Chimeras and Variegation: Patterns of Deceit

Clonal variation and stability assay of chimeric Pinot Meunier (Vitis vinifera L.) and descending sports

“…Periclinal chimeras, as described here for Pinot Meunier, are the most stable form of genetic mosaicism in angiosperms (Marcotrigiano 1997). The long existence of this cultivar and our results on its high genetic similarity suggest that Pinot Meunier is a stable form despite the rare loss of its chimeric status.…”

“…Because all publications dealing with genetically heterogeneous grapevines use the term 'chimerism', it will be used in this study. Therefore, a 'chimera' is a speciWc type of genetic mosaic, in which genetically diVerent cells form the plant body (Marcotrigiano 1997). Typically this is the result of mutation in one cell of the shoot apical meristem, spread by replication and cell division.…”

Two new grape cultivars, bud sports of Cabernet Sauvignon bearing pale-coloured berries, are the result of deletion of two regulatory genes of the berry colour locus

“…The L2 makes up most of the rest of the plant including the mesophyll and gametes. Mosaics and chimeras are common in the plant world (Marcotrigiano 1997) where many are periclinal chimeras (genetically different L1 and L2 cell layers), maintained through clonal propagation such as cuttings. In Vitis vinifera, one of the best characterised example is Pinot Meunier where a mutation in a gene involved in gibberellin perception in the L1 cell layer leads to a hairy leaf phenotype (Boss and Thomas 2002).…”

“…However, on rare occasions, some cultivars can demonstrate unstable phenotypes resulting in a portion of the plant, sometimes extending to whole branches, having different characteristics. When these branches (bud sports) are vegetatively propagated by clonal techniques, the new phenotype is generally maintained leading to a new variety, often exhibiting only one phenotypic character different from the parent (Marcotrigiano 1997). Horticulturists propagate bud sports because they continue to exhibit all of the other desirable characteristics of the parent (Franks et al 2002).…”

Effect of Variegation on Stem Exudates of Coleus and Life History Characteristics of Citrus Mealybug (Hemiptera: Pseudococcidae)

“…Genetically, leaf variegation can be caused when leaf buds produce leaf cells that either differ genetically or phenotypically in their ability to express gene products involved in the production of photosynthetic pigments (Marcotrigiano 1997). Rates of plant growth can decrease when variegation reduces the concentration of photosynthetic pigments in leaf tissues (e.g., Sadof andRaupp 1991, Yang andSadof 1995).…”