Influence of seaweed extracts and plant growth regulators on in vitro regeneration of Lycopersicon esculentum from leaf explant

An efficient in vitro regeneration protocol was developed for tomato from leaf explant using plant growth regulators, organic elicitors, polyamines, and seaweed extracts. Initially, excised leaf explant was cultured on medium containing different concentrations of auxins viz., 2,4-dichloropheonoxyacetic acid (2,4-D; 0.5–3.0 mg L−1), picloram (Pic; 0.5–3.0 mg L−1), 1-naphthaleneacetic acid (NAA; 0.5–3.0 mg L−1), and indole-3-acetic acid (IAA; 0.5–3.0 mg L−1). The most effective auxin was tested in combination with efficient cytokinins such as kinetin (Kin; 0.5–3.0 mg L−1), 6-benzylaminopurine (BAP; 0.5–3.0 mg L−1), and thidiazuron (TDZ; 0.5–3.0 mg L−1). To achieve the best organogenic capability, different elicitors (casein hydrolysate, yeast extract, glutamine and adenine sulfate), polyamines (putrescine, spermidine, and spermine), and seaweed (Gracilaria edulis and Sargassum wightii) extracts were tested at various concentrations. Among the plant growth regulators, additives, and seaweed extracts tested, the medium supplemented with 1.5 mg L−1 Pic + 1.0 mg L−1 TDZ + 80 mg L−1 casein hydrolysate induced maximum of 28.6 shoots per organogenic callus. Rapid elongation was achieved in the medium fortified with isopentenyladenine (1.2 mg L−1) and G. edulis extract (30%) and the seaweed S. wightii extract induced rooting of elongated shoots. The presence of plant growth regulators in seaweed extracts were further confirmed by FTIR and HPLC analysis. HPLC analysis of seaweed extracts and standard plant growth regulators revealed the presence of NAA and isopentenyladenine in S. wightii. The standard chromatogram of NAA correlated with the chromatogram of G. edulis. Hence this regeneration system provides an additional platform for generating transgenic plants in an efficient manner.