Abstract: 【Objective】 The main purpose of the present study was to explore the methods of evaluating shade-tolerance, analyze the shade-tolerance of different soybean genotypes, screen suitable evaluation indicators of shade-tolerance, and establish a mathematical evaluation model of shade-tolerance. 【Method】 Thirty soybean cultivars(lines) were treated under shading and natural light conditions in a field experiment. Corn-soybean strip cropping system created the shaded conditions in the field. The corn variety Zhengdan 958 was used in the experiment. At the maize tasseling stage, shading rate was 70%. Soybean single planting was used as control. Main stem height (X1), stem diameter (X2), main stem node number (X3), branch number (X4), lowest pod height (X5), internode length (X6), plant weight balance (X7), lodging (X8), pods per plant (X9), seeds per plant (X10), seeds per pod (X11), 100-seed weight (X12), seed-stem ratio (X13) and yield per plant (X14) were investigated at the mature period. Shade-tolerance coefficient (STC) of all indexes from both treatments was used to comprehensively evaluate the shade-tolerance by principal component analysis, membership function method, hierarchical cluster analysis and stepwise regression analysis. 【Result】 Firstly, the 14 single indexes were transformed into 5 independent comprehensive components through principal component analysis, which represent 87.685% information of the raw data of the traits related to shade-tolerance. The membership function method was employed to calculate comprehensive shade-tolerance value (D) and carry on cluster analysis, and 30 soybean cultivars (lines) were divided into three shade-intolerance types. Class I was the high shade-tolerance type. Class II was the medium shade-tolerance type. Class III was the shade-intolerance type. At last, a mathematical evaluation model for soybean shade-tolerance was established by stepwise regression analysis, D=-0.5495+0.2932X3+0.0592X4+0.1628X6-0.0244X8+0.5943X9+0.1345X12+0.8210X14 (R2 =0.9908), whose accuracy was higher than 93.67%. Based on the model, seven indexes closely related to the shade- tolerance, including main stem nodes, branch number, internode length, lodging resistance, pods per plant, 100-seed weight and yield per plant were screened out. 【Conclusion】 Thirty soybean cultivars (lines) were divided into three shade-tolerance types, which were the high shade-tolerance type, the medium shade-tolerance type and the shade-intolerance type. Main stem nodes, branch number, internode length, lodging resistance, pods per plant, 100-seed weight and yield per plant can be used for identification of soybean varieties to shade-tolerance.

Key words: soybean , shade-tolerance , principal components analysis , membership function method , hierarchical cluster analysis , stepwise regression analysis method