Genetic Analysis of Iron and Zinc Content of Maize Kernel
Guang-Tang PAN, Yuan-Qi WU, Ke-Cheng, YANG, Ting-Zhao, RONG
Maize Research Institute, Sichuan Agricultural University, Ya’an 625014, China
HarvestPlus is a global alliance of institutions and scientists seeking to improve
human nutrition by breeding new varieties of staple food crops consumed by the poor
that have higher levels of micronutrients, through a process called biofortification.
More than half the world's people - mostly the poor in developing countries - suffer
from the devastating consequences of micronutrient malnutrition. Micronutrients,
such as Vitamin A, Zinc, and Iron, are required only in very small amounts, but are
essential to good health. For understanding the fundamentally genetic laws of maize
iron and / or zinc content, 53 opening pollinated varieties (OPVs), 227 inbred lines
and 868 hybrid materials were mensurated the iron and / or zinc content by the atomic
absorption spectrophotometer, and the materials of high-iron content were selected
from various maize germplasm resources. To achieve these objects, 20 inbred lines (9
with higher iron content as matrilineal, 8 lower iron and 3 model lines as patrilineal)
were selected to mate 99 crosses using NCII design and all the crosses were sown in
1995 at Ya’an and Xichang, Sichuan Province, China. Simultaneity, 16 of 227 maize
inbred lines were random sampled to make a Griffing’s diallel cross (method 4) and
all the crosses were planted Ya’an, Sichuan Province, China, in spring and summer of
1995. The results were as following:
1. Iron content of OPVs, inbred lines and hybrids differed from each other, but
with a close average value, ranged from 10.9789 to 27.8734 (mean 18.3599), 11.6094
to 32.7188 (mean 19.6126), and 10.8619 to 38.0874 (mean 18.5274) mg/kg.
2. Genotype, environment (location and season), and genotype-environment
interaction acted highly significant effects to iron and zinc content of maize hybrid
crosses. GCA and SCA opposite effect values of iron and zinc contents varied greatly
among inbred lines and the crosses, among all environments. There was no clear rule
for GCA and SCA effects, some crosses with high SCA which parents both had low
opposite effect values of GCA implied that the SCA effects of crosses had a certain
relation with the GCA of parents, but not completely determined by them.
3. Iron and zinc contents varied greatly in mid-parent, over-high-parent heterosis
and over-low-parent heterosis, and represented a strong over-high-parent heterosis,
which might be possible to improve the iron and zinc content of maize hybrids by
choosing parents reasonably.
4. The narrow sense heritability (hN2) of iron content were both very low in all
environments, between 15％ and 30％, while the ones of broad zinc content ranged
from 36% to 68%, which indicated that environment effects were in-neglectable,
while genotype effects were more important for zinc than iron content of maize kernel.
The ratio of additive variances and non-additive variances of iron content varied from
0.51 to 0.85, which indicated heredity of iron character depended mainly on
non-additive effect while additive effect secondly. Moreover, the difference of hN2
between seasons (21%-24%) was smaller than between locations, implied that
additive effect of iron content exhibited comparatively steadily, but change of
non-additive was greater.
5. Parent-offspring simple correlation analysis showed that the iron and zinc content of
hybrids was significantly and positively correlated with their parents. The simple correlation
coefficients of iron content from high to low were mid-parent, high-parent, low-parent, female,
and male parents, and for zinc content, were mid-parent, high-parent, female, low-parent and male
parents in turn, which indicated that choosing the inbred lines with high iron (zinc) content and
with higher mid-parents values might improve the iron (zinc) content of hybrids. Otherwise, iron
and zinc content showed a significantly positive correlation for inbred lines and hybrids, which
suggested that it should be feasible to improve the iron and zinc content of maize kernel at the
same time.