IranIan journal of genetIcs and plant breedIng, Vol. 1, no. 2, october 2012 16 Abstract The present study was carried out to estimate ge- netic variability parameters for some traits such as pods per plant, cell membrane stability, one thousand kernel weight, fowering period, grain flling period, chlorophyll content, relative water content, leaf excised water content, seed per pod and pod length, in 16 winter rapeseed genotypes. Statistical analysis showed signifcant differences between the tested genotypes. Genotypic and phenotypic coeffcients of variations were high for yield, pods per plant and cell membrane stabil- ity. Heritability estimates were high for pods per plant, cell membrane stability, one thousand ker- nel weight and fowering period. A high genetic gain was observed for pods per plant and cell membrane stability. Correlation analysis showed a signifcant and negative relationship between the fowering and grain flling period (-0.883) and between cell membrane stability and chlorophyll content (SPAD) (-0.587). A positive and signifcant correlation was found between the grain yield and relative water content (0.603). Keywords: Genetic variability, Heritability, Genet- ic gain, rapeseed (Brassica napus L.). AbbreviAtions ppp: pods per plant; cMs: cell membrane stability; TKW: thousand kernel weight; FP: fowering period; GFP: grain flling period; SPAD: soil plant analysis development; rWc: relative water content; leWc: leaf excised water content; sp: seed per pod; pl: pod length; GCV: genotypic coeffcient of variation; PVC: phenotypic coeffcient of variation; GG; genetic gain. introduction rapeseed (Brassica napus L.) is one of the important agricultural crops especially for its edible oil. The meal remains after oil extraction is valuable as a source of protein for the livestock feed industries. In Iran, the production of rapeseed is mainly limited by drought and soil salinity. Response to selection is resulted from signifcant genetic variation and high heritability (Falconer and Mackay, 1996; Shukla et al., 2006). In plants, genet- ic variability and parameters are calculated for many crops (Kahrizi and Mohammadi, 2009; Maniee et al., 2009; Kahrizi et al., 2010 a, b; Garavandi et al., 2011; safavi et al., 2011). breeding programs depend on the knowledge of key traits, genetic systems controlling their inheritance and genetic and environmental factors that infuence their expression. To plan an effcient developmental program, it is necessary to have an understanding of the breeding systems coupled with statistical analysis of inheritance data (Srivastava and Dhamania, 1986). Analysis of variability among the traits and the associa- tion of a particular character in relation to other traits contributing to the yield of a crop would be of a great importance in planning a successful breeding program Heritability and genetic advance in rapeseed (Brassica napus L.) Zeinab Chaghakaboodi 1 , Danial Kahrizi 1,2* , Alireza Zebarjadi 1,2 1 Agronomy and Plant Breeding Department, Razi University, Kermanshah, Iran. 2 Biotechnology for Drought Tolerance Research Department, Razi University, Kermanshah, Iran. * Corresponding author, E-mail: dkahrizi@yahoo.com. Tel: +98 831 8324820. Fax: +98 831 8323731.