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Biotechnology, Breeding and
Seed Systems for African Crops
Plant Breeding
Research Abstracts from the
Biotechnology, Breeding and Seed Systems conference
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Ecologically
adapted maize open pollinated varieties development and screening
(ecosystem breeding) in Zimbabwe
X.
Mhike &
L. Muza
Maize (Zea mays)
is the staple food in Zimbabwe. However its production is limited by poor
adaptation of commercial hybrid varieties to smallholder growing conditions.
Presently-grown hybrid varieties were developed under optimum conditions and
hence are not adapted to the smallholder farmers’ conditions. This has
resulted in yields as low as 300kg/ha in some instances in the smallholder
sector which occupies 91% of the semi arid areas of the country. Such low
yields are not economically viable when considering the high costs of farm
inputs and other production costs. The result has been high incidence of
planting of recycled hybrid seed and hence a further decline in productivity,
compromising household and national food security. As a result, the national
maize program has embarked on the development and evaluation of
ecologically-adapted open pollinated varieties (OPVs), which are a better
option for the smallholder farmer compared to recycled hybrid seed. Moreover,
OPVs have been shown to be more stable under stress conditions than hybrids.
In addition, OPVseed can be recycled with minimum yield decline and seed
production costs are lower than for hybrids.
In order to identify OPVs that are adapted to the different
agro-ecological zones of the country, on-station and on-farm screening of 36
OPVs from the national program and introductions from CIMMYT and other SADC
countries was begun in the 2000/01 season. This screening has resulted in the
selection of 12 OPVs which are better adapted to the nitrogen deficient soils
in the dry target regions of the country. The selected 12 OPVs will be
extensively evaluated on farms across the country using the community-based,
participatory approach known as the ‘Mother-Baby’ evaluation approach.
The ecologically-adapted OPVs will be identified and community based
seed production schemes initiated in order to make seed available to the
different communities. Use of the Mother-Baby screening procedure has led to
the release of two synthetics, namely, ZM421 and ZM521 for commercial
production. To further develop
new OPVs, sixty-five inbred lines and varieties were evaluated across the
semi-arid areas of the country after which the best adapted materials were
crossed in a diallel fashion. The resultant hybrids and varieties were
evaluated and the best combinations were initially used in the formation of
two synthetics which will be included in the set of entries to be evaluated
using the Mother-Baby scheme starting the 2002/03 summer season. This variety
development program is on going and the resultant OPVs/Synthetics will be
included in the screening process.
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