Identification of random amplified polymorphic DNA (RAPD) markers highly linked to sex determination in the red alga Gracilaria gracilis

The random amplified polymorphic DNA (RAPD) technique was employed in the h aplo-diploid dioecious species Gracilaria gracilis to identify sex-linked P CR markers. Sixty-nine decamer oligonucleotide primers were tested on two b ulks of DNA, one from five haploid males and the other from five haploid fe males. One of these primers (OPD13) generated a 430-bp fragment specific to males and a 620-bp fragment specific to females. The diploid individuals ( tetrasporophytes) showed the co-occurrence of these two fragments. In order to verify the linkage between the sexual phenotypes and these markers, a p rogeny array of 59 haploid individuals (male and female) born on a diploid individual was analysed, in all of which the two markers produced by the OP D13 primer segregated perfectly with sex.