Sequence-related amplified polymorphism primer screening on Chinese fir

Chinese fir (Cunninghamia lanceolata (Lamb.) Hook) is one of the most important coniferous tree species used for timber production in China. Here, we conducted a sequence-related amplified polymorphism (SRAP) primer screening assay with a total of 594 primer combinations, using 22 forward and 27 reverse primers on four representative Chinese fir genotypes. The obtained results indicated that Chinese fir genomic DNA has a notable amplification bias on the employed forward or reverse primer nucleotides (3' selection bases). Out of the tested primer sets, 35 primer combinations with clearly distinguished bands, stable amplification, and rich polymorphism were selected and identified as optimal primer sets. These optimal primer pairs gave a total of 379 scorable bands, including 265 polymorphic bands, with an average of 10.8 bands and 7.6 polymorphic bands per primer combination. The produced band number for each optimal primer set ranged from 7 to 14 with a percentage of polymorphic bands spanning from 33.3 to 100.0 %. These primer combinations could facilitate the next SRAP analysis assays in Chinese fir.