The identification of resistance in 2,490 genotypes
using RME1 and NS158 markers and the further evaluation
under field conditions in an area that is highly
affected by the disease in Nigeria revealed that the accuracy
of selection based on these two markers ranged
from 70 to 80 %, depending on the progeny analyzed
(Blair et al., 2007). In another study, Okogbenin et al.
(2007) made a first introduction of the germplasm from
Latin America in Africa with materials from crosses
between elite parental from breeding programs and a
second introduction of material that was selected based
on MAS (two microsatellites and six SCARs) and a subsequent
evaluation of genotypes under natural conditions
in a field that was infested with CMD in Nigeria. In the
first set of entries, there was a devastating effect of the
disease, infecting 100 % of the plants one month after
planting. However, the results of the second introduction
indicated that an introgression of the CMD2 gene
in the cassava germplasm from Latin America via MAS
provided high resistance under field conditions, with 67
% of the genotypes showing grades 1 to 2 (grading score
in which 1 = resistant plants and 5 = highly susceptible
plants). Therefore, the MAS that is used can present
a high level of efficiency in the indication of cassava
genotypes with proven resistance under field conditions,
which is clearly due to the CMD2 gene’s dominant nature
and its efficacy against a broad range of viral strains.