To determine the drought-tolerant capacity of bromus and to screen early drought-tolerant bromus seedlings， this study measured the adaptive response of 101 accessions of B. inermis at the seedling stage to drought stress. The morphological and physiological changes of the plants including roots were analyzed， and 17 growth indexes related to drought tolerance were determined. The drought tolerance of the seedlings was evaluated and screened by comprehensive evaluation， correlation analysis， principle component analysis， membership function and cluster analysis. The results showed that plant height， average root diameter， fresh weight above ground， total root volume， root surface area， root projected area， fresh weight below ground， total primary root length， dry-weight root aboveground ratio， maximum primary root long， fresh-weight root aboveground ratio and aboveground dry weight can be important indicators for the identification of drought tolerance in the seedlings of bromus. 101 bromus materials were divided into 4 different drought-tolerant grades by cluster analysis. There were 10 germplasm materials in class I with D value ranging from 2.00 to 2.55， which were highly drought-tolerant materials. There were 38 germplasm materials in Class II with D value ranging from 1.27 to 1.81， belonging to moderate drought tolerance. There were 42 germplasm materials in Class III with D value ranging from 0.77 to 1.25， belonging to low drought tolerance. There were 11 germplasm materials in Class IV， the D value ranged from 0.37 to 0.73， belonging to drought sensitive materials. The drought-resistant germplasm W1Z755， W1Z770 and W1Z696 were selected. The drought-sensitive materials were W1Z626， W1Z587 and W1Z763. This study can provide a theoretical basis and a material basis for the drought resistance evaluation of bromus seedlings and the selection of new varieties.

Bromus inermis  /  Seedling stage  /  Drought stress  /  Drought tolerance index