Study on Effect Factors and Indirect Evaluation Method for Percentage of Head Milled Rice of Hybrid Mid-season Rice

26 combinations of Indica type hybrid mid-season rice were used as materials to study the relationship between characters of source-sink,grain and the percentage of head milled rice by analysis of correlation,regression and path analysis.The results indicated that the length of grain,the ratio of length to width,plant high,SPAD value of leaf at full panicle stage and percentage of chalky rice were the key effect factors for percentage of head milled rice.Regression equations were established,respectively,between percentage of head milled rice and the length of grain,the ratio of length to width and the percentage of chalky rice,based on those regression equations,the accuracy percentage prediction was 87.5 %-94.44 % of percentage of head milled rice over 52 % when the length of grain9mm or the ratio of length to width3 or the percentage of chalky rice70 %.This could provide a theoretical and practical way for selecting hybrids mid-season rice with good quality.