Development of a superior somaclone of rose-scented geranium and a protocol for inducing variants

Abstract

An efficient protocol has been established for generating somaclones in the Indian rose-scented geranium Pelargonium graveolens cv. Bipuli, which yields Reunion Island-type essential oil. Murashige and Skoog's (MS) medium supplemented with 4.5 mg·L-1 BA and 1.0 mg·L-1 NAA was found optimal for induction of callus from leaf explants. Callus regenerated shoots when transferred to MS medium with 2.5 mg·L-1 BA and 0.1 mg·L-1 NAA. The regeneration percentage as well as number of shoots per cm2 of callus was greatly improved by addition of ADS at a concentration of 3.0 mg·L-1. Regenerated shoots rooted within 20 days following transfer to half-strength MS medium with 0.1 mg·L-1 NAA. Plantlets were acclimatized under glasshouse conditions with 80% to 85% survival. Randomly selected 30 individual calliclones were subjected to field trial with wild-type parent in randomized block design, replicated three times with 90% survival for two successive years. Characterization of these calliclones for essential oil yield and quality traits demonstrated induction of variability in all the characteristics examined in negative and positive directions in comparison with the wild-type parent. This screening led to the identification of somaclone B22, which out-yielded the wild-type parent as well as the rest of the somaclones. The quality of the essential oil of B22 was similar to that of the parent. Chemical names used: N6-benzyladenine (BA); naphthalene acetic acid (NAA); adenine di-sulphate (ADS).