Estudio del origen genético de la variedad de vid Garnacha Blanca, de su diversidad fenotípica y de los efectos moleculares asociados a la variación en el color de la uva stars

  1. Maite Rodríguez Lorenzo
Directed by:
  1. José Miguel Martínez Zapater
  2. Pablo Carbonell Bejerano
  3. Javier Ibáñez Marcos

Defense university: Universidad de La Rioja

Year of defense: 2019

Committee:
  1. Antonio Granell Richart Chair
  2. Luis Gonzaga Santesteban García Secretary
  3. Lucie Fernández Committee member
Thesis with
  1. Mención internacional
Department:
  1. Agriculture and Food

Type: Thesis

Summary

Because of their high heterocygosity, grapevine cultivars are reproduced by vegetative multiplication in order to keep their varietal characteristic traits. In this way, somatic variation is the main source of genetic divsersity to improve traditional varieties either by clonal selection, or for the generation of new derivative varieties, like berry color variants. Garnacha Blanca (GB) is a white-berried variety derived from Garnacha Tinta (GT). Both varieties display fruit set problems that can limit production. In order to understand potential in GB for clonal selection improvement regarding production and bunch compactness, we studied the variation of related traits at plant, bunch and berry level, in several accessions during two years. We also analyzed the genetic and molecular origin of color loss variation and its relation with production and bunch compactness by SNP genotyping of chromosome 2 and next- generation sequencing strategies. In addition, we used white variants of Garnacha and Tempranillo to assess for direct and indirect consequences of the absence of anthocyanins in berry composition using metabolomic and transcriptomic analyses. Results showed us that the main variable determining variation in production and bunch compactness is fruitset rate and it has strong environmental dependece. Traits related with berry size are less relevant in determining production and bunch compactness. Regarding the genetic origin of GB, the SNP genotyping chip for chromosome 2, allowed us to detect loss of heterozigosity around the region of the berry color locus that regulates anthocyanin biosynthesis in the berry. Sequencing and comparison of GT and GB genomes confirmed that the loss of heterocigosity was caused by deletions of the functional copies of VviMYBA1 and VviMYBA2 genes. Segregation and gamete viability analyses showed that these deletions have no negative effects neither in gamete transmission nor in gamete viability, and consequently do not affect production and bunch compactness in GB. Finally, metabolome and transcriptome comparisons between berry color somatic variants unveiled the regulatory role of VviMYBA1 and VviMYBA2 genes in phenylpropanoid biosynthesis pathway and in triggering protection againts pathogens and abiotic stress in the berry skin during berry ripening. In addition, white grapes accumulated higher levels of alternative photoprotective molecules (carotenoids, phenilpropanoids and terpenoids) correlating with the transcriptional activation of light responses in white berries. These responses associate with important changes in the berry composition and may contribute to floral, white fruit and herbaceous aromatic character, typical of white wines. Altogether, the results contribute to a deeper understanding of somatic variation mechanisms and its phenotypic effects in terms of production and quality in grapes. This knowledge could help to optimize clonal selection programs and increase their efficiency.