稻种资源苗期氮素营养效率的分类、鉴定与评价

在低氮(20 mg/kg)、中氮(40 mg/kg)和高氮(60 mg/kg)3个水平下，调查了88份稻种资源的苗期性状并测定了氮素营养效率，包括氮素利用效率(NUE)、氮素吸收效率(NAE)和氮素利用效率响应度(NUER)。结果表明，苗期不同性状对低氮、中氮和高氮的敏感性不同，不同氮素水平间的单株根体积、地上部干重、吸氮量和根干重等性状变异较大，低氮胁迫加大了种质间的差异。不同水稻苗期性状对氮素的响应度不同，性状在种质间的变异服从正态分布。通过分类、 鉴定和评价，供试稻种资源分为13种氮素营养效率类型，它们存在明显的基因型差异，呈典型的正态分布，即低效和高效的较少，以NUE、NAE和NUER中效类型最多。NUE、NAE和NUER三指标间还存在很强的互补性和拮抗性，极少存在两个以上指标同为低效或高效的稻种资源类型。水稻氮素营养效率类型较陆稻丰富，但分布较分散，总体分布明显偏向于低氮素利用效率一侧。籼稻氮素营养效率的类型略多于粳稻，而粳稻类型的总体分布明显偏向于低氟素利用效率一侧。地方晶种氮素营养效亭类型较多、分布较集中，总体分布明显偏向于高氮素利用效率一侧：杂交稻氟素营养效率的类型最少、分布最集中，而常规稻氮素营养效率类型最多、分布较分散，常规稻和杂交稻品种的总体分布明显偏向于低氮素利用效率一侧。上述研究结果对探讨稻种资源蓖素营养效率的遗传特性、选育高效氮素营养的新型种质及阐明高效氮素营养的生理机制等具一定参考价值。

Classification, Identification and Evaluation of Nitrogen Nutrition Efficiencies in Rice Germplasms at Seedling Stage

The decline of nitrogen nutrition efficiencies as well as increases in crop production cost and soil and water contamination are becoming urgent problems due to heavy application of nitrogen fertilizers in rice production. Exploring and utilizing crop genetic potential is an ideal approach in improving nitrogen nutrition efficiencies. Most researches have focused on the comparison of nitrogen nutrition efficiencies among rice cultivars but paid less attention to establishing effective systems to evaluate nitrogen nutrition efficiencies of rice germplasms. In this study, pot experiments were conducted to explore a rapid method to identify, classify and screen nitrogen nutrition efficiencies of various rice germplasms. 88 rice germplasms were planted under low nitrogen (20 mg/kg), medium nitrogen (40 mg/kg) and high nitrogen (60 mg/kg) levels, and 17 seedling traits were measured to assess variations of nitrogen nutrition efficiencies including nitrogen utilization efficiency (NUE), nitrogen absorption efficiency (NAE) and NUE response (NUER) among rice germplasms. The results showed that the sensitivity of different traits to low, medium and high nitrogen were different. The genetic variations of root volume, shoot dry weight, nitrogen absorption amount and root dry weight per plant under different nitrogen treatments were greater under low nitrogen stresses. The response patterns of different traits to low, medium and high nitrogen were different, and the variation curve of the traits among rice germplasms resembled normal distribution. Classification, identification and evaluation of rice germplasms indicated that the nitrogen nutrition efficiencies of the rice germplasms were markedly different and could be classified into 13 types, with typical normal distributions. The distribution patterns showed that low efficiency or high efficiency was fewer, while medium efficiency was more and especially medium NUE, medium NAE and medium NUER were the most. The NUE, NAE and NUER of rice germplasms exhibited complementary and antagonistical actions, so that very few types were with two parameters of both low or both high nitrogen nutrition efficiencies simultaneously. The types of nitrogen nutrition efficiencies in paddy rice were more than those in upland rice, with the distributions more decentralized and significantly inclined to low NUE. The types of nitrogen nutrition efficiencies in indica rice were slightly more than those in japonica rice, and the japonica distributions were significantly inclined to low NUE. Of paddy rice germplasms, the types of nitrogen nutrition efficiencies in hybrid rice were the fewest with the most concentrative distributions and significantly inclined to low NUE, the types in local cultivars were the fewer with more concentrative distributions and significantly inclined to high NUE, and the types in conventional rice were the most with distributions most decentralized and significantly inclined to low NUE. The above results provide useful information for exploring the heredity of nitrogen nutrition efficiencies, breeding novel rice germplasms for high nitrogen efficiencies and elucidating the mechanism of high efficiency of nitrogen nutrition in rice crop(Table 2-4, Fig.1-5).