Abstract: This study separately chose ‘Huaiyin alfalfa’ and ‘PL34HQ’ as recurrent parent and nonrecurrent parent to obtain BC2 generation to study the improving effect of agronomic traits of backcrossing generation. The plant height,multifoliate rate and branching number were measured and analyzed using the analysis of correlation,cluster and principal component. The results showed that the comprehensive characters of BC2 generation material tended to the recurrent parent ‘Huaiyin alfalfa’，but many plants still retained the characteristics of high multifoliate rate. As for Euclidean distance 30,BC2 groups were divided into five types,and the Ⅴ group accounted for 51% of the population,which combined the excellent characters of recurrent parent ‘Huaiyin alfalfa’ and non-recurrent parent ‘PL34HQ’. The results of principal component analysis indicated that the cumulative contribution rate of four principal components to the variation of agronomic traits was 86.21%. The contribution rate of Y3 representing the multifoliate characteristics of alfalfa was 20.56%. Ten excellent lines were screened out through comprehensive evaluation scores. The multifoliate traits of No. 5 single plant had a very high score the third principal component,so it could be used as the key breeding object.

Key words: Medicago sativa L, Second backcrossing generation, Agronomic traits, Multifoliate characteristics

摘要： 为研究苜蓿(Medicago sativa L.)多叶品种回交后代的农艺性状改良效果，本研究以‘淮阴苜蓿’为轮回亲本,多叶苜蓿‘PL34HQ’为非轮回亲本，获得BC2(回交二代)材料，对其株高、多叶率、分枝数等数据进行相关、聚类和主成分分析。结果显示：BC2群体材料在综合性状上偏向于轮回亲本‘淮阴苜蓿’，但仍有不少植株能保留高多叶特性；在欧式距离30处，BC2群体可分为5类，综合了轮回亲本‘淮阴苜蓿’和非轮回亲本‘PL34HQ’优良性状的第Ⅴ类占群体的51%；主成分分析所得4个主成分因子对各农艺性状变异累计贡献率为86.21%，其中主成分因子Y3代表苜蓿的多叶性状，贡献率为20.56%。通过综合评价得分，本研究筛选出了10个优良株系，且5号单株代表多叶性状的第3主成分得分极高，可作为重点选育对象。

关键词: 苜蓿, 回交二代, 农艺性状, 多叶性状