Schwarzriesling
In research, Paul K. Boss and Mark R. Thomas of the CSIRO Plant Industry and Cooperative Research Centre for Viticulture in Glen Osmond, Australia, found that Pinot Meunier has a mutation ("VvGAI1") that stops it from responding to gibberellic acid, a plant growth hormone. This leads to different, white-haired, leaf and shoot growth, and also to a slight stunting in growth, explaining why Pinot Meunier plants tend to be a bit smaller than Pinot noir. The mutation exist only in the outermost cell layer of the cultivar, the L1 or 'epidermal' layer, meaning Pinot Meunier is a chimera. Through tissue culture, it is thus possible to separate out plants containing both the mutant (L1) and non-mutant (L2) genotypes, yielding a normal Pinot noir -like genotype and an unusual looking L1-genotype vine with compressed internodes and thickly clustered leaves. The mutants could not produce full-grown tendrils, it seems that gibberellic acid converts grapevine flower buds into tendrils.