In pics: Japanese superfood weed Okinawa mozuko moving towards climate resilience

Updated: Jun 09, 2022, 07:46 PM(IST)

According to scientists from the Okinawa Institute of Science and Technology Graduate University, a simple PCR (polymerise chain reaction) test might be used to improve the cultivation of the tasty brown seaweed Okinawa mozuku and even boost efforts to generate heat-tolerant strains. The PCR test detects nine genes that show the lifecycle stage and sex of the mozuku algae. 

Much-loved algal superfood in Japan

The study has been published in the journal, "Phycological Research." Okinawa mozuku (Cladosiphon okamuranus) is a much-loved algal superfood in Japan, that farmers have cultivated along the Okinawan seashore since the 1980s. In the autumn, the farmers cultivate mozuku germlings, or 'seeds' in tanks, to induce their buds. 


Two billion yen local economy

Then, the farmers transfer them to the ocean on nets to grow until they are harvested in spring. Around 15,000 to 20,000 tons of mozuku are collected each year, contributing more than 2 billion yen to the local economy.


Rising ocean temperatures stunt their growth

However, mozuku farmers currently face three major problems during the cultivation process. Firstly, some of the mozuku 'seeds' don't bud. Secondly, as the mozuku grows in the ocean, it sometimes detaches from the nets and is swept away by current and tides. Finally, the seaweed is particularly susceptible to heat, with rising ocean temperatures stunting their growth.


Need for heat-resilient strains

"In 2010, the yield fell to less than half the level of a typical year, which is thought to be due to an unusually warm winter," said Dr Koki Nishitsuji, a staff scientist in OST's Marine Genomics Unit, led by Professor Noriyuki Satoh. "As climate change occurs, the frequency of warmer winters could increase, so new heat-resilient strains are needed."


Crossbreeding maybe the solution

One of the most effective ways to engineer traits such as heat tolerance is through crossbreeding, which is when individuals from two different strains are bred together to create a new mixed strain. However, scientists have struggled to crossbreed algae due to difficulties with distinguishing male germ cells from female germ cells. "In other organisms, such as egg and sperm in mammals, there are visible differences" explained Dr Nishitsuji. "But for algae, the germlings can't be identified by eye, only by their DNA."


Genes decoded

Over the last few years, the research team from the Marine Genomics Unit decoded the genome of the four different S-, K-, O- and C-strains of Okinawa mozuku, and the related species, Nemacystus decipiens, known as ito-mozuku in Japanese. Now, by making use of this wealth of genomic information, the team were able to identify 9 key, sex-determining genes.


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