Identification of a sex-linked SCAR marker for Plecoglossus altivelis and its application for identifying gender in cultivated and wild populations

Ayu (Plecoglossus altivelis), one kinds of valuable cultured fish species, show almost no morphological difference between male and female until sexual maturity. Here, we report the identification of sex-linked markers for the ayu, based on Amplified Fragment Length Polymorphism (AFLP) generated from cultured fish (15 males and 15 females) by using 63 different primer combinations. Genomic fragments (n = 3733) were produced with a mean frequency of 59 bands per primer pair. A male-specific of 139 base pair band was amplified and converted to a sequence-characterized amplified region (SCAR marker) designated as Ayu102. Six distinct genomic fragments were produced in 12 wild samples (6 males and 6 females). The fragments designated a, b, c, d, and e were detected only in males, and one fragment (f) was detected in both genders. Nucleotide sequence analysis showed that fragments e and f were 96.67% identical. Ayu102 marker was detected in 45-d-old larvae, in both cultured and wild fish populations, and in offsprings generated by gynogenesis. Fragment e was detected in all males, and in only 6.7% of females in cultured fish. Data suggest that Ayu102 marker is a male-specific marker linked to the sex-determining locus of the male ayu and can be used for gender identification.