Liu LiJun

Grain Quality and Its Response to Nitrogen Fertilizer in Mid-season Indica Rice Varieties Planted in Different Decades from 1950s to 2010s

Understanding the changes in grain quality and its response to nitrogen (N) fertilizer during the improvement of crop varieties has great significance in both crop breeding and cultivation. This study aimed to investigate the changes in grain yield and quality during the improvement of mid-season indica rice varieties and the effect of N fertilizer application on the quality. Twelve representative mid-season indica rice varieties (including hybrid combinations) grown in Jiangsu Province during the last 70 years were used with three N application treatments: 0 kg N ha (zero N, 0N), 210 kg N ha (medium amount of N, MN), and 300 kg N ha (high amount of N, HN). These varieties were divided into four groups, including 19401950s, 19601970s, 19801990s, and 20002010s (super rice), according to their application times. With the variety improvement, grain yield was significantly increased, and the head rice percentage, chalkiness, ratio of length to width, amylose content, gel consistency, protein components, and rapid viscosity analyzer (RVA) pasting properties were all significantly improved. However, chalkiness for modern varieties was still high. Grain yield was the highest in HN for super rice varieties, and in MN, for other varieties or no signifi第 9期 陶 进等: 不同年代中籼水稻品种的米质及其对氮肥的响应 1353 cant difference between MN and HN. With the increase in N application, protein content and chalkiness increased, taste quality decreased which was evidenced by the reduction in breakdown values and the increase in setback values. The contents of K, P, S, Ca, and Mg in the head rice decreased in HN compared with those in 0N or MN. The results demonstrate that the improvement of mid-season indica rice varieties markedly improves both grain yield and quality. Generally, increasing N fertilizer application especially up to the HN level could decrease rice quality. How to increase both grain yield and quality through optimizing N management is still a question to be studied.

Growth and development characteristics of super-high-yielding mid-season japonica rice

Rice is one of the most important food crops in China. The realization of the super-high-yielding (SHY) type has great significance in ensuring food security in this country. This study investigated the growth and development characteristics of the super-high-yielding rice (grain yield > 11 t/hm2). Four mid-season japonica rice cultivars (including lines): Lianjiajing 2, Huajing 5, 0026 and 9823, were grown in the paddy field. Growth analysis was performed during the growth period, and yield components were determined at maturity. Results showed that SHY rice had more sipkelets per panicle and higher filled-grain percentage than the high-yielding rice (CK, grain yield 8.98–9.16 t/hm2). There was no significant difference in the 1 000-grain weight between the super-high-yielding and the CK. Super-high-yield rice exhibited fewer tillers at the early growth stage (from transplanting to jointing), with a higher ratio of productive tillers to total tillers, when compared with the CK. The leaf area index (LAI), photosynthetic potential and dry matter accumulation were lower for the SHY rice than those for the CK at the early growth stage, and the differences were not significant between the two rice types at heading, but were greater in the former than the latter after heading. The root-shoot ratio at each growth stage, root bleedings from heading to maturity, grain-leaf ratio, translocation percentage of the matter from stems and sheaths and harvest index of super-high-yielding rice were greater than those of CK. The indexes for the growth and development of SHY mid-season rice population were suggested, i.e. total spikelets > 4.5 × 104/m2, filled-grain percentage > 90%, 1 000-grain weight > 26 g; ratio of productive tillers > 80%, leaf area index at heading 7.5–8.0, photosynthetic potential during the whole growth period > 5 × 106 m2·d/hm2, total dry matter weight at maturity > 22 t/hm2, harvest index > 0.51; grain-leaf ratio (number of spikelets per cm2 leaf area) > 0.58; root-shoot ratio at heading > 0.25 and amount of root exudates > 5 g/m2·h. The regulation approaches and key cultivation techniques for raising the super-high-yielding population were also discussed.