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Molecular Plant Breeding 2011, Vol.2, No.11, 75
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Figure 1 Scheme of the lowland NERICA varieties development
and evaluated in tandem with NARS (shuttle breeding)
in observational nurseries under irrigated conditions
and rainfed lowland conditions for adaptation, and
with Africa rice center plant pathologist for resistance
to RYMV (rice yellow mollte virus). These lines
where evaluated for phenotypic acceptability, yield
potential, RYMV resistance, nitrogen-use efficiency
and adaptation of different water regimes.
Through a strong networking approach supporting the
shuttle breeding, undertaken with the active involve-
ment of the West and Central Africa Regional Rice
Network (ROCARIZ) and the International Network
for Genetic Evaluation of Rice (INGER-Africa), the
Africa rice center has been able to accelerate the
selection process and achieve wide adaptability of the
lowland NERICA in West Africa.
The development of interspecific rice varieties for
various ecologies is a significant international public
good. The Africa Rice Center has generated several
hundred NERICA lines, opening new gene pools and
increasing the biodiversity of rice available to the
world of science. This development of the NERICA
varieties is further advancing the farm level agro-
biodiversity of rice in the high-impact ecologies.”
By unblocking the treasure store of genes in Africa
rice (
O. glaberrima
), the Africa rice center has pre-
sented the global rice research community with an
opportunity to exploit the preferred biodiversity.
2 Major rice diseases
2.1 Resistance to diseases and pests
After the NERICA was made, it has been evaluated
and characterized for a range of agronomic traits and
reaction to key African endemic diseases and pests.
The results are like this, first, its varieties generally
have shorter growth duration than most traditional rice
varieties; second, a number of NERICA varieties
process early vigor, which is an important trait for
weed competiveness in rice, thus improving the
productivity of scarce labor; Moreover, some of them
also have tolerance to drought and soil acidity.
In the other hand, the West African common three
major diseases of key economic importance and se-
riously constrain rice production in most rice eco-
logies, such as the rice yellow mottle virus (RYMV),
bacterial leaf blight (BLB) and rice blast: result, only
blast is specific to the rainfed upland ecology for
which the NERICA varieties were developed. Blast is
rice fungal disease caused by
Pyricularia grisea
(Cke.)
Sacc. And is particularly dangerous in upland rice, but
also caused serious damage in rain fed lowland and
irrigated systems (WARDA, 1999, annual report,
www.warda.org/warda1/main/Publications/publication
s.htm). Blast is one of the major constraints to inten-
sification (Figure 2).
2.2 Irrigated management of disease
In the low-input farming systems of sub-saharian
Africa where resource-limited farmers can hardly ever
afford external inputs, the control of the above di-
seases is mainly through the use of resistant/tolerant
varieties in combination with sound management pra-
ctices, such as good weed control. One of the principal
components of an integrated management system for
diseases is varietal resistance though this can be un-
stable in space and in time depending to the structure
of the pathogen population.
Figure 2 Symptoms of some blast diseases on upland rice
(www.warda.org)
Note: A: Neck blast; B: Node blast; C: Leaf blast