Cluster analysis in rapeseed (Brassica napus L.)

Many oilseed crops (e. g. sunflower, soybeans, rapeseed/mustard, sesame, groundnuts etc) are grown in Kenya. But oilseed rape is preferred because of its high yields (1.5 tons - 4.0 tons/ha) with high oil content of 42 - 46%. It is soft seeded hence oil extraction is relatively easy. The meal is high in protein and very useful in livestock feed supplementation. The success of any crop improvement programme depends on the extent of genetic diversity in the material. Hence, it is essential to evaluate introductions for adaptation and study the similarities if any among them. Evaluation trials were carried out on 17 rapeseed genotypes (nine of Canadian origin and eight of European origin) at 4 locations in Kenya namely Endebess, Njoro, Timau and Mau Narok for two years. An analysis of variance was carried out on seed yields which indicated that the genotypes were significantly different (LSD, 0.05). Cluster analysis based on mean seed yields suggested only one major group existed within the material. In the first year, genotypes 2, 3, 8 and 9 didn't group with the rest. Genotype 8 was the only one that did not classify with the rest of the Canadian genotypes. Three European genotypes (2, 3 and 9) were however not classified with the others. In the second year, genotypes 10 and 6 didn't fall in the major cluster. Of these two, genotype 10 is of Canadian origin. Genotypes were more similar in the second year than the first year due to favorable weather. It is evident that genotypes from different geographical areas, that is, Europe and Canada fell in the same clusters suggesting that they have genetic similarity. The groupings indicated no correspondence between geographical diversity and clustering pattern.