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Molecular Plant Breeding 2011, Vol.2, No.11, 75
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As upland rice, NERICA is not restricted to growing
in paddies, thus enabling African farmers to grow rice
in places not previously thought possible.
4 Weeds control
Rice is an important staple food in West Africa,
largely grown on small family farms usually less than
4 ha in size (Johnson, 1996; Guei and Traore, 2001).
About 57% of the total rice area in West Africa is
planted to upland rice in diverse cropping systems
(Johnson, 1996). Rice is generally a weak competitor
against weeds. Thus, weeds are the major source of
yield loss in upland rice and its control is an intensive
labour (de Datta and Llagas, 1984; Fischer et al., 2001;
Labrada, 2003). Weed infection in rice field is like
watering plants with a bucket full of holes. Increase in
production is negated when weeds compete with rice
for limited light water and nutriment water.
In the SSA, smallholder farmers manage weeds in
upland rice using hand hoes and machetes but face
high costs as a result of labour shortages. Johnson et al.
(2004) noted that weeds can emerge at the same time
or before the rice plants, causing serious competition.
Consequently, the tasks of planting and weeding often
overlap and compete for labour (Rowland and
Whiteman, 1993). Many study showed that, herbicides
for weed control in upland rice are expensive and
often not available to smallholder farmers at the time
of need and, when available, farmers lack the requisite
knowledge and skill to use herbicides correctly.
Although herbicide use alleviates the problem of
labour for weeding, incorrect use may bring about
other environmental problems (Labrada, 2003).
Therefore, reducing dependence on herbicides may
bring down the costs of crop production and retard the
development of herbicide resistance in weeds (Le-
merle et al., 1996; de Vida et al., 2006).
It was known that the African rice species (
O. glaberrima
)
often has good weed competitiveness and
exhibits
resilience against some major African biotic and abi-
otic stresses (Koffi, 1980; Jones et al., 1997a). Thus,
the development and integration of more competitive
rice cultivars into the upland rice production system
may be a viable option for attaining optimum yields in
smallholder farms. Although some studies exist of
differences in competitiveness, including attempts to
relate rice traits to weed competitiveness and yield
(Jones et al., 1996; Johnson et al., 1998; Fischer et al.,
2001; Gibson et al., 2003; Koarai and Morita, 2003;
Zhao et al., 2006), only a limited number of cultivars
have been evaluated in the Guinea and Sudan
savannas of West Africa.
The Africa rice center experiments shown that, the
interspecific hybrids called New Rice for Africa
(NERICAs) have not been evaluated extensively for
weed competitiveness in the savannas of West Africa.
The potential for the adoption of NERICAs by small-
lholder farmers may depend in part on their weed
competitiveness as well as high yield potential.
Adékambi et al. (2006) cited by Rodenburg et al.
(2006) reported that cultivation of NERICAs reduced
the labour burden on school children because of the
shorter growth cycle and high weed competitiveness.
Rodenburg et al. (2006) suggested the evaluation of
the NERICAs in different ecosystems to confirm po-
ssession of weed competitive traits and provide far-
mers with a wider choice of options when cultivating
under weedy conditions.
5 NERICAs heading and yield
The concept of the NERICA varieties was to combine
the superior traits of
O. glaberrima
and
O. sativa
.
Thus lines which resemble
O. glaberrima
during early
growth stages and
O. sativa
during later stages were
developed.
The Africa rice center research’s reports shown that
the most popular NERICA lines take only three mon-
ths to ripen, as opposed to six months for the parent
species, thus allowing African farmers to “double
crop” it in a single growing season with nutriationally
rich vegetables or high-value fiber crops. In addition,
NERICAs escape late-season insects and diseases,
thus preventing yield losses. NERICAs have raised
the yield ceiling of upland rice by 50%. The new rice
can produce 6 t/ha in the best condition and up to 2.3 t/ha
under drought.
As a further bonus, some of the new lines contain up
to 12% protein, compared to about 10 percent in the