The Doaba, around Jalandhar and Kapurthala, produces a large share of India's seed potato. Punjab's winter, cold and dry with low aphid pressure at the right time, produces virus-free seed that is sold to growers across the country.
Seed potato is a specialist business with certification, cold storage and a chain of buyers, and it earns considerably more per acre than grain.
Punjab has a large cold storage capacity built for it, and that capacity is one of the few pieces of agricultural processing infrastructure in the state that is not government-run.
Table potato prices crash regularly, and in bad years Punjab farmers have dumped potatoes on roads in protest.
It is another crop that could take land out of paddy and does not, for the same reason as everything else: no guaranteed price and no guaranteed buyer.
Certified seed potato has to be grown where aphid pressure is low in the critical weeks, which in the plains means a narrow winter window. The Doaba's climate and its cold storage are why the industry sits there.
The chain runs from breeder seed through foundation stock to certified seed, and a grower who loses certification in one season loses the price premium in the next as well.
Punjab's cold storage capacity, built for potato, is among the largest in India and stands idle for part of the year. Using it for other crops has been proposed repeatedly and has not happened at scale.