NORTH-SOUTH CENTRE - ETH - North-South Centre North-South ...

Healthy rice for healthy people:
Biofortification of zinc in rice
Zinc (Zn) deficiency is one of the most widespread nutritional
disorders affecting resource poor women and children
in South and Southeast Asia. Biofortification of rice, a major
staple cereal for more than 2.5 billion people, is a cost-effective
strategy to overcome human Zn deficiency. Although
several rice lines with high grain-Zn have been developed
through conventional breeding, the grain-Zn content
is highly influenced by soil physico-chemical properties.
In order to develop a line for multiple environments or for
a specific target area, it is crucial that we understand the
physiological mechanisms underlying Zn uptake and allocation
under different soil environments. This project aims
at characterising the Zn uptake mechanisms by roots, and
Zn transport and remobilisation mechanisms from roots or
leaves to grain in existing high and low grain-Zn rice genotypes.
Furthermore, it aims at understanding how key soil
and crop management practices (Zn fertilisation x water)
affect Zn uptake and transport mechanisms within various
soil environments and rice ecologies.
The range of Zn concentration causing deficiency/toxicity in
rice is very narrow and identifying an optimum is essential.
A preliminary experiment was set up to (i) identify the optimum
concentration of Zn required for the normal growth of
rice and (ii) to establish ideal conditions for the growth of
rice in agar nutrient solution (ANS) until maturity. IR74, a Zn
deficiency-susceptible rice variety was grown in ANS in
pots, placed in a greenhouse. The ANS consisted of 0.1 %
agar +Yoshida’s nutrient solution except Zn. Different Zn
concentrations ranged from 0.0 to 6.5 μM of ZnSO 4 . The
Zn treatments were imposed for two weeks starting three
weeks after sowing.
The leaf symptoms with 0.15 and 1.5 μM ZnSO 4 were significantly
lower than 0.0 and 0.005 μM ZnSO 4 . The symptom
scores increased with higher Zn treatments, which might
be due to Zn toxicity. There were no treatment effects on
traits such as plant height, root length and root weight.
However, higher Zn treatments showed an increased shoot
dry weight, with 1.5μM ZnSO 4 showing the highest shoot
weight. Based on the initial results, 1.5 μM ZnSO 4 seems
to be the optimum Zn level for normal growth of plants in
ANS solution. Currently, we are quantifying the actual Zn
concentration in plant tissues and Zn uptake by roots at different
Zn treatments. This will further clarify the optimum
Zn for normal growth in ANS solution.
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Research fellow
Somayanda Impa Muthappa, IRRI, Philippines
Supervisors
Sarah Beebout, IRRI, Philippines;
Rainer Schulin, ETH Zurich, Switzerland
Collaborator
Abdelbagi Ismail, IRRI, Philippines
Capacity development
Research fellowships
Duration
October 2009 – August 2011
Rice (Oryza sativa L. var IR74) growing
in a greenhouse at IRRI, Philippines