Variability of yield determining components in winter rapeseed (Brassica napus L.) and their correlation with seed yield

Designing breeding programs for rapeseed (Brassica napus L.) cultivars with improved seed and oil yields require information about the genetic variability of traits effecting seed and oil production. This investigation was undertaken in order to examine phenotypic and genetic variability, broad-sense heritability, genetic gain under selection and interrelationships of some agronomic and seed quality traits of investigated genotypes. Genotypes, years and their interaction showed significant variation for all studied characters. Phenotypic variability coefficients were higher than genetic ones. Broad-sense heritability estimates ranged from 12.66% (for ripening period) up to 52.12% (for days to first pods filling). Expected genetic gain was lowest for days to maturity (0.45%) and highest for height to the first lateral branch (12.94%). The analysis of genetic correlations revealed that seed yield per plant is highly and positively associated with pods per plant, oil content, plant height and ripening period, although significant negative correlations were found between seed yield per plant and leaves per plant, days to maturity, protein content, days to first pods filling, days to flowering, height of the first lateral branch and 1000 seed weight. Genetic path-coefficient analysis indicated that pods per plant and oil content were the most important components of seed yield per plant. Their direct effects on seed yield per plant were p=0.472 and p=0.082, respectively. Protein content had highly significant negative direct effect on seed yield (p=-0.365), followed by 1000 seed weight (p=-0.017) and height to the first lateral branch (p=-0.081). These observations will support the selection of genotypes with desired traits for further rapeseed seed and oil yield improvement.