Kharb, PushpaVictoria2016-12-012016-12-012005http://krishikosh.egranth.ac.in/handle/1/88678The present investigation was carried out to optimize conditions and develop an improved protocol for micropropagation in air yam (Dioscorea bulbifera L.). Nodal and shoot tip explants were used for shoot regeneration on different media supplemented with both synthetic phytohormones as well as cell free extract of phytohormones producing bacteria (Acetobacter diazotrophicus 767-50 and Azotobacter chroococcum-103). Response for shoot regeneration was observed within a week on all the media tested for nodal explants and from shoot tip explants shoot regeneration was observed only on medium supplemented with 15 mg/l adenine sulphate and 2 mg/l kinetin. Nodal explants gave best shoot regeneration (100%) on MS medium supplemented with adenine sulphate (15 mg/l) and kinetin (2 mg/l). On the same medium after subculturing of nodal explants, when shoot induction started maximum (15-20) multiple shoots were observed in 76.66 per cent of the shoots while in the remaining shoots, 3-4 shoots per explant were observed Maximum (97.77%) rooting of shoots was observed on MS medium supplemented with 0.5 mg/l IAA. Healthy and strong rooting was observed on all the media tested within 15 days of culturing. Survival rate of regenerated plantlets was observed to be more than 90 per cent on transplantation to soil. The earliest shoot regeneration response was observed on 7th day on all the media supplemented with cell free extract of A. diazotrophicus, A. chroococcum and combination of both. Maximum 82.22 per cent and 88.88 per cent shoot regeneration response was observed on MS media supplemented with 15 mg/l adenine sulphate + 1.5 ml/l cell free extract of A. diazotrophicus and 15 mg/l. Adenine sulphate + 1.5 ml/l cell free extract of A. chroococcum, respectively from nodal explants. Shoot regeneration response was observed maximum (88.88%) on MS medium supplemented with 15 mg/l adenine sulphate + 0.5 ml/l cell free extract of A. diazotrophicus + 0.5 ml/l cell free extract of A. chroococcum. Root formation alongwith shoots was also observed on all the media supplemented with cell free extracts of both the bacterial strains. The number of shoots per explant regenerated on MS medium supplemented with cell free extracts of A. diazotophicus as well as A. chroococcum was found to be 2-3, whereas 3-4 shoots per explants were observed on the media supplemented with combination of cell free extracts of A. diazotrophicus and A. chroococcum.enThesis