Changes in Grain Yield and Morphological and Physiological Characteristics During 60-Year Evolution of Japonica Rice Cultivars in Jiangsu

Twelve typical japonica cultivars from rice (Oryza sativa L.) production in Jiangsu Province, China since the 1950s were chosen to study the evolution of plant type and grain yield. Cultivars in each decade were represented with 2 cultivars and investigated with morphological traits, source-sink related traits, grain yield, and yield components. During the cultivar alternation, grain yield was progressively increased with the main attribution of total number of spikelets, which resulted from large panicle. From the 1950s to the 1970s, the percentage of filled grains of cultivars showed an increase trend. However, it was declined since the 1980s, especially in super rice developed after the 1990s. There was no significant difference in 1000-grain weight among cultivars from different decades. Biomass and harvest index were improved with cultivar replacement, especially biomass after heading. Besides, root dry weight, root-to-shoot ratio, root oxidation activity, and photosynthetic rate of leaves at main growth stages were enhanced significantly, except that root oxidation activity and photosynthetic rate of leaves were reduced rapidly in super rice during grain filing. In the recent 60 years, japonica rice cultivars in Jiangsu Province have been obviously improved in total leaf area, effective leaf area, high-effective leaf area, ratio of total spikelet number to leaf area at heading stage, panicle length, and number of primary and secondary panicle branches. Plant height was shortened from the 1950s to the 1990s, but increased to approximately 120 cm in super rice that were mainly planted since 2000. Leaf angle of the top 3 leaves at heading stage was significantly reduced with the improvement of rice cultivar. These results indicate that agronomical traits and physiological characteristics of japonica cultivars in Jiangsu Province have been improved during the cultivar evolution, and low percentage of filled grain is a critical restraint for super rice cultivar to access its grain yield potential.

摘 要以江苏省近60年来各阶段具有代表性的12个粳稻品种(含超级稻)为材料, 依据种植推广年代结合株型和基因型将其分为20世纪50年代、60年代、70年代、80年代、90年代和2000年以后6个类型, 研究了品种演进过程中产量和形态生理的变化特征。结果表明, 随着品种演进产量逐步提高, 其原因主要是总颖花量的增加, 而这又主要由于每穗粒数的显著增多。自早期的50年代品种, 结实率逐步提高, 但90年代品种和2000年以后的超级稻品种, 结实率有下降的趋势, 穗数和千粒重无明显变化。随着品种演进, 生物产量和收获指数同步提高, 以抽穗后增加的量尤为明显, 主要生育期根干重、根冠比、根系氧化力和叶片光合速率显著增加, 但现代超级稻品种的根系活力和叶片光合速率在结实期下降较快。品种改良提高了抽穗期总叶面积、有效叶面积、高效叶面积和粒叶比, 还增加了穗长、着粒密度、一次和二次枝梗数目。由20世纪50年代到90年代品种, 植株高度降低, 而2000年以后的超级稻品种显著上升, 升至120 cm左右。抽穗期顶三叶叶片角度则随品种更替显著降低。上述结果说明随品种演进, 粳稻的农艺、生理性状和产量均有明显改良, 但超级稻较低的结实率限制了其产量潜力的发挥。