I have been tagging insect resistance gene with SSRs. one of my primer worked very nice at 60 degree anneaing temperature. However, It gave me very bright smear one month later with the same PCR condition. I thought that my primer has degraded. then, I ordered new primers (from two different company)and test them at same time. They gave me same results (Bright smear). I have tested DNA concentration, Mg concentraction, of course sequence. It just not working! I do not what is wrong and what to do.