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.
