Occurrence of somaclonal variation among somatic embryo-derived white spruces (Picea glauca, Pinaceae)

Four different variegata phenotypes were identified among 2270 white spruce plants [Picea glauca (Moench.) Voss.] produced over a period of 2 yr from the time of induction of embryogenic tissues. The four variegated plants differed from each other in the extent and distribution of chlorophyll-deficient needles. Light microscopy showed that variegated leaves of a selected variant consisted of a chimeral mixture of green and white cells. Electron microscopy showed that cells in completely white needles had large nuclei with predominant euchromatin, lacked large cytoplasmic vacuoles, and harbored vacuolized plastids with aberrant morphologies. Various observations suggest that the recovered variegata phenotypes reflect some kind of genetic instability of either chloroplastic or nuclear genomes. To elucidate the genetic basis of these variegata phenotypes in white spruce, three out of the four variants 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 DNA fragment showed no homology with any known gene, but the amplified sequence appears most likely of nuclear origin.