The white maitake
Turn the impossible into reality
CHALLENGE The Development Story of “Yukiguni Maitake
Kiwami White”

*Departments and titles are as of the time of the interview.

KIWAMI
WHITE

In August 2022, “Yukiguni Maitake Kiwami White” made its debut. Developers who had been challenged by white maitake since the 1990s—and by the strains they developed in-house—share their stories. In the research and development labs, in the factories conducting mass-production trials, their intersecting thoughts now come together in conversation.

C H A P T E R One

Production Sites Struggled with the Highly Rare White Maitake

"In the 2000s, white maitake
were truly treated as
troublemakers at the production sites."

Section Chief, Bio Center No.1
Katsunori Mukaikawato

“In the 2000s, white maitake were truly treated as troublemakers at the production sites,”
said Katsunori Mukaikawato, who was involved in mass production at the factory.
Maitake —once called “phantom”—was successfully mass-cultivated in the 1980s.
The production of white maitake, even rarer than ordinary maitake, had begun in the 1990s.
At the time, we were using Strain S, obtained from a seed manufacturer. The production teams struggled with it.
Maitake that was supposed to be white sometimes turned black. At times, every cultivated batch ended up with a panda-like pattern of black and white.
They once planned a large promotional campaign to launch white maitake on the market all at once, but the product never materialized, causing the entire event to be canceled. Mukaikawato was right in the middle of that turmoil.

"We tried to manage it through cultivation conditions, but it was hopeless. The caps frequently turned black. During mycelial growth, sweat-like metabolites appeared and turned the mushrooms yellow. Once that happened, we couldn’t ship them. When shortages occurred, the sales staff rushed to the factory, and when we told them “There’s nothing we can ship,” they replied, “We know you don’t have mushrooms— so just give us mushrooms!” It’s still a story people talk about today."

We asked the spawn manufacturer to improve the unstable and uncontrollable strain,
but it was difficult, and progress was slow.
So in 2009, they decided to begin producing white maitake spawn in-house.
From 1995 to 2000—five years—the R&D Department developed their first proprietary strain, “Kiwami (Y10M).”
Harumitsu Kojima, who had led that effort, applied his experience to the development of white maitake as well.

"First, we performed tissue isolation on Strain S, whose breeder’s rights had already expired, producing many candidate strains. Using our proprietary techniques, we selected superior strains, reducing a once-high incidence of colored maitake to just a few percent."

General Manager, R&D Department
Harumitsu Kojima

C H A P T E R Two

Desperately Searching Through Past Research Data

We managed to reduce the occurrence of mushrooms whose caps turned black. With supply stabilized, full-scale sales began, and within the company this was considered a temporary success, so production continued using improved versions of Strain S.
However, as sales increased, new concerns emerged. The caps crumbled easily, and the texture was unsatisfactory.
This brought out attention back to Strain Y10M, developed by Kojima.
We wondered: if white maitake could be produced from Y10M—with its firm caps and crisp texture—would the results be better?
The R&D team began their research using the partially white maitake that occasionally appeared as spontaneous mutations during Y10M production.
Unfortunately,there was only a limited number of these rare, occasional white maitake, and the white variants had difficulty opening their caps cleanly, making them hard to cultivate. Time passed without producing the desired results.

In 2015, six years after the start of in-house production of white maitake spawn, a major development occurred.
A change in top management brought a shift in perspective and direction.
The company’s main product, maitake, was fully switched to the in-house strain Y10M, and the product name was changed to “Yukiguni Maitake Kiwami.”
This shift once again brought attention to white maitake.
Top management ordered renewed research into white maitake derived from Y10M (the Kiwami strain).
In 2016, Takafumi Shimoda took command of the project within the R&D Department.

Manager, R&D DepartmentTakafumi Shimoda

"When Y10M was developed, I was told that our predecessors gathered many wild maitake from mountains within the prefecture and from the Tohoku region. But white maitake are rarely found in the wild, nor are they sold. In the end, we had no choice but to rely on the white mutations that appeared in the factory."

Manager, R&D DepartmentTakafumi Shimoda

Shimoda carried out breeding efforts using the white maitake that appeared from Y10M.
He repeatedly experimented and had promising candidates tested at production sites.
However, his efforts yielded no results. In less than a year, Shimoda had exhausted all his options.
He struggled, searching desperately through every document he could find.
Then, suddenly, he remembered data from earlier strain development. Reviewing records from the initial stages of white maitake research, he found a note from his predecessor stating, “This strain is good.”
It was a white variant of Y12M, the “grandchild” of Y10M.
Shimoda revived that strain, crossing the preserved white variant of Y12M with Y10M. The result was Y14M. When grown experimentally, it produced unexpectedly good white maitake.
In subsequent bag-cultivation trials at the factory, beautiful clusters emerged—almost as if “Yukiguni Maitake Kiwami” had turned white.
Shimoda rushed to Kojima and reported his findings. “Let’s investigate this further,” Kojima said, and the trials continued.

C H A P T E R Three

A Battle of pride: Developers vs. Production Sites

Once expectations were placed on Y14M and mass-production trials began at the factory, hopes were quickly shattered. In both winter and midsummer, the white maitake developed poor shapes.
In truth, the R&D team already knew from trial cultivations that Y14M required extremely strict growth conditions. If the conditions deviated even slightly, not even maitake buds would form—such was its “selfish” nature.
Even so, after a year of testing, factory-level trials were underway.
Shimoda’s hope that things would somehow work out was crushed. He and the R&D team asked the production site to adjust lighting, change airflow, and modify various temperature-control settings.
Based on the results, they devised new approaches. This cycle repeated, consuming time. It was a difficult phase for Shimoda and his team, but the factory conducting the mass-production trials was equally frustrated. Mukaikawato confides:

“During the trial cultivations, nothing resonated with me at all. I thought, ‘This is exactly what futility feels like.’ There is an old Chinese tale about Bole, a master at identifying fine horses. He taught the method for judging excellent horses to people he unfavored, but taught how to identify poor horses to those he favored—because knowing how to spot the many inferior horses was far more useful than identifying the rare exceptional ones. To me, the cultivation conditions Shimoda described sounded only like the conditions for a ‘excellent horse.’”

Mukaikawato conveyed these feelings to Shimoda by email. At times, their discussions became heated, with comments like, “Instead of giving vague instructions like grasping at clouds, tell us what not to do.” Shimoda also shares his feelings from that time:

“I felt I had to respond to and overcome the criticisms and emails from Mukaikawato. I wanted to meet his expectations. This white maitake was the first product I had seriously worked on since joining the company.”

Akihisa Namekata, Division Director of the Production Division, speaks about Y12M—the strain Shimoda rediscovered.

“Y12M existed only in storage within the R&D Department. It must have been rare as development material, and the fact that a white maitake happened to appear from Y12M was miraculous. Had Shimoda not discovered it, Y14M would never have been born. It was truly a fateful coincidence—nothing short of luck.”

Senior Executive Officer, Division Director of Production DivisionAkihisha Namekata

The strain they managed to grasp through trial and error was Y14M, born from crossing Y12M with another strain.
It was understandable that Shimoda could not give up on it. Eventually, mass-production trials at the factory were halted in order to search for the optimal cultivation conditions for Y14M, and the work was taken back to the R&D Department. Even then, progress in Y14M research was slow.
As a result, for a time, another competing strain became a candidate, and efforts shifted toward its development.
Still, no matter how much the project was scaled down,
the researchers continued cultivating and observing Y14M quietly and persistently.
As research progressed, the competing strain was found to develop discolored caps easily and was removed from consideration.
Another year passed through countless small adjustments and refinements. The glimmer of hope Shimoda held began to turn into conviction. The cultivation conditions that could satisfy Y14M’s “selfish nature” had finally come into view.

C H A P T E R Four

Rapid Progress in
Research and Cultivation
Under Conditions Suited for
White Maitake

With the new cultivation conditions established, Y14M entered mass-production trials at the factory once again. Mukaikawato, who had struggled with the delicate Y14M during earlier trials, was astonished by how much it had improved when he saw it again after several years.

“When mass production resumed, white maitake grew so smoothly that he wondered what all the previous struggles had been for. Thanks to this, he began to believe that Y14M could be cultivated even during the harsh summer and winter seasons. Out of several thousand test clusters, only one or two appeared dark—and that was only at the beginning. Gradually, the strain became more refined, and eventually none turned dark at all. He was deeply moved by how far it had come.”

Several issues that had been raised were resolved one after another.
For example, conventional white maitake crumbled easily when touched, but Y14M had firm caps and stems that rarely broke apart.
Previously, special fluorescent lights were needed to maintain the whiteness of white maitake, and strict attention had to be paid to the lighting conditions in the cultivation rooms. But with Y14M, such effort and concerns became unnecessary.
In addition, by adapting the cultivation conditions provided by the R&D Department to the actual factory environment, the winter-season quality concerns for Y14M improved dramatically.
Furthermore, during the development of “Yukiguni Maitake Kiwami,” they had successfully improved yield and quality by modifying the composition of the growth substrate used for mass production.
Applying the same approach to Y14M, they modified the growth substrate and collected data through mass-production trials. As a result, quality improved, and the number of days required for harvest was reduced to two-thirds of the previous time.
Toru Kawase, who currently oversees the production sites, recognizes Y14M’s potential as follows.

Director, Bio Center No.1
Toru Kawase

“The yield is about 10% higher than that of previous strains. In addition, the mushrooms do not crumble during harvesting or cutting, resulting in minimal waste and excellent cost performance. The snow-white color was also very appealing.”

Director, Bio Center No.1
Toru Kawase

The in-house development of white maitake began in the 1990s.
After more than 20 years, it finally made its debut in August 2022 as “Yukiguni Maitake Kiwami White.”
For the members who had been involved in the project for many years, it was a deeply emotional moment.
Namekata, Division Director of the Production Division,, said that there was one more factor that greatly propelled the development forward.

“In 2015, the management members changed, and the company’s direction shifted. The collaboration between the production sites and the R&D Department became much more active, and the two groups began working together using accumulated cultivation data. The fact that our in-house strain was completed relatively quickly from 2016 onward was a direct result of this coordination.”

It seems that the organizational restructuring brought benefits beyond the development of white maitake.
The momentum of individuals exchanging and refining their knowledge and techniques shows no signs of slowing.

As Kawase said this,
Mukaikawato also looked upward in agreement.

“There is still room to further improve white maitake, and I believe it’s possible. As production expands, I think we can make it happen.”

“In the breeding of Koshihikari rice, there is a saying: ‘A flaw that can be covered by cultivation methods is not a fatal flaw,’ and challenges continued under that belief. The excitement I experienced through working with ‘Kiwami’ and white maitake is something I now hope consumers can experience through the product itself.”

As a developer, this is still not the goal.

”I want to create an even easier-to-cultivate, truly “White Kiwami” that surpasses the original. I will continue my research with that mission in mind.”