Development of a new codominant CAPS marker for sex genotype identification in asparagus

Garden asparagus (Asparagus officinalis L.) is a dioecious species, with male [XY] and female [XX] individuals. Since male individuals are preferred over females for agricultural production, all-male cultivars have agronomic advantages over mixed-sex cultivars. To produce an all-male cultivar, it is important to obtain a supermale [YY]. Given their morphological similarities, males and supermales are usually distinguished by genetic analysis. To reduce the time required for asparagus breeding, various dominant and codominant male-specific DNA markers have been developed to date. Although two sex-linked codominant markers (Asp2-SP6 and RM17) have been reported previously, their ability to distinguish the sex in A. officinalis and other dioecious Asparagus species has not been evaluated extensively. Therefore, we analyzed the application of these markers to A. officinalis, purple asparagus cultivars and other dioecious Asparagus species in this study. Our results showed that the capacity of these markers to distinguish the sex in A. officinalis and purple asparagus cultivars was limited, thus we developed a new CAPS marker (SSM01), based on the sequence around the RM17 marker. Since SSM01 amplify ca. 470 bp fragment and only Y-specific fragment was digested into ca. 270/200 bp by XspI, this marker can discriminate between females, males and supermales. SSM01 is applicable for discrimination between X- and Y-specific sequences in various A. officinalis and purple asparagus cultivars, also in three dioecious Asparagus species.