Academic literature on the topic 'Sorghum – Breeding – Uganda'

Sorghum is one of the main food and feed crops in the world. Rapid population growth in Africa requires a growing amount of local foods such as sorghum. Therefore, breeding work aimed at developing highly productive sorghum varieties and hybrids adapted to the soil and climatic conditions of Africa and the arid conditions of southern Russia is of great urgency. Therefore, it was necessary to identify the adapted samples with valuable economically valuable traits. The current study has been carried out on the experimental plots of the laboratory for grain sorghum breeding and seed production of the FSBSI “Agricultural Research Center “Donskoy”. As objects of the study there have been used the grain sorghum varieties of the National Research Institute of Semi-Arid Resources (NaSARRI) of the Republic of Uganda ‘Seso 1’, ‘Seso 3’, ‘Narosorg 1’, ‘Narosorg 2’, ‘Narosorg 3’, ‘Narosorg 4’, ‘Epuripur’, as well as the variety ‘Zernogradskoe 88’ sown as the standard variety. The study was conducted in accordance with the Methodology of State Variety Testing of Agricultural Crops and B. A. Dospekhov’s Methodology of a field trial. The purpose of the current study was a comprehensive estimation of grain sorghum varieties developed in the research institutions in Uganda under the conditions of the Rostov region to use the selected samples in further breeding work as sources of economically valuable traits. In the conditions of the Rostov region the Ugandan varieties belonged to the group of middle ripening and late ripening varieties. The plant height in the studied varieties varied from 155 to 210 cm. According to the trait “number of grains per panicle” the varieties had a large number of grains (1829–2530 pcs.). The main share of the NaSARRI varieties had a high percentage of raw protein in grain (13.6–14.9%). A low tannin content was established in the varieties ‘Seso 1’ (0.54%), ‘Epuripur’ (0.66%) and ‘Narosorg 1’ (0.71%).

The study of genetic diversity in crops has a strong impact on plant breeding and maintenance of genetic resources. Comprehensive knowledge of the genetic biodiversity of cultivated and wild sorghum germplasm is an important prerequisite for sustainability of sorghum production. Recurrent droughts resulting from climate change scenarios’ in many East and Central Africa countries, where sorghum is a significant arable crop, can potentially lead to genetic erosion and loss of valuable genetic resources. This study aimed at assessing the extent and pattern of genetic diversity and population genetic structure among sorghum accessions from selected countries in East and Central Africa (Sudan, Kenya, Uganda, Ethiopia, Eritrea, Rwanda and Burundi) using39 microsatellites markers. The studied loci were polymorphic and revealed a total of 941 alleles in 1108 sorghum genotypes. High levels of diversity were revealed with Sudan (68.5) having the highest level of genetic diversity followed by Ethiopia (65.3), whereas Burundi (0.45) and Rwanda (0.33) had the lowest level of genetic diversity. Analysis of molecular variance indicated, all variance components to be highly significant (p<0.001). The bulk of the variation was partitioned within countries (68.1%) compared to among countries (31.9%). Genetic differentiation between countries based on FST values was high and highly significant (FST=0.32). Neighbour-joining (NJ) analysis formed two distinct clusters according to geographic regions, namely the central region (Kenya, Burundi, Uganda and Rwanda) and the eastern region (Sudan, Ethiopia, and Eritrea). Population structure analysis revealed six distinct populations corresponding to NJ analysis and geographical origin of accessions. Countries clustered independently with small integration, which indicated the role of farmers’ practices in the maintenance of landrace identity and genetic diversity. The observed high level of genetic diversity indicated that germplasm from East Africa should be preserved from genetic erosion, especially in countries with the highest diversity.

Sorghum is an important food and feed source in mixed crop-livestock production systems where its dual usage is a preferred option, especially among the resource poor small-scale farmers. Attempts to improve fodder quality traits in maize have been at the expense of grain traits and vice versa, but other studies demonstrated that it was possible to select for high stem biomass without compromising the improvement of grain yields in sorghum. As a follow up to this effort, this study was undertaken to estimate the combining ability of grain and forage sorghum genotypes and determine heterosis for several traits as a criteria for improving dual purpose sorghum cultivars. Four grain and four forage sorghum cultivars were crossed to generate 23 crosses following the half diallel mating design scheme at Makerere University Agricultural Research institute Kabanyolo (MUARIK) in 2013. The crosses were evaluated at three locations in Uganda during two rainy seasons of 2014. Data were taken and analysed on leaf area, leaf-stem ratio, plant height, seed weight, grain yield, and biomass. Results indicated that the gene action for the traits under observation was controlled by both additive and non additive genetic effects. Majority of the parental lines had significant GCA estimates for all traits except line 20 for grain yield, lines 22 and 34 for plant height, line 35 for leaf-stem ratio, and line 22 for days to flowering. Significant (P ≤ 0.05) SCA estimates were prominent in most of the individual parental combinations for all traits except leaf area and leaf-stem ratio indicating the role of dominance gene action. Bakers ratio and heritability coefficients were > 52% for biomass, flowering duration and plant height indicating that genetic gains can be achieved by conventional breeding for the three traits. Heterosis in grain yield and biomass over both the mid and better parents was shown by more than half of the crosses studied. This study suggested that both inter and intra allelic interactions were involved in the expression of the traits.

The problem to develop new early maturing grain sorghum varieties adapted to mechanized harvesting with high productivity and feed advantages, is of great urgency. The purpose of the current work was to study the inheritance of the main economically valuable traits in the first generation hybrids developed in the hybridization between samples of different ecological and geographical origin. In the first generation hybrids Zernogradskoe 88 × Seso 1 and Zernogradskoe 88 × Narosorg 1, there was identified the improvement of 1000-grain weight, number of grains per panicle, and length of a peduncle in comparison with the initial parental forms. In the hybrid combination obtained as a result of hybridization of the varieties Zernogradskoe 88 and Seso 3 there was not identified any positive manifestation of heterosis for the breeding process in the main studied traits. According to the trait ‘plant height’ in all combinations, there was identified overdominance of high-growing forms. According to the protein percentage in grains there was established depression or dominance of lower values of the trait. The inheritance of the trait ‘length of vegetation period’ in the studied hybrids corresponded to the partial dominance of both lower and higher values of the trait.

Abstract. Kumi F, Badji A, Mwila N, Odong T, Ochwo-Ssemakula M, Tusiime G, Gibson P, Biruma M, Prom KL, Cuevas HE, Agbahoungba S, Rubaihayo P. 2019. New sources of sorghum resistant genotypes to downy mildew disease in Uganda. Biodiversitas 20: 3391-3397. Sorghum downy mildew (SDM) disease is still prevalent in Uganda at varying levels of incidence and severity. In this study, a total of 100 sorghum genotypes, five (5) from (U.SA, India, and Sudan) and 95 genotypes from Uganda were evaluated for resistance to downy mildew and other agronomic traits during the second growing season of 2016 (August-December). The experiment was conducted in two locations at Makerere University Agricultural Research Institute at Kabanyolo (MUARIK) and Abi-Zonal Agricultural Research and Development Institute (Abi-ZARDI) research station at Arua. The experimental design used was 10 x 10 alpha lattice design with three replicates. Data were collected on plant disease incidence (PDI), plant disease severity (PDS), area under disease progress curve (AUDPC), days to 50% flowering, plant height, 1000 seed weight, and grain yield. Results for analysis of variance showed highly significant differences (P < 0.001) in genotypes, location, and AUDPC, yield and yield components. Disease incidence varied significantly (P < 0.001) between locations, and Arua recorded highest disease incidence and severity of 80.6 and 2.8, respectively. Results from correlation analysis showed a highly significant (P < 0.001) positive association of downy mildew disease incidence with AUDPC (0.835) which suggests that the severity of SDM disease increased with disease incidence, whiles significant (P < 0.001) negative correlation was recorded for days to 50 % flowering (-0.302), 1000 seed weight (-0.471), and grain yield (-0.585), suggesting that grain yield and yield component decreased significantly with increase in SDM incidence and severity. Two resistant (PI 656061 and PI 533831) and four moderately resistant (E 40, MAKSO 8, PI 655990 and Epuripur) genotypes were identified from this study. These genotypes were recommended for sorghum breeding program against downy mildew disease.

Sorghum (Sorghum bicolor) is the third most important cereal food crop in Uganda. However, the parasitic weed Striga hermonthica severely constraints its production. The use of Striga resistant sorghum varieties may be one of the most feasible ways of managing the Striga problem. A series of studies were carried out with the overall objective to develop new sorghum genotypes that are resistant to Striga and high yielding in Eastern Uganda. Initially, a participatory rural appraisal (PRA) was carried out with the main objectives to study the current constraints faced by farmers in sorghum production and determine their preferences for new sorghum varieties. Secondly, fifty different African sorghum accessions were evaluated to determine phenotypic and genotypic variability for Striga resistance and identify suitable parents to be used in breeding for new Striga resistant and high yielding sorghum genotypes. Thirdly, a genetics study was conducted to determine gene action responsible for Striga resistance and sorghum yield in new sorghum genotypes. Finally, laboratory studies were carried out to identify specific mechanisms of Striga resistance available in new sorghum genotypes and their parents. During the PRA, Striga was identified as the main constraint limiting sorghum production in Eastern Uganda, followed by insect pests. Farmers indicated preference for red gain sorghum with erect and compact heads, a plant height of 1.5m and a maturity period of around three months, as well as Striga resistance and drought tolerance. From farmers’ own assessments, the individual field surveys and soil seed bank analyses that were carried out, the degree of Striga infestation in farmers’ fields was found to be high. Both phenotypic and genotypic factors contributed significantly to the variability observed among the African sorghum accessions with respect to Striga resistance and sorghum crop performance indicating that Striga resistance can be improved through selection. However, techniques that minimise environmental effects need to be employed in order to improve on heritability. The values for genetic coefficient of variation (GCV) and genetic advance (GA) indicated that genetic gain for Striga resistance could be achieved by selection based on area under Striga severity progress curve (AUSVPC), area under Striga number progress curve (AUSNPC) and individual Striga emergence counts. The sorghum accessions SRN39, Brhan, Framida, Gubiye, Wahi, P9407 and N13 were found to be resistant to Striga hermonthica. These accessions consistently showed low AUSNPC, AUSVPC, and individual Striga emergence, Striga vigour and severity indices. These accessions could be used as sources of Striga resistance genes when breeding for Striga resistance in sorghum. In the study to determine gene action responsible for Striga resistance and sorghum yield, significant genetic variation for Striga resistance and sorghum yield parameters was observed among the new sorghum genotypes and their parents. The sorghum parental lines: Brhan, SRN39, Hakika and Sekedo consistently had negative GCA effects for AUSNPC and AUSVPC, while SRN39 and Hakika additionally had negative GCA effects for Striga vigour, indicating that they were effective in transferring Striga resistance into their progeny. The new genotypes: SRS1608, SRS3408, SRS2408, SRS4609, SRS3108, SRS2908, SRS2609, SRS609 and SRS1708 had negative SCA effects for AUSNPC, AUSVPC and Striga vigour meaning that they were resistant to Striga. Sorghum parental lines: Sekedo, Brhan, Framida and Hakika had positive GCA effects for head length, meaning that they increased head length in their crosses. The genotypes: SRS3408, SRS5309, SRS1608 and SRS2908 derived from the above parents had the longest heads compared to other progenies, which were on average, 20% longer than their parents. The genotypes: SRS609, SRS1408, SRS2608 and SRS3408 were the highest grain yielders and yielded 11-51% better than the highest yielding parent (Sekedo) under the non Striga environment. The parental lines; Sekedo, Brhan and Framida had positive GCA effects for grain yield indicating that they could act as sources of genes for grain yield increase. The genotypes; SRS609, SRS4609 and SRS2908 had large positive SCA effects for grain yield. The relative contributions of GCA effects to the observed genotypic variances were 80.5%, 43.3%, 65%, 92.6% and 53.2% for AUSNPC, AUSVPC, Striga vigour, sorghum head length and plant height respectively. This shows that additive gene action was important in controlling Striga resistance, sorghum head length and plant height in the present sorghum populations. Laboratory studies aimed at investigating the specific mechanisms of Striga resistance available in new sorghum genotypes found that two new sorghum genotypes, SRS1608 and SRS1208 expressed both the low germination stimulant character and low haustoria initiation as mechanisms of resistance to S. hermonthica. The sorghum genotypes, SRS2808 and SRS1108, and two fixed lines, Brhan and Hakika expressed only the low germination stimulant character, while the genotypes, SRS608, SRS3408, SRS4109 and SRS2308 expressed only the low haustoria initiation mechanism. The inheritance patterns of the low germination stimulant character in the present sorghum genotypes varied. In some genotypes, it appeared to be controlled by a single gene while in others; it appeared to be controlled by more than one gene.
Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.