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Introduction
Productivity of
maize in Eastern and Southern Africa is constrained by a
number of biotic and abiotic factors which include diseases,
drought, low N, stem borers, leaf blight, maize streak virus
and gray leaf spot (Moshi et al., 1988). Deployment of
improved varieties is considered to be the most
cost-effective and sustainable strategy for solving these
problems. The main strategy for increasing production in
Tanzania has been to breed for high yielding, widely adapted
open pollinated varieties that are resistant to major
diseases.
Diseases are one
of the major constraints to maize production in Tanzania.
Major
Diseases of maize
in Tanzania include gray leaf spot (Cercospora zeae
maydis), northern leaf blight (Exerohilum turcicum),
maize streak virus (MSV), southern leaf blight (Helminthosporium
maydis) common rust (Puccinia sorghi), ear rots
(Diplodia maydis, D. macrospora and
Fusarium spp.), Phaeosporia leaf spot (P. maydis),
Fusarium stalk rot and head smut (Sphacelotheca reiliana).
Gray leaf spot (GLS)
was of minor occurrence in Tanzania until early 1990’s when
it erupted to epidemic levels in southern Tanzania. It
spread to northern Tanzania in the late 1990’s (Kuwite and
Mduruma, unpublished data). Crop loss due to this disease
has ranged from 10-60% (Mduruma, unpublished data) depending
on the crop variety and prevailing weather conditions.
Recently, there has been a decline in the severity of this
disease in northern Tanzania. This could be due to a decline
in moisture level and changes in temperature. Northern leaf
blight (turcicum blight) is found in the same environments
in Tanzania as GLS. This disease causes considerable yield
loss and of recent has appeared more important than GLS.
Resistance to turcicum blight is oligogenic (Jenkins et al.,
1957). Other major diseases in northern Tanzania include
MSV and common rust.
A proposal to breed and screen for high yielding OPVs and
hybrid maize varieties with resistance to GLS and turcicum
blight was initiated in 2004 with support of funds from the
Rockefeller Foundation. The project also intends to select
for other attributes such as farmer preferred grain colour,
grain type, early maturity, plant vigour and wide
adaptability. During the first year, a total of 141 inbred
lines and varieties were evaluated for the desired
characteristics. A few lines and varieties were selected
and evaluated for the second season or used to make crosses
in 2005. More material including 111 varieties and inbred
lines from Zimbabwe and 50 landraces from Tanzania were
evaluated in 2005. Most of the material was tested in
Madiira and Arusha Foundation Seed Farm in Arumeru district
in northern Tanzania whereas 70 inbred lines and varieties
were tested in Uyole and Njombe in the southern highlands.
Objectives
To
develop farmer acceptable high yielding maize varieties resistant to
gray leaf spot and northern leaf blight.
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