Heterotic patterns in rapeseed (Brassica napus L.): Crosses between spring-type and winter-type genotypes

Genetic improvement in a crop, viz. Brassica species, through plant breeding essentially requires the presence of adequate genetic diversity within the gene pool. Winter rapeseed is known to be genetically different from spring rapeseed and can therefore be used for extending genetic diversity in the progenies produced via crossing methods. Using line?tester analyses of two spring types of testers and six lines of winter-type rapeseed varieties, heterotic patterns of phenological traits, plant height and seed yield were estimated. Significant mean squares between parents and crosses revealed significant heterosis for all the traits. Line?tester mean squares, indicating the non-additive genetic effects, were significant only for plant height and seed yield. High narrow-sense heritability estimates for phenological traits underline the importance of additive genetic effects and thus the efficiency of selection for improving these traits. Based on the significant and positive expression of heterosis effects for phenological traits and plant height in the winter parents, it was concluded that the F1 progenies had earlier and shorter maturity than the winter parents. F1 progenies were also early flowering, early maturing and taller than the spring-type parents. Significant positive heterosis of the crosses for seed yield was observed in 75% and 42% of F1 progenies compared to the spring and winter parents, respectively, indicating a higher yield potential of the F1 hybrids than the spring and winter parents.