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Regional
disease nursery (REGNUR): A unique opportunity for developing
multiple-disease-resistant maize
B. Vivek,
K. Pixley, O. Odongo, J. Njuguna, J. Imanywoha, G. Bigirwa & A. Diallo
Maize is grown on 15 million ha in eastern and
southern Africa. Several
diseases, like streak virus (MSV), grey leaf spot (GLS) and turcicum leaf blight (TLB) are of common occurrence in the region
and can result in complete crop failure.
With funding from The Rockefeller Foundation, a regional disease
nursery (REGNUR) project was initiated in 1998 to promote and enhance regional
collaboration to address the common disease and insect problems of maize.
The REGNUR project aimed to identify and increase access to disease
resistant germplasm, generate and disseminate information on disease and
insect resistance sources, and facilitate National Programs to develop
resistant varieties. A recent
REGNUR project was a diallel mating among 12 elite inbred lines identified by
REGNUR collaborators. The trial
was grown at 12 sites during 2001. Results
from 6 locations show that both general combining ability (GCA) and specific
combining ability (SCA) effects were highly significant for GLS, MSV, head
smut, Phaeosphaeria Leaf Spot (PLS),
turcicum and rust (P. sorghi), whereas only GCA was important for ear rot resistance.
On average, GCA determined 69% of resistance to diseases while SCA
determined 63% of variation for grain yield.
This implies that the approach to developing multiple disease
resistance should involve identifying lines with good per se resistances to
diseases with final selection for good combining ability for yield.
Correlations between GCAs for disease scores were generally
non-significant. This underlies
the need for screening specific diseases using artificial inoculation or
reliable “hot-spots” and highlights the importance of a project like
REGNUR, which enables such collaboration.
Details of the above results and findings from the concluded first
phase of REGNUR will be presented.
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