In Japan, heat-resistant rice varieties becoming more common

SAITAMA VARIETY: Yoshitaka Funakawa checks a paddy where young rice plants are growing on June 12 in Satte, Saitama prefecture, Japan.

Concerns over crop damage due to global warming have spurred the development of heat-resistant rice varieties around Japan.

While these varieties are grown in less than 10% of the total area cultivated for rice used as a staple food, the hectarage has increased by about 2.5 times since 2010.

Several of these varieties have received high taste assessments and many believe they will only become more widespread going forward.

In late May, an agricultural corporation was planting a paddy in Satte, Saitama prefecture, with heat-resistant variety Sainokizuna.

"It withstands hot weather and tastes good," company president Yoshitaka Funakawa, 68, said.

Sainokizuna is a Saitama variety that was registered in 2014. Its brown rice tends to maintain high quality and harvest levels even in high temperatures. The Japan Grain Inspection Association gave it the highest grade – toku-A – in its 2017 taste ranking, the same grade as given to Koshihikari from Niigata prefecture.

About 19,480 tons of Sainokizuna was harvested in 2018, about 13% of the about 150,000 tons of rice that was harvested in Saitama prefecture that year.

Summers recently have been brutally hot. Taking Koshihikari – a common, good-tasting variety that is grown nationwide – as an example, if temperatures are high during the time when the ears of rice emerge, the quality of brown rice decreases.

Sainokizuna, however, has greater capacity in terms of moisture evaporation from pores in the surfaces of the leaves, which lowers the temperature from the heat of vaporization.

In 2018, which saw "disaster-level heat," the percentage of grade-one rice, which refers to the ratio of rice in the harvest that is of the highest quality, for Saitama Koshihikari was 21%, compared to 84% for Sainokizuna.

Tochiginohoshi, a Tochigi prefecture variety that was registered in 2015, has received the toku-A grade three times, in 2015, 2017 and 2018. The percentage of grade-one rice in 2018's 22,500-ton harvest was 98%. It was grown on 8% of the total hectarage in the prefecture, the third-biggest variety by area.

"The quality is good and harvests are big, so more farmers are growing it," an official at the Tochigi Prefectural Agricultural Experiment Station said.

Natsukirari, an Aichi prefecture variety that is said to taste similar to Koshihikari, was registered as a variety in 2017 and is undergoing test cultivation.

Rising temperatures

According to a February 2018 report by the Environment Ministry and others, average temperatures in Japan have risen by about 1.2 degrees Celsius in the last 100 years and are predicted to rise by as much as 5.4 C in the 21st century.

Rice harvests in the plains of the Kanto region and in the Hokuriku region and westward are expected to drop, which is behind the push to develop heat-resistant varieties.

Heat-resistant varieties were grown on about 37,700 hectares nationwide in 2010, and on about 93,800 hectares in 2017, according to the Agriculture, Forestry and Fisheries Ministry. This equals to about 7% of the 1.37 million hectares cultivated for rice as a staple food in 2017.

"It is believed that warming will continue, which will make it necessary to switch from conventional varieties to resistant varieties," said Hiroyuki Sato, 50, a senior program officer at the Agriculture, Forestry and Fisheries Research Council.

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