Molecular epidemiology of cassava mosaic disease in Madagascar

Abstract

Cassava is the staple food for hundreds of millions of people in Africa but its cultivation is seriously constrained by cassava mosaic disease (CMD) in Madagascar, and in Africa in general. This study identified the cassava mosaic geminiviruses (CMGs) involved in CMD in Madagascar and their associated epidemiological characteristics from countrywide surveys. Molecular characterization of CMGs in Madagascar revealed an unprecedented diversity and co-occurrence of six viruses: African cassava mosaic virus (ACMV), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Kenya virus (EACMKV), East African cassava mosaic virus (EACMV), South African cassava mosaic virus (SACMV) and the recently described Cassava mosaic Madagascar virus (CMMGV). Distinct geographical distributions were observed for the six viruses. While ACMV was more prevalent in the central highlands, EACMV and EACMKV were prevalent in lowlands and coastal regions. Both EACMCV and SACMV occurred in almost all the localities visited. PCR diagnosis revealed that mixed infection (up to four co-infected viruses) occurred in 21% of the samples and were associated with higher symptom severity scores. Pairwise comparisons of virus associations showed that EACMCV was found in mixed infections more often than expected while ACMV and SACMV were mostly found in single infections. A greater abundance of whiteflies was observed in lowland and coastal areas. Nevertheless, infected cuttings remain the primary source of CMD propagation (95%) in Madagascar. (Résumé d'auteur

South West and North Central Nigeria: Assessment of cassava mosaic disease and field status of African cassava mosaic virus and East African cassava mosaic virus

“…The low occurrence of EACMV in Nigeria is probably because EACMV has not been present in Nigeria as long as ACMV (Ogbe et al, 2006 Besides the presence of single ACMV and EACMV infection, ACMV occurred in mixed infections with EACMV. This is similar to previous studies conducted across West Africa (Ariyo et al, 2005;Fondong et al, 2000;Ogbe, Thottappilly, Dixon, Atiri, & Mignouna, 2003;Pita et al, 2001) and East Africa (Chikoti et al, 2013;Harimalala et al, 2015;Were et al, 2016). The percentage of mixed infection recorded in this study (< 7%) was lower than the percentage found in previous country-wide survey conducted in Nigeria in 1997-1998 (9.3%) and 2006 (24.1%) (Ogbe et al, 2006).…”

“…Several strains of CMBs have been identified to cause CMD in Africa namely African cassava mosaic virus (ACMV) South African cassava mosaic virus (SACMV), East African cassava mosaic virus (EACMV), East African cassava mosaic Cameroon virus (EACMCV), East African cassava mosaic Zanzibar virus (EACMZV), East African cassava mosaic Malawi virus (EACMMV), and East African cassava mosaic Kenya virus (EACMKV). Recently, two species have also been described: African cassava mosaic Burkina Faso virus (ACMBFV) and Cassava mosaic Madagascar virus (Harimalala et al, 2015;Tiendrébéogo et al, 2012).…”

First report of cassava mosaic geminiviruses and the Uganda strain of East African cassava mosaic virus (EACMV‐UG) associated with cassava mosaic disease in Equatorial Guinea

“…In December 2013, 30 leaves from local cultivars of cassava exhibiting moderate to very severe CMD symptoms were collected at nine different locations in Equatorial Guinea (Table 1). Sixteen leaf samples tested positive by PCR for the presence of CMGs using degenerate and specific primers (Harimalala et al , 2015). Each detection of the virus was confirmed by direct sequencing of the amplification products.…”

“…Sixteen leaf samples tested positive by PCR for the presence of CMGs using degenerate and specific primers (Harimalala et al, 2015). Each detection of the virus was confirmed by direct sequencing of the amplification products.…”

Identification and analysis of cassava genotype TME3 bacteria artificial chromosome libraries for characterization of the cassava mosaic disease

“…In subSaharan Africa, cassava production is constrained by two viral diseases namely Cassava mosaic disease (CMD) caused by multiple species of single stranded DNA viruses in the family geminiviridae, and Cassava brown streak disease (CBSD) caused by two species of RNA viruses in the family Potyviridae (Legg et al, 2011(Legg et al, , 2015. CMD is endemic to all cassava production regions of subSaharan Africa (Harimalala et al, 2015;Legg et al, 2015;Patil and Fauquet, 2009). As a result, classical breeding programs have focused significant attention on mitigating the negative effects caused by CMD.…”