An update on Hydrangea macrophylla breeding targets and genomics

Hydrangea macrophylla (Thunb. Ex J.A. Murr.) Ser. was cultivated in Japan and China long before it was introduced to England and France in the late 19^th to early 20^th century. Modern breeding work began in Europe in the early 1900s, resulting in the development of over 300 cultivars prior to the 1940s. But only limited germplasm was available during that time and for forty years H. macrophylla cultivars were “bred one to another, and in that time almost every possible combination of the available genes has been given birth”. Therefore, USDA-ARS research efforts from the last decade focused on expanding the genetic pool and breeding options for new, improved cultivars by introducing modern breeding methods such as wide hybridization, mutagenesis, ploidy manipulation, marker development, and genomics research. Here we describe the latest results to establish a reference transcriptome, mapping populations for association studies, and a whole genome sequence.