Have rats eaten my Rattes?

Hello all,
 I've tried a few different methods and varieties with potatoes this year. I put a few Rattes in a couple of 55L plastic pots and submerged them in the polytunnel soil to about half their depth. I also tried the same method outdoors. Everything seemed to be going well until I've pulled them up!! Almost every one has been munched by an intruder. I strongly suspect rats although I haven't actually seen any this year. My Sarpo Mira have remained untouched. Has anybody had any similar experience, and if so, what is the solution?