The ST25 trademark, created by farmer-scientist Ho Quang Cua, received the World’s Best Rice title in 2019. The brand is being registered by five U.S. companies, according to the United States Patent and Trademark Office (USPTO).

These companies, based in California, had begun registering the trademarks "ST25" and "World’s Best Rice" since last June. Their applications are pending.

They also registered to patent trademark phrases to describe the famous Vietnamese rice, such as "a specialty of Soc Trang," referring to the southern province where Cua grows the rice, and "No.1 Vietnam’s ST25 rice."

Should any of them receive licenses for this trademark, Cua and Vietnamese rice exporters won’t be able to use the ST25 trademark for their rice sold in the U.S.

However, observers have said that Cua still has an opportunity to secure the trademark.

The USPTO is still reviewing the applications of these five companies, and this process usually takes six months, meaning Cua can still register his rice there, said Vu Ba Phu, head of the trade promotion agency under the Ministry of Industry and Trade.

Cua now needs to prove that he owns the ST25 trademark by showing how he has researched and cross-bred the rice and entered it in the World’s Best Rice Contest, Phu told VnExpress.

Cua told local media Thursday that he was looking into how he can register the trademark for his rice.

The ST25 rice is the result of 25 years of work by Cua and his colleagues who cross-bred the premium fragrant rice of Soc Trang which is described as having a sweet taste and a hint of pineapple flavor.

In 2019, the ST25 rice was named the winner of the World's Best Rice Contest in the Philippines, marking the first time a Vietnamese rice variety won the title in the contest’s 11-year history.