Callus induction and elicitation for enhanced cyanidin accumulation coupled with antioxidant activities in tropical roses (Rosa spp.)

Cyanidin is one of the most predominately found anthocyanins that plays a significant role in the pigment formation of rose, having industrial market demand. For the first time, this study aimed to investigate the impact of elicitation on the biosynthesis of cyanidin and the antioxidant activities in the callus of Rosa spp., comprising four commercially-renowned varieties (First Red, Himroz, Jantar Mantar, and Mrinalini). The surface disinfected leaf explants were inoculated in Murashige and Skoog (MS) medium supplemented with 2,4-dichlorophenoxyacetic acid (2,4-D), α-naphthalene acetic acid, and 6-benzylaminopurine (BAP) at varied combinations and concentrations. MS medium supplemented with 2 mg/L 2,4-D + 1 mg/L BAP was recorded to be the best callus proliferation medium, irrespective of the varieties. Himroz recorded the earliest callus initiation (10.4 days), with 100% callusing frequency and 70.62% callus index with 1.34 g and 0.29 g fresh weight (FW) and dry weight, respectively, on MS medium supplemented with 2 mg/L 2,4-D + 1 mg/L BAP within 6-week growth period. Furthermore, elicitation was carried out using jasmonic acid (JA) and yeast extract in varied concentrations. Irrespective of varieties, 50 µM JA showed the best performance in the cyanidin accumulation and antioxidant activities after a 10-week growth period. The cyanidin content was found to be highest (109.50 µg/100 mg FW) in First Red, followed by Himroz (87.60 µg/100 mg FW). The highest DPPH inhibition (67.46%) in Himroz, maximum ABTS inhibition (58.32%) in First Red, and the highest FRAP activities (431.76 µmol TE/g FW) in Jantar Mantar were recorded when the calli elicited with 50 µM JA. The correlation study confirmed strong positive correlations of cyanidin with ABTS radical scavenging (0.688) and FRAP activity (0.608). Furthermore, application of JA at a lower (50 µM) concentration showed potential for augmentation of cyanidin levels and might prove to be an attractive alternative for non-conventional production of this commercially important pigment. This is the first report on studying the influence of plant growth regulators and elicitors on these four rose varieties for in vitro callus induction, improving cyanidin content and antioxidant activities.

First report on comparative callusing of four tropical roses wherein 2 mg/l 2,4-D with 1 mg/l BAP resulted in maximum callusing% and addition of 50 µM JA proved as the best elicitor for ameliorated cyanidin accumulation and antioxidant activities.