Chitosan seed priming enhanced germination and seedling growth in Ashwagandha (Withania somnifera (L.) Dunal.)

Ashwagandha, Withania somnifera (L.) Dunal., has a variety of therapeutic uses and the roots of this plant are used in the preparation of numerous ayurvedic formulations. The aim of the study was to investigate the effect of seed priming with chitosan in W. somnifera. The seeds primed with chitosan were grown in protrays and the effect on germination parameters was studied. Chitosan solutions of different concentrations, viz., 0.5 mg/mL, 1 mg/mL, 2.5 mg/mL and 5 mg/mL were used and the seeds were soaked for three different durations i.e., 2 h, 4 h and overnight (24h). It was observed that seed priming with chitosan improved different traits related to germination, i.e., germination per cent, survival per cent, germination index, seedling vigour index, allometric index and mean germination time. Seeds primed with 5 mg/mL chitosan for 4 h (T₈) resulted in significantly higher germination per cent (76%), survival per cent (73.33%), allometric index (0.82), germination index (1.72) and seedling vigour index I (8890). Thus, the treatment involving seeds primed with chitosan solution of concentration 5 mg/mL for 4 h was selected as the best priming treatment. However, overnight priming treatments of chitosan were found to be inhibitory with respect to the germination parameters. Our results suggested that W. somnifera seed priming with chitosan has a positive effect on the germination and vigour of the plant but the period of priming also has a profound influence on germination.