Abstract:

To provide a scientific basis for rice planting and high-yield breeding of salt-tolerant rice in coastal tidal flats, the effects of different salt gradients on panicle characters and yield components of salt-tolerant rice were studied. ‘Yangnongdao 1’(V₁), ‘Nanjing 5055’(V₂) and ‘Tonghaijing 18-2’(V₃) were used as test materials. The panicle length, panicle weight, grain number per panicle, branch number, seed setting rate and other panicle characters of rice and yield component factors were measured and analyzed by split zone test under no salt stress 0 g/kg (S₀) and salinity stress 1.5 g/kg (S₁), 3 g/kg (S₂). The results were as follows. (1) Under different salt stress, grain number per panicle and 1000-grain weight under S₁ level were significantly lower than those under S₀ level, and rice yield, effective panicle, grain number per panicle, 1000-grain weight and seed setting rate under S₂ level were lower or significantly lower than those under S₀ and S₁ level; compared with the level of S₀, the branch number, total grains, total filled grains and total grain weight of the primary branches per panicle decreased by 9.10%, 8.69%, 10.03% and 14.47% under the S₂ level, respectively; the branch number, total grains, total filled grains, seed setting rate, total grain weight, 1000-grain weight of the secondary branches per panicle decreased by 14.69%, 18.05%, 22.49%, 8.04%, 17.21%, 5.95% under the S₂ level, respectively. (2) Among different rice cultivars, compared with non-salt stress, the yield, grain number per panicle, and the branch number, total grain number and total filled grains of the primary and secondary branches under the salt stress (S₁, S₂) showed that: V₃>V₁>V₂. (3) The relative inhibition rate showed that the grain number per panicle of V₁ and V₂ was mainly inhibited by salt stress, especially the secondary branch number and the total grain number of secondary branches; however, the relative inhibition rate of salt stress on all the panicle traits of V₃ was low. (4) The correlation analysis showed that rice yield had extremely and significantly positive correlation with grain number per panicle, secondary branch number, and had positive correlation with total grain number of the secondary branches; there were significantly positive correlations between rice yield and panicle length, panicle weight, branch number and total grain number of the primary branches, branch number and total grain number of the secondary branches, 1000-grain weight and seed setting rate under salt stress. Salt stress has negative effects on rice yield, and the main reason for the decrease of rice yield under salt stress could be the obvious decrease of grain number per panicle, especially the obvious decrease of the number of the secondary branches and the total grain number and the total grain weight of the secondary branches.

Key words: coastal tidal flats, salt stress, salt-tolerant rice, grain number per panicle, branch number