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.

Regenerating sweet potato from field-derived plant material requires careful management of several critical factors, including the effectiveness of the disinfectant, the age of the explant, and the genotype used. In this context, establishing a reliable aseptic protocol is essential for successful in vitro culture. This study aimed to assess the effects of two disinfectants (sodium hypochlorite and mercuric chloride), three sweet potato genotypes (Nakabo, Boyapleu, and Irene), and three explant ages (2, 3, and 4 weeks) on clean culture establishment and regeneration efficiency from nodal explants. The findings revealed that regeneration success is significantly influenced by the type and concentration of disinfectant, explant age, and genotype. Treatment with 10% sodium hypochlorite markedly reduced contamination, achieving clean culture and regeneration rates of 75.72 ± 3.36% and 86.83 ± 3.02%, respectively, regardless of explant age. In contrast, higher concentrations of mercuric chloride induced necrosis in the explants. The highest clean culture rate (93.82 ± 1.16%) was observed in 3-week-old explants, which also showed a regeneration rate of 54.93 ± 3.19%. Furthermore, the Boyapleu and Irene genotypes demonstrated good suitability for in vitro culture, whereas the Nakabo genotype performed poorly under the tested conditions.

In vitro micropropagation is a rapid method of multiplying healthy planting material to control Cassava mosaic disease (CMD), one of a major constraint to cassava production in Africa. However, some cassava varieties have a low propagation ratio under in vitro conditions. The main objective of this study was to improve the in vitro propagation rate of five difficult to grow, farmer-preferred cassava varieties using plant growth regulators. Microcuttings from in vitro plantlets of five recalcitrant cassava varieties (Agbablé 3, Ampong, Bayérè, Bocou 5, Olékanga) were evaluated for their capacity to rapidly regenerate plantlets. Time to root or leaf formation, number of nodes, number of roots, and the in vitro plantlet length were evaluated on nine culture media combinations. We found that among all the cassava varieties studied, the shortest times for leaf (4 to 7 days) or root (9 to 14 days) formation were recorded when the two types of MS media were supplemented with kinetin and thidiazuron as well as on the medium contain half-strength MS without these plant growth regulators. These two hormones evaluated were better for regeneration of leaves, nodes and elongation of in vitro plantlets with optimum concentration of 5 and 10 nM or thidiazuron, and 0.12 or 0.24 µM for KIN. A survival rate between 85-91% was recorded under tunnel conditions and the plantlets appeared to be morphologically normal. The information obtained during this study will be useful for mass multiplication programs of elite cassava varieties.

Cassava Mosaic Disease (CMD) is a major constraint to cassava production in Côte d’Ivoire, causing significant yield and income losses for smallholder farmers. Despite its high prevalence, farmers’ knowledge and understanding of the disease remain limited. To address this issue, the Central and West African Virus Epidemiology (WAVE) Regional Center of Excellence provided capacity building for farmers in the major cassava growing regions. This study assesses the impact of the WAVE’s trainings and awareness campaigns on farmers’ knowledge of the disease and the management methods they adopted. Mixed socio-agronomic data were collected from 290 farmers, and CMD epidemiological parameters were assessed in 82 farms. Data were analysed using propensity score matching (PSM), followed by a Tobit regression model to assess the determinants and intensity of adoption of CMD management practices, using Stata. The results showed that trained farmers had a better understanding of CMD compared to untrained farmers. On average, trained farmers adopted 2.36 disease management practices (DMPs) compared to 1.55 DMPs for untrained farmers. Participation in WAVE’s training sessions and a sound knowledge of CMD positively influenced both the adoption and intensity of adoption of DMPs. However, there was no significant difference in CMD incidence between beneficiary areas (54.55%) and non-beneficiary areas (54.95%), likely due to the unavailability of disease-free planting material, inadequate agricultural practices, and high populations of whiteflies (Bemisia tabaci). This study shows the importance of awareness campaigns in the sustainable management of crop diseases in general and CMD in particular and suggests the need to train farmers on disease management and provide them with healthy planting materials.

Cassava mosaic disease (CMD) is caused by begomoviruses and can result in yield losses of up to 90% in susceptible varieties. Using disease-free planting material from in vitro cultures is one of the most effective ways of controlling this disease. A CMD epidemiological assessment was conducted in fields established with disease-free plantlets in Bouaké, Dabou, and Man, selected for their contrasting agroecological and CMD prevalence conditions. Virus and whitefly species characterisation was performed using PCR and sequencing. CMD incidence and severity were lowest at the Man site and highest at the Dabou site. Although whitefly abundance was relatively low at the Man and Bouaké sites compared to the Dabou site, they were a significant factor in the spread of the disease. While all resistant varieties remained asymptomatic, susceptible and tolerant varieties became infected, and some tolerant varieties were able to recover from the disease. Molecular analyses revealed the presence of two viral species: Begomovirus manihotis (ACMV) and Begomovirus manihotiscameroonense (EACMCMV). No viral infection was detected 4 weeks after planting (WAP). Cases of single infection and double infection were observed at 12 and 20 WAP. Also, no double infections were found at the Man site, in contrast to the Bouaké site (12 WAP: 2.36%) and Dabou site (12 WAP: 2.59%; 20 WAP: 5.76%). EACMCMV was found in a single infection in Bouaké (12 WAP: 1.39%) and Man (20 WAP: 0.66%). The whitefly species Bemisia tabaci and Bemisia afer were most commonly found feeding on all cassava varieties. A high diversity of whitefly species was observed in Bouaké and Dabou compared to Man. Furthermore, the Bemisia tabaci species identified in this study was found to be able to transmit ACMV and EACMCMV viruses. These highlights would contribute to improving CMD management and control strategies.

Sugarcane streak mosaic disease (SCSMD) can reduce sugarcane yields by up to 70%. Since the first confirmation of SCSMD in 2018 in Sucrerie d’Afrique de Côte d’Ivoire (SUCAF-CI) plantations in Ferkessédougou, the epidemiology of the disease has never been studied. Therefore, the aim of this work was to evaluate various SCSMD parameters within the SUCAF-CI sugarcane germplasm, which comprises sugarcane varieties from diverse geographic origins. To that end, an epidemiological and molecular assessment was conducted on 548 varieties of SUCAF-CI sugarcane germplasm, preserved at two sites (Ferké 1 and Ferké 2) to evaluate SCSMD incidence and severity, determine the diversity of SCSMV strains infecting sugarcane at SUCAF-CI, identify sugarcane varieties that are potentially resistant to sugarcane streak mosaic virus (SCSMV), and investigate the presence of alternative hosts in SUCAF-CI plantations. The results reveal a very high incidence of the disease three months after planting (91.27 ± 23.28% in Ferké 1; 90.73 ± 22.80% in Ferké 2), followed by a significant increase at eight months (97.32 ± 11.79% and 96.45 ± 15.55%, respectively). The mean severity of the disease was low at both sites, with an average of 1.31 ± 0.02 at Ferké 1 and 1.05 ± 0.02 at Ferké 2. The varieties M292/70 and M700/86, which proved to be potentially resistant in the germplasm, showed symptoms in the industrial plots. Molecular analyses confirmed the presence of SCSMV in the germplasm studied, with a high overall prevalence of 71.32%. The infection rate was lower at Ferké 1 (55.8%) than at Ferké 2 (85.8%). Phylogenetic analysis of the SCSMV sequences obtained in this study showed that they are closely related to sequences from Côte d’Ivoire, India, Iran and Pakistan. No alternative hosts for SCSMV were identified. These findings highlight the critical importance of rigorously monitoring the importation of plant material and establishing a global management strategy that prioritizes the production of certified pathogen-free sugarcane plants.