Abstract:

Hexie’ is the first distant hybrid between Section Moutan and Section Paeonia bred in China. In this paper we study the hybrid reproductive biology, including morphology of reproductive organs, pollen viability, pollination and seed-set conditions. The results showed that ‘Hexie’ flower had approximately 50 to 100 stamens, and the filaments were in various lengths from about 0.1 to 2.5 cm. There were four or five pistils, and the flower disc was succulent, and covered about two thirds of the carpel. Most of the pollens were abortive; and the vital pollen accounted for 4.1% tested by TTC. The mixed pollen grains from tree peony and herbaceous peony had a high germination rate on the stigma of ‘Hexie’. Most of the pollen tubes stopped growing and crimping on the stigma, while only the minority could enter the stigma. Moreover, the entered pollen tube swelled at the front end and twisted in the style, and the pollen tube growth was blocked by accumulated callose. The results demonstrated that pre-fertilization barriers resulted in the infertility of ‘Hexie’. When ‘Hexie’ was used as male parent, crossing with herbaceous peony cultivar 'Yanzi’ and 'Fen Hudie’ showed some compatibility, from which a few seeds and seedlings were obtained, indicating that ‘Hexie’ could be used as parent material for breeding various distant hybrids between tree peony and herbaceous peony.

Key words: tree peony, herbaceous peony, distant hybrid, fertility, pollination