Somatic embryogenesis is an effective strategy for dissecting chimerism phenomena in Vitis vinifera cv Nebbiolo

The tendency of somatic embryogenesis to regenerate plants only from the L1 layer, associated with the spread of chimerism in grapevine, must be carefully considered in the framework of biotechnological improvement programmes. Grapevine is an important fruit crop with a high economic value linked to traditional genotypes that have been multiplied for centuries by vegetative propagation. In this way, somatic variations that can spontaneously occur within the shoot apical meristem are fixed in the whole plant and represent a source of intra-varietal variability. Previously identified inconsistencies in the allelic calls of single nucleotide variants (SNVs) suggested that the Vitis vinifera 'Nebbiolo' CVT185 clone is a potential periclinal chimera. We adopted the somatic embryogenesis technique to separate the two genotypes putatively associated with the L1 and L2 layers of CVT185 into different somaclones. Despite the recalcitrance of 'Nebbiolo' to the embryogenic process, 58 somaclones were regenerated and SNV genotyping assays attested that the genotype of all them differed from that of the mother plant and was only attributable to L1. The results confirmed that L2 has low or no competence for differentiating somatic embryos. After one year in the greenhouse, the somaclones showed no phenotypic alterations in comparison with the mother plant; however further analyses are needed to identify potential endogenous sources of variation. The tendency of somatic embryogenesis to regenerate plants only from L1 must be carefully considered in the framework of biotechnological improvement programmes in this species.