Abstract: 【Objective】Based on a series of polyploid indica-japonica hybrid plant lines obtained from a new breeding strategy of using double heterosis of wide cross and polyploidization to select super rice, two polyploid indica-japonica hybrids, PSR073 and PSR120 were studied in their growth period to show the powerful heterosis in a larger scale and study the characters of polyploid indica-japonica hybrids more completely. 【Method】The leaf age, tiller growth, flowering habit and morphology characteristics of them were observed to analyze their growth habits and characteristics. 【Result】The results showed that the agronomic traits of PSR073 and PSR120, such as plant height, length of panicles, grain length, grain width and 1000-grain weight, all took on obvious predominance of polyploid. And the seed-setting percentage was more than 83%. No difference was observed between the two tetraploids and common diploids in leaf age, tiller growth and flowering habit. 【Conclusion】It is concluded that the characteristics of the two powerful heterosis polyploid hybrids are different from those of the polyploid rice reported before. Wide cross and polyploidization have no negative effects on the growth habits and characteristics of them, on the contrary they have powerful heterosis. This has provided theoretic and practical evidences for their application to agricultural production.

Key words: Polyploid, Indica-japonica hybrids, Growth habits and characteristics, Heterosis