S05 - Session O2 - Evaluation of salinity-stress assays in wild Japanese Hydrangea

Authors: Hayato Morimoto *, Harada Senjiro, Haruna Saito, Syogo Syukuya, Maho Fujii, Sho Yamamoto, Takashi Handa

Hydrangea is an important woody ornamental plant that is widely used as a garden tree, potted plant and cut flower. The original species used as breeding materials for hydrangea cultivars are Hydrangea macrophylla , H . serrata and H. serrata var. yesoensis , which are native to Japan. H . macrophylla inhabits in coastal areas directly affected by sea breeze and splash. Thus, it has a high salinity tolerance. Salinity tolerance is an important horticultural trait for planting in coastal areas as well as along road sides where salt is frequently used as an antifreeze. However, the assessment of salinity tolerance in wild hydrangea species remains inadequate. Thus, in order to evaluate salinity tolerance of wild hydrangea species, we conducted two assays; a spray assay to assess sea-breeze tolerance and a simple salinity-tolerance assay which is soaking up salt water from the petiole of the detached leaves. In the spray assay, necrosis was significantly observed in H. serrata , whereas few necrosis was observed in H. macrophylla . Furthermore, necrosis was related with thickness of cuticle layer to restrict penetration of Na + amount into the leaf blades. In the simple salinity-tolerance assay, H. macrophylla indicated higher salinity tolerance than the other species by the degree of necrosis and water contents in the leaves. Here, we evaluated availability of two assays for salinity tolerance of hydrangeas.