Effect of Naphthalene Acetic Acid (NAA) on in vitro rooting of regenerated microshoots of groundnut (Arachis hypogaea L.)

Successful utilization of tissue culture for the improvement and conservation of groundnut will be made possible only with an efficient shoot proliferation, formation of well-developed root system in microshoots, successful acclimatization and final establishment in field. A regeneration protocol ensuring a high frequency rooting of microshoots derived from embryonic axes of four groundnut genotypes was achieved using naphthalene acetic acid (NAA). Microshoots of 3cm length were subcultured on Murashige and Skoog (MS) medium plus 30% sucrose, supplement with 1.0 or 1.5mg/L NAA and compared with a hormone free medium (control). Rooting was significantly influenced by the presence and concentration of NAA. Microshoots subcultured in medium supplemented with 1mg/L NAA rooted within 2weeks of subculture, producing the highest number of roots/plantlet and root-induction frequency. However, increasing the concentration of the auxin suppressed root length with the hormone free medium having the longest roots. Significant genotypic effect was also observed, with Samnut 22 having more number of roots/plantlet and root-induction frequency.