A Database for Triticeae and Avena
Faculty of Agriculture, 1-1 Yanagido, Gifu 501-1193 Japan.
Wheat Near-isogenic Lines (156 pp, Sankeiha, Nagoya, Japan;
ISBN 4-88361-131-0) have been the theoretical basis to catalogue
the NILs of the spring wheat Novosibirskaya 67 developed by S.
F. Koval and V. S. Koval and durum wheat LD222 developed by N.
Watanabe. Near-isogenic lines developed by the other research
groups also have been included. The book is available upon request
to the author (E-mail: firstname.lastname@example.org). See p. 13 for further information.
A NIL for brittle rachis in Ae. tauschii is now available.
Aegilops tauschii is diploid species and donor
of D genome to hexaploid wheat. The tough-rachis mutant of Ae.
tauschii is known as a spontaneous mutant. The tough-rachis
mutant was used as a recurrent parent. The isogenic pair can
be utilized as material for studying the domestication of wheat.
JAPAN INTERNATIONAL RESEARCH CENTER
FOR AGRICULTURAL SCIENCES (JIRCAS)
Tsukuba, Ibaraki 305-8686, Japan.
Hexaploid wheat appeared about 7-10 thousand years ago in the
Middle and Near East (the west coast of the Caspian Sea) and was
then transmitted from its origin to Europe, Africa, southern Asia
(Pakistan, India, and Nepal), and China. We know that some hexaploid
wheat varieties were transported along the Silk Road through China
to the Far East and Japan. Little is known, however, about the
actual route of transmission of hexaploid wheat into Japan.
In this study, we analyzed the distribution of the Glu-D1f
allele throughout Asia to determine the route by which hexaploid
wheat reached Japan, the most geographically remote region of
hexaploid wheat production in the world. These studies concentrated
predominantly on the variation of the HMW-glutenin Glu-D1f
allele and the factors that affected its distribution in different
parts of the world. The allelic composition of the HMW-glutenin
subunit from 131 improved Japanese cultivars and 174 Japanese,
353 Chinese, 150 Turkish, 3 Syrian, 6 Israeli, 4 Iranian, 1 Iraqi,
23 Indian, 15 Pakistani, 7 Bhutanese, 66 Nepalese, 1 Myanmar,
1 Filipino, 2 Thai, 3 Indonesian, 46 Taiwanese, and 21 Afghani
landraces of hexaploid wheat were investigated using SDS-PAGE.
The 353 Chinese wheat cultivars were from Heilongjiang, Jilin,
Liaoning, Hebei, Beijing, Shandong, Shanxi, Hangzhou, Zhejiang,
Henan, Jiangsu, Ningxia, Gansu, Xinjiang, Sichuan, Anhui, and
Jiangxi provinces. The Japanese, Chinese, and other Asian hexaploid
wheat materials were provided by the National Institute of Agrobiological
Resources (NIAR) at Tsukuba in Japan.
The Glu-D1f allele has been reported to be a rare allele
when studying the worldwide distribution of Glu-1 alleles.
Data also indicate that the products of this allele are more
common in Japanese wheat seed-storage proteins than anywhere else
bread wheat is grown. We have shown that the Glu-D1f allele
is more common in Japan than elsewhere in Asia. The allelic frequency
of this subunit is in excess of 35 % among improved Japanese cultivars
and 25.3 % among Japanese landraces, whereas it was found in only
five cultivar of Chinese (two Xinjiang, one Jiangsu, one Zhejiang,
and one Beijing cultivar) and two Afghani wheats.
The carriers of the Glu-D1f allele are distributed across
a limited region of Asia, only in southern (Kanto, Tokai, Kinki,
Chugoku, Shikoku, and Kyushu areas) and northern (Hokkaido, Tohoku,
Hokuriku, and Nagano areas) Japan; in Xinjiang (northwest), Jiangsu
and Zhejiang (southeast), and Beijing (northeast) China; and in
Afghanistan. However, the allele is rare in wheat varieties from
north Japan, China, and Afghanistan. The frequencies of Glu-A1,
Glu-B1, and Glu-D1 alleles in hexaploid wheat cultivar
from different countries are known to differ. A noticeable geographical
cline has been reported in the frequency of the Glu-D1f
allele in Japan. To elucidate the factors involved in the establishment
of this cline, I investigated the association between the occurrence
of the Glu-D1f gene with winter habit and with flour hardness.
Because the Japanese islands extend a considerable distance from
north to south, they provide a diverse range of environments in
which wheat is cultivated. Improved Japanese cultivars and different
locally grown landraces are diverse in their type of winter habit.
The degree of winter habit in Japanese wheats is the most important
factor for hexaploid-wheat production. Generally, the weaker
winter-habit wheat cultivars are grown in southern Japan and those
with a stronger winter habit are grown in the north. A strong
correlation was observed between the intensity of the winter habit
and the occurrence of the Glu-D1f allele. Improved cultivars
with weaker winter habit tended to have the Glu-D1f allele
more frequently than those with strong winter habits, whereas
the allele was absent in the cultivars with the strongest winter
The Glu-1 alleles were previously reported not to be
associated with ecogeographical parameters in a worldwide context.
However, results from our studies suggest that the Glu-D1f
allele is associated with ecogeographical parameters within Japan,
a finding of great interest to Japanese wheat breeders and cereal
chemists. In Afghanistan, Xinjiang in northwest China, Jiangsu
and Zhejiang provinces in southeast China, and in southern Japan,
spring and facultative types are sown in the autumn or in the
spring, respectively. This type of cultivation is specific to
these regions. Genotypes that were suitable for this type of
hexaploid-wheat cultivation in China may have been selected for
during the process of transmission to Japan. All cultivars with
the Glu-D1f allele in northern Japan are sown in the autumn,
both spring and facultative types. These results suggest that
there are no other wheat cultivars in any other region in Asia
that possess the Glu-D1f allele.
Until recently, Japanese hexaploid wheat breeders did not manipulate
the Glu-1 alleles intentionally. Japanese hexaploid wheat
is characterized by the high frequency of alleles such as Glu-D1f.
Natural and artificial selection in Japan is thought to have
narrowed the genetic base of Japanese hexaploid wheat and this
conclusion is supported by the frequent occurrence of the Glu-D1f
allele. The unique composition of Glu-1 alleles in Japanese
hexaploid wheat will be of considerable interest to both Japanese
wheat breeders and cereal chemists. Japanese, hexaploid wheat-breeding
objectives mainly determine the requirements for the production
of soft white noodles (Udon) in areas where they are eaten frequently.
On the other hand, in areas where bread is more commonly consumed,
the similarity in Glu-1 allele composition among countries
seems to be mainly determined by similar breeding objectives.
This study has shown that the Glu-1 allele frequencies
differ between noodle-culture zones such as Asia and bread-culture
zones such as Europe and the U.S.A. The Glu-1 alleles
are reported to directly affect wheat-gluten quality. Therefore,
in Japan, Japan-specific differences in Glu-1 patterns
are likely to occur because of the intensity of selection pressure
towards good, soft noodle-making qualities as compared to selection
for good bread-making qualities.
In the course of its long journey and adaptation to diverse
local environments, Japanese hexaploid wheat appears to have depleted
its genetic diversity. The frequency of the Glu-D1f allele
differs between the Japanese and the other Asian, hexaploid-wheat
cultivars. Therefore, all Japanese wheat cultivars possibly have
a common heritage, which explains the similarities in Glu-1
patterns for all Japanese wheat. There were four routes by which
people moved across Asia in ancient times. The first of these
routes, the so-called Silk Road, ran through Afghanistan; Xinjiang
(northwest), Gansu and Shanxi (northeast), and Jiangsu and Zhejiang
(southeast) provinces in China, eventually reaching Japan. The
second route ran through Pakistan, India, Myanmar, and then to
the Yunnan province in China. A third route ran through Nepal
or Pamir, Tibet, and into the Sichuan province in southwest China
or the Shanxi province in northeast China. The final route was
directly into southern China by boat from India. The distribution
of the Glu-D1 alleles is very interesting considering these
four routes across Asia. Of all the Glu-D1 alleles, Glu-D1a
and Glu-D1f are common in Japanese hexaploid wheat. The
Glu-D1a allele was common in wheat cultivars from all over Japan,
whereas Glu-D1f is present predominantly in the south.
This finding may suggest a transmission pattern for hexaploid
wheat in Japan. The first hexaploid wheat (characterized by Glu-D1a
or Glu-D1f alleles) arrived in Japan and became distributed
across southern Japan. Wheat was then distributed northwards
through Japan. As a consequence, northern Japanese hexaploid
wheat cultivars predominantly have the Glu-D1a allele.
This allele is linked to a gene that makes the wheat suitable
for cultivation in the colder winters of northern Japan. The
Glu-D1f allele is not linked to this trait. The high frequency
of the Glu-D1f allele in southern Japanese wheats may be
due to the selective advantage conferred either by Glu-D1f
itself or by the action of another linked gene. Whichever gene
is responsible, it confers a trait that is suitable for cultivation
in southern Japan, such as the intensity of winter habit or be
responsible for wheat-flour quality.
The Glu-D1f allele has been regarded as a characteristic
glutenin allele for Japanese hexaploid wheat cultivars. In fact,
although many hexaploid wheat cultivars in southern Japan possess
Glu-D1f, most of the northern Japanese cultivars do not.
By comparison, a-amylase isozyme types shows that both types
A and J are common in Japan. Type A was found throughout Japan,
whereas type J was present predominantly in southern regions.
This distribution of a-amylase isozyme types is similar to that
of Glu-D1f alleles in Japanese hexaploid wheat. In this
study, the specific distribution of an adaptively neutral characteristic
(the Glu-D1f allele) suggested a transmission route for
hexaploid wheat into eastern China and far-east Japan. Introduced
from Afghanistan, Glu-D1f moved through the Xinjiang province
in northwest China, into the Jiangsu and Zhejiang provinces in
southeast China, and then into southern Japan along the so-called
Silk Road. The results presented here indicate that analysis
of the Glu-D1f allele is a powerful tool for investigating
the real transmission routes of hexaploid wheat across Asia and
into far-east Japan.
Acknowledgments. The author thank Drs. T. Hayashi and
H. Fujimaki for helpful discussion and comments. Thanks are due
to National Institute of Agrobiological Resources (NIAR) at Tsukuba,
Japan, for providing hexaploid wheat samples in this study.