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Wheat Information
Service
Number 76:45-48 (1993)
The
simple method for testing grain fading tolerance and mechanism of
fading in wheat
Y. Taniguchi, M. Fujita and K. Ujihara
Department of Lowland Farming, Kyushu National Agricultural
Experiment Station, M.A.F.F Chikugo, Fukuoka 833, Japan
Wheats are harvested during the rainy season in Japan, thus grain
colors are often faded by rainfall and the grain quality is
deteriorated. In this study, we developed a simplified method for the
evaluation of grain fading in wheat cultivars by rainfall and
selected the tolerance gene sources. Hear after, it will be released
the cultivars of high grain fading tolerance by those method and gene
sources, and search possibility of breeding cultivar which has
tolerance for rain damage in respect of flour quality thorough the
study of grain fading tolerance.
Evaluated method of grain fading tolerance
It was investigated a method that steep the ears of wheat in
distilled water in order to make artificial faded grain.1) In this
method, mature ears were cut at the sheltered field against rainfall.
These ears were dryed in the sun for two days and they were stored by
a low temperature for two weeks, and they were steeped in distilled
water for 8, 16, 24, 48 hours in order to fade grains. After being
dried up, these ears were threshed, and the faded degree of threshed
grain were classified into six gropes by observation and were
measured by a color meter (L*a*b*). By using this method, it
confirmed the varietal differences in grain fading tolerance. In
faded grain color, it was found that the value of L* (luminosity)
increased, the value of a* (reddish) decreased and the value of
DeltaE*ab (difference of color between normal grain) increased. The
value of b* (yellowish) also decreased, but the correlation between
these degrees of decrease and faded degrees by observation was low.
It was found that faded degrees had highly correlated with the value
of DeltaL* and DeltaE*ab, this indicated that faded degrees could be
evaluated by the value of DeltaL* and DeltaE*ab. Artificial faded
grain color by this method had slightly higher value of a* than
naturally faded grain color, but directions of both color changes
were almost same (Fig.1).
These results indicated that this method could be used generally for
to evaluate.of grain fading tolerance. the grains from ears cut
before maturing stage had lower faded degrees than grains from ears
cut at maturing stage, and grains from ears cut after maturing stage
had higher faded degree than its. The grains from ears which was not
dryed up after cutting had not faded too mutch. The grains from ears
which had been wet in field without shelter from rainfall had higher
faded degree.
Mechanism of fading
It investigated to clearly the mechanism of fading why they
looked as faded color. In this examination, threshed grains (20g)
from ears were cut at maturing stage time and were steeped in
distilled water (100ml) for 24 hours, then these grains and color of
water were measured by a color meter, and glassiness of grains were
also measured. As a result, it was observed that there were the
varietal differences in the concentration of exuded color in water,
and it was associated that this exudation was related with fading of
grain, but no correlation between concentration of exuded color and
degree of fading was observed (Table1).
However, we need another examination in consideration of original
grain color, because it seems that there was no correlation by the
differences of original grain color among varieties. the glassiness
of steeped grain had been lower than glassiness of original
(Table
2). Generally,
mealy grain looked pale color, therefore it was thought that decrease
of glassiness was related to the fading.
Relation between faded degree and flour quality
The stock harvested at maturing stage in field were steeped in
water for 24 hours immediately after harvest, and after dried up by
sunlight, they were steeped in water again for 24 hours. After dried
up by sunlight, stock were threshed and these grain were milled by
brabender junior testmill. In all cultivars, flour yield of faded
grains were lower than normal grains (Table
3). Then faded
grains had lower ash content and protein content and better
brightness of flour than normal grain. It was cousidered that these
fluctuation were caused by low flour yield. Maximum viscosity became
lower, but the degree of decrease make no problem in practical use.
Therefore in this experiment, it was proved that only flour yield had
become by fading.
Reference
Taniguchi Y, M Fujita and K Ujihara Evaluation of grain fading
tolerance of wheat by rainfall (point of lecture). Japan J Breed 42
(supple 2): 392-393.
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