Abstract: RSA-01, RSA-02, RSA-03 and their parent materials including ‘Qingshui’ and ‘WL168’ were used as the research object in this experiment. The objective of this study was to analyze phenotypic and physiological characteristics of hybrid materials in the 5th year of planting. The above-ground biomass of RSA-01 and RSA-02 were significantly lower than that of ‘WL168’, but RSA-03 was significantly higher than that of ‘Qingshui’. The stem thickness of RSA-02 and RSA-03 were significantly higher than that of ‘Qingshui’ and ‘WL168’, but their leaf-stem ratio was significantly lower than that of ‘Qingshui’.The coefficient of variation of stem diameter was the smallest among the phenotypic indexes, and the value of RSA-03 was 2.17%. Path analysis showed that the D.E. of leaf-stem ratio and above-ground biomass of RSA-01, RSA-02 and RSA-03 were -0.649, -0.700 and -0.858, respectively. The D.E. of stem diameter and above-ground biomass of RSA-01, RSA-02 and RSA-03 were 0.709, 0.422 and 0.189. The results showed that the leaf-stem ratio and stem diameter were the key factors affecting above-ground biomass. The POD activity of RSA-01, and RSA-03 were significantly lower than that of ‘Qingshui’ and ‘WL168’. Compared with ‘Qingshui’ alfalfa, RSA-03 had significant heterosis in aboveground biomass and stem diameter, but its resistance to stress was reduced. This study provided a theoretical basis for yield improvement and stress resistance research in the later period.

Key words: Alfalfa, Heterosis, Phenotype, Physiology

摘要： 本研究以‘清水’紫花苜蓿（Medicago sativa L.‘Qingshui’）与‘WL168’紫花苜蓿（Medicago sativa L.‘WL168’）的杂交后代选育系RSA-01，RSA-02和RSA-03为研究对象，于种植第5年对其表型特征及生理特性进行观测分析。结果表明：RSA-01，RSA-02地上生物量显著低于‘WL168’（P<0.05），而RSA-03显著高于‘清水’；RSA-02，RSA-03茎粗显著高于‘清水’和‘WL168’，而茎叶比均低于‘清水’；各形态指标中，茎粗变异系数最小，且RSA-03值最小，为2.17%；通径分析表明，RSA-01，RSA-02和RSA-03的茎叶比、茎粗与其地上生物量的直接通径系数分别为-0.649和0.709，-0.700和0.422，-0.858和0.189，茎叶比、茎粗是影响地上生物量的关键因素；RSA-01，RSA-03的过氧化物酶活性显著低于‘清水’和‘WL168’。与亲本‘清水’相比，RSA-03的地上生物量和茎粗都具有显著的杂种优势，但其抗逆性减弱，该研究结果为后期产量改良及抗逆性研究提供理论依据。

关键词: 苜蓿, 杂种优势, 表型, 生理