I don't have any idea of these genes associated to ease peeling testa. I suggest you to check online if someone has published something. if not look in other crop specie and tray to find the homologue gens in cashew by design your primers on the crop specie gene found and amplify your cashew gene. and try to confirm it the phenotype. that will be good to have some known ( ease /hard peeling) genotypes with traits you are looking for. Thus, you will have to sequence the gene in the two categories to compare them. if I have found something I will send to you.