Comparison of Growth,Pod Distribution and Canopy Structure of Old and New Cultivars of Oilseed Rape ( Brassica napus L.)

Growth, canopy structure and yield components of four selected spring-type cultivars of oilseed rape (Derby, Cyclone, Gulle and Christa) were studied in a field experiment conducted in 1993. Growth analysis was carried out by taking six samples at two-weekly intervals. Area indices of leaves, stems and pods as well as dry matter of plant components were measured. The cultivars showed two different patterns of development and were classified into two groups: old and new cultivars. The first group (Derby and Cyclone) was characterized by short plants, bearing more branches that started branching earlier and on a low position on the stem, while the second group (Gulle and Christa) were characterized by tall plants with thick stems and few branches, starting higher on the stem. Yield could not be directly related to differences in the canopy structure between old and new types. The highest yielding cultivar (Cyclone) belonged to the new category, but the second highest yielding cultivar (Gulle) was of the old type. The study of canopy structure revealed that the pods were distributed evenly on the uppermost branches of the cultivar Cyclone, while for the other cultivars most of the pods were on the main stem, especially in cultivars Gulle and Christa (old group). The cultivars differed significantly in most yield components. In addition to stem and pod development, number of branches and leaf area after anthesis were important characteristics for yield improvement. There were significant differences between cultivars in oil and protein content.