Genetic Analysis on Flowering Time and Root System in Brassica napus L.

Rapeseed or canola (Brassica napus L.) exhibits both winter and spring growth habit. Vernalization is required to induce flower in the winter type whereas the spring type does not require vernalization to flower. The winter type has a vigorous root system whereas the spring type has a weakly developed root system. The inheritance of flowering time and root system were studied using seven winter parents and three spring parents. Crosses (F-1) and reciprocal crosses (F'(1)) were made between the winter- and spring-type parents. The F-1, F'(1), and F-2 progenies were grown in the greenhouse. The vernalization requirement for flowering was observed as a recessive trait. Significant flowering delays (3-5 d) in F-1's of the spring x winter crosses were observed compared with winter x spring crosses. Segregation of flowering time indicated that one major gene is responsible for flower initiation in the population. The F-1 and F'(1) of winter and spring crosses showed a vigorous root system, indicating the dominant nature of vigorous root system in B. napus. The vigorous root system phenotype was found to be controlled by three genes. Positive and significant correlations were observed between several yield contributing characteristics. Root length showed a positive significant correlation with seed yield per plant for both cross and reciprocal cross whereas dry root weight was not significantly correlated with seed yield. A significant positive correlation was also observed between late flowering vs. root length and late flowering vs. dry root weight. This is the first report on genetics of root system and its contribution to seed yield in B. napus.