In-vitro Callogenesis in Safflower (Carthamus tinctorius L.) Genotypes from Leaf, Hypocotyl, and Floral Bud Explants under Differential Phytohormone Regimes
Pooja Vijay Jadhav
*
Department of Plant Biotechnology, Vilasrao Deshmukh College of Agricultural Biotechnology, Latur-413 512, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani-431402, Maharashtra, India.
Sarika Bhalerao
Department of Plant Biotechnology, Vilasrao Deshmukh College of Agricultural Biotechnology, Latur-413 512, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani-431402, Maharashtra, India.
Gaurav Pramod Thorat
Department of Plant Biotechnology, Vilasrao Deshmukh College of Agricultural Biotechnology, Latur-413 512, Vasantrao Naik Marathwada Krishi Vidyapeeth, Parbhani-431402, Maharashtra, India.
*Author to whom correspondence should be addressed.
Abstract
Safflower (Carthamus tinctorius L.) is widely recognized for its pharmacologically active metabolites; however, its seasonal cultivation restricts consistent extraction of bioactive compounds. Plant tissue culture presents a sustainable strategy by enabling continuous and standardized metabolite production independent of field constraints. This study optimized callus induction from leaf, hypocotyl, and floral bud explants of two safflower genotypes, GMU-7931-1 and GMU-7923, using Murashige and Skoog (MS) medium supplemented with differential concentrations of NAA, BAP, 2,4-D, and TDZ. Marked explant and genotype specific responses were observed. In leaf explants, GMU-7931-1 exhibited the highest callus induction (86.66%) at 3.0 mg/L NAA + 1.0 mg/L BAP, while GMU-7923 responded maximally (90.00%) at 4.0 mg/L NAA + 1.0 mg/L BAP. Hypocotyl-derived callus was optimal at 2.0 mg/L NAA + 1.0 mg/L BAP for GMU-7931-1 (90%) and 3.0 mg/L NAA + 1.0 mg/L BAP for GMU-7923 (86.66%), whereas higher auxin levels (≥5.0 mg/L) suppressed callogenesis. For 2,4-D, peak responses were recorded at 5.0 mg/L in GMU-7931-1 (90%) and 3.0 mg/L in GMU-7923 (86.66%), with lower and higher levels resulting in reduced callus proliferation. Floral bud explants demonstrated robust callus formation and biomass accumulation on 0.5 mg/L NAA + 5.0 mg/L TDZ in both genotypes, with GMU-7923 showing superior performance. Notably, successful bud-derived callus induction reported here represents a novel addition to safflower tissue culture literature. Collectively, these findings establish remarkable response of NAA (2.0–4.0 mg/L) with BAP (1.0 mg/L) for leaf and hypocotyl and 0.5 mg/L NAA + 5.0 mg/L TDZ for bud followed by GMU-7923 (10–12 day remarkable response at 3.0 mg/L 2,4-D). Across explants, leaf tissues consistently displayed superior callus induction, while GMU-7931-1 showed the earliest visible callus formation (8–10 days) under optimal 2,4-D treatments (5.0 mg/L) as highly effective regimes for efficient and reproducible callus induction, supporting their application in scalable metabolite and pigment production in Carthamus tinctorius.
Keywords: 2,4-D, BAP, bud explants, callus induction, Carthamus tinctorius, genotype specificity, hypocotyl, metabolite production, NAA, TDZ.