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Bioscience Methods 2014, Vol.5, No.2, 1-8
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2
mineral binding properties is believed to prevent colon
cancer by reducing oxidative stress in the lumen of the
intestinal tract (Vucenik and Shamsuddin, 2003; Jenab
and Thompson, 2000). The chelating effect may serve
to prevent, inhibit, or even cure some cancers by
depriving those cells of the minerals (especially iron)
they need to reproduce (Klopfenstein et al
.,
2002).
Antinutrients are found in almost all foods. However,
their levels are reduced in most common food crops
probably through selection during the process of
domestication. Nevertheless, the large fraction of
human diets that come from these crops raise concern
about the possible effects of anti-nutrients on human
health (Cordain, 1999). The possibility now exists to
eliminate anti-nutrients entirely using genetic
engineering, but since these compounds may also
have beneficial effects, such genetic modifications
could make the food crops more nutritious without the
capacity to improve other aspects of human health
(Welch, 2004).
Phytic and oxalic acids are among the major
anti-nutrients present in plant protein sources (Akande
et al
.,
2010), both being anti-minerals. Phytic acid,
also known as inositolhexakisphosphate (IP6), or
phytate when in salt form is the principal storage form
of phosphorus in many plant tissues, especially bran
and seeds (Klopfenstein et al., 2002). It is not
digestible to humans or non-ruminant animals,
because these animals lack the digestive enzyme
(phytase) required to remove phosphate from the
inositol in the phytate molecule. On the other hand,
ruminants readily digest phytate because of the
phytase produced by microorganisms in their rumen
(Klopfenstein et al., 2002). Phytate is well
documented to block absorption of not only
phosphorus, but also of other minerals such as calcium,
magnesium, iron and zinc (Ramiel, 2010;
Klopfenstein et al., 2002).
However, soaking, cooking, boiling and other food
processing methods generally achieve significant
reduction of the anti-nutrients (Udensi et al., 2005;
2007; Ekop et al
.,
2004; Ekop and Eddy, 2005). Thus,
foods high in these anti-nutrients should be adequately
processed to make them wholesome for consumers. In
ruminants however, dietary oxalic acid can be
degraded by rumen microbes into CO
2
and formic acid
(Allison et al
.
, 1990). The amount of antinutrients in
food crops is highly variable and depends on factors
including environmental condition, use of
high-phosphate fertilizers in cultivation and genotypic
variation (Offor et al.,
2011). In this study, thirty-one
cowpea cultivars were investigated for their
anti-nutritional factors to determine their susceptibility
to cowpea bruchid,
C. maculatus
infestation.
1 Materials And Methods
1.1 Sources of Experimental Insects and cowpea
cultivars
Newly emerged adult
C. maculatus
used for this study
were obtained from already existing culture in the
Postgraduate Research Laboratory of the Department
of Biology, Federal University of Technology, Akure,
Ondo State, Nigeria. Insect rearing and the
experiments were carried out at ambient temperature
of 28+2
o
C and 75+5% relative humidity.
The thirty one cowpea,
Vigna unguiculata
cultivars:
MIT04K-339-1, MIT07K-291-92, MIT07K-211-108,
MIT07K-292-10, EIT07K-303-1, EIT07K-243-1-10,
EITO7K- 234-1-5, IT067-154-1, IT96-619, IT845-2246-4,
IFE BROWN, MIT06K-128, MIT07K-188-49,
MIT0K-835-45, MIT07K-318-33, MIT07K-309-44,
MIT06K-281-1, MIT07K-187-24, MIT06K-124,
MIT04K-219-2, MIT04K-321-2, MIT07K-304-9,
MIT03K-337-6, MIT06K-121, MIT07K-194-3,
MIT98K-503-1, EIT04K-221-1, EIT07-291-69,
EIT07K-299-4, EIT03K-369-3 and EIT97K-499.35
used for this study were provided by the Cowpea
Seeds Unit, International Institute for Tropical
Agriculture, Ibadan, Oyo State, Nigeria.
1.2 Susceptibility of Cowpea Cultivars to
C.
maculatus
Twenty grammes of each cowpea cultivar was
weighed into 250ml plastic containers and ten pairs of
adult
C. maculatus
(2 to 3 days old) were introduced
into each container. The containers were covered with
tight lid that have been cut at centre and sealed with
muslin cloth for aeration. This was replicated three
times. The infested cowpea seeds was left for 7 days
in an insect cage in the laboratory during which the
insects fed and laid eggs. On day 7
of infestation,
beetles were removed and discarded. Numbers of eggs
laid by adult beetles were counted and recorded.
Twenty five days after infestation with beetles, the
containers were checked daily for emerged adults.