[permaculture] Fwd: [SANET-MG] Improving the nutritional quality of crops
Lawrence F. London, Jr.
venaurafarm at bellsouth.net
Tue May 10 11:44:52 EDT 2011
-------- Original Message --------
Subject: [SANET-MG] Improving the nutritional quality of crops
Date: Tue, 10 May 2011 11:36:56 -0400
From: Joel Gruver <jgruv at HOTMAIL.COM>
To: SANET-MG at LISTS.IFAS.UFL.EDU
the following abstracts are a small window into current research on
improving the nutritional quality of crops.
Gregorio GB. 2002. Progress in breeding for trace minerals in staple
crops. J Nutr. 132(3):500S-502S.
Staples are not considered an important source of minerals in the diet.
However, because of high staple consumption, any increase in mineral
concentration might well have a significant effect on human nutrition
and health. The nutritional quality of staple crops (rice, cassava,
wheat, maize and beans) can be improved by breeding. Studies have shown
the potential to exploit the genetic variation in seed concentration of
iron and other minerals without the general negative effect on yield of
adding new traits. The relationship between yield and mineral
concentration may be positive, particularly in mineral-deficient soil.
Initial evaluations have shown that some crop varieties have high Fe, Zn
and carotene in their edible portions. The next step for conventional
breeding will be to study the genetics of trace mineral inheritance to
determine the best selection technique. Initial investigations of the
genetics for high iron in rice have indicated a complex mode of
inheritance, demonstrating additive and dominant gene and environmental
effects. Breeding strategies have been developed based on these genetic
findings. The use of biotechnological tools, such as molecular
marker-assisted selection, will significantly increase the pace and
prospects of success for breeding to improve the nutritional value of
staple food crops.
Holtz C. 2009. The potential to improve zinc status through
biofortification of staple food crops with zinc. Food Nutr Bull. 30(1
Biofortification is an agricultural strategy that aims to increase the
content of select micronutrients, including zinc, in staple food crops
such as rice, wheat, maize, pearl millet, and others. When consumed
among zinc-deficient populations, zinc-biofortified staple foods should
improve the adequacy of zinc intakes and hence reduce the risk of
dietary zinc deficiency. Several conditioning factors will contribute to
the potential for this strategy to meet its goal, including the
additional amount of zinc that can be bred into the staple crop food,
the amount of zinc that remains in the staple crop food following usual
processing methods, and the bioavailability of zinc from the staple
crop food in the context of the usual diet. Reduction of the phytate
content of cereals with the use of agricultural techniques is a
potential complementary strategy for improving the bioavailability of
zinc. The feasibility of biofortification to result in a meaningful
increase in the adequacy of population zinc intakes and to reduce the
consequences of zinc deficiencies still needs to be determined through
efficacy trials. At the program level, the ability to widely disseminate
biofortified crop varieties and the willingness of farmers to adopt them
will also affect the magnitude of the impact of this strategy.
Alloway BJ. 2009. Soil factors associated with zinc deficiency in crops
and humans. Environ Geochem Health. 31(5):537-48.
Zinc deficiency is the most ubiquitous micronutrient deficiency problem
in world crops. Zinc is essential for both plants and animals because
it is a structural constituent and regulatory co-factor in enzymes and
proteins involved in many biochemical pathways. Millions of hectares of
cropland are affected by Zn deficiency and approximately one-third of
the human population suffers from an inadequate intake of Zn. The main
soil factors affecting the availability of Zn to plants are low total Zn
contents, high pH, high calcite and organic matter contents and high
concentrations of Na, Ca, Mg, bicarbonate and phosphate in the soil
solution or in labile forms. Maize is the most susceptible cereal crop,
but wheat grown on calcareous soils and lowland rice on flooded soils
are also highly prone to Zn deficiency. Zinc fertilizers are used in the
prevention of Zn deficiency and in the biofortification of cereal
Broadley MR et al. 2006. Biofortification of UK food crops with
selenium. Proc Nutr Soc. 65(2):169-81.
Se is an essential element for animals. In man low dietary Se intakes
are associated with health disorders including oxidative stress-related
conditions, reduced fertility and immune functions and an increased risk
of cancers. Although the reference nutrient intakes for adult females
and males in the UK are 60 and 75 microg Se/d respectively, dietary Se
intakes in the UK have declined from >60 microg Se/d in the 1970s to 35
microg Se/d in the 1990s, with a concomitant decline in human Se status.
This decline in Se intake and status has been attributed primarily to
the replacement of milling wheat having high levels of grain Se and
grown on high-Se soils in North America with UK-sourced wheat having low
levels of grain Se and grown on low-Se soils. An immediate solution to
low dietary Se intake and status is to enrich UK-grown food crops using
Se fertilisers (agronomic biofortification).
Such a strategy has been adopted with success in Finland. It may also be
possible to enrich food crops in the longer term by selecting or
breeding crop varieties with enhanced Se-accumulation characteristics
(genetic biofortification). The present paper will review the potential
for biofortification of UK food crops with Se.
Johnson CC et al. 2010. Symposium on 'Geographical and geological
influences on nutrition': Factors controlling the distribution of
selenium in the environment and their impact on health and nutrition.
Proc Nutr Soc. 69(1):119-32.
Se is essential to human and animal health but can be toxic in excess.
An interest in its geochemistry has developed alongside a greater
understanding of its function in a number of health conditions. Geology
exerts a strong control on the Se status of the surface environment;
low-Se rock-types (0.05-0.09 mg Se/kg) make up the majority of rocks
occurring at the Earth's surface, which in turn account for the
generally low levels of Se in most soils. However, there are exceptions
such as associations with sulfide mineralisation and in some types of
sedimentary rocks (e.g. black shales) in which contents of Se can be
much higher. Baseline geochemical data now enable a comparison to be
made between environmental and human Se status, although a direct link
is only likely to be seen if the population is dependent on the local
environment for sustenance. This situation is demonstrated with an
example from the work of the British Geological Survey in the
Se-deficiency belt of China. The recent fall in the daily dietary Se
intake in the UK is discussed in the context of human Se status and
declining use of North American wheat in bread making. Generally, US
wheat has ten times more Se than UK wheat, attributed to the fact that
soils from the wheat-growing belt of America are more enriched in Se to
a similar order of magnitude. In agriculture effective biofortification
of crops with Se-rich fertilisers must be demonstrably safe to the
environment and monitored appropriately and baseline geochemical data
will enable this process to be done with confidence.
School of Agriculture
Western Illinois University
jgruv at hotmail.com
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