paul; Edema, Richard; Bisikwa, Jenipher
Six elite cassava clones were chosen from cassava breeding program at the National Crops Resource Research Institute (NaCRRI) based on their flowering characteristics and seed set. The clones were planted in randomized complete block experimental design with 3 replications. The floral biology of these cassava clones were studied, focusing on morphological traits and developmental timing. Since cassava develops branches in levels, data was sourced from the 1st level of branching through the 4th level of branching. The result indicated that days to branching generally varied among all the genotypes studied, indicating the need to use different planting dates for different genotypes to ensure synchronization of flowering. The time difference among genotypes from branching to visible inflorescence was not larger than one and a half days and this difference did not seem be a factor for synchronization. The general number of female flowers was low in all genotypes across branching levels. This suggests there is a need to apply techniques that could enhance flowering in cassava. Conversely, the number of male flowers outnumbered the female flowers, suggesting that male flower production may not be a limiting factor to hybrid seed production. Male flower opened 20 to 30 days later after the opening of the female flowers. This calls for delayed planting of the early flowering genotypes when used as female parent. It was recommended that in order to synchronize flowering, the late flowering genotypes have to be planted ahead of the early flowering genotypes. In addition, applying techniques such as growth regulators, red light and finding the most optimal locations for flowering is recommended for further study as a way of enhancing flowering among cassava genotypes.
Genetic analysis of maize streak virus isolates from Uganda reveals widespread distribution of a recombinant variant
(Journal of general virology, 2007) Owor, Betty E.; Martin, Darren P.; Shepherd, Dionne N.; Edema, Richard; Monjane, Ade´ rito L.; Rybicki, Edward P.; Thomson, Jennifer A.; Varsani, Arvind
Maize streak virus (MSV) contributes significantly to the problem of extremely low African maize yields. Whilst a diverse range of MSV and MSV-like viruses are endemic in sub-Saharan Africa and neighbouring islands, only a single group of maize-adapted variants – MSV subtypes A1–A6 – causes severe enough disease in maize to influence yields substantially. In order to assist in designing effective strategies to control MSV in maize, a large survey covering 155 locations was conducted to assess the diversity, distribution and genetic characteristics of the Ugandan MSV-A population. PCR–restriction fragment-length polymorphism analyses of 391 virus isolates identified 49 genetic variants. Sixty-two full-genome sequences were determined, 52 of which were detectably recombinant. All but two recombinants contained predominantly MSV-A1-like sequences. Of the ten distinct recombination events observed, seven involved inter-MSV-A subtype recombination and three involved intra-MSV-A1 recombination. One of the intra-MSV-A1 recombinants, designated MSV-A1UgIII, accounted for .60% of all MSV infections sampled throughout Uganda. Although recombination may be an important factor in the emergence of novel geminivirus variants, it is demonstrated that its characteristics in MSV are quite different from those observed in related African cassava-infecting geminivirus species.
Genetic Analysis of Weevil (Cosmopolites Sordidus) Resistance in an F2 Diploid Banana Population
(Journal of Plant Breeding and Genetics, 2015) Arinaitwe, Ivan K.; Barekye, Alex; Kubiriba, Jerome; Sadik, Kassim; Karamura, Eldad; Edema, Richard
The East African highland bananas (Musa spp. AAA), an important staple food in Uganda, are highly susceptible to the banana weevil (Cosmopolites sordidus Germar). Sources of host plant resistance to the banana weevil exist in wild diploid bananas. The use of wild diploid bananas to improve East African highland bananas can be facilitated by studying genetics of host plant resistance of inter-diploid crosses. The objectives of this study were a) to identify segregating weevil resistance and agronomic traits in an F2 diploid population, and, b) to determine the inheritance of banana weevil resistance and agronomic traits based on an F2 banana diploid population. An F1 population developed from Musa acuminata subsp. banksii acc. Kasaska (ITC0591) and M. acuminata subsp. microcarpa acc. Borneo (ITC0253) was selfed to generate an F2 diploid population. The F2 population was screened against weevil resistance and agronomic traits in the laboratory, pot and field experiments. There were significant differences (P < 0.05) among the different genotypes for banana weevil resistance traits such as head capsule width, body length, body weight, larval mortality, total damage, peripheral damage, dead weevils and larvae retrieved. There were also significant differences (P < 0.05) for agronomic traits such as inner corm hardness and total corm hardness. The histograms for the banana weevil resistance traits such as head capsule width, body length, body weight and larval mortality, total damage, peripheral damage, cross sectional inner and outer damage, larvae retrieved and dead weevils showed continuous distribution. Similarly, histograms for agronomic parameters such as height of plant at flowering and girth at 1 meter at flowering showed continuous distribution. The Chi-square test of goodness of fit indicated that weevil growth and damage parameters had significant modifications of the expected 9:3:3:1 ratio for two independent loci, thus suggesting epistasis affects their inheritance.
Genetic inheritance of resistance to Fusarium redolens in cowpea
(Journal of Plant Breeding and Crop Science, 2017) Wanjala, Namasaka Roy; Tusiime, Geoffrey; Orawu, Martin; Paul, Gibson; Agbahoungba, Symphorien; Mahulé Elysé Boris, Alladassi; Edema, Richard
Fusarium related root rots have been associated with reduced cowpea productivity in Uganda. Sources of genetic resistance to Fusarium redolens which was found to be the most virulent have been identified but the mode of inheritance of the genes conferring the resistance is unknown. This study aims to investigate how the genes for resistance to F. redolens are inherited in cowpea. Four F. redolens root rot resistant cowpea genotypes were crossed with four intermediately resistant and 2 susceptible cowpea genotypes using North Carolina mating design II. The F1 and the parents were evaluated and data were collected on resistance to seed rot, leaf chlorophyll amount, produced lateral roots, response to plant mortality and root rot severity. Results revealed that additive gene effects were significant for all evaluated traits and non-additive genetic effects were significant in resistance to seed rot and chlorophyll amount. General combining ability (GCA) effects showed that the Asontem genotype was a good combiner for increased lateral roots production and resistance to root rot. Degree of dominance estimates revealed that response to plant mortality, root rots and increased lateral root production traits were recessively inherited while seed rot and amount of leaf chlorophyll were dominantly inherited.
Genetic Variation Among Tropical Maize Inbred Lines from NARS and CGIAR Breeding Programs
(Plant Molecular Biology Reporter, 2022) Bigirwa Ayesiga, Stella; Rubaihayo, Patrick; Oloka, Bonny Michael; Onziga Dramadri, Isaac; Edema, Richard; Sserumaga, Julius Pyton
The use of molecular markers allows for precise estimates of genetic diversity, which is an important parameter that enables breeders to select parental lines and designing breeding systems. We assessed the level of genetic diversity and population structure in a panel of 151 tropical maize inbred lines using 10,940 SNP (single nucleotide polymorphism) markers generated through the DArTseq genotyping platform. The average gene diversity was 0.39 with expected heterozygosity ranging from 0.00 to 0.84, and a mean of 0.02. Analysis of molecular variance showed that 97% of allelic diversity was attributed to individual inbred lines within the populations while only 3% was distributed among the populations. Both neighbor-joining clustering and STRU CTU RE analysis classified the inbred lines into four major groups. The crosses that involve inbred lines from most divergent subgroups are expected to generate maximum heterosis and produce wide variation. The results will be beneficial for breeders to better understand and exploit the genetic diversity available in the set of maize inbred lines we studied.
Genotype by environment interaction effects on grain yield of highland maize (Zea mays L) hybrids
(Maydica, 2018) Ninsiima Kayaga, Hellen; Ochwo-Ssemakula, Mildred; Kagoda, Frank; Mahulé Elysé Alladassi, Boris; Asea, Godfrey; Gibson, Paul; Edema, Richard
Maize varieties adapted to highland environments are generally scarce in East and Central Africa (ECA) since most breeding efforts have focused on mid-altitude maize. As a result, farmers in the highlands of Uganda mainly grow varieties that are bred for the mid-altitude zones. Since these maize varieties are not adapted to highland conditions, their productivity in this region rarely exceeds 2 t ha-1. This study was aimed at determining the effect of genotype by environment interactions (GEI) on the grain yield of highland maize hybrids. The study was conducted in three highland locations of Uganda in the maize growing season of March to October 2015. Thirty-six F1 hybrids and two checks were arranged in a 2 x18 (0, 1) alpha lattice design with two replications. Hybrid by location interaction had highly significant differences (P ≤ 0.001) and explained 46.2% of phenotypic variance. Genotype by environment interactions (GEI), thus, had a strong effect on grain yield. Analyses revealed two maize megaenvironments, with AMH701-9/AMH703-22 hybrid emerging the best genotype in Kachwekano and Kalengyere (6.69 t ha-1 and 14.30 t ha-1), and AMH701-9/AMH701-20 hybrid being the best in Buginyanya (14.39 t ha-1). Efforts to breed for high yielding maize cultivars for the highland areas of Uganda should therefore focus more on specific adaptation than broad adaptation.
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, Martin
This 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.
Identication Of New Sources Of Rice Genotypes (Oryza Sativa L.) Tolerant To Cold Stress
(Research Square, 2022) Tolosa Entele, Kidist; Edema, Richard; Lamo, Jimmy; Tilahun, Nigat; Abebe, Desta; Kebede, Worku
Rice crop is adversely affected by cold stress which is a common problem in the highland areas of central East Africa (Uganda, Rwanda, north east Tanzania and Kenya) and Madagascar. Cold stress is known to cause 26% to 80% yield loss. Currently, rice production in Uganda is mostly growing to the low altitude areas as there is lack of cold-tolerant varieties that can grow in the higher altitudes of the country. None of the released varieties in Uganda are tolerant cold. The few cold-tolerant lines that have been identified are short-grain types, though Ugandan consumers generally prefer long-grain size. This research aimed at identifying new sources of cold tolerant rice genotypes with preferred traits. A total of 50 lines arranged in a 5x10 alpha lattice design with two replications were used for both stressed and non-stressed experiments. Twenty one (21) days old seedlings were stressed at 10oC in cold air for 10 days and the other remained under normal ambient temperature. IRRI Standard Evaluation System (SES, 2013) was used to score the effect of cold stress on leaf morphology (leaf wilting score) and on leaf color (leaf yellowing score) after 7 day recovery. This study revealed eight highly cold tolerant (SCRID091-20-2-2-4, GIZA 177, NERICA 1, MET P27, MET P23, MET P60, MET P20 and MET P5) in which only GIZA 177 was short grain and fifteen tolerant varieties (MET P32, MET P11, MET P2, MET P17, MET P3, MET P24, MET P16, MET P37, MET P18, MET P9, MET P40, MET P31, MET P39, MET P22, MET P36) were identified.

Browsing by Author "Edema, Richard"

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