Abstract:

Elongated uppermost internode was firstly found in 1981 by Rutger and Carnahan. They named the recessive gene controlling this character as elongated uppermost internode (eui) gene. It is regarded as the forth genetic factor besides CMS line, maintain line and restoring line, improving panicle exsertion and reducing the applying amount of GA₃ in three-line hybrid rice seed production. Since then, several eui mutants have been found. 02428h is one of such resessive tall rice mutants with eui from somaclonal variation of a wide compatibility japonica rice 02428. Pei’ai 64S is a photo- and thermo-sensitive sterile line with stable sterility and good combining ability. It is widely used in rice breeding of two-line hybrid and some super high yielding rice hybrids such as Liangyoupeijiu (Pei’ai 64S/9311). However, its panicle exsertion is not so good and 450–600 g ha-1 GA3 must be applied in its seed production. In order to improve the panicle exsertion of photo- and thermo-sensitive sterile line “Pei’ai 64S”, a breeding program transferring the eui gene into Pei’ai 64S through successive backcrossing was conducted by using eui gene of 02428h in the study. In BC₁F₁ and BC₂F₁, the plant used for backcrossing was self pollinated and harvested for investigating the segregation of eui gene in next generation. A new photo- and thermo-sensitive sterile line “P8hS” with the character of elongated uppermost internode was bred through three generations of successive backcrossing. Compared with Pei’ai 64S, P8hS had no difference in sterility and sterility period. The plant height of P8hS was 35.6 cm higher resulted from the elongation of the uppermost internode and the second internode from the top. The panicle extrusion of P8hS was completely improved with its panicle neck length of 13.8 cm long. The panicle length of P8hS was 2.2 cm longer and the number of spikelets per panicle was 35 more in P8hS than in Pei’ai 64S. The plant height was significantly higher, panicle length and panicle neck length were longer, the number of secondary branches, spikelets and grains per panicle were more in the hybrid of P8hS/9311 than in Pei’ai 64S/9311. The successful breeding of P8hS is of great significance in reducing the cost of seed production, improving the seed quality and decreasing the environmental pollution.

Key words: Rice (Oryza sativa L.), Recessive tall height, eui gene, Inheritance, Backcrossing