Estimation of Genetic Effects for Different Traits in Rapeseed (Brassica napus L.) using Line × Tester Crosses under Water-Stressed and Well-Watered Conditions

In order to estimate the effects of general (GCA) and specific (SCA) combining ability, heterosis and genetic control of different traits in rapeseed including yield and seed oil content, six lines of spring type and three testers Opera, Parade and Licord of winter type were crossed in 2014-2015. The 18 progenies and their parents were evaluated in a randomized complete block design at the Dryland Agricultural Research Institute (Sararood) under water-stressed (WS) and well-watered (WW) conditions in 2015-2016 cropping season.The results of line × tester analysis revealed that the GCA due to lines in all traits except for pod length in WW and the SCA due to line × tester in all of the traits except for seeds per pod and oil content in WS, and pod length in WW were significant for both environments.The genetic control of the traits was different in both conditions indicating that the gene effects were influenced by the environment for most studied traits. For seed yield, additive and non-additive effects were more important in WS and WW environments, respectively. Seed oil content had relatively low narrow sence heritability in both conditions. The most heterosis for seed yield was belonged to Comet × Opera (168%, WS) and Amica × Licord (171%, WW) hybrids The highest heterosis for seed oil content was observed in Shiralee × Opera hybrid in both environments (12.6% in WS and 6.4% in WW). The testers Opera and Licord were suitable to improve yield in WS and WW environments, respectively. The lines Comet and Dalgan had the highest GCA and the Dalgan × Licord hybrid had the highest SCA (Top cross) for seed yield in both conditions.