关键词: 玉米-大豆间作, 大豆品种（系）, 耐荫性, 主成分分析, 隶属函数法, 逐步回归

Abstract: 【Objective】Screening shade-tolerant soybean varieties（lines） suitable for maize-soybean intercropping planting mode in northern Jiangsu,and constructing an accurate and reasonable soybean shade tolerance evaluation system.【Methods】The natural shade environment created by maize-soybean intercropping in northern Jiangsu was used as the treatment,and the clear seed was used as the control. 12 agronomic traits such as plant height,pod height,and branch number of 24 soybean varieties（lines） were measured at maturity stage. Principal component analysis,membership function method,and multiple linear stepwise regression analysis were used to construct shade tolerance coefficients and evaluate the comprehensive shade tolerance of each soybean variety（lines） under intercropping mode.【Results】Index of shade tolerance coefficient of 12 agronomic traits were transformed into 4 independent comprehensive indexes,representing 74.771% of the original data information. The results of comprehensive shade tolerance evaluation value（D） and cluster analysis showed that 24 soybean varieties（lines） could be divided into 3 categories according to their adaptability under shade stress,including strong shade-tolerant（six varieties/lines）,moderate shade-tolerant（nine varieties/lines）and weak shade-tolerant（nine varieties/lines）. The regression equation of shade tolerance was constructed by multiple linear stepwise regression analysis：D=-1.158+0.062X₂+0.249X₅+0.201X₇+1.002X₁₀+0.665X₁₁（R²=0.972 2）,and the fitting accuracy was more than 89.14%. Five shade tolerance identification indexes of pod height,pod number per plant,seed number per plant,100-seed weight and yield were selected.【Conclusion】According to the shade tolerance ability,the 24 soybean varieties（lines） were divided into three categories：strong shade-tolerant,moderate shade-tolerant and weak shade tolerant. Under the maize-soybean intercropping model in northern Jiangsu,five traits,including pod height,number of pods per plant,number of grains per plant,100 grain weight,and yield,can be selected for comprehensive evaluation of soybean shade tolerance. Under the maize-soybean intercropping mode in northern Jiangsu,five traits,including pod height,pod number per plant,seed number per plant,100 seed weight,and yield,could be selected to comprehensively evaluate the shade tolerance ability of soybean.

Key words: Maize-soybean intercropping, Soybean varieties（lines）, Shade tolerance, Principal component analysis, Membership function method, Stepwise regression