Diversification within grapevine cultivars goes through chimeric states

Abstract

Vitis vinifera 'Pinot' clones were analysed at 50 microsatellite loci to assess intravarietal genetic diversity. When analysing leaf tissue DNAs, polymorphism mainly resulted from the appearance of a third allele when two were expected for heterozygous loci in a diploid species. The sequencing of the three microsatellite alleles at two loci has confirmed their simultaneous presence in the leaf tissues. A hypothesis explaining the triallelic profiles at a locus is the presence of a periclinal chimera meristem structure, in which genetically different cell layers coexist. The periclinal chimeric state of two Vitis vinifera 'Pinot gris' clones was confirmed by splitting and analysing the genotypes resulting from L1 and L2 cell layers in progeny derived from self-fertilization, in root tissues, and in plants regenerated from somatic embryogenesis. Prevalence of chimerism in polymorphic clones observed in a collection of 145 accessions belonging to 'Pinot gris', 'Pinot noir', Pinot blanc', 'Pinot meunier', and 'Pinot moure' cultivars was demonstrated. The accumulation of somatic mutations and cell layer rearrangements allowed us to deduce the relationships between the various genotypes and to open a way for understanding the diversification process and the phylogeny in the 'Pinot' group.

Selection of high heterozygosity popcorn varieties in Brazil based on SSR markers

“…using the UMC1446, UMC1590 and UMC2343 primers (Rupp et al, 2009). The triallelic pattern in SSR loci has been considered evidence of chimeras, a mechanism of genetic diversification well characterized by Hocquigny et al (2004) occurring in grapevine clones (Crespan, 2004;Moncada et al, 2006). The detection of 3 alleles at the same locus could be the result of a chimeric structure in which genotypes of different cell layers displayed different alleles.…”

“…The observation of three or more alleles was justified by authors either as more than one locus that is being amplified in the PCR or alternatively as the result of DNA contamination and/or PCR artifacts, and were treated as missing data. However, the triallelic pattern in SSR loci has also been detected in progenies of sweet corn (Rupp et al, 2009) and has been considered as evidence of chimeras and as a mechanism of genetic diversification in grapevine clones (Hocquigny et al, 2004;Crespan, 2004;Moncada et al, 2006), which have vegetative propagation. Although the reproductive system in maize plants happens by out-or self-crossing, where the chimerism effect has minor importance, the presence of a third allele in SSR locus is indicative of the potential of loci in molecular diversification and variability.…”

Evolution of the VvMybA gene family, the major determinant of berry colour in cultivated grapevine (Vitis vinifera L.)

“…Furthermore, most of the antique cultivars have a complete series of coloured mutants such as Pinot or Grenache noir, gris and blanc. The determinants of such variation corresponding to major genomic re-arrangements, such as Gret1 instability (Lijavetzky et al, 2006;Walker et al, 2007), and possibly maintained in chimeric states (Hocquigny et al, 2004) have not been investigated in this study. Multiple Gret1 insertion/excision or recombination events may explain the contrasting pattern of selection in the Rs haplogroup.…”

Genotyping of Vitis vinifera L. within the Slovak national collection of genetic resources

“…Such somatic mutation and its accumulation were designated as a way of diversification process and phylogeny [21] and as a slow but constant evolution ongoing in grapevine [2]. Generally, mutations are important genetic events in grapevine, generating variation (phenotypes) in important traits such as berry colour and flavour, date of ripening, size and compactness of bunches, yield, and others.…”