Abstract: Screening and breeding low phosphorous(P)tolerant rice genotype is one of the effective alternatives to alleviate the scarcity of mineral P resource and to increase the utilization efficiency of P fertilizer.Selecting a simple and scientific screening index plays an important role in the screening and breeding program.In this study,a hydroponic culture experiment and a field trial were carried out to approach the screening index for low P tolerant rice genotypes.The results showed that among all the rice characters studied,total dry weight demonstrated a significant genotypic variation at both normal and low P supply(the CV was 21.73% and 19.54%,respectively).Relative total dry weight(low P supply/normal P supply)also demonstrated significant genotypic variation(CV was 19.60%),which was significantly correlated to relative root dry weight,relative plant height,relative total P uptake,relative shoot P accumulation,relative P utilization efficiency and relative P concentration(P<0.01).Therefore,the relative total dry weight of rice would be an important evaluation or screening index for the low P tolerance ability of rice at its seedling stage.The relative total dry weight of rice in hydroponic culture system was not correlated to the relative grain yield(minus-P/plus-P)in field trial,which meant that it could not be used as an index to evaluate the low P tolerance ability of rice.The internal P utilization efficiency of rice grown in low P solution was significantly correlated to that of rice grown in P-deficient soil(r=0.798^**,n=8).Therefore,screening rice genotypes by using internal P utilization efficiency of rice grown in low P solution at seedling stage as screening index and subsequently testing in field trial would probably be an effective alternative to screen rice genotype with high P utilization efficiency.

Key words: Oryza sativa, Low P tolerance, Genotype, Screening index, Evaluation index