Nobody seems to attempt:

I can think of 2 possible causes ; ( 1) genetics of the variety (2) Environmental/growing conditions, such as temps, light and fertilizer. I think it is most probably genetics if it occurs widely.

Sey

Fairly common, especially in potato leaf varieties and no problem.

Dave

Ah, good. Many thanks--I've never had one do that before and couldn't find any info if that was normal.