超级杂交稻模式株型的光合优势

Photosynthetic Advantages of Model Plant-type in Super Hybrid Rice

以三系杂交稻汕优63为对照,比较研究表明,具有超级杂交稻模式株型的培矮64S/E32有以下生理优势:(1)叶面积指数前期较小,中期稳健,后期衰减缓慢、维持较高水平;(2)抽穗后剑叶和倒2叶的比叶重显著或极显著大于对照;(3)后期上3叶叶绿素含量衰减缓慢,变化平稳;(4)上3叶单位叶面积气孔数目比对照多19.2%,达极显著;(5)群体光合生产力比对照高,耐低浓度CO2胁迫能力强;(6)抽穗后具有较快的干物质积累速率,与对照相比总干物质积累速度高18.1%,群体生长率高14.6%。对现阶段超级杂交稻育种中的有效“增源”途径进行了讨论。

Looking back at the history of rice breeding, two breakthroughs resulted largely from identification and utilization of dwarfing genes in 1960s and the wild abortive cytoplasmic male sterility （CMS） in 1970s had significantly raised rice yield potential. But the yield potential of both inbred and hybrid rice cultivars have apparently stagnated for over 20 years afterwards. Because of population growth pressure and shrinking of arable land going with industrialization in the world, food security is increasingly focused on by governments and scientists. Rice breeders try to further raise rice yield ceiling by carrying out kinds of breeding programs for super high-yield since 1980s. In 1997, Professor Yuan L-P put forward a super hybrid rice breeding strategy of combining morphological improvement and heterosis utilization, based on analysis of morphological features and genetic background of Pei＇ ai 64S/E32, a pioneer super hybrid rice variety which reached the first goal 10.5 t/ha in Super Rice Program by Chinese Agricultural Ministry and created a yield record 17.09 t/ha in 1999 at Yunnan Province, China. The canopy structure of Pei＇ ai 64S/E32 characterized with ＂long, erect, narrow, V-shaped and thick＂ of uppermost 3 leaves, is now considered as model plant type for super hybrid rice breeding at Yangtze River Area. The objective of this research was to explore the morphological and physiological mechanism of super high yield in rice and to give suggestions for further super high yielding breeding by using Pei＇ ai 64S/E32, the pioneer super hybrid rice variety, as main experimental material with the control Shanyou 63, the most popularized three-line hybrid in China. The randomized complete block design was used in field plotting design with 3（varieties） × 3（replications） × 3（ sowing time） plots. The area of each plot was at 33.75 m^2 with plant density （30 ＋ 20）cm × 15 cm. Several physiological items related to photosynthetic capacity such as specific leaf weight （SLW）, leaf area index （LAI）, canopy photosynthetic rate, chlorophyll content, stomata density and accumulative and distributive rate of dry matter were measured and investigated on uppermost 3 leaves at different growth stage. Results indicated that, in comparison with the control Shanyou 63, Pei＇ ai 64S/E32 had many photosynthetic advantages as follows： （1） LAI and chlorophyll content declined much slowlier in late growth stage; （2） SLW was significantly higher, except for the third leaf at waxy stage; （3） total number of stomata was 19.2% more; （4） canopy photosynthetic rate was higher, especially when the CO2 concentration in environment was low; （5） the dry matter weight was higher and the accumulative rate of total dry matter was 14.6% higher after heading stage. In conclusion, the essential features of Pei＇ ai 6dS/E32 were with steadier growth rate in early and middle stage and declining much slow to keep at a higher energy level for a longer period at late growth stage. The feasible way to further increase of source capacity of biomass was also discussed from the viewpoint of super high-yielding breeding.