Developing Cassava Mosaic Disease resistant cassava varieties in Ghana using a marker assisted selection approach

Cassava is a major staple and food security
crop in Africa which can produce a crop under
uncertain rainfall and low fertility conditions. How-
ever, it suffers from several pests and diseases, with
Cassava Mosaic Disease (CMD) being the main biotic
constraint in production in sub-Saharan Africa. It is
caused by cassava mosaic geminiviruses. Plants
infected with CMD usually produce a few or no
storage roots. Markers associated with resistance
genes to CMD have been mapped, including a major
dominant gene,
CMD2
. Eight CMD resistant geno-
types from CIAT were used in crosses with three
cassava landraces and one IITA breeding genotype.
CMD evaluation was done on the parents and 525 F
1
progenies comprising of individuals pre-selected for
CMD resistance based on average severity scores of 1
and 2. Multiple marker analysis was used to screen for
the
CMD2
gene, where four markers associated with
this gene were used. Of the tested genotypes 83 %
showed at least one marker allele for the
CMD2
gene.
Two CIAT genotypes (CR52A-31 and AR14-10) had
all four marker alleles. TMEII had three alleles
associated with
CMD2
while Dabodabo had one
marker allele. This suggests that Dababo may have
alternative genes than
CMD2
for CMD resistance. The
F
1
families showed segregation for the
CMD2
gene. A
total of 88 individuals (17 %) had all four marker
alleles associated with the
CMD2
gene. A total of 179
individuals had between one to three marker alleles
each associated with
CMD2
. A total of 91 individuals
had no marker allele associated with the
CMD2
geneCassava is a major staple and food security
crop in Africa which can produce a crop under
uncertain rainfall and low fertility conditions. How-
ever, it suffers from several pests and diseases, with
Cassava Mosaic Disease (CMD) being the main biotic
constraint in production in sub-Saharan Africa. It is
caused by cassava mosaic geminiviruses. Plants
infected with CMD usually produce a few or no
storage roots. Markers associated with resistance
genes to CMD have been mapped, including a major
dominant gene,
CMD2
. Eight CMD resistant geno-
types from CIAT were used in crosses with three
cassava landraces and one IITA breeding genotype.
CMD evaluation was done on the parents and 525 F
1
progenies comprising of individuals pre-selected for
CMD resistance based on average severity scores of 1
and 2. Multiple marker analysis was used to screen for
the
CMD2
gene, where four markers associated with
this gene were used. Of the tested genotypes 83 %
showed at least one marker allele for the
CMD2
gene.
Two CIAT genotypes (CR52A-31 and AR14-10) had
all four marker alleles. TMEII had three alleles
associated with
CMD2
while Dabodabo had one
marker allele. This suggests that Dababo may have
alternative genes than
CMD2
for CMD resistance. The
F
1
families showed segregation for the
CMD2
gene. A
total of 88 individuals (17 %) had all four marker
alleles associated with the
CMD2
gene. A total of 179
individuals had between one to three marker alleles
each associated with
CMD2
. A total of 91 individuals
had no marker allele associated with the
CMD2
geneCassava is a major staple and food security
crop in Africa which can produce a crop under
uncertain rainfall and low fertility conditions. How-
ever, it suffers from several pests and diseases, with
Cassava Mosaic Disease (CMD) being the main biotic
constraint in production in sub-Saharan Africa. It is
caused by cassava mosaic geminiviruses. Plants
infected with CMD usually produce a few or no
storage roots. Markers associated with resistance
genes to CMD have been mapped, including a major
dominant gene,
CMD2
. Eight CMD resistant geno-
types from CIAT were used in crosses with three
cassava landraces and one IITA breeding genotype.
CMD evaluation was done on the parents and 525 F
1
progenies comprising of individuals pre-selected for
CMD resistance based on average severity scores of 1
and 2. Multiple marker analysis was used to screen for
the
CMD2
gene, where four markers associated with
this gene were used. Of the tested genotypes 83 %
showed at least one marker allele for the
CMD2
gene.
Two CIAT genotypes (CR52A-31 and AR14-10) had
all four marker alleles. TMEII had three alleles
associated with
CMD2
while Dabodabo had one
marker allele. This suggests that Dababo may have
alternative genes than
CMD2
for CMD resistance. The
F
1
families showed segregation for the
CMD2
gene. A
total of 88 individuals (17 %) had all four marker
alleles associated with the
CMD2
gene. A total of 179
individuals had between one to three marker alleles
each associated with
CMD2
. A total of 91 individuals
had no marker allele associated with the
CMD2
gene