National / Science & Health

Okayama researcher boasts nontropical banana success

Kyodo

Bananas grown in Okayama Prefecture, where the temperature drops below zero in winter, are attracting attention at home and abroad.

After some 40 years of research, Setsuzo Tanaka, 69, who had no farming experience, developed a method of making bananas survive cold weather by using plants that were slowly frozen. His work enables the cultivation of the fruit outside tropical or subtropical regions.

“They look splendid, don’t you think?” said Tanaka in December, after the city of Okayama went through some extremely chilly days, as he showed off bunches of bananas at the greenhouse of an agricultural corporation D&T Farm.

Named Monge, meaning “super” in the Okayama dialect, the banana was developed based on Gros Michel — a variety that had been widely grown worldwide until about 50 years ago. Monge bananas are often sold out, even though a box of three sells for a hefty price of ¥4,860, as the pesticide-free fruit is gaining popularity for its rich and sweet taste and edible skin.

“I wanted to grow bananas myself so that I can eat them as much as I want,” said Tanaka, explaining why he first set about the research in his 20s, at a time when bananas were a luxury food.

He used the funds he gained from his shipping and shipbuilding business to try cultivating bananas. He brought banana plants from Okinawa and planted them in a greenhouse warmed by a heater, but the plants failed to survive.

Then he came up with a different idea while watching a TV program about fossil cycads.

Since tropical plants survived the Ice Age, he thought if he put a banana plant in a similar environment, he might be able to bring out in banana plants the same ability to adjust to cold weather.

After failing to recover banana plants that had been placed in a freezer or in liquid nitrogen, he tried soaking parts of the plants in a special liquid and freezing them slowly by gradually decreasing the temperature of a freezer to minus 60 degrees Celsius over six months.

The plants that went through this freezing procedure managed to grow. In fact, he found that they grow faster than typical bananas and that more fruit can be harvested in a shorter period. He said the method could be used with other tropical plants, such as coffee beans and papayas, and that the crops can be cultivated mostly without pesticides.

Although the bananas can be cultivated outdoors, he grows them in a greenhouse to protect them from typhoons.

Tanaka established a company in 2015 and began full-scale production last year.

“I hope crops will be grown in cold places with large plots of land, such as Siberia, to provide food to people around the world,” Tanaka said.