Abstract
Problem statement: This study was carried out to demonstrate that the severity of Cassava Mosaic Disease (CMD) in Togo, is not only influenced by synergism between cassava Begomoviruses in presence, but essentially by recombination between the different Begomoviruses infecting cassava. Approach: Foliar samples presenting typical biological features of Begomoviruses infection were collected from cassava and wild infected plants from different regions of Togo and analysed by PCR targeting the Coat Protein (CP). The PCR products obtained from different isolates of two major Begomoviruses species infecting cassava in Togo were then sequenced and compared with the sequenced of the African cassava mosaic Begomoviruses identified to date and available in NCBI GenBank database by phylogenetic analysis. Results: The results indicate that not only the two major Begomoviruses could be in synergistic interaction in infected cassava in Togo as it has been shown between African Cassava Mosaic Virus (ACMV) and East African Cassava Mosaic Virus (EACMV) elsewhere, but could also create recombinants which would be highly interfering in the development of symptom severity in the country. Conclusion/Recommendations: The study confirmed the assumption that the symptom severity in cassava fields in Togo is rather caused by recombination between different Begomoviruses in presence than by synergistic interaction. More investigations should be done to give insight to this founding.
Highlights
Cassava (Manihot esculenta Crantz) is a staple crop grown throughout Africa and it is the most important source of dietary carbohydrate in subSaharan Africa[1,2]
Cassava mosaic Begomoviruses disease and symptoms severity in the fields: Symptom severity caused by cassava mosaic Begomovirus disease in the different investigated regions is various and complex through the expression of the infections (Fig. 1)
Six hundred ninety seven collected foliar samples were analyzed by Polymerase Chain Reaction (PCR) with degenerate primers specific to African Cassava Mosaic Virus (ACMV), East African Cassava Mosaic Virus (EACMV) and ICMV
Summary
Cassava (Manihot esculenta Crantz) is a staple crop grown throughout Africa and it is the most important source of dietary carbohydrate in subSaharan Africa[1,2]. The crop is able to produce acceptable yields even on very marginal soils and in drought conditions, but is susceptible to a number of pathogens and losses to cassava production occur in all areas due to Cassava Mosaic Disease (CMD), caused by various Begomoviruses (family Geminiviridae) transmitted whiteflies[3,4,5,6]. It was shown in Cameroon that EACMV-CM was a double recombinant capable of synergism with ACMV[8]. The association of these Begomoviruses recombinants with the severe cassava mosaic disease epidemic was obvious no explanations for the advantage of the heterogonous combination at the level of their CP genes, over the pre existing homologous association, could be provided. The aim of this study is to describe the complexity of symptom severity in different cassava production regions of Togo caused by cassava mosaic Begomovirus disease by presenting some biological features of their infection which could be created by intermolecular recombination events
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