SOMACLONAL VARIATION IN PLANTS REGENERATED FROM CALLUS-CULTURE OF HYBRID ASPEN (POPULUS-ALBA LXP GRANDIDENTATA MICHX)

Calli-clones of hybrid poplar are known to exhibit high levels of soma clonal variation. This study was undertaken to understand the causes o f this variation. Multiple-shoot regeneration from callus cultures was obtained using woody plant medium (WPM) supplemented with 20 muM zeat in. Of the 400 calli-clones maintained in vitro for 6 weeks on WPM wit hout plant growth regulators (PGR) 75.5% appeared to be growing normal ly, while the rest were putative albino (7.5%), slow-growing (8.25%), and rapid-growing (16.3%) variants. For the 200 calli-clones grown in the greenhouse for 6 months after transplanting. 4%) were slow-growing , 6% were rapid-growing and 10% had aberrant leaf morphology. Chromoso me studies using in vitro calli-clones showed a broad range of variati on from haploidy to tetraploidy. Protein studies using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) revealed a stron g relationship between the staining intensity of specific bands and ca lli-clone growth patterns. Finally, the albino phenotype was associate d with the loss of at least two proteins.