Thanks for the reference! I was wondering how this is possible. So looks like it is actually possible to get a trademark on a plant. How any country would want to agree to this is beyond me. Article 64:

64. Infringement.—Subject to the provisions of this Act, a right established under this Act is infringed by aperson— (a) who, not being the breeder of a variety registeredunder this Act or a registeredagent orregisteredlicensee of that variety, sells, exports, imports or produces such variety without thepermission of its breeder or within thescope of a registeredlicence or registeredagencywithout permission of the registeredlicensee or registeredagent, as the case may be; (b) who uses, sells, exports, imports or produces any other variety giving such variety, thedenomination identical with or deceptively similar to the denomination of a variety registeredunder this Act in such manner as to cause confusion in themind or general people inidentifying such variety so registered.

There do seem to be protections in article 39. With that limitation the whole thing does sound a lot more benign. Like they could just use a new name for the variety:

(iv) a farmer shall be deemed to be entitled to save, use, sowresow, exchange, share or sell his farmproduce including seed of a variety protected under this Act in the same manner as he wasentitled before the coming into force of this Act:Provided that the farmer shall not be entitled to sell branded seed of a variety protected underthis Act.

Explanation.—For the purpose of clause (iv),“branded seed”means any seed put in a package orany other container and labelled in a manner indicating that such seed is of a varietyprotected under this Act.

They should sell it as 'PepsiCo Wala Alu' meaning 'PepsiCo's Potato'

Well, yes there are many varieties of potatoes that you can grow as a farmer. Heck, you and your friends can get together and trademark your own and do a lot of selective breeding to make it unique. I can see some desire to grow what you have on hand however.