Evaluation of Cassava Cultivars for Resistance to Cassava Mosaic Disease and Yield Potential in Central African Republic

Abstract

Eleven cassava genotypes were tested against cassava mosaic disease (CMD) and compared to a local susceptible cultivar in field conditions from June 2011 to July 2012 in Central African Republic (CAR) at two sites representative of the savanna (Damara) and forest (Pissa) zones of the country. The mean number of whiteflies observed on plants varied among genotypes within each site, but was found nearly three times higher at Damara than at Pissa, resulting in a CMD incidence nearly five times higher at Damara than at Pissa. However, no relation was observed between the number of insect on the plants and the level of susceptibility/resistance of the genotypes. The difference of disease pressure between the two sites revealed high level of resistance in several genotypes, while some other ones indicated rather only a partial resistance. Nevertheless, none of the genotypes tested was found immune, in the end, the virus being detected at least in one site in every genotype, including those ones presenting no symptoms in both sites. The impact of CMD on yield components was assessed on the local susceptible check and three partially resistant genotypes, showing that the disease has no significant effect on the tuberous roots number as well as their weight in both sites. The yield potential varied among different genotypes and between the two sites, the mean number of tuberous roots as well as their mean weight being higher in Damara than in Pissa. This study identified highly resistant genotypes such as ‘Gabon’ that performed well in both sites, and ‘91/02322’ that was symptomless and presented a yield potential equivalent to the local check. These genotypes could be distributed to growers with the main advantage to be resistant to CMD and, therefore, reducing the risk to spread sources of inoculum all over the cassava cropping areas in the country.

Evaluation of Ten Cassava Varieties for Resistance to Cassava Mosaic Disease in Burkina Faso

“…No relationship was found between whiteflies abundance and severity of the CMD symptoms, nor between whitefly abundance and incidence of the disease. This result agrees with some previous studies [1], [50] where no clear association between whitefly abundance and CMD symptom severity was observed.…”

“…The pressure of whiteflies populations was different in the three experimental locations. This agrees with results of Zinga et al (2016) [1], who found that populations of whiteflies mainly change with environmental conditions. No relationship was found between whiteflies abundance and severity of the CMD symptoms, nor between whitefly abundance and incidence of the disease.…”

“…Cassava (Manihot esculenta Crantz, Family: Euphorbiaceae) is an important food crop in most of the tropical regions of Africa, Asia and Latin America [1]. It is native from the Northern Amazonian basin [2], [3] and was probably introduced into West Africa (Gulf of Guinea) in the 16th century by Portuguese [4].…”

Optimisation de l’acclimatation de vitroplants d’une accession de manioc (Manihot esculenta Crantz) de la République Centrafricaine par la méthode de culture ex vitro

“…La culture du manioc comme pour toutes les plantes cultivées présentent des rendements très variables selon que les conditions du sol et du climat lui sont favorables ou défavorables (Tandzi et al, 2020). L'effet des fumiers et des termitières sur la croissance et le rendement du manioc et l'effet des régulateurs de croissance sur la culture in vitro du manioc étaient étudiés et documentés, ces facteurs sont importants pour la qualité de la culture Ballot et al, 2016 b). La culture du manioc dans le champ se fait plus par bouturage à partir d'un échantillon mur.…”

“…Cette technique nécessite plusieurs étapes qui peuvent être résumées en la phase d'initiation de culture in vitro et d'acclimatation sous serre avant le transfert en champ. Plusieurs cultivars de la RCA ont fait l'objet de culture in vitro permettant d'évaluer les conditions opératoires et les performances agronomiques en analysant le taux de survie, la taille, les racines et le nombre de feuilles (Zinga et al, 2016). Cependant, l'acclimatation des vitroplants à la sortie du laboratoire reste une étape difficile à maitriser et qui varie en fonction de la spécificité de chaque accession.…”