Screening and identification of rice cultivars with relatively high nitrogen use efficiency for tolerance to phosphorus deficiency at seedling stage.

A hydroponic experiment was carried out to study the responses of 36 rice cultivars with relatively high nitrogen use efficiency to low-phosphorus at the seedling stage and to explore the differences in physiological mechanism between the low-phosphorus tolerant rice cultivars and the low-phosphorus sensitive ones. Great variation existed in the relative values of root dry weight,shoot dry weight,ratio of root to shoot dry weight and tiller number (coefficient of variation:16.9%,10.9%,11.4%,16.3%) in different rice cultivars. In addition,correlation analysis showed their relativity was significant or highly significant. Therefore,these four indexes were employed to evaluate the tolerance to phosphorus deficiency comprehensively. Based on these indexes,three rice cultivars were preliminarily screened out as low-phosphorus tolerant and two rice cultivars as low-phosphorus sensitive,respectively. Comparing with the low-phosphorus sensitive cultivars,the low-phosphorus tolerant ones were characterized by more extensive root system coupled with its higher activity,lower Km and Cmin,but higher Vmax and APase activity. However,the low-phosphorus tolerant cultivars differed in physiological mechanism. The research proved the feasibility for screening double efficient rice cultivars of both nitrogen and phosphorus uses. The screened rice cultivars could be used for identifying genes involved in phosphorus efficiency.