In Vitro Regeneration Strategies in Woody Citrus of Northeast India (Citrus jambhiri and Citrus aurantifolia)

Since the status of C. jambhiri is “rare” and C. aurantifolia is endowed with folk medicinal properties, our study aimed at producing true-to-type seedlings for further conservation by using PGRs, ferrous sulfate, and casein hydrolysate in MS medium to induce in vitro germination and “callus” formation from seeds of C. jambhiri Lush. It also focused on evaluation of suitable species and the best type of explant for organogenesis. The present study was undertaken to develop an efficient micropropagation protocol for C. jambhiri Lush. and C. aurantifolia. The frequency of callus induction increased to its maximum when 2.0 mg/L 2,4-D and 1.0 mg/L picloram were added individually. The calli derived from 2,4-D exhibited maximum regeneration potentiality. In addition, sucrose (30 g/L), dextrose (60 g/L), and coconut water (10 mL/L and 15 mL/L) also enhanced callus induction. Regarding heavy metals, 100 ppm of Fe2SO4 exhibited maximum germination percentage (84.33%) from seeds of C. jambhiri Lush. However, maximum callus induction (50.00%) was induced from the seeds of C. aurantifolia incubated in Fe2SO4 (400 ppm). The maximum number of shoots per callus was produced (5.13) with the addition of 200 mg/L casein hydrolysate in the callus-induction medium. Pearson correlation analysis revealed a positive and significant association of the number of plantlets/calluses with shoot length and regeneration percentage, respectively. It was phenotypically observed that the tissue culture traits performed better from explants derived from C. jambhiri Lush. than C. aurantifolia when subjected to varying concentrations of PGRs, carbon sources, organic adjuvants, and heavy metals, respectively.