One option that is becoming quite inexpensive is AFLPs, they are quite reliable and allow you to distinguish (or associate) genetic variants. The use of flouroscent dyes and capillary electrophoresis can allow you to multiplex different primer combinations so you can reduce the costs of fragment analysis.
I suggest to use the SRAP method. The candidate forward and reverse primer sequence referred to "Zheng HQ, Duan HJ, Hu DH, Wei RP, Li Y (2015) Sequence-related amplified polymorphism primer screening on Chinese fir (Cunninghamia lanceolata (Lamb.) Hook). Journal of Forestry Research 26(1):101–106.