Optimizing Callus Induction in Guar (Cyamopsis tetragonoloba L.): Impact of Hormonal Compositions and Explant Types

Callus induction and regeneration can greatly help in improving the progress of genetic modification and help in gene transfer. Accordingly, this study investigated the optimal explant and growth regulators for callus formation. The experiment was performed in a factorial experiment based on a completely randomized design in 5 replications with hormonal composition (13 levels) and explant types (rootlet, leaf and stem) as factors. The levels of hormonal composition contained NAA, BAP, 2,4-D and TDZ applied to the MS media. After 80 days, the explants were measured for various traits, including days to callus formation, callus formation percentage, fresh and dry weight, and mass moisture percentage. According to the analysis of variance, hormonal composition, the type of explant, and their interaction had significant effects on fresh and dry weight and callus formation. [2,4-D (2 mg L-1) + TDZ (2 mg L-1)] and [NAA (2 mg L-1) + BAP (1 mg L-1)] treatments had the highest and lowest percentage of callus formation, respectively. The correlation test revealed a significant relationship between callus formation and both fresh weight and mass moisture percentage. However, callus formation did not show a significant correlation with dry weight. In general, treating leaves with the TDZ resulted in the highest dry and fresh weights compared to treating roots with the BAP. To enhance callus production and achieve better weight in this plant, it is recommended to use leaf explants combined with TDZ (2 mg L-1) and 2,4-D (2 mg L-1).