In many parts of Japan, researchers are working to develop new varieties and cultivation methods to cope with heat waves and other extreme weather events linked to global warming.
Recently, droughts have caused frequent spikes in grain prices around the world, prompting concern over a potential worldwide food crisis as the world’s population increases. Under these circumstances, preemptive measures against global warming will attract great interest.
Improvements to cultivated varieties
The Shiga Prefecture Agricultural Promotion Center launched Mizukagami rice last autumn. “The variety is resistant to extremely hot weather and has a wonderful taste. [With this rice] we can deal more effectively with future global warming,” said Yoshihiko Yamada, a deputy technical manager at the center.
Normally, extended high temperatures in summer cause the flavor of rice to deteriorate, and rice grains become a cloudy white. In the prefecture, located in western Japan where high temperatures are common, the ratio of rice classified as “itto mai (first-class rice)” has fallen below the national average since the late 1990s. In 2010, a year with many extremely hot days, the national ratio of top-class rice dropped to 62 percent from the previous year’s 85 percent, and Shiga Prefecture saw an even sharper decline from 79 percent to 40 percent.
In the past, development of new rice varieties has focused on producing rice resistant to cold weather. For example, cold-tolerant Hitomebore rice grew common after Sasanishiki rice harvests were affected by cold weather.
“We [now] face an age when rice resistant to high temperatures is required,” a senior official at the Agriculture, Forestry and Fisheries Ministry said.
In 2009, the Shiga prefectural government enclosed a rice paddy in a vinyl greenhouse, creating an indoor environment with an air temperature 2 C higher than that outside. The local government used the field to grow about 200 varieties of rice and ultimately selected the Mizukagami variety, a cross of Hinohikari, Hitomebore and several other rice varieties.
The itto mai-class ratio of Mizukagami harvested last autumn was 87.9 percent as of the end of January, above the national average of 79.2 percent, and far surpassing that of Koshihikari rice produced in the prefecture at 61.3 percent.
In February, Mizukagami received the top “special A” ranking from the Japan Grain Inspection Association in its rice-tasting test for crops harvested in 2013, in which it was tested as a reference rice variety. Among other varieties that received the special A ranking, many are resistant to high temperatures, including Mori no Kumasan produced in Kumamoto Prefecture and Sagabiyori in Saga Prefecture.
New fruits for warmer climates
In anticipation of rising temperatures, some areas have introduced fruit suited to a warmer climate.
In Tobishima, an island in the northernmost part of Yamagata Prefecture, sudachi citrus was harvested for the first time in October. The fruit is mainly produced in Tokushima Prefecture. While the island does not offer a warm climate suitable for sudachi cultivation, it is believed to take at least 50 years of research and work to disseminate the fruit after sudachi trees are introduced.
“If we wait until temperatures actually increase, it will be too late,” said an official at the Yamagata prefectural government’s agricultural technology and environment section. “We also have started test-planting lime and lemon trees, with an eye toward ‘exploiting’ global warming.”
In the southern Boso Peninsula in Chiba Prefecture, cultivation of subtropical passion fruit started in 2007. About a dozen farmers have planted passion fruit trees, partly in the hopes of making the fruit a major attraction of a tourism-oriented farm in the future. Aichi Prefecture has introduced a yellow-green grape called shine muscat, as darker grapes have suffered from color imperfections due to high temperatures.
Genetic resources from abroad
Researchers have also looked overseas to plants that do not exist in Japan for use in the development of new varieties of crops. Crops including rice, eggplants and cucumbers originated in the Asian mainland, and it is believed that extensive genetic diversity remains in the region.
An agriculture ministry project will start a joint research with other Asian countries by supporting domestic research institutions and other bodies beginning next fiscal year. The project is aimed at discovering useful genes that have been difficult to isolate using the technological capacity of the countries involved, including genes that offer resistance to high temperatures, diseases and pests. Thailand and Vietnam are likely candidate sites for the project.
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