Genetic diversity and inter-relationships of fruit bio-chemicals and antioxidant activity in Iranian wild blackberry species

Blackberries are a rich source of bio-chemicals such as anthocyanins and polyphenolic antioxidants. The evaluation of the extent of variation among wild genetic resources can provide useful information for the establishment of effective conservation strategies and future breeding programs. In this study, variations and inter-relationship of berry weight, total phenol (TP), total soluble solids (TSS), titratable acidity (TA), ascorbic acid (AA), anthocyanin and antioxidant activity were estimated in their values among 57 accessions belonging to 4 different Rubus spp. native to Iran. The experiments were performed during two consecutive years (2014 and 2015). Combine analysis showed that there is no significant difference between the data of 2 years in all measured traits. High or very high levels of variations were detected in berry weight (0.14–1.30 g), antioxidant activity (40.21–88.08%), anthocyanin (80.74–145.09 mg/100 g), TSS (7.9–17.8 °Brix), TA (0.36–0.83%) and AA (9.56–20.92 mg/100 g). This is while TP showed very low levels of variation (109.5–129.1 mg/100 g). Correlation analysis showed that antioxidant activity correlated highly and positively with all of the measured characteristics including ascorbic acid (r = 0.927), anthocyanin (r = 0.752), total phenol (r = 0.681), TSS (r = 0.473) and berry weight (r = 0.541) except for TA. Cluster analysis based on all measured characteristics showed a partial differentiation between the accessions based on their species and, to lesser extent, according to their origin within the main clusters. Based on the bi-plot of the first two PCAs, genotypes and traits classified into four quadrants. This grouping was in agreement with that of cluster analysis, considering the fact that almost all of accessions in quadrants II and III (with a few exceptions) were same to those in the first clade of cluster analysis and the genotypes grouped in quadrants I and IV, represents the accessions of clade 2 in cluster analysis. The projection of the traits vectors in PCA were also fully in accordance to that of correlation analysis in almost all of studied traits. Results showed that a rich source of variations is available considering berry weight, fruit bio-chemical and antioxidant activity in the Iranian wild Rubus species, which needs immediate conservation and worth to be utilized in commercial breeding programs.