Dissecting the molecular bases of the clonal phenotypic diversity observed in Vitis vinifera cv. Malbec

CALDERÓN, LUCIANO; LIJAVETZKY, D; MARTINEZ-ZAPATER, JM; MUÑOZ, CJ

Simposio; XIIIth International Symposium for Grapevine Breeding and Genetics; 2022

Cultivated grapevines are clonally propagated, mainly to maintain phenotypic traits of productive interest; this turns particularly relevant in the wine industry to preserve the varietal typicity. Nonetheless, a wide clonal phenotypic diversity has been reported for several cultivars. Malbec is appreciated for producing high-quality red wines and recognized world-wide as the flag cultivar of the Argentine viticulture. Previous analyses demonstrated a notorious clonal phenotypic diversity for Malbec, in technologically relevant traits. On the other hand, clonal genetic diversity was shown to be scarce, affecting mostly the intergenic regions. In order to dissect the molecular bases of the observed phenotypic diversity, we studied here 27 clonal accessions grown under the same conditions at Vivero Mercier Argentina experimental vineyard. Analytical, biochemical and productive measurements were performed on berries at technological maturity (23º Brix), during two consecutive seasons (2017-2019). Afterwards, we chose the six clones exhibiting extreme contrasting behavior for the evaluated features. More precisely: i) phenolic composition (total polyphenols and anthocyanins), ii) analytical profile (total acidity, ºBrix and PH) and iii) skin weight (as a productivity proxy). Whole RNA extractions were performed from veraison berries (75% colored), from the six selected clones. Illumina stranded paired-end reads (150 bp) were obtained, totaling 122 Gb of transcriptomic data for 18 samples (6 clones x 3 biological replicates). To perform differential gene expression (DEG) and gene ontology (GO) enrichment analyses, transcriptomic data was aligned to a de novo assembled and annotated Malbec genome, recently generated by our group. After performing a discriminant analysis including all samples, clone Cot-595 exhibited a highly differentiated transcriptomic profile. Moreover, this clone showed the highest total polyphenols and anthocyanins concentration, while clones Mb-506 and Cot-596 showed the lowest concentrations. Therefore, we focused the DEG and GO analysis to the pairwise comparisons among the three mentioned accessions. Consistently, Cot-595 exhibited GO enrichment for genes involved in the anthocyanins biosynthesis pathways, while Mb-506 and Cot-596 showed enrichment for genes involved in pathways that regulate vegetative growth. These results suggest that phenotypic diversity observed among Malbec clones, has more solid bases on the transcriptomic profiles differences than on the genetic diversity.