Multidimensional Analysis of Diversity in DH Lines and Hybrids of Winter Oilseed Rape (Brassica napus L.)

Limited genetic variability is a major problem in rapeseed breeding, whose strict selection, limited geographical range and a short period of domestication has led to a reduction in genetic and phenotypic diversity. Assessing specific populations for the greatest genetic diversity for many traits simultaneously, requires the evaluation of multi-feature characteristics. The aim of this study was to estimate the variability of DH (doubled haploid) lines and two generations of winter oilseed rape hybrids. In addition, the relationship between the Mahalanobis distances of parental forms and the effect of heterosis in hybrids was investigated. The results of MANOVA showed that the genotypes and years as well as genotype × year interaction were significantly different (p < 0.001) for all eight observed traits. The first (V₁) and the second (V₂) canonical variate explained 38.57% and 27.55% of the total variation in 2015, and 50.19% and 31.84% in 2016, respectively Canonical variate analysis showed that the traits, flowering time and number of branches per plant had a very large influence on the differentiation of genotypes. Graphs demonstrated that the tested DH lines and hybrids are characterized by a similar, wide range of variability. It was observed, that when using a diverse population of DH lines for crossbreeding with only one CMS/Rfo line, there was no significant reduction of variation in hybrid generations and between these generations. The phenotypic distance values determined by the results of Mahalanobis analysis were similar in both years, but slightly wider in 2016. The observed minimum and maximum ranged from 1.324 to 22.356 in 2015, and from 1.105 to 27.792 in 2016, respectively. No significant correlation was observed between the hybrid heterosis effect and the Mahalanobis distance of the parental lines.