Feature

THE JAPANESE AND RICE

The varieties bred andrice produced by NARO:
left: Eminokizuna; center,Koshihikari; right, Itadaki

Rice Breeding
Past and Present
The objectives of rice breeding in Japan havechanged over time, reflecting the social conditions that prevail. An initial focus on yield gave
way to a focus on eating quality, shifting in more
recent times to high-yield and good eating quality rice produced at low cost for home markets aswell as for export. Today, the accomplishments oftechnology over more than a century are expected
to help improve the world’s food situation.

KATO KYOKO

T

he cultivation of rice in paddies in Japanis said to have started about 3,000 years
ago. Until the Meiji period (1868–1912),
people bred rice varieties by selecting
those that were best suited to their region fromamong the mutants that had arisen by a rare natural mutation. Since this was not based on genetics,
rice breeding progressed slowly, and farmers often
had to deal with poor harvests when crops weredamaged by cold weather or pests, often resulting
in deaths due to famine. All people could do waspray for a successful rice harvest.
At the end of the nineteenth century, the Japanese government established agricultural experiment stations and the full-scale breeding of rice
began with the aim of improving its yield, disease
resistance, cold resistance, and so on. The firstsuperior variety produced by artificial crossing inJapan, Rikuu 132, was developed in 1921. Rikuu 132
is a hybrid that is resistant to cold-weather damage
and has good eating quality. Koshihikari, Japan’s
top-ranking rice bred in 1956, is the descendant ofRikuu 132.
Ishii Takuro, Director of the Division of RiceResearch, Institute of Crop Science, at the National
Agriculture and Food Research Organization
All photos: Courtesy of NARO

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(NARO), says, “Currently, there are more than 300
varieties of rice grown in Japan. Koshihikari accounts
for the largest percentage (33.9%) of the area planted
in 2019. The most widely grown cultivars after
Koshihikari are Hitomebore followed by Hinohikari,then Akita Komachi and Nanatsuboshi. These are alldescendants of Koshihikari and are the most popular
rice varieties with consumers.”
Until the period of high economic growth, thepurpose of breeding was yield to achieve self-sufficiency of rice. However, the emergence of rice overproduction in around 1970 brought a shift toward
prioritizing eating quality. Despite the drawbacks ofKoshihikari, namely lodgingi during cultivation andsusceptibility to disease, it has become popular for
its plump cooked rice, sticky texture, and its richumami taste that suits the Japanese palate. Ishii says
it has become important to breed varieties that havegood eating quality while also being high-yield anddisease resistant, reducing production costs.
“Restaurants and take-out food establishments
demand rice that is reasonably priced and tastes
good. One technique that has been introduced tolower production costs is direct seeding, whichmeans sowing seeds directly into the rice paddies
rather than using the conventional method of growing seedlings first and then planting them in thefields. Chihominori, developed by NARO, is a highyield and tasty variety with short plant height andresistance to lodging, making it suitable for direct
seeding. More and more growers in Japan are now
introducing the direct seeding technique, especiallythose with large-scale operations.
With Japanese food such as sushi spreading
around the world, rice breeding is also being carried out with an eye to export. Eminokizuna, one ofthe varieties bred by NARO, is suitable for sushi ricebecause when cooked it is less sticky so sushi vinegar can penetrate the cooked rice well and the grains
separate easily, imparting a light texture. Emino­kizuna is now being exported, mainly to Singapore
and other Asian countries.
There is a demand too for varieties that cope withglobal warming. If the temperature is too high in the

Rice immediately before and after harvestingsummer when the grains are developing and growing, the grains become chalky and the quality drops
significantly. At the same time, there is still a risk ofcold damage, so NARO is researching varieties thatcan cope with both high and low temperatures.
“From 1998 to 2004, the rice genomeii wassequenced by an international consortium led by
Japan. Based on this information, it is now possible
to determine characteristics such as the disease
resistance of a rice plant simply by extracting DNA
from its leaves. Selection techniques that use ricegenome information could make a significant contribution to the world’s food situation, by enabling
efficient breeding of varieties with the purpose ofimproving disease resistance and yield,” says Ishii.
The rice breeding techniques developed in Japanover many years are expected to offer major benefits
for the world at large.
i The weakening of plant stems under the weight of grain.
ii Sequence of the four types of bases inside a nucleic acid molecule: adenine (A),thymine (T), guanine (G), and cytosine (C).

NOVEMber 2020| 11