Begomoviruses are a major threat to cassava production in Africa. Indeed, during the 1990s, the emergence of a recombinant begomovirus (East African cassava mosaic virus-Uganda, EACMV-Ug) resulted in crop devastation and severe famine in Uganda. In 2023, during a pre-survey of cassava farms at Forécariah, South-West Guinea, 22 samples showing peculiar cassava mosaic disease (CMD) symptoms were collected, and subsequent laboratory analysis confirmed the presence of EACMV-Ug in the samples. Deep analysis of DNA-A and DNA-B of the EACMV-Ug isolates from Guinea indicated that they are similar to those associated with the severe CMD epidemic in Uganda in the 1990s. Therefore, a country-wide survey was conducted throughout Guinea in April 2024 to evaluate the extent of the spread of EACMV-Ug in the country and to collect critical CMD epidemiological data. Findings showed a high whitefly population in Lower Guinea averaging 17 per plant; however, the data suggest a spread of EACMV-Ug via infected cuttings. High CMD incidence was found in Lower Guinea and Forest Guinea, whereas the highest CMD severity was observed in Forest Guinea (2.70 ± 0.06) and the lowest CMD severity was found in Middle Guinea (2.20 ± 0.05). Several cases of double and triple infections involving African cassava mosaic virus, East African cassava mosaic virus, East African cassava mosaic Cameroon virus, and EACMV-Ug were observed. EACMV-Ug was detected throughout Guinea, as well as from samples collected in 2022 in Kambia (Sierra Leone). The 63 accessions cultivated in Guinea that were assessed in this study were found susceptible to at least one of the viruses cited above. This study alerts us to an alarming situation in development in West Africa and provides scientific evidence to guide the rapid response needed to contain and stop the progression of EACMV-Ug in West Africa.

A study was conducted in Sierra Leone to identify cassava plants that are asymptomatic and symptomatic to cassava mosaic disease (CMD) and collect planting materials for field trial establishment; determine the prevalence of CMD caused by African cassava mosaic virus (ACMV) and East African cassava mosaic virus (EACMV) using the Nuru App and virus indexing techniques; and assess selected agronomic traits in cassava. A total of 80 cassava farms spanning four provinces (Southern, Eastern, Northern, and North-West) were surveyed in April 2022. Findings showed that the cassava variants of the experiment and locations significantly (p < 0.001) affected CMD incidence, severity, growth, and fresh storage root yield traits. The CMD incidence (87.0%) and whitefly abundance (144.8) were highest, and the CMD severity was moderate (4.0) for the plants derived from cuttings obtained from symptomatic Cocoa mother plants, while plants derived from cuttings of improved mother plants exhibited no visible symptoms of the disease and the lowest population (45.1) of whiteflies. The Nuru app is inefficient for phenotypically detecting CMD at 3 months after planting (MAP), while at 6, 9 and 12 MAP, the app efficiently detected the disease using a molecular analysis technique. Resistant, non-diseased plants derived from cuttings obtained from SLICASS 4 mother plants produced the highest fresh storage root yield (54.9 t ha⁻¹). The highest storage root yield loss was recorded in the plants obtained from cuttings of symptomatic variety Cocoa mother plants harvested at Matotoka grassland ecology, Bombali District (90.2%), while those harvested from cuttings of asymptomatic variety Cocoa mother plants grown at the four test environments had a similar storage root yield loss ranging from 40.3 to 46.2%. Findings suggest the importance of genetic variability, environmental adaptation, utilization of diseased-free materials, and phytosanitation as disease management strategies for increased production. These findings provide important insights into the distribution, impact, and spread of CMD and whitefly abundance in the studied areas in Sierra Leone that could be exploited for cassava production, productivity, conservation, and population improvement.

The dearth of information on the extent of genetic variability in cassava limits the genetic improvement of cassava in Sierra Leone. This study aimed at assessing the genetic variability and relationships within 103 cassava genotypes using agro-morphological and culinary markers. A field trial was conducted in the School of Agriculture and Food Sciences research site. The experiment was laid out in an augmented randomized block design. Morphological classification based on qualitative and quantitative traits categorized the germplasm into three different groups. A total of ten principal components (PCs) in the qualitative and six PCs in the quantitative trait sets accounted for 66.74% and 67.27% of the total genetic variation, respectively. Traits with significantly strong and positive correlations included presence of fruit (PFRT) and presence of seeds (PSE) (r = 0.86 ***), root yield per plant (RYPP) and number of storage roots (NSR) (r = 0.76 ***), RYPP and number of commercial roots (NCR) (r = 0.68 ***), length of leaf lobes (LLL) and width of leaf lobes (WLL) (r = 0.66 ***), and between NSR and NCR (r = 0.84 ***). The cooking time, cooking percentage, texture, mealiness, taste, and aroma varied widely among the accessions. The findings established that the cassava germplasm possesses useful genetic variability that could be exploited through selection for short-term release programs, genetic conservation of the valuable germplasm, and genetic improvement of the crop.

A dearth of knowledge exists on identifying the begomoviruses and distributing cassava mosaic viruses across key cassava-growing regions of Sierra Leone. The study aimed to identify and map the distribution of cassava mosaic disease (CMD)-associated viruses in farmers’ fields in Sierra Leone. Cassava (Manihot esculenta Crantz) leaf samples were collected in 109 smallholder farms during a geo-referenced survey conducted from 10th May to 5th June 2024. Molecular diagnostics were carried out to identify the viral strains associated with CMD. Findings revealed that infection by stem cutting was more predominant in the south, east, north, and northwest regions than in the west region. In contrast, infection by whitefly was predominant in the west, north, and northwest regions. PCR screening of 426 samples coupled with sequence analysis revealed the presence of African cassava mosaic-like (ACMV-like) viruses, and East African cassava mosaic-like (EACMV-like) viruses as single infections at 78.1% and 1.3%, respectively. Co-infections of ACMV-like and EACMV-like viruses were detected in 20.6% of the tested samples. In addition, 70.6% of the samples positive for EACMV-like virus (single and mixed infections) were found to be positive for East African cassava mosaic Cameroon virus (EACMCMV). The ACMV and co-infection of ACMV and EACMV viruses were present in all regions, while EACMCV was detected in all regions except the western area. The results indicate more prevalence of the EACMCMV variant in Sierra Leone. This study suggests utilization of participatory surveillance and good agronomic practices to manage CMD in Sierra Leone.

Cassava ( Manihot esculenta Crantz ) is a vital staple crop in sub-Saharan Africa, underpinning food security, rural livelihoods, and agro-industrial development. Despite its resilience to marginal soils and drought, cassava productivity is severely constrained by viral and bacterial diseases, notably cassava mosaic disease (CMD), cassava brown streak disease (CBSD), and cassava bacterial light (CBB). Conventional breeding approaches for disease resistance remain limited by long phenotyping cycles, genotype-by-environment interactions, and inadequate spatial integration. This review highlights the emerging role of geospatial genomics, an interdisciplinary framework that integrates Geographic Information Systems (GIS), remote sensing, and genomic tools to accelerate cassava improvement. GIS enables spatial mapping of disease incidence and environmental gradients, while remote sensing technologies such as satellite indices and drone-based hyperspectral imaging provide real-time crop health monitoring. Advances in genomics, including SNP genotyping, genotyping-by-sequencing, and marker-assisted selection, facilitate the identification of resistance loci and predictive breeding. Integrating spatial datasets with genomic information through environmental association analyses enhances understanding of genotype-environment interactions and supports climate-resilient breeding strategies. Applications of geospatial genomics in cassava include disease surveillance, predictive modeling of outbreaks, targeted germplasm deployment, and improved selection efficiency across diverse agro-ecological zones. Through linking environmental variability, disease dynamics, and genetic diversity, geospatial genomics offers a comprehensive pathway to develop disease-resistant cassava varieties, thereby strengthening food security and sustainable agriculture in Africa.

Dearth of information on extent of genetic variability in cassava limits the genetic improvement of cassava in Sierra Leone. This study aimed at assessing the genetic variability and relationships within 103 cassava genotypes using agro-morphological and culinary markers. A field trial was conducted in the School of Agriculture and Food Sciences research site. The experiment was laid in an augmented randomized block design. Morphological classification based on qualitative and quantitative traits categorized the germplasm into three different groups. A total of ten principal components (PCs) in the qualitative and six PCs in the quantitative trait sets accounted for 66.74% and 67.27% of the total genetic variation, respectively. Traits with significantly strong and positive correlations included presence of fruit (PFRT) and presence of seed (PSE)(r = 0.86***),root yield per plant (RYPP) and number of storage root (NSR) (r = 0.76***), RYPP and number of commercial root (NCR) (r = 0.68***), length of leaf lobe (LLL) and width of leaf lobe (WLL) (r = 0.66***),and between NSR and NCR (0.84***). Cooking time, cooking percentage, texture, mealiness, taste and aroma varied widely among the accessions. Findings established that the cassava germplasm possess useful genetic variability that could be exploited through selection for short term release programme, genetic conservation of valuable germplasm and genetic improvement of the crop.