Research Highlights of the CIMMYT Wheat Program 1999-2000

in ECSA rely heavily on CIMMYT wheat
germplasm (i.e., 75% of released cultivars are
derived directly from CIMMYT germplasm).
Regarding germplasm requirements, South Africa
is unique in ECSA, with spring and winter types
grown, as well as F 1
hybrids. Of the 71 wheat and
triticale cultivars released in South Africa since
1980, 40% involved CIMMYT-derived germplasm,
21% were of unknown origin (i.e., the parentage of
commercial F 1
hybrids), with the remaining
releases—primarily winter habit types—utilizing
non-CIMMYT germplasm.
Diseases Prevalent in ECSA
In recent years, yellow rust has supplanted stem
rust as the rust pathogen of primary concern in
ECSA. Over the past ten years, single step
mutations have resulted in the evolution of new
virulences in the yellow rust pathogen in Kenya,
demonstrating the danger of breeding for racespecific
resistance. From 1969 to 1989, at least 19
races were identified. In August 1996, yellow rust
was observed for the first time in South Africa, and
within a year, the disease had spread to most wheat
producing areas in the country. Infected grass
species serving as accessory hosts were also
observed in the Western Cape and Eastern Free
State, with “6E16” identified as the originating
race. MWIRNET/RSA is currently sponsoring a
germplasm shuttle breeding program whereby
South African wheat germplasm is screened for
resistance to yellow rust in a location in
southwestern Uganda considered to be a global
hot-spot for this pathogen.
CIMMYT is also supporting distribution of a Sub-
Saharan Wheat Disease Monitoring Nursery. This
nursery is intended to validate regional varietal
disease performance while monitoring potential
performance criteria important for farmers and
NARS cooperators throughout East, Central, and
Southern Africa.
Septoria nodorum, S. tritici and S. avenae f.sp.
triticeae, loose smut, scab, root rot, take-all and
Helminthosporium spp. cause significant yield losses
in ECSA. Cereal aphids (Schizaphis graminum,
Rhopalosiphum padi, R. maidis, Sitobion avenae and
Diuraphis noxia) can also be major pests of wheat in
this region, and several species serve as vectors in
the transmission of barley yellow dwarf virus.
Yield losses of up to 47% due to BYDV have been
reported in Kenya. Yield losses of >60% due to D.
noxia have been reported in South Africa, and, at
present, all bread wheat cultivars grown in the
summer rainfall zone of RSA require genetic
resistance to this pest. MWIRNET/RSA is currently
supporting research to identify an indicator
capable of differentiating Dn resistance genes by
assessing differences in aphid feeding behavior.
Industrial Quality
The free-market, global economy promotes the
production and consumption of the lowest cost
products. Throughout ECSA, however, limited and
unscientific information (i.e., market biased) is
available on the relative milling and baking quality
of nationally produced wheat. ECAMAW and
MWIRNET have promoted Regional Industrial
Quality Cooperative Testing Trials to enable
regional wheat breeders, producers, processors,
and grain marketing organizations to better
understand the inherent milling, baking, and
nutritional quality aspects of advanced germplasm
and cultivars.
Agronomic Research
A special feature of the ECAMAW collaboration is
agronomic research targeted at farm-level problems
that must be resolved to promote long-term
agricultural productivity in the region. Wheat crop
production recommendations that have recently
been provided to extension services due to
ECAMAW research activities include:
• The semidwarf bread wheat cultivars HAR604
(“Galama”) and HAR1685 (“Kubsa”) recently
released in Ethiopia exhibit the highest
productivity and profitability across a range of
crop management systems, and result in the
highest marginal rates of return under increased
input levels. The profitability of bread wheat
production in the central highlands of Ethiopia can
be markedly increased by focusing the application
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