microliters of PCR product of each individual were mixed with 5 μL of denaturing buffer (98% formamide, 0.09% xylene cyanole FF, and 0.09% bromophenol blue) and then denatured at 94°C for 5 min followed by a rapid chill on ice for 10 min. The denatured PCR products were electrophoresed for 14 h at 8 V/cm on 12% acrylamide gels. The DNA bands on the gel were stained by 0.2% AgNO3 for 20 min, and then 3% Na2CO3 for about 5 min (Qu et al., 2005). Genotypes were recorded according to band patterns.