Yield and agronomic traits of winter rapeseed cultivars registered in China from 2001 to 2010

To understand the relationship between yield and agronomic traits of registered rapeseed in China,205 cultivars from 2001 to 2010 were investigated and compared using correlation and path analysis.Results showed that average yield increased from 2 388.78kg/hm2(during 2001 to 2005) to 2 670.13kg/hm2(during 2006 to 2010) with 11.12% increase.Effective siliquae per plant,seed per siliqua and thousand-seed weight increased 4.03%,0.36% and 7.10% respectively.Yield had significant or highly significant correlations to seed per siliqua,branch number,yield stability and growth duration in 2001-2005 and 2006-2010.Moreover,yield also had highly significant correlation(r=0.38) to effective siliquae per plant in 2006-2010.Thus the effective siliquae per plant and thousand-seed weight were the main factors contributing to yield improvement.Other traits were also important to yield.The order of direct strong effect of traits on yield was incidence of Sclerotinia stem rot,index of Sclerotinia stem rot,index of viral disease,incidence of viral disease,seed per silique and effective siliquae per plant in 2001-2005.The order of direct strong effect of traits on yield was seed per siliqua,incidence of Sclerotinia stem rot,plant height,growth duration,effective siliquae per plant and thousand-seed weight in 2006