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Coordinated
ecosystem breeding in Kenya: Progress, challenges and opportunities
J. Ininda,
M.Gethi, O. Odongo, J. Njuguna & J.A.W. Ochieng’
On-farm maize yields in Kenya are reduced
significantly by the incidences of pests and diseases.
Heavy outbreaks of maize streak virus occurred in 1988 and 1994.
Outbreak of turcicum blight was reported in 1999. Meanwhile,
Kenya has experienced increasingly severe incidences of head smut.
All such cases indicate the genetic vulnerability of Kenyan maize
germplasm to pests and diseases. This
has prompted a need to breed maize with genetic resistance to the full
range of endemic pests and diseases.
Maize breeders in Kenya have placed increased emphasis on
breeding for resistance to priority pests and diseases as the most
cost-effective control option for the risk-prone resource poor farmers.
“Coordinated Ecosystem Breeding” (CEB) was the approach adopted by
maize researchers in Kenya in 1998 to developing adopted, high-yielding
hybrids and open-pollinated varietie with high levels of
tolerance/resistance to major pests and diseases. The objectives of this
project were to focus on genetic improvement for turcicum blight (Setosphaeria
turcica), gray leaf spot (Cercospora
Zea maydis), common rust (Puccinia
sorghi) stem borers (Chilo
partellus and Buseola fusca),
head smut (Sphaelothica reliana),
maize streak virus and stalk and ear rots.
Since 1984, maize variety development in Kenya had stalled
because of staff changes,
restructuring of the institute and many Kenyans proceeding for further
training outside the country. During
1999-2000, disease resistant lines available from African networks or
spill-over from previous and existing projects in Kenya were distributed
and exchanged among maize breeders working in different maize growing
ecosystems in Kenya. Both local and exotic lines were used construct
single-, double-, or three-way cross hybrids, targeting specific traits
in the maize improvement process. New products with an immediate potential for deployment by
resource poor farmers in Kenya and with genetic tolerance and/or
resistance to most economically important diseases have been recently
constituted. Susceptability
to MSV in the most popular varieties is currently rated at 5.0
(completely susceptible). This
has been altered to an improved disease resistant level of 2.5 (mild
reactions to streak) in the newly developed hybrids without compromising
yield levels. One
single-cross hybrid has also been obtained showing a mean foliar damage
score of 3.5 (tolerant to stem borers), compared to the popular
resistant check, which normally shows a mean foliar score of between
7.0-9.0. Perfomance of the new hybrids in presence of turcicum blight has also been improved from a score 4.0 to a score
of 1.5. Single- and three-way cross hybrids with a high level of
resistance to head smut have been obtained.
By introgressing germplasm from a wide range of sources, the CEB
effort has developed a wealth of inbred lines and
finished and semi-finished products that can directly impact on
future breeding programs and change the livelihood of resource poor
farmers.
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