Improvement of Brassica napus Restorers Using a Recurrent Selection Strategy.

The ogu-INRA CMS system in canola and rapeseed (Brassica napus L.) uses a cytological variant of the radish- (Raphanus sativus L.) derived ogu CMS pollination control system introduced through interspecific introgression. The restorers (R-lines) contain an introgression that is associated with poor agronomic performance due to a large undesired piece of the radish chromosome that was introgressed along with the Rfo gene. The introgression contains pentatricopeptide (PPR) motif repeats that confer fertility restoration abilities to the R-lines. The objective of this research was to test the hypothesis that multiple cycles of crossing will result in R-lines with improved agronomic performance. A base population was developed by designing five R-line by R-line crosses. Twenty plants from each initial cross were grown and chain-crossed at random, without any pre-selection other than the presence of the Rfo SCAR marker. Twelve pods from each plant were crossed and the remainder of the plant was selfed. Three intermating crossing cycles (C₀, C₁ and C₂) were completed and each was selfed once in order to compare all populations at the C₀S₂, C₁S₂ and C₂S₂. This generation was then selfed again in order to compare the crossing cycles at C₀S₃, C₁S₃ and C₂S_3. The two experiments consisted of a selection of 60 genotypes from each cycle from which four plants were planted per replicate with three replicates including the original parents as controls. The following traits were evaluated for each experiment: days to flowering, number of pods, pod rating, thousand seed weight, yield per plant and harvest index. All experiments were conducted in an Argus-controlled greenhouse. Data from this experiments was analyzed using AGROBASE®. The impact of recurrent selection cycles and selfing on R-line agronomic improvement will be discussed.