Explant autonomy in Indian tobacco cultivars under in vitro

Abstract

Hormonal autonomy in leaf explants of 15 Flue-cured Virginia tobacco varieties grown under Indian conditions was studied. Most of the varieties responded in 19-30 days on MS basal media. Multiple shoot initiation was observed in cultivars Hema, FCV Special and Rathna, while rhizogenesis was observed in Kanakaprabha, VT 1158, CM 12 and Kanthi. These results indicated the hormonal autonomy of the tobacco cultivars. Most of the varieties that showed different types of organogenesis on MS basal media showed callus initiation on callus media indicating that hormone supplement in the in-vitro media regulating the endogenous hormone levels in the explants or the growing tissues. The study suggested that varieties, Jayasri, VT-1158 and Kanakaprabha have inherited hormonal autonomy from their ancestral variety Delcrest. Hema leaf explants that gave multiple shoots on basal media showed callus induction on auxin (NAA) supplemented MS media indicating cytokinin autotrophy of its explants and their balance through the addition of auxin. Jayasri that gave rooting on MS basal media, produced hairy roots on MS media supplemented with NAA suggesting the synergic effect of supplemented NAA on the already available free auxin in its explants. Cultivars adapted to reduced moisture conditions showed hormonal autonomy indicating the possibility of using this trait for the selection of stress tolerant lines.