OCCURRENCE OF SOMACLONAL VARIATION AMONG SOMATIC EMBRYO-DERIVED WHITESPRUCES (PICEA-GLAUCA, PINACEAE)

Four different variegata phenotypes were identified among 2270 white s pruce plants [Picea glauca (Moench.) Voss.] produced over a period of 2 yr from the time of induction of embryogenic tissues. The four varie gated plants differed from each other in the extent and distribution o f chlorophyll-deficient needles. Light microscopy showed that variegat ed leaves of a selected variant consisted of a chimeral mixture of gre en and white cells. Electron microscopy showed that cells in completel y white needles had large nuclei with predominant euchromatin, lacked large cytoplasmic vacuoles, and harbored vacuolized plastids with aber rant morphologies. Various observations suggest that the recovered var iegata phenotypes reflect some kind of genetic instability of either c hloroplastic or nuclear genomes. To elucidate the genetic basis of the se variegata phenotypes in white spruce, three out of the four variant s were subjected to randomly amplified polymorphic DNA (RAPD) analysis . Out of more than 250 RAPD markers screened, only one correlated with white needles of variegated plants. The nucleotide sequence of this D NA fragment showed no homology with any known gene, but the amplified sequence appears most likely of nuclear origin.