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Genetic
variation, utilization and potential of African landraces in the genetic
improvement of cassava in Sub-Saharan Africa (SSA)
A.G.O.
Dixon, J.B.A. Whyte, N.M. Mahungu, B. W. Khizzah, M.
Fregene, A. A. Akano & M. Gedil
The
goal of genetic improvement of cassava in Sub-saharan Africa is to
contribute to the increased and sustained production, utilization,
commercialization and trade of cassava through the development,
evaluation, and promotion of improved and adapted cassava germplasm.
Varieties should be targeted toward different uses, markets and
agroecological zones, and the interaction between public and private
sector fostered. Cassava improvement strategies being pursued at IITA
are discussed in relation to cassava varietal needs, and the genetic
variability, diversity and utilization of African landraces by both
conventional and molecular approaches in order to diversify resistance
to the major biotic stresses, and expand the gene pool. of adapted
germplasm for a range of agroecologies and production systems.
Combined with the previously improved cultivars, genetic
variation generated within the introgression of previously untapped
African landraces has proven useful for improving our broad and special
trait populations for desirable food and feed quality traits through
evaluation, selection and recombination at locations representative of
the target agroecologies. Several improved genotypes expressing multiple
pest and disease resistance, early vigor, desireable plant architecture,
early bulking of storage roots and desirable food characteristics (e.g.
mealiness, high dry matter content, low cyanide content, high carotene
content, ease of peeling, root shape, food quality) were developed for
the moist and dry savannas, midaltitudes and inland valleys.
Improved germplasm, either as improved seed populations or
specific genotypes, is shared throughout the region for evaluation and
selection under specific local conditions. This effort has provided many
national programs with a broader genetic base of cassava from which they
can select those with desirable traits. While the potential gains in
genetic improvement of cassava seem impressive in themselves, the
enhancement of sustainable multiplication and distribution of certified
planting material of the improved genotypes is fundamental to the
acceleration of impact at the farm level. To ensure that cassava is
viewed as a viable farming enterprise, greater attention is being given
to the broad area of postharvest handling, including assessment of
various root and leaf characteristics for primary processing, product
development and marketing. These are key requirements to stimulate
consumer demand for food and feed products based on cassava.
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