Abstract
Biofortification, a process of adding micronutrients to food crops, is
accomplished by breeding or agronomic approach. This study aimed
biofortification of Zn and Fe in rice grain through an agronomic approach via
variety screening and fertilizer applications. A series of field experiments have
been done at BAU farm, Mymensingh (AEZ 9, non-calcareous soils) and BINA
farm, Ishwardi (AEZ 11, calcareous soils) for three consecutive years. In these
experiments, 29 varieties of Boro rice and 36 varieties of T. Aman rice were
tested for 3 treatments: control, Zn and Zn + Fe; the Zn rate being 3 kg ha-1 and
Fe rate 4 kg ha-1 added as ZnSO4.7H2O and FeSO4.7H2O, respectively. Other
nutrients such as N, P, K and S were used at a recommended rate to all plots.
The experiment was laid out in a split plot design, distributing the treatments to
the main plots and rice cultivars to the sub-plots, with three replications. The
grain Zn and Fe concentrations markedly varied with varieties showing a
greater ability of some rice varieties to uptake and accumulate Zn and Fe in
grain, with a further possibility to enhance Zn and Fe levels by fertilizer
application. The genetically Zn enriched varieties having grain-Zn greater than
20 µg g-1 in Boro season were BRRI dhan36, 50, 64 & 66, Binadhan-8, 12, 15 & 16;
and Kheyali Boro and in T. Aman season, the varieties were Kalojira,
Sakkarkhana, Jhul, Kutiaugni, Chinigura, Lal Chikon and BRRI dhan32, 49, 54 &
62. Similarly, the Fe-dense Boro rice varieties with grain-Fe above 10 µg g-1 were
BR 16, BRRI dhan45, 47 & 66, Binadhan-5 and Kheyali Boro, and the Fe-dense T.
Aman variety was Hori. These varieties can be regarded as Zn or Fe efficient rice
varieties which in turn would serve as breeding materials for the development
of high yield potential varieties with higher grain Zn and Fe contents.
Application of Zn fertilizer had an additive effect on the grain Zn concentration,
with an increase of 2-4 µg g-1 Zn across the varieties. Generally, the rice yields
considerably increased due to Zn application since the soils were Zn deficient,
but the yield remained unaffected by Fe application as the soil was sufficient in
Fe content. This study also indicated that Zn application helped protein
synthesis via increasing grain N content. Biofortification by use of fertilizer and
selective cultivars could be an effective strategy to reduce malnutrition of people
whose major diet is rice based.