Role of plant growth regulators in preservation of Pyrus germplasm in vitro

In vitro established shoots of nine pear genotypes namely; Khurolli, Bagugosha, Pathar nakh, Desi nakh, Kotharnul, Btangi, Frashishi, Kashmiri nakh, and Raj btung, were preserved by lowering concentration of growth regulators [(0.00, 0.25 or 0.50mg l -1 6-benzyaminopurine (BAP) or adding growth retardants, 10 mg L-1 Alar (diaminazide or B-9), or abscisic acid (ABA)] in the culture medium. The cultures were assessed for their survival and regenerability percentages after 3, 6, 9 and 12 months of storage. The genotypes differed significantly for survival and regeneration percentage. The culture medium supplemented with 0.50 mg L -1 BAP was comparatively more effective and resulted in higher survival rate and re-growth after transferring onto the fresh medium. Storage for short duration (3 months) resulted in significantly higher survival and regeneration rates than other storage periods. As storage period was prolonged, survival and regenerability of shoots progressively decreased. Overall results indicated that the shoots of Desi nakh had the highest survival (73.33 %) and Pathar nakh showed the maximum regenerability (67.66 %) when cultured on the medium supplemented with 0.50 mg L -1 BAP and stored for 3 months. However, no shoots of Kotharnul survived when cultured on the medium without any growth regulator and kept for 12 months. Key words : Growth retardants, in vitro preservation, pear genotypes, slow growth.