The overall mean similarity index for Brassica oleracea accessions calculated based on all AFLP fragments amplified using Nei’s (1978) similarity index, ranged from 0.297 to 0.999 with an average of 0.744 (Table 3). The highest similarity indices (0.999) and the lowest genetic distance (0.001) were between the accessions of the same crop variety and geographical region, e.g. spring cabbage HRIGRU4564 and HRIGRU4571 from Cork. Accessions having close proximity in their origin, breeding strategies and morphological traits are likely to have less genetic distance from each other. The second highest similarity indices (0.998) were between the accessions of cabbages HRIGRU4497 from Roscommon and HRIGRU4564 …show more content…
The first 4 variables of the principal component analysis accounted for 91% of the total variation in AFLP data generated. The first component (PC1) explained 59.7% of the total variation, whereas the second (PC2), the third (PC3) and the fourth (PC4) components contributed 18.93%, 7.77% and 4.6% of the total variation, respectively (Table 4).
Table 4 shows the matrix of eigenvalues of the principal component analysis for all accessions of Brassica oleracea studied. All the accessions of cauliflowers and cabbages studied showed the highest variability on the first component. The 2 accessions of brussels sprouts and the accession of fodder kale HRIGRU4502 showed their greatest variability on the third component, while all other accessions of kales showed an intermediate level of variation on the fourth component (Table 4). Figure 2 shows PCA plot for the 25 accessions of Brassica oleracea and reveals 4 groups (kales, sprouts, caulifowers and cabbages). …show more content…
A total of 471 AFLP fragments were scored across these 11 AFLP primer pairs, of which 423 (89.8%) were polymorphic and could differentiate the accessions analysed, reflecting a rich allelic diversity in the cultivars. This percentage of polymorphic loci (89.8%) was higher than that reported by Lázaro and Aguinagalde (1998a) and Faltusová et al. (2011) for Brassica oleracea (54% and 45%, respectively), and Das et al. (1999) for Brassica campestris