Friday, December 16, 2016

In search for hay-fever-less trees in Japan



Because of historical and cultural reason, direct engagement in forest management is one item in the job description of all the prefectural governors in Japan. Anyway, it gives Dr. Hidetsugu Saitoh of Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター a job to improve reproductive process of trees in Kanagawa. One urgent to do list for him is to establish supply system of seedlings for cedar and cypress that produce fewer or no pollen, since their pollens are major allergen of hay fever for the mass of people these days.


Using Mendel’s Law, the methodology of creating such cedars and cypresses is relatively straight-forward. ... I didn’t know using male sterility is a well-established way to create “higher utility” crops and veggies. The defining gene for pollen counts in cedar and cypress is like human genes about blood types. Let’s call “AA” the gene of cedar that creates lots of pollens. We can also find “aa” gene in another cedar that does not produce pollen at all (i.e. “male sterility”). From here, it’s a high-school biology class. If we can match over 2 “aA” trees, there is ¼ chance of producing “aa” tree that is pollen-less. i.e. Recessive Inheritance. Better still, when a mom has “aa”, the chances of “aa” baby coming out is 50%. (… We can never have an “aa” dad, OK?) It’s same for cypress. So, the challenge for Dr. Saitoh is to make the plan operational.

The experimental scion garden for few / no pollen cedars
in the Kanagawa Natural Environment Conservation Center

Although, say, in 2010 cedar afforestation was done only for 1ha in Kanagawa, people did not plant just one tree in 100m*100m field. Actually, 13,000 cedar babies from “fewer pollen” lineage was planted in that year, where many of them will be thinned eventually. Moreover, trees are long-living plants that are definitely different from Mendel’s peas whose reproduction cycle can be less than one year. The number of original fewer pollen family lines was 17 in Kanagawa. Sure, it could be a matter of opinion if the biodiversity is enough at the gene level with 17 families for 13,000 seedlings of slowly maturing species … Everybody agrees the more diverse, the better the sustainability. “We need more families of aA and aa mom-trees.”

The cedars in the experimental scion garden in the Center

In Japan, a person who first found aa cedar tree in 1992 was Dr. Hideaki Taira who is now the professor emeritus for Niigata University. Dr. Taira’s approach was a standard mass-mobilization of college kids. They were dispatched into the deep forests of Toyama Prefecture early spring, each armed with a high-twig shear. They tap a flowering cedar one by one. When a tree was looked like emitting fewer or no pollen, the kids collected male flowers from the high-above twigs and brought them back to the Professor’s labo to inspect each anther under electron microscopes. The result was, statistically speaking, one in 5,000 cedars in Toyama has male sterility. … I haven’t read Dr. Taira’s celebrated paper, but I guess for reaching to this conclusion the army of kids must have tapped tens of thousands of cedars, and carried tens of thousands of anthers for checking. Even under a luckier scenario, Dr. Saitoh has to tap 5,000 cedars to identify one “aa,” doesn’t he? Fortunately, along with this “go fishing” approach, Dr Saitoh could use 17 families of aA in Kanagawa. He checked 888 (yet!) seedlings in the scion garden and found one aa in 2004. As of October 2016, the prefectural scientists who found their local sterile males in cedar forests are in Toyama, Ishikawa, Shizuoka, Oamori, and Kanagawa, i.e. 5 prefectures out of 47 … hmmmm, it’s a difficult task. Dr. Saitoh has managed it and is still searching for more aa.

The young cedars and cypresses in the Center’s field.
They are still too young to be moved to the scion garden.

Finding a tree is one thing. Preparing for the replacement of allergen spewing forest is another. The next task for Team Saitoh is realizing the mass production of aa cedar seedlings. Dr. Saitoh paired the pistil of this aa with aA pollen in a secluded glass house for controlled fertilization. It takes one more year after pollination for cedars to produce a fruit. He harvested 92g (2007) and 37g (2008) of seeds eventually. The Team then sowed the seeds in the professional cedar seedling farm (who is under the strict national regulation; more to this in the later post J). Cedars take 2 years from seeds to seedlings for planting. In the 2nd year, the Team Saitoh manually collected the male flowers from all the 4,816 seedlings to see if any of them were sterile. In the end, there were 1130 male sterile seedlings (39% of total). Dr. Saitoh keeps producing cousins for the 39% from the first aa and the other newly found aA and aa to expand the DNA pool ... His quest for achieving theoretically expected value of 50% from aa –aA is continuing ...

The fruits of cedar harvested this October.
They are handpicked one-by-one
from the trees in the scion garden.
They then are dried for a while.
Like pine, with enough dryness
they start to open their cones to release the seeds ...
Like these.

Dr. Saitoh is also doing the same for cypress … painstakingly labor intensive tasks all over again. According to him, for cedars or cypresses, the entire process is sometimes difficult to be understood by his non-scientist peers. Going into forest to tap trees, coming back to shut yourself for microscopic study, fertilize tiny flowers one-by-one by hands in a quiet glass house, harvesting Ø1cm cones in fine October day, tending carefully the seedlings in the fresh-air garden … all sounds quite a fun for uninitiated office workers. Especially for cypress, the pollen season of theirs is short and overlaps with the transition period of Japanese fiscal years. His office being in bureaucracy, the people are very busy to wrap up previous year’s documentations when Dr. Saitoh says “I go to mountain for cypress.” An inevitable reaction, it seems to me, has been “WHAT!?” I myself did not know harvesting cedar and cypress cones make your hands bruised with lots of scabs and hard-to-remove tree resins ...



The lesson learned from Japanese hay fever and Dr. Saitoh’s struggle is, once we’ve messed up with the nature it can bring us unintended consequences that is difficult to modify. We patients can only treat symptoms from the attack of pollens … We forest volunteers may be able to do something more, I guess. The easiest thing I can think of now is, joining afforestation exercise with aa cedars, or broadleaved trees … Planting trees are not that simple, in the end.


Seeds are sown first in pods.


The contact address for Kanagawa Natural Environment Conservation Center 神奈川県自然環境保全センター is

657 Nanasawa, Atsugi City, 243-0121 2430121 厚木市七沢657
Phone: 046-248-0323

You can send an enquiry to them by clicking the bottom line of their homepage at http://www.pref.kanagawa.jp/div/1644/

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