Genetic diversity and population structure of Brassica oleracea germplasm in Ireland using SSR markers

The most economically important Brassica oleracea species is endangered in Ireland, with no prior reported genetic characterization studies. This study assesses the genetic diversity, population structure and relationships of B. oleracea germplasm in Ireland using microsatellite (SSRs) markers. A total of 118 individuals from 25 accessions of Irish B. oleracea were genotyped. The SSR loci used revealed a total of 47 alleles. The observed heterozygosity (0.699) was higher than the expected one (0.417). Moreover, the average values of fixation indices (F) were negative, indicating excess of heterozygotes in all accessions. Polymorphic information content (PIC) values of SSR loci ranged from 0.27 to 0.66, with an average of 0.571, and classified 10 loci as informative markers (PIC\u3e0.5) to differentiate among the accessions studied. The genetic differentiation among accessions showed that 27.1% of the total genetic variation was found among accessions, and 72.9% of the variation resided within accessions. The averages of total heterozygosity (H(T)) and intra-accession genetic diversity (H(S)) were 0.577 and 0.442, respectively. Cluster analysis of SSR data distinguished among kale and Brussels sprouts cultivars. This study provided a new insight into the exploitation of the genetically diverse spring cabbages accessions, revealing a high genetic variation, as potential resources for future breeding programs. SSR loci were effective for differentiation among the accessions studied

Assessment of Morphological Variation in Irish Brassica oleracea Species

This study aimed at assessing the morphological variation in 25 accessions of an Irish collection of Brassica oleracea using 44 morphological traits. The morphological traits showed a pronounced variation among accessions. Vegetative preflowering and maturity traits revealed higher variation than seedling traits. Of the 44 morphological descriptors used, 28 were significantly different and proved useful in examining diversity and differentiating among accessions studied. Principal component analysis (PCA) showed variation among accessions, where 87.24% of the total variation in the morphological data was separated on the first five components, indicating a high degree of correlation among traits studied. Cluster analysis grouped the 25 accessions into 4 main groups, corresponding to kales, cauliflowers, cabbages and sprouts, and also showed a sort of correlation between clustering pattern and eco-geographical distribution of the accessions. Furthermore, this study identified 9 highly diverse accessions, providing opportunities for optimising parental sources in future breeding programs to develop new or more productive Brassica varieties. Morphological traits were deemed useful for assessing the diversity and relationships in Irish Brassica oleracea species