Use of isozyme analysis in the breeding of synthetic rapeseed cultivars

Eleven winter rapeseed inbred lines (I₄) were characterized according to isozyme banding patterns from seven polymorphic enzyme systems. All lines could be qualitatively and quantitatively distinguished using two enzyme systems, shikimate dehydrogenase (SDH) and diaphorase (DIA). Genetic distances were calculated among lines and 15 selected two-line hybrids were planted as experimental synthetics in field-trials. Syn-0 populations produced seed yields between 0.4% lower and 12.9% higher than the mean yields of the respective parental lines. Syn-1 seed yields were 11–24.1% higher than the respective parental lines and the yield improvement was positively correlated with the genetic distance between the parental lines. This tendency suggests that genetic distances between cross components, calculated from isozyme polymorphism, can be used in prognosis of yield performance of synthetic rapeseed cultivars. Isozyme analysis was also applied to study fertilization behaviour in line mixtures, and differences among parental lines were observed with regard to the tendency for self-pollination or out-crossing. The partially very high outcrossing rate suggests the possible existence of a self-incompatibility system.