An international team of breeders and genome scientists together with biologists from the University of Georgia (UGA) have sequenced the genome of garden asparagus as a model for sex chromosome evolution. This research is the first confirmation of early models on how sex chromosomes diverge within the same species.

While most flowering plants are hermaphrodites, garden asparagus plants are typically either male (XY) or female (XX). However, YY "supermales" can be produced in the greenhouse. Growers prefer all-male plants, because they live longer and do not self-seed. Breeders produce all-male XY seed by crossing an XX female with a YY supermale. Until now the differences between asparagus X and Y chromosomes are not fully understood, and breeders are unable to distinguish XY males from YY supermales without time-consuming test crosses.

Identification of genes that determine sex paved the way for the development and production of valuable hybrid asparagus plants. The research team found that as predicted, linkage of a gene necessary for male function with a gene stunting development of female organs on a small portion of the Y chromosome was the starting point for the evolution of asparagus sex chromosomes.

For more details, read the UGA Today.

Figure: Jim Leebens-Mack