Pretreatment of seeds with thidiazuron delimits its negative effects on explants and promotes regeneration in chickpea (Cicer arietinum L.)

Abstract

Thidiazuron (TDZ) is an important cytokinin-like substance used in plant tissue culture. However, long exposure of plant tissues to TDZ results in abnormal regeneration. The present study reports an efficient regeneration protocol that avoids the TDZ overexposure to chickpea (Cicer arietinum L.) tissues. Two separate experiments were designed for seed pretreatment with TDZ, of which the first one involved short-term pretreatment with various concentrations of TDZ (15, 20 and 25 µM), whereas the second one lacked TDZ pretreatment. Axillary meristem explants prepared from TDZ-pretreated and TDZ-non-pretreated seeds were then analyzed in shoot induction medium (SIM) with or without 4 µM TDZ. Thus, four conditions were chosen to analyze the effect of TDZ: (i) TDZ pretreatment only without TDZ in SIM, (ii) TDZ pretreatment along with TDZ in SIM, (iii) no TDZ pretreatment but there was TDZ in SIM, and (iv) there was neither TDZ pretreatment nor TDZ supplied in SIM (control). The response in terms of percent regeneration (69%), number of shoots per explant (20.66 ± 0.5), minimum number of days taken for multiple shoot induction (7.3 ± 0.5) and effective rooting was the highest under the condition (i) with 20 μM TDZ pretreatment without subsequent TDZ supplementation into the SIM. In addition, shoot elongation medium (SEM-3) having 5 μM benzyladenine, 2 μM kinetin and 2 μM gibberellic acid showed the highest branching and maximum shoot length. In conclusion, we reported an easy and efficient regeneration method in chickpea using TDZ pretreatment only, which showed qualitative multiple shooting and effective rooting.