Genetic analysis for oil and protein contents of rapeseed (Brassica napus L.) at different developmental times M. T. Variath J. G. Wu Y. X. Li G. L. Chen C. H. Shi Received: 27 June 2008 / Accepted: 17 November 2008 / Published online: 6 December 2008 Ó Springer Science+Business Media B.V. 2008 Abstract The dynamic expression of genes for oil and protein contents of rapeseed (Brassica napus L.) was carried out with time-dependent measures by using the developmental genetic models for quanti- tative traits in diploid plant. The unconditional and conditional analysis showed that the accumulated genetic effects or net genetic effects from diploid embryo nuclear genes, cytoplasmic genes and diploid maternal plant nuclear genes were all important for the performance of both nutrient quality traits at most developmental times/stages. Results from the condi- tional analysis further revealed that the activation of quantitative genes was gradually carried through the developmental process with maternal genes playing more active role at most developmental stages. Additive effects from embryo and maternal plant were found more important than the dominant effects at most developmental times/stages for both traits, and especially for protein content of rapeseed. Heritability analysis confirmed that the maternal heritability for protein contents were considerably stronger throughout developmental period except for the developmental time at 22 days, while for oil content the heritability components were dynamic and time dependent. The differences of genetic relationships from various genetic systems were found for oil and protein contents among the developmental times or between the two quality traits. Keywords Rapeseed  Developmental genetics  Genetic variances and conditional genetic variances  Heritability  Genetic correlations  Oil content  Protein content Introduction Oil and protein are two important quality traits in rapeseed which has derived a lot of attention from plant breeders. The genetic factors involved in the control of these two traits have already been well documented. These studies have shown that both oil and protein contents are important quantitative traits which may be controlled by embryo (cotyledon) genetic effects (Brandle and McVetty 1988; Pai and Kumar 1991; Han 1990), cytoplasmic genetic effect (Mc Vetty and Pinnisch 1994), diploid maternal plant genetic effects (Grami and Stefansson 1977; Wang 1992), or the simultaneous effects of all these (Wu et al. 2005, 2006). Most of these studies have however utilized the final phenotypic value of traits at maturity and hence incapable of providing M. T. Variath and J. G. Wu are contributed equally to this paper. M. T. Variath  J. G. Wu  Y. X. Li  G. L. Chen  C. H. Shi (&) Department of Agronomy, Zhejiang University, Hangzhou, China e-mail: chhshi@zju.edu.cn 123 Euphytica (2009) 166:145–153 DOI 10.1007/s10681-008-9851-x