Genetic Diversity Of Cassava Mosaic Gemniviruses (Cmgs) In The Volta Region Of Ghana And Resistance Screening Of Improved Cassava Vareties To Cassava Mosaic Disease (Cmd)

Abstract

Cassava Mosaic Disease is one of the major virus diseases limiting cassava production in Ghana and Africa. The disease accounts for low yields of cassava with over forty (40) improved cassava varieties (ICVs) bred and released to improve cassava production in Ghana. Household surveys in six cassavagrowing districts in the Volta Region indicates that all 180 respondents had experienced CMD on their farms but did not know the cause and majority (74.4%) do not control the disease. A field survey in the six districts showed CMD was prevalent and severe with high incidence of coinfections with ACMV and EACMV after serological analysis. PCR detected ACMV (78.9%), EACMV (1.1 %) and co-infection (20%) in all the districts but not in all the farms surveyed. Next generation sequencing of field samples using lllumina MiSeq sequencing platform led to the assembly of twelve full length CMGs genomes (6 ACMV DNA-A components, 3 ACMV DNA-B components and 3 DNA-A EACMV components) which aligned closely to already published isolates identified in West Africa. TAS ELISA screening of21 ICVs evaluated in 2018/2019 detected ACMV in all varieties but not 'Hemaa' and' AGRA' from the coastal savannah. EACMV was detected in varieties' Ampong, TEK, Sika, Lamesese, Abasafita, Amansan, and Esam'from the Coastal savannah and varieties 'Ampong, Lamesese, Botan, Sika, AGRA, IFAD, and Capevars' from the Forest zone. Graft challenge of rcvs in the screen house using CMDinfected rootstocks showed that all the rcvs are resistant to EACMV except Amansan, Abrabopa and AGRA. Generally, all the rcvs are showed mild to moderate infection to CMD following screening using T AS-ELISA, PCR and graft challenge with infected rootstocks in two years.