Biology Reference
In-Depth Information
Table 15.1.
CIAT shipment of cassava mosaic disease (CMD) resistant genotypes in
combination with other traits to Africa and Asia
Country
Trait
Number of Genotypes shipped
Tanzania
r-CMD, r-CGM
530
Nigeria
r-CMD, r-CGM, RQ
765
Uganda
r-CMD, r-CGM
530
Ghana
r-CMD, r-CGM, RQ
765
Kenya
r-CMD, r-CGM, Dr
850
Mozambique
r-CMD, r-CGM, RQ
150
South Africa
r-CMD, r-CGM
80
India
r-CMD, r-CGM
530
Thailand
r-CMD, r-CGM
50
r-CMD - resistance to Cassava Mosaic Disease; r-CGM - resistance to cassava green mite; RQ-
root quality; Dr - dry matter
elite materials in its pedigree were developed
between 2003 and 2005. Subsets of the materi-
als developed after MAS were shipped to sev-
eral countries in Africa and Asia. The shipments
are listed in Table 15.1. The low number of
genotypes shipped to each country is a sharp con-
trast to the huge number (hundreds of thousands)
of genotypes shipped as seeds in the 1990s,
reflecting a huge reduction in cost and manage-
ment in a breeding program through MAS.
Field evaluations in Africa have resulted in
the successful selection of LA genotypes in the
breeding scheme, through seedling nursery to
regional trials, leading to a collection of top per-
forming elite lines assembled in the gene pool
of NARS in Africa in Ghana, Nigeria, Tanzania,
and Uganda. These materials have also been inte-
grated into the recurrent selection activities of
the breeding program aimed at combining CMD
resistance with other farmer-preferred traits in
these countries, in order to develop lines bet-
ter suited to meet consumer needs (culinary
qualities).
The LA CMD-resistant lines were integrated
into the breeding scheme of African NARS,
and then evaluated, leading to release or use
in crosses with local African farmer-preferred
lines to develop better adapted lines. The LA
germplasm shipped was developed for character-
istics such as high yield, vigor, high dry matter
content, and high starch content. A good num-
ber of these materials have been selected and
incorporated into gene pools of these African
countries for continuous use in their breeding
programs, a step intended to reduce genetic gaps
in African germplasm. This is a landmark break-
through that has largely facilitated the broaden-
ing of the germplasm base. A good number of the
LA materials, which have been evaluated in the
breeding scheme, have been selected by farmers
under the participatory varietal selection (PVS)
and plant participatory breeding (PPB) activi-
ties of NARS. For example CR41-10 was prefer-
ably selected for its culinary and root quality
characteristics at on-farm testing stages. Results
indicated that a high proportion of the materials
are showing good resistance to CMD in the dif-
ferent countries. Through the success of MAS
using CMD markers, several elite genotypes of
Latin America were successfully introduced into
Africa (Nigeria, Ghana, Tanzania, and Uganda)
under the CGIAR Generation Challenge Pro-
gram (GCP).
The successful use of the CMD markers also
implies that they could be used by breeders to
breed for CMD resistance in parts of Africa
were disease pressures are low, or in seasons
of low disease pressure where heritability is
low or near zero, and could minimize the cost
associated with maintaining several screening
sites for breeding programs. It also means that
breeders can quickly downsize on the number of
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