College of Agronomy， Hebei Agricultural University/Hebei Sub-center of National Maize Improvement Center/ Key Laboratory for Crop Germplasm Resources of Hebei， Baoding 071001
Foundation project： The Key Research and Development Project of Hebei Province （21326325D）
Based on 220 maize inbred lines， 6 bract related traits were evaluated in field experiments at two locations in two years. The genetic diversity analysis， principal component analysis， clustering analysis and stepwise regression analysis were applied for statistical analysis and identifying the evaluation indicators. The results showed that the genetic variations at bract related traits were abundant， with the coefficient of variation ranged from 13.41% to 51.79% as well as the genetic diversity index ranged from 1.71 to 2.08. Principal component analysis simplified the six traits into three principal components， showing the cumulative contribution rate of 86.674%. The first principal component was mainly related to the bract mass and the bract length. The second principal component and the third principal component were mainly related to the bract wrapping degree and the bract number， respectively. The comprehensive evaluation D value ranged from 0.161 to 0.728， of which 101314 and 7026B showed the highest and lowest D value， respectively. 220 inbred lines were divided into three groups by cluster analysis， among which 62 inbred lines were in group I， with few bract numbers， shorter and narrower bracts， lower bract mass and wrapping degree. Stepwise regression analysis showed that bract length， bract width and wrapping degree could be used as the important indicators for the comprehensive evaluation of bract traits in maize. Collectively， these results provided a theoretical reference for the accurate identification of bract traits in maize germplasm resources suitable for mechanical harvest.